TY - SOUND TI - Tips for Laboratory TAs AU - Cooper, M. DA - 2012/// PY - 2012/// M3 - Workshop ER - TY - JOUR TI - Syngas Chemical Looping Process: Design and Construction of a 25 kWth Subpilot Unit AU - Sridhar, Deepak AU - Tong, Andrew AU - Kim, Hyung AU - Zeng, Liang AU - Li, Fanxing AU - Fan, Liang-Shih T2 - Energy & Fuels AB - The syngas chemical looping (SCL) process employing the gas–solid counter-current flow pattern demonstrates an innovative approach to generate hydrogen and/or electricity from syngas accompanied with in situ carbon capture. Iron-based oxygen carriers donate oxygen for complete syngas conversion in the reducer. The reduced oxygen carriers are then oxidized by steam and/or air to generate hydrogen and/or heat in the oxidizer and/or the combustor, respectively. Previous studies have reported the performance of the iron-based oxygen carriers, the advantages of a moving bed reducer and oxidizer, and simulation of various parametric effects on the reactor design of the reducer, oxidizer, and combustor for a continuous system. In this study, a 25 kWth subpilot SCL unit was designed based on the simulated criteria and constructed to demonstrate the feasibility of generating high purity hydrogen with in situ carbon capture. Two test runs were presented using 4.5 mm × 2.5–4.5 mm cylindrical oxygen carriers comprising of 60 wt % iron oxide (Fe2O3). The first test resulted in a syngas conversion of 99.96% and trace amounts of hydrogen generation highlighting the importance of the extent of oxygen carrier conversion. The second test demonstrated the continuous production of hydrogen with an average purity of 94.4% and a maximum of 98.4% when the conversion of the oxygen carriers exiting the reducer was 35.54%. The initial test results support the concept of continuous hydrogen generation with in situ carbon capture using the SCL process and also highlight the advantage of adopting the counter-current moving bed reactor design. DA - 2012/3/15/ PY - 2012/3/15/ DO - 10.1021/ef202039y VL - 26 IS - 4 SP - 2292–2302 SN - 0887-0624 1520-5029 UR - http://dx.doi.org/10.1021/ef202039y ER - TY - JOUR TI - Environmental effects of ozone depletion and its interactions with climate change: progress report, 2011 AU - Andrady, Anthony L. AU - Aucamp, Pieter J. AU - Austin, Amy T. AU - Bais, Alkiviadis F. AU - Ballaré, Carlos L. AU - Björn, Lars Olof AU - Bornman, Janet F. AU - Caldwell, Martyn AU - Cullen, Anthony P. AU - Erickson, David J. AU - de Gruijl, Frank R. AU - Häder, Donat P. AU - Helbling, Walter AU - Ilyas, Mohammad AU - Longstreth, Janice AU - Lucas, Robyn AU - McKenzie, Richard L. AU - Madronich, Sasha AU - Norval, Mary AU - Paul, Nigel D. AU - Redhwi, Halim Hamid AU - Robinson, Sharon AU - Shao, Min AU - Solomon, Keith R. AU - Sulzberger, Barbara AU - Takizawa, Yukio AU - Tang, Xiaoyan AU - Torikai, Ayako AU - van der Leun, Jan C. AU - Williamson, Craig E. AU - Wilson, Stephen R. AU - Worrest, Robert C. AU - Zepp, Richard G. T2 - Photochemical & Photobiological Sciences AB - The parties to the Montreal Protocol are informed by three panels of experts. One of these is the Environmental Effects Assessment Panel (EEAP), which deals with two focal issues. The first focus is the effects of increased UV radiation on human health, animals, plants, biogeochemistry, air quality, and materials. The second focus is on interactions between UV radiation and global climate change and how these may affect humans and the environment. When considering the effects of climate change, it has become clear that processes resulting in changes in stratospheric ozone are more complex than believed previously. As a result of this, human health and environmental problems will be longer-lasting and more regionally variable. Like the other panels, the EEAP produces a detailed report every four years; the most recent was published in 2010 (Photochem. Photobiol. Sci., 2011, 10, 173-300). In the years in between, the EEAP produces less detailed and shorter progress reports, which highlight and assess the significance of developments in key areas of importance to the parties. The next full quadrennial report will be published in 2014-2015. DA - 2012/// PY - 2012/// DO - 10.1039/C1PP90033A VL - 11 IS - 1 SP - 13–27 ER - TY - JOUR TI - Hyperthermophilic Thermotoga Species Differ with Respect to Specific Carbohydrate Transporters and Glycoside Hydrolases AU - Frock, Andrew D. AU - Gray, Steven R. AU - Kelly, Robert M. T2 - Applied and Environmental Microbiology AB - Four hyperthermophilic members of the bacterial genus Thermotoga (T. maritima, T. neapolitana, T. petrophila, and Thermotoga sp. strain RQ2) share a core genome of 1,470 open reading frames (ORFs), or about 75% of their genomes. Nonetheless, each species exhibited certain distinguishing features during growth on simple and complex carbohydrates that correlated with genomic inventories of specific ABC sugar transporters and glycoside hydrolases. These differences were consistent with transcriptomic analysis based on a multispecies cDNA microarray. Growth on a mixture of six pentoses and hexoses showed no significant utilization of galactose or mannose by any of the four species. T. maritima and T. neapolitana exhibited similar monosaccharide utilization profiles, with a strong preference for glucose and xylose over fructose and arabinose. Thermotoga sp. strain RQ2 also used glucose and xylose, but was the only species to utilize fructose to any extent, consistent with a phosphotransferase system (PTS) specific for this sugar encoded in its genome. T. petrophila used glucose to a significantly lesser extent than the other species. In fact, the XylR regulon was triggered by growth on glucose for T. petrophila, which was attributed to the absence of a glucose transporter (XylE2F2K2), otherwise present in the other Thermotoga species. This suggested that T. petrophila acquires glucose through the XylE1F1K1 transporter, which primarily serves to transport xylose in the other three Thermotoga species. The results here show that subtle differences exist among the hyperthermophilic Thermotogales with respect to carbohydrate utilization, which supports their designation as separate species. DA - 2012/3/15/ PY - 2012/3/15/ DO - 10.1128/aem.07069-11 VL - 78 IS - 6 SP - 1978-1986 J2 - Appl Environ Microbiol LA - en OP - SN - 0099-2240 1098-5336 UR - http://dx.doi.org/10.1128/aem.07069-11 DB - Crossref ER - TY - JOUR TI - Stochastic Models of Cell Protrusion Arising From Spatiotemporal Signaling and Adhesion Dynamics AU - Welf, Erik S. AU - Haugh, Jason M. T2 - Computational Methods in Cell Biology AB - During cell migration, local protrusion events are regulated by biochemical and physical processes that are in turn coordinated with the dynamic properties of cell-substratum adhesion structures. In this chapter, we present a modeling approach for integrating the apparent stochasticity and spatial dependence of signal transduction pathways that promote protrusion in tandem with adhesion dynamics. We describe our modeling framework, as well as its abstraction, parameterization, and validation against experimental data. Analytical techniques for identifying and evaluating the effects of model bistability on simulation simulation results are shown, and implications of this analysis for understanding cell protrusion behavior are offered. DA - 2012/// PY - 2012/// DO - 10.1016/b978-0-12-388403-9.00009-6 SP - 223-241 ER - TY - JOUR TI - Structure-Guided Directed Evolution of Highly Selective P450-Based Magnetic Resonance Imaging Sensors for Dopamine and Serotonin AU - Brustad, Eric M. AU - Lelyveld, Victor S. AU - Snow, Christopher D. AU - Crook, Nathan AU - Jung, Sang Taek AU - Martinez, Francisco M. AU - Scholl, Timothy J. AU - Jasanoff, Alan AU - Arnold, Frances H. T2 - Journal of Molecular Biology AB - New tools that allow dynamic visualization of molecular neural events are important for studying the basis of brain activity and disease. Sensors that permit ligand-sensitive magnetic resonance imaging (MRI) are useful reagents due to the noninvasive nature and good temporal and spatial resolution of MR methods. Paramagnetic metalloproteins can be effective MRI sensors due to the selectivity imparted by the protein active site and the ability to tune protein properties using techniques such as directed evolution. Here, we show that structure-guided directed evolution of the active site of the cytochrome P450‐BM3 heme domain produces highly selective MRI probes with submicromolar affinities for small molecules. We report a new, high‐affinity dopamine sensor as well as the first MRI reporter for serotonin, with which we demonstrate quantification of neurotransmitter release in vitro. We also present a detailed structural analysis of evolved cytochrome P450‐BM3 heme domain lineages to systematically dissect the molecular basis of neurotransmitter binding affinity, selectivity, and enhanced MRI contrast activity in these engineered proteins. DA - 2012/9// PY - 2012/9// DO - 10.1016/j.jmb.2012.05.029 VL - 422 IS - 2 SP - 245-262 KW - directed evolution KW - cytochrome P450 KW - MRI contrast agents KW - neurotransmitter KW - biosensors ER - TY - JOUR TI - Linking Yeast Gcn5p Catalytic Function and Gene Regulation Using a Quantitative, Graded Dominant Mutant Approach AU - Lanza, Amanda M. AU - Blazeck, John J. AU - Crook, Nathan C. AU - Alper, Hal S. T2 - PLoS ONE AB - Establishing causative links between protein functional domains and global gene regulation is critical for advancements in genetics, biotechnology, disease treatment, and systems biology. This task is challenging for multifunctional proteins when relying on traditional approaches such as gene deletions since they remove all domains simultaneously. Here, we describe a novel approach to extract quantitative, causative links by modulating the expression of a dominant mutant allele to create a function-specific competitive inhibition. Using the yeast histone acetyltransferase Gcn5p as a case study, we demonstrate the utility of this approach and (1) find evidence that Gcn5p is more involved in cell-wide gene repression, instead of the accepted gene activation associated with HATs, (2) identify previously unknown gene targets and interactions for Gcn5p-based acetylation, (3) quantify the strength of some Gcn5p-DNA associations, (4) demonstrate that this approach can be used to correctly identify canonical chromatin modifications, (5) establish the role of acetyltransferase activity on synthetic lethal interactions, and (6) identify new functional classes of genes regulated by Gcn5p acetyltransferase activity--all six of these major conclusions were unattainable by using standard gene knockout studies alone. We recommend that a graded dominant mutant approach be utilized in conjunction with a traditional knockout to study multifunctional proteins and generate higher-resolution data that more accurately probes protein domain function and influence. DA - 2012/4// PY - 2012/4// DO - 10.1371/journal.pone.0036193 VL - 7 IS - 4 SP - e36193 ER - TY - JOUR TI - Innovation at the intersection of synthetic and systems biology AU - Lanza, Amanda M AU - Crook, Nathan C AU - Alper, Hal S T2 - Current Opinion in Biotechnology AB - The promises of modern biotechnology hinge upon the hope that we can understand microscopic cellular complexity and in doing so create novel function. In this regard, the fields of systems and synthetic biology are important for accelerating both our understanding of biological systems and our ability to quantitatively engineer cells. At the nexus of these two fields is a unique synergy that can help attain these goals. Thus, the next greatest advances in biology and biotechnology are arising at the intersection of the top-down systems approach and the bottom-up synthetic approach. Collectively, these developments enable the precise control of cellular state for systems studies and the discovery of novel parts, control strategies, and interactions for the design of robust synthetic function. This review seeks to highlight this activity as well as provide a perspective for future directions. Combining these efforts can provide novel insights into cellular function and lead to robust, novel synthetic design. DA - 2012/10// PY - 2012/10// DO - 10.1016/j.copbio.2011.12.026 VL - 23 IS - 5 SP - 712-717 ER - TY - JOUR TI - Classical Strain Improvement AU - Crook, Nathan AU - Alper, Hal S. T2 - Engineering Complex Phenotypes in Industrial Strains AB - This chapter contains sections titled: Introduction The Approach Defined Mutagenesis Genotypic Landscapes Screening Conclusions References DA - 2012/10// PY - 2012/10// DO - 10.1002/9781118433034.ch1 SP - 1-33 ER - TY - JOUR TI - Cyclodextrin fibers via polymer-free electrospinning AU - Manasco, Joshua L. AU - Saquing, Carl D. AU - Tang, Christina AU - Khan, Saad A. T2 - RSC Advances AB - Cyclodextrins (CDs) are intriguing amphiphilic molecules that consist of a hydrophilic outer structure and a hydrophobic core with the ability to act as hosts for both nonpolar and polar guests. Electrospinning is a facile yet effective method for producing non-woven mats of fibers with high aspect ratios. Cyclodextrin fibers would leverage the distinctive properties of these molecules with the unique properties of nanofibers. We report the fabrication of submicron hydroxypropyl-β-cyclodextrin (HPβCD) fibers from highly concentrated aqueous solutions by electrospinning without the addition of a carrier polymer. We focus on exploring solution properties that make fiber formation possible contrary to the widely accepted premise that molecular entanglement of macromolecules is required for electrospinning. The ability to electrospin these solutions is attributed to hydrogen-bonded aggregation between HPβCD molecules at high concentrations, as evidenced from an exponential increase in zero-shear viscosity and bound water as a function of concentration, as well as disruption of fiber formation upon addition of urea to the system. DA - 2012/// PY - 2012/// DO - 10.1039/c2ra00004k VL - 2 IS - 9 SP - 3778-3784 SN - 2046-2069 UR - http://dx.doi.org/10.1039/c2ra00004k ER - TY - JOUR TI - Effect of pH on Protein Distribution in Electrospun PVA/BSA Composite Nanofibers AU - Tang, Christina AU - Ozcam, A. Evren AU - Stout, Brendon AU - Khan, Saad A. T2 - Biomacromolecules AB - We examine the protein distribution within an electrospun polymer nanofiber using polyvinyl alcohol and bovine serum albumin as a model system. We hypothesize that the location of the protein within the nanofiber can be controlled by carefully selecting the pH and the applied polarity of the electric field as the pH affects the net charge on the proteins. Using fluorescently labeled BSA and surface analysis, we observe that the distribution of BSA is affected by the pH of the electrospinning solution. Therefore, we further probe the relevant forces on the protein in solution during electrospinning. The role of hydrodynamic friction was assessed using glutaraldehyde and HCl as a tool to modify the viscosity of the solution during electrospinning. By varying the pH and the polarity of the applied electric field, we evaluated the effects of electrostatic forces and dielectrophoresis on the protein during fiber formation. We surmise that electrostatic forces and hydrodynamic friction are insignificant relative to dielectrophoretic forces; therefore, it is possible to separate species in a blend using polarizability contrast. A coaxial distribution of protein in the core can be obtained by electrospinning at the isoelectric point of the protein, whereas surface enrichment can be obtained when the protein carries a net charge. DA - 2012/4/18/ PY - 2012/4/18/ DO - 10.1021/bm2017146 VL - 13 IS - 5 SP - 1269-1278 J2 - Biomacromolecules LA - en OP - SN - 1525-7797 1526-4602 UR - http://dx.doi.org/10.1021/bm2017146 DB - Crossref ER - TY - JOUR TI - Rheological and structural properties of β-lactoglobulin and basil seed gum mixture: Effect of heating rate AU - Rafe, Ali AU - Razavi, Seyed M.A. AU - Khan, Saad T2 - Food Research International AB - The effects of heating rate and addition of basil seed gum (BSG) as a novel hydrocolloid on the rheology and microstructure of β-lactoglobulin (BLG) gel were studied using low amplitude dynamic oscillatory shear (SAOS) and confocal laser scanning microscopy (CLSM) measurements. BLG solution and BLG–BSG mixtures at different ratios (20:1, 10:1, 5:1 and 2:1) were heated from 20 to 90 °C at four heating rates (0.5, 1, 5 and 10 °C/min). Gelation temperature of β-lactoglobulin was reduced by decreasing of heating rate and increasing BSG ratio. The maximum G′ at the end of heating period was reduced greatly by decreasing the BLG–BSG ratio. BLG–BSG mixed systems developed a relatively weak gel, which it enhanced when the ratio was changed from 20:1 to 2:1. Addition of BSG to 10% BLG solution makes a separated phase network in which increasing BSG content induced very fine stranded structure of protein. Therefore, it is possible to achieve distinct structures by mixing different ratios of hydrocolloids at various heating rates. DA - 2012/11// PY - 2012/11// DO - 10.1016/j.foodres.2012.07.017 VL - 49 IS - 1 SP - 32-38 J2 - Food Research International LA - en OP - SN - 0963-9969 UR - http://dx.doi.org/10.1016/j.foodres.2012.07.017 DB - Crossref KW - beta-lactoglobulin KW - CLSM KW - Heating rate KW - Gel KW - Gelling point KW - Microstructure ER - TY - JOUR TI - Upstream process optimization of polyhydroxybutyrate (PHB) by Alcaligenes latus using two-stage batch and fed-batch fermentation strategies AU - Wang, Bingqing AU - Sharma-Shivappa, Ratna R. AU - Olson, Jonathan W. AU - Khan, Saad A. T2 - Bioprocess and Biosystems Engineering DA - 2012/5/18/ PY - 2012/5/18/ DO - 10.1007/S00449-012-0749-6 VL - 35 IS - 9 SP - 1591-1602 J2 - Bioprocess Biosyst Eng LA - en OP - SN - 1615-7591 1615-7605 UR - http://dx.doi.org/10.1007/S00449-012-0749-6 DB - Crossref KW - Biodegradable plastics KW - Polyhydroxyalkanoate (PHA) KW - Ralstonia eutropha KW - Sucrose fermentation KW - Nitrogen limitation ER - TY - BLOG TI - ChE-style Manufacturing Moves into the Spotlight AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/9/26/ PY - 2012/9/26/ UR - https://www.aiche.org/chenected/2012/09/che-style-manufacturing-moves-spotlight ER - TY - BLOG TI - More ChE Manufacturing: Rebuilding the Body AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/10/3/ PY - 2012/10/3/ UR - https://www.aiche.org/chenected/2012/10/more-che-manufacturing-rebuilding-body ER - TY - BLOG TI - Shale Gas in the Middle of the Worldwide Energy Drama AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/10/10/ PY - 2012/10/10/ UR - https://www.aiche.org/chenected/2012/10/shale-gas-middle-worldwide-energy-drama ER - TY - BLOG TI - The New Energy Mix: Abundance and Sustainability?” AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/10/17/ PY - 2012/10/17/ UR - https://www.aiche.org/chenected/2012/10/new-energy-mix-abundance-and-sustainability ER - TY - BLOG TI - Biology and ChE: Applying a Molecular Science (Part I) AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/10/24/ PY - 2012/10/24/ UR - https://www.aiche.org/chenected/2012/10/biology-and-che-applying-molecular-science-part-i ER - TY - BLOG TI - Entering a New Golden Age of Chemical Engineering AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/9/19/ PY - 2012/9/19/ UR - https://www.aiche.org/chenected/2012/09/entering-new-golden-age-chemical-engineering ER - TY - BLOG TI - Seizing the Future of Chemical Engineering AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/12/20/ PY - 2012/12/20/ UR - https://www.aiche.org/chenected/2012/12/seizing-future-che ER - TY - BLOG TI - Embracing the Breadth and the Unity of ChE AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/12/14/ PY - 2012/12/14/ UR - https://www.aiche.org/chenected/2012/12/embracing-breadth-and-unity-che ER - TY - BLOG TI - From Big Data to Smart Manufacturing AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/12/5/ PY - 2012/12/5/ UR - https://www.aiche.org/chenected/2012/12/big-data-smart-manufacturing ER - TY - BLOG TI - Massively Parallel Computing and Massive Impacts for ChE AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/11/29/ PY - 2012/11/29/ UR - https://www.aiche.org/chenected/2012/11/massively-parallel-computing-and-massive-impacts-che ER - TY - BLOG TI - ChE Computing Becomes Cyberinfrastructure AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/11/14/ PY - 2012/11/14/ UR - https://www.aiche.org/chenected/2012/11/che-computing-becomes-cyberinfrastructure ER - TY - BLOG TI - Biology and ChE: Applying a Molecular Science (Part II) AU - Westmoreland, P.R. T2 - We Are ChE: Entering a Golden Age DA - 2012/11/7/ PY - 2012/11/7/ UR - https://www.aiche.org/chenected/2012/11/biology-and-che-applying-molecular-science-part-ii ER - TY - JOUR TI - Formation of Polyampholyte Brushes via Controlled Radical Polymerization and Their Assembly in Solution AU - Jhon, Young K. AU - Arifuzzaman, Shafi AU - Özçam, Ali E. AU - Kiserow, Douglas J. AU - Genzer, Jan T2 - Langmuir AB - We describe the formation of polyampholytic block copolymer brushes and their assembly in solution. Specifically, we employ "surface-initiated" activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) sequentially to form diblock copolymer grafts comprising blocks of poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) and poly(sodium methacrylate) (PNaMA) on flat impenetrable silica surfaces, i.e., SiO(x)/PNaMA-b-PDMAEMA and SiO(x)/PDMAEMA-b-PNaMA. Protonation of the PNaMA block results in formation of poly(methacrylic acid) (PMAA). We demonstrate that ARGET-ATRP of NaMA provides a convenient route to preparation of PMAA, which is an alternative method to the more traditional approach based on preparing PMAA by polymerizing tert-butyl methacrylate (tBMA) followed by cleavage of the tert-butyl group. We also discuss conformational changes of the individual polyelectrolyte blocks in solution as a function of solution pH by monitoring adsorption behavior of functionalized polystyrene spheres. DA - 2012/1/10/ PY - 2012/1/10/ DO - 10.1021/la203697a VL - 28 IS - 1 SP - 872–882 SN - 0743-7463 1520-5827 UR - http://dx.doi.org/10.1021/la203697a ER - TY - JOUR TI - Three-Dimensional Electrospun Alginate Nanofiber Mats via Tailored Charge Repulsions AU - Bonino, Christopher A. AU - Efimenko, Kirill AU - Jeong, Sung In AU - Krebs, Melissa D. AU - Alsberg, Eben AU - Khan, Saad A. T2 - Small AB - The formation of 3D electrospun mat structures from alginate-polyethylene oxide (PEO) solution blends is reported. These unique architectures expand the capabilities of traditional electrospun mats for applications such as regenerative medicine, where a scaffold can help to promote tissue growth in three dimensions. The mat structures extend off the surface of the flat collector plate without the need of any modifications in the electrospinning apparatus, are self-supported when the electric field is removed, and are composed of bundles of nanofibers. A mechanism for the unique formations is proposed, based on the fiber-fiber repulsions from surface charges on the negatively charged alginate. Furthermore, the role of the electric field in the distribution of alginate within the nanofibers is discussed. X-ray photoelectron spectroscopy is used to analyze the surface composition of the electrospun nanofiber mats and the data is related to cast films made in the absence of the electric field. Further techniques to tailor the 3D architecture and nanofiber morphology by changing the surface tension and relative humidity are also discussed. DA - 2012/3/28/ PY - 2012/3/28/ DO - 10.1002/smll.201101791 VL - 8 IS - 12 SP - 1928-1936 J2 - Small LA - en OP - SN - 1613-6810 UR - http://dx.doi.org/10.1002/smll.201101791 DB - Crossref KW - biomimetics KW - nanostructures KW - hierarchical structures KW - tissue engineering KW - relative humidity ER - TY - JOUR TI - Thermorheological behavior of coexisting physical networks: combining SAFIN and SAMIN organogels AU - Krishnan, Arjun S. AU - Vargantwar, Pruthesh H. AU - Spontak, Richard J. T2 - Soft Matter AB - Organogels, like their hydrogel analogs in aqueous media, consist of chemically or physically cross-linked networks that endow simple (or even viscoelastic) organic liquids with solid-like characteristics. Of particular interest here are physical networks composed of either low-molar-mass organic gelators, which tend to form self-assembled fibrillar networks (SAFINs) by site-specific interactions such as hydrogen bonding and/or π–π stacking, or microphase-separated triblock copolymers, which form self-assembled micellar networks (SAMINs) due primarily to bridged midblocks that connect neighboring micelles. In this study, we combine these two physical networks by mixing the gelator 1,3:2,4-dibenzylidene-D-sorbitol with a series of midblock-swollen triblock copolymers differing in molecular weight to produce coexisting SAFIN/SAMIN networks in two midblock-selective solvents differing in polarity. The thermorheological properties of the resultant mixed network systems are investigated for three cases: (i) the order–disorder transition temperature (TODT) of the SAMIN is much lower than the dissolution temperature (Td) of the SAFIN, (ii) TODT < Td and (iii) TODT ≈ Td. Employing dynamic rheology, we show how these transitions are affected by the order in which self-organization occurs. DA - 2012/// PY - 2012/// DO - 10.1039/c2sm26698a VL - 8 IS - 48 SP - 12025 J2 - Soft Matter LA - en OP - SN - 1744-683X 1744-6848 UR - http://dx.doi.org/10.1039/c2sm26698a DB - Crossref ER - TY - JOUR TI - Midblock sulfonation of a model long-chain poly(p-tert-butylstyrene-b-styrene-b-p-tert-butylstyrene) triblock copolymer AU - Vargantwar, Pruthesh H. AU - Brannock, Molly C. AU - Smith, Steven D. AU - Spontak, Richard J. T2 - Journal of Materials Chemistry AB - Homopolymers containing ionic moieties such as sulfonic acid groups are suitable as fuel-cell, water-purification and ion-exchange membranes or, alternatively, as electroactive or otherwise stimuli-responsive soft materials. Block ionomers constitute a class of ionomers in which (i) long sequences of repeat units are sufficiently incompatible to microphase-separate and (ii) at least one sequence possesses ionic groups along its backbone. In this study, the midblock of a model poly(p-tert-butylstyrene-b-styrene-b-p-tert-butylstyrene) (TST) triblock copolymer has been selectively sulfonated to different degrees by reaction with acetyl sulfate. Self-assembly of the unaffected endblocks prevents the resultant block ionomers from dissolving in water and imparts water-swollen ionomer films with sufficient mechanical integrity to remain intact. The degree of sulfonation is controlled by varying the concentration of acetyl sulfate, as confirmed by spectroscopic analyses. An increase in ionic content promotes a reduction in thermal stability due to sulfonic acid cleaving, but a significant increase in water sorption that increases with increasing temperature. Although the parent TST copolymer is disordered according to small-angle X-ray scattering, moderate levels of midblock sulfonation induce microphase ordering and simultaneously increase the intermicrodomain distance due to swelling considerations. DA - 2012/// PY - 2012/// DO - 10.1039/c2jm35504c VL - 22 IS - 48 SP - 25262 J2 - J. Mater. Chem. LA - en OP - SN - 0959-9428 1364-5501 UR - http://dx.doi.org/10.1039/c2jm35504c DB - Crossref ER - TY - JOUR TI - Macromol. Rapid Commun. 1/2012 AU - Vargantwar, Pruthesh H. AU - Roskov, Kristen E. AU - Ghosh, Tushar K. AU - Spontak, Richard J. T2 - Macromolecular Rapid Communications AB - Back Cover: Ionic polymer-metal composites which bend in response to electric potential are fabricated using selectively-solvated block ionomers possessing a sulfonated midblock and hydrophobic endblocks. The electroactuation performance is comparable or superior to existing systems. Further details can be found in the article by P. H. Vargantwar, K. E. Roskov, T. K. Ghosh, and R. J. Spontak* on page 61. DA - 2012/1/3/ PY - 2012/1/3/ DO - 10.1002/marc.201290003 VL - 33 IS - 1 SP - 100-100 J2 - Macromol. Rapid Commun. LA - en OP - SN - 1022-1336 UR - http://dx.doi.org/10.1002/marc.201290003 DB - Crossref ER - TY - JOUR TI - Experimental and Computational Study of the Effect of Alcohols on the Solution and Adsorption Properties of a Nonionic Symmetric Triblock Copolymer AU - Liu, Xiaomeng AU - He, Feng AU - Salas, Carlos AU - Pasquinelli, Melissa A. AU - Genzer, Jan AU - Rojas, Orlando J. T2 - The Journal of Physical Chemistry B AB - This study investigates the effect of alcohols on the solution and adsorption properties of symmetric triblock nonionic copolymers comprising blocks of ethylene oxide (EO) and propylene oxide (PO) (EO(37)PO(56)EO(37)). The cloud point, surface tension, critical micelle concentration (CMC), and maximum packing at the air-water interface are determined, and the latter is compared to the amount of polymer that adsorbs from solution onto polypropylene (PP) and cellulose surfaces. The interaction energy and radius of micelles are calculated by using molecular dynamics (MD) simulations. Equivalent MD bead parameters were used in dynamic density functional theory (DDFT) simulations to study the influence of alcohols on the phase behavior of EO(37)PO(56)EO(37) and its adsorption on PP from aqueous solutions. The simulation results agree qualitatively with the experimental observations. Ethanol acts as a good cosolvent for EO(37)PO(56)EO(37) and reduces the amount of EO(37)PO(56)EO(37) that adsorbs on PP surfaces; however, little or no influence is observed on the adsorption on cellulose. Interestingly, longer chain alcohols, such as 1-pentanol, produce the opposite effect. Overall, the solution and adsorption properties of nonionic symmetric triblock copolymers in the presence of alcohols are rationalized by changes in solvency and the hydrophobic effect. DA - 2012/1/23/ PY - 2012/1/23/ DO - 10.1021/jp207190c VL - 116 IS - 4 SP - 1289-1298 J2 - J. Phys. Chem. B LA - en OP - SN - 1520-6106 1520-5207 UR - http://dx.doi.org/10.1021/jp207190c DB - Crossref ER - TY - JOUR TI - Formation and Antifouling Properties of Amphiphilic Coatings on Polypropylene Fibers AU - Goli, Kiran K. AU - Rojas, Orlando J. AU - Genzer, Jan T2 - Biomacromolecules AB - We describe the formation of amphiphilic polymeric assemblies via a three-step functionalization process applied to polypropylene (PP) nonwovens and to reference hydrophobic self-assembled n-octadecyltrichlorosilane (ODTS) monolayer surfaces. In the first step, denatured proteins (lysozyme or fibrinogen) are adsorbed onto the hydrophobic PP or the ODTS surfaces, followed by cross-linking with glutaraldehyde in the presence of sodium borohydride (NaBH4). The hydroxyl and amine functional groups of the proteins permit the attachment of initiator molecules, from which poly (2-hydroxyethyl methacrylate) (PHEMA) polymer grafts are grown directly through “grafting from” atom transfer radical polymerization. The terminal hydroxyls of HEMA’s pendent groups are modified with fluorinating moieties of different chain lengths, resulting in amphiphilic brushes. A palette of analytical tools, including ellipsometry, contact angle goniometry, Fourier transform infrared spectroscopy in the attenuated total reflection mode, and X-ray photoelectron spectroscopy is employed to determine the changes in physicochemical properties of the functionalized surfaces after each modification step. Antifouling properties of the resultant amphiphilic coatings on PP are analyzed by following the adsorption of fluorescein isothiocyanate-labeled bovine serum albumin as a model fouling protein. Our results suggest that amphiphilic coatings suppress significantly adsorption of proteins as compared with PP fibers or PP surfaces coated with PHEMA brushes. The type of fluorinated chain grafted to PHEMA allows modulation of the surface composition of the topmost layer of the amphiphilic coating and its antifouling capability. DA - 2012/10/11/ PY - 2012/10/11/ DO - 10.1021/bm301223b VL - 13 IS - 11 SP - 3769-3779 J2 - Biomacromolecules LA - en OP - SN - 1525-7797 1526-4602 UR - http://dx.doi.org/10.1021/bm301223b DB - Crossref ER - TY - JOUR TI - Ibuprofen impregnation into submicron polymeric films in supercritical carbon dioxide AU - Hussain, Yazan A. AU - Grant, Christine S. T2 - The Journal of Supercritical Fluids AB - The impregnation of ibuprofen into submicron films (25–250 nm) of poly(methyl methacrylate), PMMA, under supercritical CO2 conditions (at 40 °C and 50 °C and 13.8 and 20.7 MPa) was studied. The quartz crystal microbalance (QCM) was used to perform real-time, in situ impregnation measurements. The amount of ibuprofen uptake into the polymer film was calculated directly from the QCM results. Different aspects of the process were studied including: the effect of CO2 density on uptake, distribution uniformity across the film thickness, and impregnation rate. The partitioning coefficient of ibuprofen PMMA and CO2 was high, whereas the diffusivity of ibuprofen was found to be order of magnitudes lower than that of CO2. These two effects are believed to result in high drug loading in the polymer. It was also concluded that CO2 helped in producing uniform concentration profiles of ibuprofen in the PMMA films. Finally, preliminary studies on the impregnation of poly(vinyl pyrrolidone), PVP, with ibuprofen were performed. The QCM response in the case of PVP films was significantly larger than that with PMMA at the same conditions. Some possible causes for this unusual behavior are discussed. DA - 2012/11// PY - 2012/11// DO - 10.1016/j.supflu.2012.07.014 VL - 71 SP - 127-135 J2 - The Journal of Supercritical Fluids LA - en OP - SN - 0896-8446 UR - http://dx.doi.org/10.1016/j.supflu.2012.07.014 DB - Crossref KW - Superciritical carbon dioxide KW - Impregnation KW - Ibuprofen KW - PMMA KW - QCM ER - TY - JOUR TI - Influence of Nanoscale Particle Roughness on the Stability of Pickering Emulsions AU - San-Miguel, Adriana AU - Behrens, Sven H. T2 - Langmuir AB - The wetting behavior of solid surfaces can be altered dramatically by introducing surface roughness on the nanometer scale. Some of nature's most fascinating wetting phenomena are associated with surface roughness; they have inspired both fundamental research and the adoption of surface roughness as a design parameter for man-made functional coatings. So far the attention has focused primarily on macroscopic surfaces, but one should expect the wetting properties of colloidal particles to be strongly affected by roughness, too. Particle wettability, in turn, is a key parameter for the adsorption of particles at liquid interfaces and for the industrially important use of particles as emulsion stabilizers; yet, the consequence of particle roughness for emulsion stability remains poorly understood. In order to investigate the matter systematically, we have developed a surface treatment, applicable to micrometer-sized particles and macroscopic surfaces alike, that produces surface coatings with finely tunable nanoscale roughness and identical surface chemistry. Coatings with different degrees of roughness were characterized with regard to their morphology, charging, and wetting properties, and the results were correlated with the stability of emulsions prepared with coated particles of different roughness. We find that the maximum capillary pressure, a metric of the emulsions' resistance to droplet coalescence, varies significantly and in a nonmonotonic fashion with particle roughness. Surface topography and contact angle hysteresis suggest that particle roughness benefits the stability of our emulsions as long as wetting occurs homogeneously (Wenzel regime), whereas the transition toward heterogeneous wetting (Cassie-Baxter regime) is associated with a loss of stability. DA - 2012/8/9/ PY - 2012/8/9/ DO - 10.1021/la302224v VL - 28 IS - 33 SP - 12038-12043 J2 - Langmuir LA - en OP - SN - 0743-7463 1520-5827 UR - http://dx.doi.org/10.1021/la302224v DB - Crossref ER - TY - JOUR TI - Soft microenvironments promote the early neurogenic differentiation but not self-renewal of human pluripotent stem cells AU - Keung, Albert J. AU - Asuri, Prashanth AU - Kumar, Sanjay AU - Schaffer, David V. T2 - Integrative Biology AB - Journal Article Soft microenvironments promote the early neurogenic differentiation but not self-renewal of human pluripotent stem cells Get access Albert J. Keung, Albert J. Keung Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720, USA. Web: http://www.cchem.berkeley.edu/schaffer/; Fax: +1 510-642-4778; Tel: +1 510-643-5963 Search for other works by this author on: Oxford Academic Google Scholar Prashanth Asuri, Prashanth Asuri Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720, USA. Web: http://www.cchem.berkeley.edu/schaffer/; Fax: +1 510-642-4778; Tel: +1 510-643-5963 Search for other works by this author on: Oxford Academic Google Scholar Sanjay Kumar, Sanjay Kumar Department of Bioengineering, University of California, Berkeley, CA 94720, USA. Web: http://kumarlab.berkeley.edu; Fax: +1 510 642-5835; Tel: +1 510 643-0787 E-mail: skumar@berkeley.edu Search for other works by this author on: Oxford Academic Google Scholar David V. Schaffer David V. Schaffer Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720, USA. Web: http://www.cchem.berkeley.edu/schaffer/; Fax: +1 510-642-4778; Tel: +1 510-643-5963Department of Bioengineering, University of California, Berkeley, CA 94720, USA. Web: http://kumarlab.berkeley.edu; Fax: +1 510 642-5835; Tel: +1 510 643-0787Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720, USA E-mail: schaffer@berkeley.edu Search for other works by this author on: Oxford Academic Google Scholar Integrative Biology, Volume 4, Issue 9, September 2012, Pages 1049–1058, https://doi.org/10.1039/c2ib20083j Published: 02 August 2012 Article history Received: 13 April 2012 Accepted: 16 July 2012 Published: 02 August 2012 DA - 2012/8/2/ PY - 2012/8/2/ DO - 10.1039/c2ib20083j VL - 4 IS - 9 SP - 1049-1058 LA - en OP - SN - 1757-9708 UR - http://dx.doi.org/10.1039/c2ib20083j DB - Crossref ER - TY - JOUR TI - A Genetic Strategy for the Dynamic and Graded Control of Cell Mechanics, Motility, and Matrix Remodeling AU - MacKay, Joanna L. AU - Keung, Albert J. AU - Kumar, Sanjay T2 - Biophysical Journal AB - Cellular mechanical properties have emerged as central regulators of many critical cell behaviors, including proliferation, motility, and differentiation. Although investigators have developed numerous techniques to influence these properties indirectly by engineering the extracellular matrix (ECM), relatively few tools are available to directly engineer the cells themselves. Here we present a genetic strategy for obtaining graded, dynamic control over cellular mechanical properties by regulating the expression of mutant mechanotransductive proteins from a single copy of a gene placed under a repressible promoter. With the use of constitutively active mutants of RhoA GTPase and myosin light chain kinase, we show that varying the expression level of either protein produces graded changes in stress fiber assembly, traction force generation, cellular stiffness, and migration speed. Using this approach, we demonstrate that soft ECMs render cells maximally sensitive to changes in RhoA activity, and that by modulating the ability of cells to engage and contract soft ECMs, we can dynamically control cell spreading, migration, and matrix remodeling. Thus, in addition to providing quantitative relationships between mechanotransductive signaling, cellular mechanical properties, and dynamic cell behaviors, this strategy enables us to control the physical interactions between cells and the ECM and thereby dictate how cells respond to matrix properties. DA - 2012/2// PY - 2012/2// DO - 10.1016/j.bpj.2011.12.048 VL - 102 IS - 3 SP - 434-442 J2 - Biophysical Journal LA - en OP - SN - 0006-3495 UR - http://dx.doi.org/10.1016/j.bpj.2011.12.048 DB - Crossref ER - TY - JOUR TI - Multiple factors dictate target selection by Hfq-binding small RNAs AU - Beisel, Chase L AU - Updegrove, Taylor B AU - Janson, Ben J AU - Storz, Gisela T2 - The EMBO Journal AB - Hfq-binding small RNAs (sRNAs) in bacteria modulate the stability and translational efficiency of target mRNAs through limited base-pairing interactions. While these sRNAs are known to regulate numerous mRNAs as part of stress responses, what distinguishes targets and non-targets among the mRNAs predicted to base pair with Hfq-binding sRNAs is poorly understood. Using the Hfq-binding sRNA Spot 42 of Escherichia coli as a model, we found that predictions using only the three unstructured regions of Spot 42 substantially improved the identification of previously known and novel Spot 42 targets. Furthermore, increasing the extent of base-pairing in single or multiple base-pairing regions improved the strength of regulation, but only for the unstructured regions of Spot 42. We also found that non-targets predicted to base pair with Spot 42 lacked an Hfq-binding site, folded into a secondary structure that occluded the Spot 42 targeting site, or had overlapping Hfq-binding and targeting sites. By modifying these features, we could impart Spot 42 regulation on non-target mRNAs. Our results thus provide valuable insights into the requirements for target selection by sRNAs. DA - 2012/3/2/ PY - 2012/3/2/ DO - 10.1038/emboj.2012.52 VL - 31 IS - 8 SP - 1961-1974 LA - en OP - SN - 0261-4189 UR - http://dx.doi.org/10.1038/emboj.2012.52 DB - Crossref KW - base-pairing KW - Escherichia coli KW - Spot 42 KW - target prediction ER - TY - JOUR TI - Purification of polyclonal antibodies from Cohn fraction II + III, skim milk, and whey by affinity chromatography using a hexamer peptide ligand AU - Menegatti, Stefano AU - Naik, Amith D. AU - Gurgel, Patrick V. AU - Carbonell, Ruben G. T2 - Journal of Separation Science AB - HWRGWV , a peptide that binds specifically to the F c fragment of human immunoglobulin G ( I g G ), was used for the purification of I g G from C ohn fraction II + III of human plasma and from bovine skim milk and whey. The concentration of sodium chloride and sodium caprylate in the binding buffer as well as the pH of the elution buffer were optimized to achieve high I g G yield and purity. Under optimized conditions, I g G was recovered from plasma fractions with yield and purity up to 84% and 95%, respectively. I g G was also purified from skim milk with 74% yield and 92% purity and from whey with 85% yield and 93% purity. Purification experiments were also performed with Protein A resin and the results were found to be similar to those obtained with the peptide adsorbent. DA - 2012/7/2/ PY - 2012/7/2/ DO - 10.1002/jssc.201200199 VL - 35 IS - 22 SP - 3139-3148 J2 - J. Sep. Science LA - en OP - SN - 1615-9306 UR - http://dx.doi.org/10.1002/jssc.201200199 DB - Crossref KW - Affinity chromatography KW - Immunoglobulin G KW - Milk KW - Peptide ligands KW - Plasma ER - TY - JOUR TI - A Green Chemistry Approach to Synthesize CTAB Templated Silica Xerogels from Sodium Silicate T2 - Journal of Chemical Society of Pakistan DA - 2012/// PY - 2012/// UR - https://publons.com/publon/11419303/ ER - TY - JOUR TI - Erratum to: Stochastic Dynamics of Membrane Protrusion Mediated by the DOCK180/Rac Pathway in Migrating Cells AU - Welf, Erik S. AU - Haugh, Jason M. T2 - Cellular and Molecular Bioengineering AB - In our previously published article, we described a computational model and analysis investigating the stochastic dynamics of cell protrusion during cell migration. In that work, we presented results of stochastic simulations plotted in two-dimensional parameter space. To supplement this analysis, the associated region of model bistability was identified by analysis of the deterministic model equations, and this region was plotted on the same graphs (panels a & b in each of Figs. 2–6). Since publication of our article, we became aware that certain parameter combinations thought to lie in the bistable region are, in fact, monostable. We wish to thank Dr. Michael Savageau (Biomedical Engineering, UC Davis), who studied our model during the preparation of his review article, for bringing the matter to our attention. We traced the error to the use of incorrect values of certain parameters in the bistability analysis. Whereas the values reported in the paper are correct for the stochastic model results, the bistability analysis was performed using three incorrect parameter values as shown in Table C1. Shown below as Fig. C1 are the corrected figure panels, which now show the bistability regions using the correct parameter values as used in the stochastic simulations. One of our previous conclusions concerned the lack of a definitive relationship between phenotypic switching in the stochastic simulations and model bistability. This conclusion was based, in part, on stochastic simulations for parameter sets that were supposed to lie in regions of bistability (Fig. 2e and Fig. 5e of the paper). Since the corrected results show that the parameter sets in question do not lie in the bistable regime, we have performed additional simulations to confirm that the original conclusions are valid (Figure C2). In these simulations, the analysis shown in Fig. 5 of the original paper was repeated with a larger value of the Cs parameter in order to expand the region of bistability. Comparison of stochastic runs on either side of the bistability region, as originally intended, confirms that although switching between protrusion and adhesion phenotypes is likely to occur in regions of parameter space that are close to the region of bistability, model bistability is not required for this behavior. As explained in the original article, bistable regions of parameter space usually lie between those regions that give monostable low and monostable high protrusion, and in the vicinity of the interface between the two, the stochastic model readily produces transient departures from the stable state. DA - 2012/10/3/ PY - 2012/10/3/ DO - 10.1007/S12195-012-0252-9 VL - 5 IS - 4 SP - 514-516 J2 - Cel. Mol. Bioeng. LA - en OP - SN - 1865-5025 1865-5033 UR - http://dx.doi.org/10.1007/S12195-012-0252-9 DB - Crossref ER - TY - JOUR TI - Extreme thermophiles: moving beyond single-enzyme biocatalysis AU - Frock, Andrew D AU - Kelly, Robert M T2 - Current Opinion in Chemical Engineering AB - Extremely thermophilic microorganisms have been sources of thermostable and thermoactive enzymes for over 30 years. However, information and insights gained from genome sequences, in conjunction with new tools for molecular genetics, have opened up exciting new possibilities for biotechnological opportunities based on extreme thermophiles that go beyond single-step biotransformations. Although the pace for discovering novel microorganisms has slowed over the past two decades, genome sequence data have provided clues to novel biomolecules and metabolic pathways, which can be mined for a range of new applications. Furthermore, recent advances in molecular genetics for extreme thermophiles have made metabolic engineering for high temperature applications a reality. DA - 2012/11// PY - 2012/11// DO - 10.1016/j.coche.2012.07.003 VL - 1 IS - 4 SP - 363-372 J2 - Current Opinion in Chemical Engineering LA - en OP - SN - 2211-3398 UR - http://dx.doi.org/10.1016/j.coche.2012.07.003 DB - Crossref ER - TY - JOUR TI - Nanofiber-based energy-storage materials T2 - Abstracts of Papers of the American Chemical Society DA - 2012/// PY - 2012/// UR - https://publons.com/publon/7178358/ ER - TY - JOUR TI - alpha-Fe2O3 nanoparticle-loaded carbon nanofibers as stable and high-capacity anodes for rechargeable lithium-ion batteries AU - Ji, L. W. AU - Toprakci, O. AU - Alcoutlabi, M. AU - Yao, Y. F. AU - Li, Y. AU - Zhang, S. AU - Guo, B. K. AU - Lin, Z. AU - Zhang, X. W. T2 - ACS Applied Materials & Interfaces DA - 2012/// PY - 2012/// VL - 4 ER - TY - JOUR TI - Carbon nanotube-loaded electrospun LiFePO4/carbon composite nanofibers as stable and binder-free cathodes for rechargeable lithium-ion batteries AU - Toprakci, O. AU - Toprakci, H. A. K. AU - Ji, L. W. AU - Xu, G. J. AU - Lin, Z. AU - Zhang, X. W. T2 - ACS Applied Materials & Interfaces DA - 2012/// PY - 2012/// VL - 4 ER - TY - JOUR TI - Role of isostaticity and load-bearing microstructure in the elasticity of yielded colloidal gels AU - Hsiao, L. C. AU - Newman, R. S. AU - Glotzer, S. C. AU - Solomon, M. J. T2 - Proceedings of the National Academy of Sciences AB - We report a simple correlation between microstructure and strain-dependent elasticity in colloidal gels by visualizing the evolution of cluster structure in high strain-rate flows. We control the initial gel microstructure by inducing different levels of isotropic depletion attraction between particles suspended in refractive index matched solvents. Contrary to previous ideas from mode coupling and micromechanical treatments, our studies show that bond breakage occurs mainly due to the erosion of rigid clusters that persist far beyond the yield strain. This rigidity contributes to gel elasticity even when the sample is fully fluidized; the origin of the elasticity is the slow Brownian relaxation of rigid, hydrodynamically interacting clusters. We find a power-law scaling of the elastic modulus with the stress-bearing volume fraction that is valid over a range of volume fractions and gelation conditions. These results provide a conceptual framework to quantitatively connect the flow-induced microstructure of soft materials to their nonlinear rheology. DA - 2012/9/17/ PY - 2012/9/17/ DO - 10.1073/pnas.1206742109 VL - 109 IS - 40 SP - 16029-16034 J2 - Proceedings of the National Academy of Sciences LA - en OP - SN - 0027-8424 1091-6490 UR - http://dx.doi.org/10.1073/pnas.1206742109 DB - Crossref KW - colloids KW - confocal microscopy KW - suspensions KW - shear flow ER - TY - JOUR TI - Interview: From traditional polymer science to nanomedicine: the interplay between disciplines to drive innovation AU - DeSimone, Joseph T2 - Nanomedicine AB - Professor Joseph DeSimone speaks to Hannah Stanwix, Assistant Commissioning Editor Professor Joseph DeSimone attended Ursinus College (PA, USA) where he received his Bachelor of Science Degree in Chemistry. He completed his PhD in Chemistry in 1990 at Virginia Polytechnic Institute and State University (VA, USA). Professor DeSimone moved to the University of North Carolina at Chapel Hill (UNC-CH; NC, USA) where he was Assistant Professor of Chemistry until 1994. He was appointed Mary Ann Smith Professor of Chemistry at UNC-CH and Professor of Chemical Engineering at North Carolina State University (NC, USA) in 1995 and subsequently became William R Kenan Jr Distinguished Professor of Chemistry at UNC-CH in 1999. He is currently the Chancellor’s Eminent Professor of Chemistry at UNC-CH and the William R. Kenan Jr Distinguished Professor of Chemical Engineering at NC State. In 2004, Professor DeSimone founded Liquidia Technologies (NC, USA) which received the first ever equity investment by the Bill and Melinda Gates Foundation in a for-profit biotechnology company. He has received over 50 awards and accolades throughout his career, including the 2008 Lemelson-MIT Prize. Professor DeSimone has authored over 290 papers, as well as issuing 130 patents. DA - 2012/8// PY - 2012/8// DO - 10.2217/nnm.12.89 VL - 7 IS - 8 SP - 1125-1128 J2 - Nanomedicine LA - en OP - SN - 1743-5889 1748-6963 UR - http://dx.doi.org/10.2217/nnm.12.89 DB - Crossref ER - TY - JOUR TI - In vitro and in vivo assessment of targeting lipid-based nanoparticles to the epidermal growth factor-receptor (EGFR) using a novel Heptameric ZEGFR domain AU - Benhabbour, S. Rahima AU - Luft, J. Christopher AU - Kim, Dongwook AU - Jain, Anekant AU - Wadhwa, Saurabh AU - Parrott, Matthew C. AU - Liu, Rihe AU - DeSimone, Joseph M. AU - Mumper, Russell J. T2 - Journal of Controlled Release AB - Lipid-based oil-filled nanoparticles (NPs) with a high concentration of surface-chelated nickel (Ni-NPs) were successfully prepared using a Brij 78-NTA-Ni conjugate synthesized with Brij 78 (Polyoxyethylene (20) stearyl ether) and nitrilotriacetic acid (NTA). The facile incorporation of the Brij 78-NTA-Ni conjugate into the NP formulation allowed up to 90% Ni incorporation, which was a significant improvement over the previously used standard agent DOGS-NTA-Ni which led to ~6% Ni incorporation. The Ni-NPs were targeted to the highly epidermal growth factor receptor (EGFR)-overexpressing epidermoid carcinoma cells A431. This was accomplished using a novel high affinity histidine×6-tagged EGFR-binding Z domain (heptameric Z(EGFR) domain). In vitro cell uptake studies showed enhanced internalization (up to 90%) of the targeted Ni-NPs in A431 cells with only ≤10% internalization of the untargeted Ni-NPs. ICP-MS analysis used to quantify the amount of Ni in the cells were in close agreement with flow cytometry studies, which showed a dose dependent increase in the amount of Ni with the targeted Ni-NPs. Cell uptake competition studies showed that internalization of the targeted Ni-NPs within the cells was competed off with free heptameric Z(EGFR) domain at concentrations of 8.75ng/mL or higher. In vivo studies were carried out in nude mice bearing A431 tumors to determine the biodistribution and intracellular delivery. Near Infrared (NIR) optical imaging studies using Alexa750-labeled heptameric Z(EGFR) domain showed localization of 19% of the total detected fluorescence intensity in the tumor tissue, 28% in the liver and 42% in the kidneys 16h post i.v. injection. ICP-MS analysis showed almost a two-fold increase in the amount of intracellular Ni with the targeted Ni-NPs. These new Ni-NPs could be a very useful tool for targeting and drug delivery to a wide range of EGFR positive cancers. DA - 2012/2// PY - 2012/2// DO - 10.1016/j.jconrel.2011.10.013 VL - 158 IS - 1 SP - 63-71 J2 - Journal of Controlled Release LA - en OP - SN - 0168-3659 UR - http://dx.doi.org/10.1016/j.jconrel.2011.10.013 DB - Crossref KW - Lipid-based nanoparticles KW - Nickel KW - Histidine-tagged proteins KW - EGFR targeting KW - Heptameric Z(EGFR) domain ER - TY - JOUR TI - The effect of particle size on the biodistribution of low-modulus hydrogel PRINT particles AU - Merkel, Timothy J. AU - Chen, Kai AU - Jones, Stephen W. AU - Pandya, Ashish A. AU - Tian, Shaomin AU - Napier, Mary E. AU - Zamboni, William E. AU - DeSimone, Joseph M. T2 - Journal of Controlled Release AB - There is a growing recognition that the deformability of particles used for drug delivery plays a significant role on their biodistribution and circulation profile. Understanding these effects would provide a crucial tool for the rational design of drug delivery systems. While particles resembling red blood cells (RBCs) in size, shape and deformability have extended circulation times and altered biodistribution profiles compared to rigid, but otherwise similar particles, the in vivo behavior of such highly deformable particles of varied size has not been explored. We report the fabrication of a series of discoid, monodisperse, low-modulus hydrogel particles with diameters ranging from 0.8 to 8.9 μm, spanning sizes smaller than and larger than RBCs. We injected these particles into healthy mice, and tracked their concentration in the blood and their distribution into major organs. These deformable particles all demonstrated some hold up in filtration tissues like the lungs and spleen, followed by release back into the circulation, characterized by decreases in particles in these tissues with concomitant increases in particle concentration in blood. Particles similar to red blood cells in size demonstrated longer circulation times, suggesting that this size and shape of deformable particle is uniquely suited to avoid clearance. DA - 2012/8// PY - 2012/8// DO - 10.1016/j.jconrel.2012.06.009 VL - 162 IS - 1 SP - 37-44 J2 - Journal of Controlled Release LA - en OP - SN - 0168-3659 UR - http://dx.doi.org/10.1016/j.jconrel.2012.06.009 DB - Crossref KW - Hydrogel KW - Deformability KW - Biodistribution KW - Long circulating KW - Biomimetic ER - TY - JOUR TI - Surfactant templated silica xerogels as adsorbents for Rhodamine 6G AU - Pirzada, T. AU - Shah, S.S. T2 - Journal of the Chinese Chemical Society AB - Abstract A series of silica xerogels was synthesized by using TEOS as the silica precursor and a non ionic surfactant Triton X100 (TX100) and a cationic surfactant Hexadecyltrimethylammonium Bromide (CTAB) as templates. The xerogels were synthesized through 2‐way catalysis using ultrasonic radiations for homogeneous mixing of the precursors and template. The surfactant template was later removed through calcination at 550 °C. It was found out that gels having CTAB as the template had higher surface area (612.08 m 2 /g) than the gels templated by TX100 (539.6 m 2 /g). High surface area xerogels were used in adsorption experiments for aqueous solutions of Rhodamine 6G (R6G). UV visible spectroscopy was used to find out the concentrations of dye solutions. The adsorption data of both the types of xerogels was found to follow Freundlich's adsorption model pointing towards the possibility of adsorption of the dye molecules on the heterogeneous surface of the adsorbent. DA - 2012/// PY - 2012/// DO - 10.1002/jccs.201100574 VL - 59 IS - 7 SP - 891-898 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84863582425&partnerID=MN8TOARS KW - Surfactant templated silica KW - Adsorption KW - Rhodamine 6G KW - CTAB KW - TX100 ER - TY - JOUR TI - Hybrid Silica–PVA Nanofibers via Sol–Gel Electrospinning AU - Pirzada, Tahira AU - Arvidson, Sara A. AU - Saquing, Carl D. AU - Shah, S. Sakhawat AU - Khan, Saad A. T2 - Langmuir AB - We report on the synthesis of poly(vinyl alcohol) (PVA)-silica hybrid nanofibers via sol-gel electrospinning. Silica is synthesized through acid catalysis of a silica precursor (tetraethyl orthosilicate (TEOS) in ethanol-water), and fibers are obtained by electrospinning a mixture of the silica precursor solution and aqueous PVA. A systematic investigation on how the amount of TEOS, the silica-PVA ratio, the aging time of the silica precursor mixture, and the solution rheology influence the fiber morphology is undertaken and reveals a composition window in which defect-free hybrid nanofibers with diameters as small as 150 nm are obtained. When soaked overnight in water, the hybrid fibers remain intact, essentially maintaining their morphology, even though PVA is soluble in water. We believe that mixing of the silica precursor and PVA in solution initiates the participation of the silica precursor in cross-linking of PVA so that its -OH group becomes unavailable for hydrogen bonding with water. FTIR analysis of the hybrids confirms the disappearance of the -OH peak typically shown by PVA, while formation of a bond between PVA and silica is indicated by the Si-O-C peak in the spectra of all the hybrids. The ability to form cross-linked nanofibers of PVA using thermally stable and relatively inert silica could broaden the scope of use of these materials in various technologies. DA - 2012/3/22/ PY - 2012/3/22/ DO - 10.1021/la300049j VL - 28 IS - 13 SP - 5834-5844 J2 - Langmuir LA - en OP - SN - 0743-7463 1520-5827 UR - http://dx.doi.org/10.1021/la300049j DB - Crossref ER - TY - JOUR TI - A green chemistry approach to synthesize CTAB templated silica xerogels from sodium silicate AU - Pirzada, T. AU - Demirdoogen, R.E. AU - Shah, S.S. T2 - Journal of the Chemical Society of Pakistan DA - 2012/// PY - 2012/// VL - 34 IS - 1 SP - 177-183 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84856982578&partnerID=MN8TOARS ER - TY - JOUR TI - Molecular behavior of water in TiO2 nano-slits with varying coverages of carbon: a molecular dynamics simulation study AU - Wei, Ming-Jie AU - Zhang, Luzheng AU - Lu, Linghong AU - Zhu, Yudan AU - Gubbins, Keith E. AU - Lu, Xiaohua T2 - Physical Chemistry Chemical Physics AB - It is well known that titanium dioxide (TiO2) is biocompatible and environmentally friendly. Consequently, TiO2 is widely applied in many fields, such as implant materials, photocatalysis, pigments, cosmetic additives, etc. Mesoporous TiO2 finds many industrial applications, because of its high surface area and stable structure. However, the strong interaction between TiO2 and water molecules sometimes limits its application to solution environments. Our previous computational work showed that changes to the surface chemistry of TiO2 can affect the hydrogen bond network of water molecules on the TiO2 surface, and so influence the diffusion of water in the slits. Thus, a carbon-modified TiO2 surface could be an alternative way to avoid this limitation. In this work, a slit pore model with a modified TiO2 surface (pore widths 1.2 nm, 1.6 nm and 2.0 nm) with varying carbon coverages (0%, 7%, 47%, 53%, 93% and 100%) was presented. Molecular dynamics (MD) simulations were then performed to investigate the sorption and diffusion of water in these slits. Simulation results showed that the interfacial water molecules on bare TiO2 regions were little affected by the neighboring carbon, and they have the same properties as those on bare TiO2 surfaces. However, the diffusion of water molecules in the center of the slit was enhanced on increase of carbon coverage, because the carbon layer broke the hydrogen bond network between the interfacial water molecules and those on the bare TiO2 surface. It was found that in the slits (>1.2 nm) fully covered by carbon the diffusion coefficients of water are larger than that of bulk water. Moreover, large pore sizes caused an increase in the mobility of water molecules in carbon-modified TiO2, in agreement with previous experimental work. DA - 2012/// PY - 2012/// DO - 10.1039/C2CP40687J VL - 14 IS - 48 SP - 16536 J2 - Phys. Chem. Chem. Phys. LA - en OP - SN - 1463-9076 1463-9084 UR - http://dx.doi.org/10.1039/C2CP40687J DB - Crossref ER - TY - JOUR TI - Microfluidic elastomer composites with switchable vis-IR transmittance AU - U?ar, A.B. AU - Velev, O.D. T2 - Soft Matter AB - We demonstrate a class of simple and versatile soft microfluidic materials that can be made optically transparent or coloured on demand. These materials are in the form of flexible sheets containing microchannel networks embedded in polydimethylsiloxane (PDMS). The channels are filled with liquids whose refractive index is matched with the one of the PDMS matrix. By pumping dye solutions into the channel networks and consecutively replacing the medium, we can control the material's colour and light transmittance in the visible and near-infrared regions. DA - 2012/// PY - 2012/// DO - 10.1039/c2sm26635k VL - 8 IS - 44 SP - 11232-11235 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84874851786&partnerID=MN8TOARS ER - TY - BOOK TI - Materials deposition in evaporating menisci - Fundamentals and engineering applications of the convective assembly process AU - Prevo, B. AU - Velev, O. DA - 2012/// PY - 2012/// DO - 10.1142/9789814304696_0003 SE - 109-156 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84969592286&partnerID=MN8TOARS ER - TY - JOUR TI - Development and applications of a microfluidic reactor with multiple analytical probes AU - Greener, Jesse AU - Tumarkin, Ethan AU - Debono, Michael AU - Kwan, Chi-Hang AU - Abolhasani, Milad AU - Guenther, Axel AU - Kumacheva, Eugenia T2 - The Analyst AB - We report the development of a versatile microfluidic (MF) reactor with multiple analytical probes, which can be used for (i) quantitative characterisation of molecular vibrational signatures of reactants or products, (ii) the localised real-time monitoring of temperature and (iii) site-specific measurements of pH of the reaction system. The analytical probes utilised for in situ reaction analysis include an ATR-FTIR probe, a temperature probe, and a pH probe. We demonstrate the applications of the MF reactor with integrated probes for the parallel monitoring of multiple variables in acid/base neutralisation reaction, of changes in buffer pH, temperature, and vibrational absorption bands, and for monitoring the kinetics of the reaction between CO2 and a buffer system with therapeutic applications. DA - 2012/// PY - 2012/// DO - 10.1039/c1an15940b VL - 137 IS - 2 SP - 444-450 ER - TY - JOUR TI - Cruise control for segmented flow AU - Abolhasani, Milad AU - Singh, Mayank AU - Kumacheva, Eugenia AU - Günther, Axel T2 - Lab on a Chip AB - Capitalizing on the benefits of microscale segmented flows, e.g., enhanced mixing and reduced sample dispersion, so far requires specialist training and accommodating a few experimental inconveniences. For instance, microscale gas-liquid flows in many current setups take at least 10 min to stabilize and iterative manual adjustments are needed to achieve or maintain desired mixing or residence times. Here, we report a cruise control strategy that overcomes these limitations and allows microscale gas-liquid (bubble) and liquid-liquid (droplet) flow conditions to be rapidly "adjusted" and maintained. Using this strategy we consistently establish bubble and droplet flows with dispersed phase (plug) velocities of 5-300 mm s(-1), plug lengths of 0.6-5 mm and continuous phase (slug) lengths of 0.5-3 mm. The mixing times (1-5 s), mass transfer times (33-250 ms) and residence times (3-300 s) can therefore be directly imposed by dynamically controlling the supply of the dispersed and the continuous liquids either from external pumps or from local pressurized reservoirs. In the latter case, no chip-external pumps, liquid-perfused tubes or valves are necessary while unwanted dead volumes are significantly reduced. DA - 2012/// PY - 2012/// DO - 10.1039/c2lc40513j VL - 12 IS - 22 SP - 4787 ER - TY - JOUR TI - Automated microfluidic platform for studies of carbon dioxide dissolution and solubility in physical solvents AU - Abolhasani, Milad AU - Singh, Mayank AU - Kumacheva, Eugenia AU - Günther, Axel T2 - Lab on a Chip AB - We present an automated microfluidic (MF) approach for the systematic and rapid investigation of carbon dioxide (CO2) mass transfer and solubility in physical solvents. Uniformly sized bubbles of CO2 with lengths exceeding the width of the microchannel (plugs) were isothermally generated in a co-flowing physical solvent within a gas-impermeable, silicon-based MF platform that is compatible with a wide range of solvents, temperatures and pressures. We dynamically determined the volume reduction of the plugs from images that were accommodated within a single field of view, six different downstream locations of the microchannel at any given flow condition. Evaluating plug sizes in real time allowed our automated strategy to suitably select inlet pressures and solvent flow rates such that otherwise dynamically self-selecting parameters (e.g., the plug size, the solvent segment size, and the plug velocity) could be either kept constant or systematically altered. Specifically, if a constant slug length was imposed, the volumetric dissolution rate of CO2 could be deduced from the measured rate of plug shrinkage. The solubility of CO2 in the physical solvent was obtained from a comparison between the terminal and the initial plug sizes. Solubility data were acquired every 5 min and were within 2–5% accuracy as compared to literature data. A parameter space consisting of the plug length, solvent slug length and plug velocity at the microchannel inlet was established for different CO2–solvent pairs with high and low gas solubilities. In a case study, we selected the gas–liquid pair CO2–dimethyl carbonate (DMC) and volumetric mass transfer coefficients 4–30 s−1 (translating into mass transfer times between 0.25 s and 0.03 s), and Henry's constants, within the range of 6–12 MPa. DA - 2012/// PY - 2012/// DO - 10.1039/c2lc21043f VL - 12 IS - 9 SP - 1611 ER - TY - JOUR TI - Differential response of macrophages to core-shell Fe3O4@Au nanoparticles and nanostars AU - Xia, W. AU - Song, H. M. AU - Wei, Q. S. AU - Wei, A. T2 - Nanoscale AB - Murine RAW 264.7 cells were exposed to spheroidal core–shell Fe3O4@Au nanoparticles (SCS-NPs, ca. 34 nm) or nanostars (NSTs, ca. 100 nm) in the presence of bovine serum albumin, with variable effects observed after macrophagocytosis. Uptake of SCS-NPs caused macrophages to adopt a rounded, amoeboid form, accompanied by an increase in surface detachment. In contrast, the uptake of multibranched NSTs did not induce gross changes in macrophage shape or adhesion, but correlated instead with cell enlargement and signatures of macrophage activation such as TNF-α and ROS. MTT assays indicate a low cytotoxic response to either SCS-NPs or NSTs despite differences in macrophage behavior. These observations show that differences in NP size and shape are sufficient to produce diverse responses in macrophages following uptake. DA - 2012/// PY - 2012/// DO - 10.1039/c2nr32070c VL - 4 IS - 22 SP - 7143-7148 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000310978100032&KeyUID=WOS:000310978100032 ER - TY - JOUR TI - Ultrastretchable Fibers with Metallic Conductivity Using a Liquid Metal Alloy Core AU - Zhu, Shu AU - So, Ju-Hee AU - Mays, Robin AU - Desai, Sharvil AU - Barnes, William R. AU - Pourdeyhimi, Behnam AU - Dickey, Michael D. T2 - Advanced Functional Materials AB - Abstract The fabrication and characterization of fibers that are ultrastretchable and have metallic electrical conductivity are described. The fibers consist of a liquid metal alloy, eutectic gallium indium (EGaIn), injected into the core of stretchable hollow fibers composed of a triblock copolymer, poly[styrene‐ b ‐(ethylene‐ co ‐butylene)‐ b ‐styrene] (SEBS) resin. The hollow fibers are easy to mass‐produce with controlled size using commercially available melt processing methods. The fibers are similar to conventional metallic wires, but can be stretched orders of magnitude further while retaining electrical conductivity. Mechanical measurements with and without the liquid metal inside the fibers show the liquid core has a negligible impact on the mechanical properties of the fibers, which is in contrast to most conductive composite fibers. The fibers also maintain the same tactile properties with and without the metal. Electrical measurements show that the fibers increase resistance as the fiber elongates and the cross sectional area narrows. Fibers with larger diameters change from a triangular to a more circular cross‐section during stretching, which has the appeal of lowering the resistance below that predicted by theory. To demonstrate their utility, the ultrastretchable fibers are used as stretchable wires for earphones and for a battery charger and perform as well as their conventional parts. DA - 2012/// PY - 2012/// DO - 10.1002/adfm.201202405 VL - 23 IS - 18 SP - 2308-2314 KW - stretchable electronics KW - eutectic gallium indium KW - conductive fibers ER - TY - BOOK TI - Light converts 2D shapes into 3D shapes AU - Liu, Y. AU - Genzer, J. AU - Dickey, M.D. DA - 2012/// PY - 2012/// PB - SPIE ER - TY - JOUR TI - Development of Glucose Sensors Composed of Soft Materials AU - Jain, D. AU - Morales, D. AU - Dickey, M.D. AU - Velev, O. T2 - NC State Undergraduate Research Journal DA - 2012/// PY - 2012/// ER - TY - JOUR TI - A Pressure Responsive Fluidic Microstrip Open Stub Resonator Using a Liquid Metal Alloy AU - Khan, M. Rashed AU - Hayes, Gerard J. AU - Zhang, Silu AU - Dickey, Michael D. AU - Lazzi, Gianluca T2 - IEEE Microwave and Wireless Components Letters AB - This letter describes a fluidic microstrip bandstop filter with transmission properties that change in discrete states. The filter consists of a liquid metal alloy - eutectic gallium indium (EGaIn) - as the conductive component in microfluidic channels. The fluidity of EGaIn allows the open stub resonator of the filter to change its length by flowing in response to an applied pressure. A series of posts in the channel defines the length of the stub filled by the metal and dictates the pressure needed for the liquid metal to flow and thereby extend the stub length. The frequency response of the filter changes in response to the changes in the length of the resonator stub. This approach is a simple method for creating tunable filters and impedance matching sections using soft materials that change dimensions in response to pressure. DA - 2012/11// PY - 2012/11// DO - 10.1109/lmwc.2012.2223754 VL - 22 IS - 11 SP - 577-579 KW - Eutectic gallium indium (EGaIn) KW - liquid metal filter KW - microstrip filter KW - polydimethylsiloxane (PDMS) ER - TY - JOUR TI - Nanofiber-based energy-storage materials AU - Zhang, Xiangwu T2 - Abstracts of Papers of the American Chemical Society DA - 2012/// PY - 2012/// VL - 243 ER - TY - JOUR TI - Li₂MnSiO₄ Carbon Composite Nanofibers as a High-Capacity Cathode Material for Li-Ion Batteries AU - Zhang, Shu AU - Li, Ying AU - Xu, Guanjie AU - Li, Shuli AU - Lu, Yao AU - Topracki, Ozan AU - Zhang, Xiangwu T2 - Soft Nanoscience Letters AB - Li2MnSiO4 has an extremely high theoretical capacity of 332 mAh?g?1. However, only around half of this capacity has been realized in practice and the capacity retention during cycling is also low. In this study, Li2MnSiO4/carbon composite nanofibers were prepared by a combination of electrospinning and heat treatment. The one-dimensional continuous carbon nanofiber matrix serves as long-distance conductive pathways for both electrons and ions. The composite nanofiber structure avoids the aggregation of Li2MnSiO4 particles, which in turn enhances the electrode conductivity and promotes the reaction kinetics. The resultant Li2MnSiO4/carbon composite nanofibers were used as the cathode material for Li-ion batteries, and they delivered high charge and discharge capacities of 218 and 185 mAh?g?1, respectively, at the second cycle. In addition, the capacity retention of Li2MnSiO4 at the first 20th cycles increased from 37% to 54% in composite nanofibers. DA - 2012/// PY - 2012/// DO - 10.4236/snl.2012.23010 VL - 02 IS - 03 SP - 54-57 ER - TY - JOUR TI - High-rate capability of LiFePO(4) cathode materials containing Fe(2)P and trace carbon AU - Yin, Y. H. AU - Gao, M. X. AU - Pan, H. G. AU - Shen, L. K. AU - Ye, X. AU - Liu, Y. F. AU - Fedkiw, P. S. AU - Zhang, X. W. T2 - Journal of Power Sources AB - Carbon coating and nano-scale particle size are two impactful factors in improving the rate capability of LiFePO4 cathode materials for lithium-ion batteries. However, both factors decrease the tap density of the materials and are possibly causing unfavorable effect on the volumetric capacity of the cathode materials and thus the batteries, which is undesirable in commercial application. In the present study, LiFePO4 materials with moderate particle size of sub-micron and trace carbon content (0.5–0.9 wt.%) are synthesized by a mechanical activation method. High-electronic conductivity iron phosphides (Fe2P/FeP) are in situ introduced into the LiFePO4 materials and the amount is modified by the calcination temperature. Electrochemical testing shows that Fe2P/FeP plays an important role in improving the high-rate capability of LiFePO4 with moderate particle size. The product calcined at 700 °C, which has a high-tap density of 1.37 g cm−3 correlating to a specific surface area approximately of 4 m2 g−1, possesses discharge capacities of 110 and 100 mAh g−1 at discharge rates of 5 C and 10 C, respectively. The introduction of Fe2P/FeP in an amount of ca. 5 wt.% rather than carbon coating and the moderate particle size of LiFePO4 are promising approaches to obtain LiFePO4 cathode material of high-rate capability without unduly compromising its volumetric capacity. DA - 2012/// PY - 2012/// DO - https://doi.org/10.1016/j.jpowsour.2011.10.042 VL - 199 ER - TY - JOUR TI - High-capacity Li2Mn0.8Fe0.2SiO4/carbon composite nanofiber cathodes for lithium-ion batteries AU - Zhang, S. AU - Li, Y. AU - Xu, G. J. AU - Li, S. L. AU - Lu, Y. AU - Toprakci, O. AU - Zhang, X. W. T2 - Journal of Power Sources AB - Li2MnSiO4 has been considered as a promising cathode material with an extremely high theoretically capacity of 332 mAh g−1. However, due to its low intrinsic conductivity and poor structural stability, only about half of the theoretical capacity has been realized in practice and the capacity decays rapidly during cycling. To realize the high capacity and improve the cycling performance, Li2Mn0.8Fe0.2SiO4/carbon composite nanofibers were prepared by the combination of iron doping and electrospinning. X-ray diffraction, scanning electron microscope, and transmission electronic microscope were applied to characterize the Li2Mn0.8Fe0.2SiO4/carbon nanofibers. It was found that Li2Mn0.8Fe0.2SiO4 nanoparticles were embedded into continuous carbon nanofiber matrices, which formed free-standing porous mats that could be used as binder-free cathodes. The iron doping improved the conductivity and purity of the active material, and the carbon nanofiber matrix facilitated ion transfer and charge diffusion. As a result, Li2Mn0.8Fe0.2SiO4/carbon nanofiber cathodes showed promising improvement on reversible capacity and cycling performance. DA - 2012/// PY - 2012/// DO - https://doi.org/10.1016/j.jpowsour.2012.04.011 VL - 213 ER - TY - JOUR TI - Cr-doped Li2MnSiO4/carbon composite nanofibers as high-energy cathodes for Li-ion batteries AU - Zhang, Shu AU - Lin, Zhan AU - Ji, Liwen AU - Li, Ying AU - Xu, Guanjie AU - Xue, Leigang AU - Li, Shuli AU - Lu, Yao AU - Toprakci, Ozan AU - Zhang, Xiangwu T2 - Journal of Materials Chemistry AB - Li2MnSiO4 with an extremely high theoretical capacity of 332 mA h g−1 has recently gained tremendous interest. However, only around half of this capacity has been realized in practice and the cycling performance is also poor due to the low intrinsic conductivity and unsatisfactory structure stability. In this study, Li2Mn(1−x)CrxSiO4/carbon composite nanofibers are prepared by the combination of electrospinning and Cr doping. The electrospinning process leads to the formation of a conductive carbon nanofiber matrix, which provides fast ion transport and charge transfer. Cr doping further improves crystal structure stability by increasing the unit cell volume and inducing defects in the lattice. The resultant Li2Mn(1−x)CrxSiO4/carbon composite nanofibers exhibit a high discharge capacity of 314 mA h g−1 at the 5th cycle and stable cycling performance. DA - 2012/// PY - 2012/// DO - 10.1039/c2jm32213g VL - 22 IS - 29 SP - 14661-14666 UR - https://publons.com/publon/674389/ ER - TY - JOUR TI - Polyvinylidene fluoride-co-chlorotrifluoroethylene and polyvinylidene fluoride-co-hexafluoropropylene nanofiber-coated polypropylene microporous battery separator membranes AU - Lee, Hun AU - Alcoutlabi, Mataz AU - Watson, Jill V. AU - Zhang, Xiangwu T2 - Journal of Polymer Science Part B: Polymer Physics AB - Abstract Nanofiber‐coated polypropylene (PP) separator membranes were prepared by coating a Celgard® microporous PP membrane with electrospun polyvinylidene fluoride‐ co ‐chlorotrifluoroethylene (PVDF‐ co ‐CTFE) and PVDF‐ co ‐CTFE/polyvinylidene fluoride‐ co ‐hexafluoropropylene (PVDF‐ co ‐HFP) nanofibers. Three PVDF polymer solutions of varying compositions were used in the preparation of the nanofiber coatings. Two of the polymer solutions were PVDF‐ co ‐CTFE blends made using different types of PVDF‐ co ‐HFP copolymers. The PVDF‐ co ‐CTFE and PVDF‐ co ‐CTFE/PVDF‐ co ‐HFP blend nanofiber coatings have been found to have comparable adhesion to the PP microporous membrane substrate. The electrolyte uptakes and separator–electrode adhesion properties of nanofiber‐coated membranes were evaluated. Both the electrolyte uptake and the separator–electrode adhesion were improved by the nanofiber coatings. The improvement in electrolyte update capacity is not only related to the gelation capability of the PVDF copolymer nanofibers, but also attributed to the increased porosity and capillary effect on nanofibrous structure of the electrospun nanofiber coatings. Enhancement of the separator–electrode adhesion was owing to the adhesion properties of the copolymer nanofiber coatings. Compared with the PVDF‐ co ‐CTFE/PVDF‐ co ‐HFP blend nanofiber coatings studied, the PVDF‐ co ‐CTFE coating was more effective in improving the electrolyte uptake and separator–electrode adhesion. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 DA - 2012/11// PY - 2012/11// DO - 10.1002/polb.23216 VL - 51 IS - 5 SP - 349-357 KW - Adhesion KW - Coatings KW - Electrospinning KW - Lithium-ion batteries KW - Nanofibers KW - PVDF-co-CTFE KW - PVDF-co-HFP KW - Separators ER - TY - JOUR TI - Novel Atmospheric Plasma Enhanced Silk Fibroin Nanofiber Gauze Composite Wound Dressings AU - Nawalakhe, Rupesh AU - Shi, Quan AU - Vitchuli, Narendiran AU - Bourham, Mohamed A. AU - Zhang, Xiangwu AU - McCord, Marian G. T2 - Journal of Fiber Bioengineering and Informatics DA - 2012/9/5/ PY - 2012/9/5/ DO - 10.3993/jfbi09201201 VL - 5 IS - 3 SP - 227-242 ER - TY - JOUR TI - Multifunctional and durable nanofiber-fabric-layered composite for protective application AU - Shi, Quan AU - Vitchuli, Narendiran AU - Nowak, Joshua AU - Jiang, Shan AU - Caldwell, Jane M. AU - Breidt, Frederick AU - Bourham, Mohamed AU - Zhang, Xiangwu AU - McCord, Marian T2 - Journal of Applied Polymer Science AB - Abstract The effect of filler surface treatment on the dynamic rheological behaviors of polystyrene filled with Sn–Pb alloy particles was tested below and above the melting temperature ( T m ) of the alloy. The mechanical relaxation relevant to the T m of the alloy in the composite was diminished by the filler surface pretreatment. In the whole temperature range of interest, there existed a secondary plateau of the storage modulus at low frequencies. The effect of alloy particle surface treatment on the plateau was related to the matter‐state change (from solid to liquid) of the alloy. Above the T m of the alloy, the surface treatment of the alloy affected the secondary plateau, but below the T m , it did not. The analyses of Cole–Cole diagrams of the systems suggested that untreated and pretreated alloy fillers all retarded the relaxation processes in the molten state of polystyrene below the T m of the alloy and that the relaxation process was separated into the high‐frequency relaxation of the phases and the low‐frequency relaxation of the droplets above the T m . The surface treatments of the alloy filler further enhanced this action. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3173–3179, 2002 DA - 2012/9/1/ PY - 2012/9/1/ DO - 10.1002/app.11352 VL - 128 IS - 2 SP - 1219-1226 KW - surfaces KW - rheology KW - composites KW - alloys KW - melting point ER - TY - CONF TI - Lithium-Ion Batteries: Amorphous Carbon Coating of Silicon-Carbon Nanofibers as Anode Materials C2 - 2012/8// C3 - 11th Annual NC State Summer Undergraduate Research Symposium DA - 2012/8// ER - TY - BOOK TI - Soft matter gradient surfaces: methods and applications AU - Genzer, Jan AB - Contributors vii Preface xi 1 Gradient Libraries: Harnessing a Ubiquitous Phenomenon to Accelerate Experimentation 1 Michael J. Fasolka 2 Classification of Key Attributes of Soft Material Gradients 19 Jan Genzer and Rajendra R. Bhat 3 Discovery and Optimization of Sensing Materials Using Discrete and Gradient Arrays 47 Radislav A. Potyrailo 4 Colliding Self-Assembly Waves in Organosilane Monolayers 93 Kirill Efimenko, Ali E. Ozcam, Jan Genzer, Daniel A. Fischer, Fredrick R. Phelan, and Jack F. Douglas 5 Orientational Anchoring of Liquid Crystals on Surfaces Presenting Continuous Gradients in Composition 109 Jugal K. Gupta, Kirill Efimenko, Daniel A. Fischer, Jan Genzer, and Nicholas L. Abbott 6 Continuous Infusion Microchannel Approach to Generate Composition Gradients from Viscous Polymer Solutions 129 Pratyay Basak, Pedro Zapata, Keith Reed, Ismael Gomez, and J. Carson Meredith 7 Gradient Assembly of Complex Surfaces for Sensing, Fabrication, and High Throughput Analysis 145 Andrew C. Hillier 8 Making Gradient Patterns by Electron-Beam Chemical Lithography with Monomolecular Resists 199 Nirmalya Ballav, Andreas Terfort, and Michael Zharnikov 9 Electrochemical Mapping for Polymer Chemical and Physical Gradients 229 Roger H. Terrill, Xuejun Wang, and Paul W. Bohn 10 Directed Assembly of Block Copolymer Films: Effects of Rough Substrates and Thermal Fields 257 Manish M. Kulkarni, Alamgir Karim, and Kevin G. Yager 11 Hydrogel Gradients by Self-Initiated Photografting and Photopolymerization: Preparation, Characterization, and Protein Interactions 279 Tobias Ekblad, Andreas Larsson, and Bo Liedberg 12 Polymer Gradients: Responsive Grafted Layers 303 Igor Luzinov and Sergiy Minko 13 Bioactive Self-Assembled Monolayer Gradients 329 Nicole M. Moore and Matthew L. Becker 14 Morphology Gradients on Different Size Scales and Their Application in Biological Studies 365 Christian Zink and Nicholas D. Spencer 15 Molecularly Defined Peptide Spacing Gradients for Cell Guidance 383 Vera C. Hirschfeld-Warneken and Joachim P. Spatz 16 Motion of Drops on Gradient Surfaces 407 R. Shankar Subramanian Index 431 DA - 2012/// PY - 2012/// DO - 10.1002/9781118166086 PB - Hoboken, N.J.: Wiley ER - TY - JOUR TI - Caprolactone Ring-Opening Molecular Layer Deposition of Organic-Aluminum Oxide Polymer Films AU - Gong, Bo AU - Parsons, Gregory N. T2 - ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY AB - New hybrid organic-inorganic thin films are finding use in electronics, biomedical, chemical protection, and energy storage systems applications. In a unique vapor-source molecular layer deposition film formation reaction, we find that cyclic ɛ-caprolactone reacts with surface-adsorbed methyl-aluminum species to build a metal-organic hybrid coordination polymer thin film at substrate temperatures between 60 and 120°C. Infrared and X-ray photoelectron spectroscopy analysis confirms (–Al–O–(C8H16)–O–)n bonding, expected from the a Lewis acid catalyzed surface ring-opening reaction. In-situ IR analysis confirms the surface reaction sequence. The materials show good stability and maintain their physical structure in ambient. This surface acid-catalyzed vapor process could extend to other metal organics and vapor/surface ring opening reactions to yield new organic-inorganic film materials for use in gas diffusion barriers, separation membranes and chemical resistance coatings. DA - 2012/// PY - 2012/// DO - 10.1149/2.023204jss VL - 1 IS - 4 SP - P210-P215 SN - 2162-8769 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000319446800014&KeyUID=WOS:000319446800014 ER - TY - JOUR TI - Molecular Simulation 25th Anniversary Symposium: A Festschrift for Professor N. Quirke AU - Gubbins, Keith E. AU - Meunier, Marc T2 - MOLECULAR SIMULATION AB - Having obtained his B.Sc. in Physics from the University of Leicester in 1973, Nick went on to take his Ph.D., also in Physics, from the University of Leicester with Professor J.L. Beeby as his adv... DA - 2012/// PY - 2012/// DO - 10.1080/08927022.2012.709633 VL - 38 IS - 14-15 SP - 1169-1170 SN - 1029-0435 ER - TY - JOUR TI - Analysis of the solvation structure of rubidium bromide under nanoconfinement AU - Phillips, Katherine A. AU - Palmer, Jeremy C. AU - Gubbins, Keith E. T2 - MOLECULAR SIMULATION AB - Abstract We report results from a molecular simulation study of aqueous rubidium bromide solutions confined in slit-shaped carbon pores 6.5–16 Å in width, which encompasses the range typically found in nanoporous carbon electrode materials. For each slit-pore model, the structure of the solvation shells surrounding the Rb+ and Br− ions in 0.1, 0.5 and 1.0 M solutions was examined using the ion–water radial distribution functions. The impact of pore geometry on solvation structure of ions was also investigated using a disordered carbon model that morphologically resembles real nanoporous carbon electrodes. Monte Carlo simulations were used to determine the propensity of ions to reside in pores of specific sizes in the model carbon, allowing the solvation structure of Rb+ and Br− ions to be analysed as a function of pore size. We find that a dramatic drop in the solvation number occurs in pore sizes below 10 Å for slit-shaped pores, while more complex geometries see a steady decrease in solvation number as pore size is decreased. Our results suggest that, when compared to the disordered carbon model, the slit-pore model may not provide qualitatively accurate predictions regarding the structural properties of electrolytes confined in complex electrode materials. Keywords: nanoconfinementsolvationporous carbon electrodemolecular simulation Acknowledgements We thank the National Science Foundation for support of this work under Grant no. CBET-0932656. K.A.P. is grateful for support from the US Department of Education under a GAANN fellowship. DA - 2012/// PY - 2012/// DO - 10.1080/08927022.2012.713484 VL - 38 IS - 14-15 SP - 1209-1220 SN - 1029-0435 KW - nanoconfinement KW - solvation KW - porous carbon electrode KW - molecular simulation ER - TY - JOUR TI - The Comprehensive Assessment of Team Member Effectiveness: Development of a Behaviorally Anchored Rating Scale for Self- and Peer Evaluation AU - Ohland, Matthew W. AU - Loughry, Misty L. AU - Woehr, David J. AU - Bullard, Lisa G. AU - Finelli, Cynthia J. AU - Layton, Richard A. AU - Pomeranz, Hal R. AU - Schmucker, Douglas G. T2 - ACADEMY OF MANAGEMENT LEARNING & EDUCATION AB - Instructors often incorporate self- and peer evaluations when they use teamwork in their classes, which is common in management education. However, the process is often time consuming and frequently does not match well with guidance provided by the literature. We describe the development of a web-based instrument that efficiently collects and analyzes self- and peer-evaluation data. The instrument uses a behaviorally anchored rating scale to measure team-member contributions in five areas based on the team effectiveness literature. Three studies provide evidence for the validity of the new instrument. Implications for management education and areas for future research are discussed. DA - 2012/12// PY - 2012/12// DO - 10.5465/amle.2010.0177 VL - 11 IS - 4 SP - 609-630 SN - 1537-260X ER - TY - JOUR TI - Targeted Proteomics of the Secretory Pathway Reveals the Secretome of Mouse Embryonic Fibroblasts and Human Embryonic Stem Cells AU - Sarkar, Prasenjit AU - Randall, Shan M. AU - Muddiman, David C. AU - Rao, Balaji M. T2 - MOLECULAR & CELLULAR PROTEOMICS AB - Proteins endogenously secreted by human embryonic stem cells (hESCs) and those present in hESC culture medium are critical regulators of hESC self-renewal and differentiation. Current MS-based approaches for identifying secreted proteins rely predominantly on MS analysis of cell culture supernatants. Here we show that targeted proteomics of secretory pathway organelles is a powerful alternate approach for interrogating the cellular secretome. We have developed procedures to obtain subcellular fractions from mouse embryonic fibroblasts (MEFs) and hESCs that are enriched in secretory pathway organelles while ensuring retention of the secretory cargo. MS analysis of these fractions from hESCs cultured in MEF conditioned medium (MEF-CM) or MEFs exposed to hESC medium revealed 99 and 129 proteins putatively secreted by hESCs and MEFs, respectively. Of these, 53 and 62 proteins have been previously identified in cell culture supernatants of MEFs and hESCs, respectively, thus establishing the validity of our approach. Furthermore, 76 and 37 putatively secreted proteins identified in this study in MEFs and hESCs, respectively, have not been reported in previous MS analyses.The identification of low abundance secreted proteins via MS analysis of cell culture supernatants typically necessitates the use of altered culture conditions such as serum-free medium. However, an altered medium formulation might directly influence the cellular secretome. Indeed, we observed significant differences between the abundances of several secreted proteins in subcellular fractions isolated from hESCs cultured in MEF-CM and those exposed to unconditioned hESC medium for 24 h. In contrast, targeted proteomics of secretory pathway organelles does not require the use of customized media. We expect that our approach will be particularly valuable in two contexts highly relevant to hESC biology: obtaining a temporal snapshot of proteins secreted in response to a differentiation trigger, and identifying proteins secreted by cells that are isolated from a heterogeneous population. Proteins endogenously secreted by human embryonic stem cells (hESCs) and those present in hESC culture medium are critical regulators of hESC self-renewal and differentiation. Current MS-based approaches for identifying secreted proteins rely predominantly on MS analysis of cell culture supernatants. Here we show that targeted proteomics of secretory pathway organelles is a powerful alternate approach for interrogating the cellular secretome. We have developed procedures to obtain subcellular fractions from mouse embryonic fibroblasts (MEFs) and hESCs that are enriched in secretory pathway organelles while ensuring retention of the secretory cargo. MS analysis of these fractions from hESCs cultured in MEF conditioned medium (MEF-CM) or MEFs exposed to hESC medium revealed 99 and 129 proteins putatively secreted by hESCs and MEFs, respectively. Of these, 53 and 62 proteins have been previously identified in cell culture supernatants of MEFs and hESCs, respectively, thus establishing the validity of our approach. Furthermore, 76 and 37 putatively secreted proteins identified in this study in MEFs and hESCs, respectively, have not been reported in previous MS analyses. The identification of low abundance secreted proteins via MS analysis of cell culture supernatants typically necessitates the use of altered culture conditions such as serum-free medium. However, an altered medium formulation might directly influence the cellular secretome. Indeed, we observed significant differences between the abundances of several secreted proteins in subcellular fractions isolated from hESCs cultured in MEF-CM and those exposed to unconditioned hESC medium for 24 h. In contrast, targeted proteomics of secretory pathway organelles does not require the use of customized media. We expect that our approach will be particularly valuable in two contexts highly relevant to hESC biology: obtaining a temporal snapshot of proteins secreted in response to a differentiation trigger, and identifying proteins secreted by cells that are isolated from a heterogeneous population. Human embryonic stem cells (hESCs) 1The abbreviations used are:CMconditioned mediumECMextracellular matrixERendoplasmic reticulumFGFfibroblast growth factorGDF3growth and differentiation factor-3GOGene OntologyHESCshuman embryonic stem cellsIE-MSiterative exclusion MSIGFinsulin-like growth factorMEFmouse embryonic fibroblastNSAFnormalized spectral abundance factorTGF-βtransforming and growth factor-β. 1The abbreviations used are:CMconditioned mediumECMextracellular matrixERendoplasmic reticulumFGFfibroblast growth factorGDF3growth and differentiation factor-3GOGene OntologyHESCshuman embryonic stem cellsIE-MSiterative exclusion MSIGFinsulin-like growth factorMEFmouse embryonic fibroblastNSAFnormalized spectral abundance factorTGF-βtransforming and growth factor-β. are pluripotent cells isolated from the inner cell mass of a pre-implantation blastocyst stage embryo (1Thomson J.A. Itskovitz-Eldor J. Shapiro S.S. Waknitz M.A. Swiergiel J.J. Marshall V.S. Jones J.M. Embryonic stem cell lines derived from human blastocysts.Science. 1998; 282: 1145-1147Crossref PubMed Scopus (12273) Google Scholar). They have potential applications in regenerative medicine, are an attractive source of human cells for drug evaluation, and are useful models for understanding human development. The self-renewal or differentiation of hESCs is controlled by endogenous proteins secreted by hESCs and by exogenous factors present in cell culture medium (2Bendall S.C. Hughes C. Campbell J.L. Stewart M.H. Pittock P. Liu S. Bonneil E. Thibault P. Bhatia M. Lajoie G.A. An enhanced mass spectrometry approach reveals human embryonic stem cell growth factors in culture.Mol. Cell. Proteomics. 2009; 8: 421-432Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar, 3Peerani R. Rao B.M. Bauwens C. Yin T. Wood G.A. Nagy A. Kumacheva E. Zandstra P.W. Niche-mediated control of human embryonic stem cell self-renewal and differentiation.EMBO J. 2007; 26: 4744-4755Crossref PubMed Scopus (330) Google Scholar). For instance, hESCs are routinely cultured on feeder layers of mouse embryonic fibroblasts (MEFs) or on Matrigel-coated plates in mouse embryonic fibroblast–conditioned medium (MEF-CM). In these cases, cytokines secreted by MEFs and present in MEF-CM, together with cytokines and extracellular matrix (ECM) proteins secreted by hESCs, form a localized microenvironment that regulates hESC fate. conditioned medium extracellular matrix endoplasmic reticulum fibroblast growth factor growth and differentiation factor-3 Gene Ontology human embryonic stem cells iterative exclusion MS insulin-like growth factor mouse embryonic fibroblast normalized spectral abundance factor transforming and growth factor-β. conditioned medium extracellular matrix endoplasmic reticulum fibroblast growth factor growth and differentiation factor-3 Gene Ontology human embryonic stem cells iterative exclusion MS insulin-like growth factor mouse embryonic fibroblast normalized spectral abundance factor transforming and growth factor-β. The comprehensive identification of proteins secreted by MEFs and hESCs—their cellular secretome—can help unravel the molecular mechanisms that regulate hESC fate. Yet the use of MS-based approaches for secretome analysis remains challenging. In general, secretome studies of various cell types have relied on MS analysis of cell culture supernatants (reviewed in Ref. 4Skalnikova H. Motlik J. Gadher S.J. Kovarova H. Mapping of the secretome of primary isolates of mammalian cells, stem cells and derived cell lines.Proteomics. 2011; 11: 691-708Crossref PubMed Scopus (161) Google Scholar). However, such an approach typically results in the identification of small numbers of extracellular proteins. This was indeed the case with MS analysis of conditioned medium (CM) from MEFs or other feeder cells that support the maintenance of undifferentiated hESCs (5Chin A.C. Fong W.J. Goh L.T. Philp R. Oh S.K. Choo A.B. Identification of proteins from feeder conditioned medium that support human embryonic stem cells.J. Biotechnol. 2007; 130: 320-328Crossref PubMed Scopus (56) Google Scholar, 6Lim J.W. Bodnar A. Proteome analysis of conditioned medium from mouse embryonic fibroblast feeder layers which support the growth of human embryonic stem cells.Proteomics. 2002; 2: 1187-1203Crossref PubMed Scopus (144) Google Scholar, 7Prowse A.B. McQuade L.R. Bryant K.J. Marcal H. Gray P.P. Identification of potential pluripotency determinants for human embryonic stem cells following proteomic analysis of human and mouse fibroblast conditioned media.J. Proteome Res. 2007; 6: 3796-3807Crossref PubMed Scopus (69) Google Scholar, 8Prowse A.B. McQuade L.R. Bryant K.J. Van Dyk D.D. Tuch B.E. Gray P.P. A proteome analysis of conditioned media from human neonatal fibroblasts used in the maintenance of human embryonic stem cells.Proteomics. 2005; 5: 978-989Crossref PubMed Scopus (63) Google Scholar). A low abundance of secreted proteins of interest and a high concentration of serum proteins in cell culture media significantly impede MS analysis. To overcome these limitations, Bendall et al. implemented an iterative-exclusion MS (IE-MS) strategy, in conjunction with the use of medium without serum or serum replacer, for the identification of proteins secreted by MEFs and hESCs (2Bendall S.C. Hughes C. Campbell J.L. Stewart M.H. Pittock P. Liu S. Bonneil E. Thibault P. Bhatia M. Lajoie G.A. An enhanced mass spectrometry approach reveals human embryonic stem cell growth factors in culture.Mol. Cell. Proteomics. 2009; 8: 421-432Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar). Using this approach, large numbers of previously unreported proteins secreted by MEFs and hESCs could be identified, showing that IE-MS is a powerful strategy for the identification of low abundance proteins. However, the use of medium without serum or serum replacer for secretomic analysis can be problematic. Specifically, the use of a “blank” or serum-free medium might alter cellular physiology and, consequently, the profile of secreted proteins. Indeed, we observe that hESCs are highly prone to apoptosis under such growth conditions. Moreover, an analysis of the cell culture supernatant is not specifically targeted toward endogenously secreted ECM proteins, which are also an important component of the cellular microenvironment. ECM proteins form a matrix that associates with the cell and might not be present in the cell culture supernatant. Moreover, many growth factors are known to be sequestered by ECM proteins and might not be released into the culture medium (9ten Dijke P. Arthur H.M. Extracellular control of TGFbeta signalling in vascular development and disease.Nat. Rev. Mol. Cell Biol. 2007; 8: 857-869Crossref PubMed Scopus (608) Google Scholar). Here we present a rigorous evaluation of an alternate strategy to interrogate the entire cellular secretome, including cytokines and ECM proteins. Notably, our approach does not require the use of customized media lacking serum and serum replacers, and it is compatible with cell culture systems utilizing media of unknown or poorly defined composition, such as CM from MEFs. To identify the secretome of MEFs and hESCs, we carried out an MS analysis of their subcellular fractions that were enriched in secretory pathway organelles. The secretory pathway comprises the endoplasmic reticulum (ER), the Golgi apparatus, and the associated transport vesicles. Detailed MS analysis of these organelles identifies the secretory cargo (i.e. proteins destined to be secreted) in addition to the secretory pathway proteome (10Gilchrist A. Au C.E. Hiding J. Bell A.W. Fernandez-Rodriguez J. Lesimple S. Nagaya H. Roy L. Gosline S.J. Hallett M. Paiement J. Kearney R.E. Nilsson T. Bergeron J.J. Quantitative proteomics analysis of the secretory pathway.Cell. 2006; 127: 1265-1281Abstract Full Text Full Text PDF PubMed Scopus (385) Google Scholar). Indeed, we have previously identified several secreted proteins in hESCs as a result of contamination by the ER and Golgi (11Sarkar P. Collier T.S. Randall S.M. Muddiman D.C. Rao B.M. The subcellular proteome of undifferentiated human embryonic stem cells.Proteomics. 2012; 12: 421-430Crossref PubMed Scopus (18) Google Scholar) in our subcellular fractions. In light of these reports, we hypothesized that targeted proteomic analysis of the secretory pathway is a viable approach for comprehensive characterization of the cellular secretome. Accordingly, we developed protocols to isolate subcellular fractions enriched in the ER and Golgi compartments from MEFs and hESCs, and we subsequently carried out MS analysis on these samples. Several proteins secreted by MEFs and hESCs could be identified in this manner. Strikingly, the numbers of proteins identified were comparable to those obtained with the highly efficient IE-MS approach. Furthermore, we also show that short-term changes in medium composition affect the profile and quantitative levels of several proteins that transit through the secretory pathway, including secreted and membrane proteins. Taken together, our results validate the use of targeted secretory pathway proteomics as a powerful alternate approach to interrogate the cellular secretome. MEFs were isolated from E13.5 pregnant CD-1 mice embryos (Charles River, Wilmington, MA) and cultured in MEF medium comprising DMEM-High Glucose (Invitrogen, Carlsbad, CA), 10% fetal bovine serum (Sigma-Aldrich, St. Louis, MO), 1% penicillin-streptomycin (Invitrogen), and 1% l-glutamine (Invitrogen). H1 and H9 hESCs (WiCell, Madison, WI) were cultured on MEF feeders as described elsewhere (12Collier T.S. Sarkar P. Rao B. Muddiman D.C. Quantitative top-down proteomics of SILAC labeled human embryonic stem cells.J. Am. Soc. Mass Spectrom. 2010; 21: 879-889Crossref PubMed Scopus (39) Google Scholar). hESCs were passaged upon confluence, every 5 to 7 days. Feeder free culture of hESCs was carried out on Growth Factor Reduced MatrigelTM (BD Biosciences, Bedford, MA) in the presence of MEF-CM. For passaging, confluent colonies were scored manually, and subcolonies were lifted off the plate using Collagenase IV (Invitrogen). MEF-CM was prepared using previously published protocols (13Xu C. Inokuma M.S. Denham J. Golds K. Kundu P. Gold J.D. Carpenter M.K. Feeder-free growth of undifferentiated human embryonic stem cells.Nat. Biotechnol. 2001; 19: 971-974Crossref PubMed Scopus (1585) Google Scholar), using passage-3 MEFs. H1 and H9 colonies were dissociated using Trypsin/EDTA (Sigma) and fixed in 4% paraformaldehyde (Fisher Scientific, Fair Lawn, NJ). Cells were permeabilized in saponin buffer containing 1 mg/ml saponin (Sigma-Aldrich) and 1% BSA in PBS. Cells were incubated with rabbit anti-human OCT4 antibody (Cell Signaling, Danvers, MA) at 1:200 dilution and mouse anti-human SSEA4 antibody (Millipore, Billerica, MA) at 1:1000 dilution for 1 h at room temperature and subsequently with goat anti-rabbit ALEXA-633 (Invitrogen) and goat anti-mouse ALEXA-488 (Invitrogen) antibodies at 1:500 dilution for 1 h at 4 °C. Cells were analyzed using a BD FacsAria flow cytometer. Mitomycin C-treated MEFs were exposed to hESC medium, as per the protocol for making MEF-CM, prior to harvesting the cells. hESC medium comprised DMEM/F12 (Invitrogen), 20% knockout serum replacement (Invitrogen), 1 mm l-glutamine (Invitrogen), 0.1 mm β-mercaptoethanol (Sigma-Aldrich), 1% non-essential amino acids (Invitrogen), and 4 ng/ml basic fibroblast growth factor (Sigma-Aldrich). MEFs were exposed to fresh hESC medium every day for 4 days to allow the cells to adapt to the medium. MEFs were then washed with Dulbecco's PBS without Ca2+ and Mg2+ (DPBS) (Sigma-Aldrich) and incubated in hypotonic PBS (25% DPBS in water) for 20 min at 4 °C. The sheet of MEF cells that subsequently detached from the flask was collected and vigorously vortexed to dislodge individual cells from the ECM. Cells were centrifuged at 300g for 5 min at 4 °C, and the supernatant was discarded. The cell pellet was resuspended in sucrose buffer comprising 250 mm sucrose (Fisher), 25 mm potassium chloride (Fisher), 5 mm magnesium chloride (Fisher), 10 mm triethanolamine (Sigma-Aldrich), 10 mm acetic acid (Fisher), and cØmplete mini® protease inhibitor mixture tablets (Roche, Indianapolis, IN) with the pH adjusted to 7.6 using triethanolamine and/or acetic acid. The cells were lysed by being passed through a 25-gauge needle twice and centrifuged at 3000g for 10 min at 4 °C to remove nuclei (14Graham J.M. Rickwood D. Subcellular Fractionation: A Practical Approach. IRL Press at Oxford University Press, Oxford, UK1997Google Scholar). The supernatant was incubated with 50 μl anti-Tom22 magnetic microbeads (Miltenyi Biotec, Auburn, CA) at 4 °C for 1 h. The magnetic microbeads loaded with mitochondria were cleared using a DynaMag-15 magnet (Invitrogen) via incubation at 4 °C for 5 h. The cleared lysate was centrifuged at 15,000g for 30 min at 4 °C. The pellet was enriched for ER and Golgi (14Graham J.M. Rickwood D. Subcellular Fractionation: A Practical Approach. IRL Press at Oxford University Press, Oxford, UK1997Google Scholar) and was solubilized in 8 m urea (Sigma) and 50 mm ammonium bicarbonate (VWR, West Chester, PA) and stored at −80 °C until further use. H1 and H9 cells were grown until confluence and washed with DPBS. For experiments with unconditioned medium, H1 and H9 cells were exposed to unconditioned hESC medium for 1 day, and cultures were washed with DPBS to remove dead cells. Cultures were incubated in DPBS with 1 mm EDTA (ACROS, Geel, Belgium) to dissociate colonies into single cells. The suspension was centrifuged at 300g for 5 min at 4 °C. The cell pellet was resuspended in sucrose buffer, and cells were lysed by being passed through a 25-gauge needle twice. The lysate was centrifuged at 3000g for 10 min at 4 °C to remove nuclei. The supernatant was incubated with anti-TOM22 magnetic microbeads (Miltenyi Biotec) at 4 °C for 1 h. Magnetic microbeads were cleared via incubation with a DynaMag-15 magnet at 4 °C for 5 h. The cleared lysate was centrifuged at 15,000g for 30 min at 4 °C, and the pellet was solubilized in 8 m urea with 50 mm ammonium bicarbonate. Samples were stored at −80 °C until further use. To obtain the whole cell lysate, H9 cells were directly lysed in 8 m urea with 50 mm ammonium bicarbonate and passed vigorously through a 22-gauge needle until the lysate was no longer viscous. The lysate was stored at −80 °C until further use. Approximately 100 μg of total protein was digested using filtered-aided sample preparation, a protocol adapted from that of Mann and coworkers (15Wisniewski J.R. Zougman A. Nagaraj N. Mann M. Universal sample preparation method for proteome analysis.Nat. Methods. 2009; 6: U359-U360Crossref PubMed Scopus (5041) Google Scholar). Vivacon 30k molecular weight cutoff filters (Sartorius Stedim Biotech, Goettingen, Germany) were used as reaction vessels; samples were reduced with dithiothreitol, alkylated with iodoacetamide, and digested overnight with trypsin. The digestion was quenched by the addition of 1% formic acid solution, and the peptides were collected via centrifugation. Peptides were fractionated by means of an anion exchange protocol previously described by Wisniewski et al. (16Wisniewski J.R. Zougman A. Mann M. Combination of FASP and StageTip-based fractionation allows in-depth analysis of the hippocampal membrane proteome.J. Proteome Res. 2009; 8: 5674-5678Crossref PubMed Scopus (437) Google Scholar). 200 μl pipette tips were filled with a solid phase anion exchange resin (3M, St. Paul, MN) to create StageTips for peptide fractionation (17Ishihama Y. Rappsilber J. Mann M. Modular stop and go extraction tips with stacked disks for parallel and multidimensional peptide fractionation in proteomics.J. Proteome Res. 2006; 5: 988-994Crossref PubMed Scopus (224) Google Scholar). Britton & Robinson buffer pH 5.0 (Ricca Chemical Company, Arlington, TX) was titrated with either HCl or NaOH to different pH readings (3.0, 4.0, 5.0, 6.0, 8.0, and 11.0) to create a total of six different buffers. StageTips were conditioned with methanol followed by 1 m NaOH, followed by pH 11 buffer. Peptides were loaded in pH 11 buffer and subsequently eluted with each of the aforementioned buffers in descending order via centrifugation. Fractions were collected and evaporated under vacuum before being reconstituted in mobile phase A for LC-MS/MS analysis. An Eksigent 1D+ nano-LC system (Eksigent, Dublin, CA) utilizing a cHiPLC-Nanoflex system for reversed-phase separation of peptides was employed with a trap and elute configuration. The dimensions of the nano cHiPLC analytical column were 75 μm inner diameter × 15 cm, and the nano cHiPLC trapping column measured 200 μm inner diameter × 0.5 mm. Both columns were packed with ChromXP C18-CL (3 μm, 120 Å) by the manufacturer (Eksigent). LC solvents were purchased from Burdick and Jackson (Muskegon, MI). Mobile phase A contained 98% water, 2% acetonitrile, and 0.2% formic acid, and mobile phase B consisted of 2% water, 98% acetonitrile, and 0.2% formic acid. Peptides were loaded on the trap column at 2 μl/min before switching in-line with the analytical column at a flow rate of 350 nL/min. The gradient was initiated at 2% B and adjusted to 7% B over the first 5 min. The gradient was then slowly ramped to 40% B over the next 211 min before being adjusted to 95% B over 2 min. The gradient was held at 95% B for 8 min before being adjusted to 2% B over the course of 2 min and was held at 2% B for an additional 10 min for re-equilibration. Mass measurements were made using an LTQ-Orbitrap XL mass spectrometer (Thermo Fisher Scientific, Bremen, Germany) using parameters optimized in a previous study (18Andrews G.L. Dean R.A. Hawkridge A.M. Muddiman D.C. Improving proteome coverage on a LTQ-Orbitrap using design of experiments.J. Am. Soc. Mass Spectrom. 2011; 22: 773-783Crossref PubMed Scopus (48) Google Scholar). A broadband scan using 60,000 resolving power at 400 m/z was collected in profile mode by the Orbitrap mass analyzer, followed by eight data-dependent MS/MS scan events collected in centroid mode in the LTQ using collision-induced dissociation. Charge state screening was enabled, and unassigned, 1+, and ≥4+ charge states were rejected from MS/MS analysis. Dynamic exclusion was also enabled and set to 180 s with a repeat count of 1, a repeat duration of 0 s, and an exclusion list size as large as 500 ions. Automatic gain control settings were 8 × 103 ions for the LTQ and 1 × 106 ions for the Orbitrap. For analysis of the whole cell lysate, 50 μg of protein was loaded onto a gel and separated at a constant 200 V before staining with BioSafe Coomassie stain (BioRad, Hercules, CA). The gel lane was cut into 10 sections which were reduced with dithiothreitol, alkylated with iodoacetamide, and digested with trypsin. Digested peptides were separated using an Eksigent 1D+nano-LC system (Eksigent, Dublin, CA) with a vented column configuration (19Andrews G.L. Shuford C.M. Burnett J.C. Hawkridge A.M. Muddiman D.C. Coupling of a vented column with splitless nanoRPLC-ESI-MS for the improved separation and detection of brain natriuretic peptide-32 and its proteolytic peptides.J. Chromatogr. B. 2009; 877: 948-954Crossref PubMed Scopus (46) Google Scholar). A 15 cm PicoFrit column (New Objective, Woburn, MA) and a 5 cm IntegraFrit trap column (New Objective) were packed in-house with Magic C18AQ stationary phase (5 μm particles, 200 Å pore size) (Microm Biosources, Auburn, CA). Data were acquired with a 7T LTQ-FT-ICR Ultra (Thermo Fisher Scientific, San Jose, CA) mass spectrometer using 100,000FWHM resolving power at 400 m/z. Up to eight data dependent MS/MS scan events were triggered for every precursor scan. RAW data files generated from LC-MS/MS analyses were analyzed using MASCOT Distiller version 2.4.2.0 (Matrix Science, Boston, MA) to create peak lists and subsequently searched using the MASCOT search engine version 2.3.2 (Matrix Science) (20Perkins D.N. Pappin D.J.C. Creasy D.M. Cottrell J.S. Probability-based protein identification by searching sequence databases using mass spectrometry data.Electrophoresis. 1999; 20: 3551-3567Crossref PubMed Scopus (6761) Google Scholar). The parameters used for searching included the variable modifications asparagine and glutamine deamidation, as well as methionine oxidation. Cysteine carbamidomethylation was set as a fixed modification. Trypsin was selected as the protease, and a maximum of two missed cleavages were allowed. Search tolerances were set to ±5 ppm and ±0.6 Da for the precursor ions and product ions, respectively. The SwissProt human database containing 20,255 target sequences (downloaded January 28, 2012) was appended with reverse sequences for use as the target/decoy database. Search results were imported into ProteoIQ version 2.3.05 (NuSep, Athens, GA) to create protein lists filtered using a 1% false discovery rate. Normalized spectral abundance factor (NSAF) values were manually calculated using the raw spectral count data exported from ProteoIQ using the following formula: (NSAF)x=(SpC/L)x∑i=1N(SpC/L)i×(104)(Eq.1)EQ. 1 L = number of amino acids. SpC = total number of MS/MS spectra that identify protein x. Search results were imported into ProteoIQ version 2.3.05 to create protein lists filtered using a 1% false discovery rate to perform spectral counting normalization and relative quantification across hESC samples. All data reported are from three technical replicates for single biological replicates corresponding to MEFs, H1 and H9 hESCs cultured in MEF-CM, and H1 and H9 hESCs exposed to unconditioned hESC medium for 24 h. Gene Ontology (GO) enrichment analysis of identified proteins was carried out using DAVID (21Huang da W. Sherman B.T. Lempicki R.A. Bioinformatics enrichment tools: paths toward the comprehensive functional analysis of large gene lists.Nucleic Acids Res. 2009; 37: 1-13Crossref PubMed Scopus (10263) Google Scholar, 22Huang da W. Sherman B.T. Lempicki R.A. Systematic and integrative analysis of large gene lists using DAVID bioinformatics resources.Nat. Protoc. 2009; 4: 44-57Crossref PubMed Scopus (25331) Google Scholar). Briefly, the DAVID algorithm maps the list of proteins to their GO annotations and outputs a statistical measure of over-representation of various GO terms (22Huang da W. Sherman B.T. Lempicki R.A. Systematic and integrative analysis of large gene lists using DAVID bioinformatics resources.Nat. Protoc. 2009; 4: 44-57Crossref PubMed Scopus (25331) Google Scholar). Lists of proteins annotated to the secretory pathway organelles—namely, the endoplasmic reticulum (GO:0005783), endoplasmic reticulum–Golgi intermediate compartment (GO:0005793), ER to Golgi transport vesicle (GO:0030134), Golgi apparatus (GO:0005794), secretory granule (GO:0030141), transport vesicle (GO:0030133), and ribosome (GO:0005840)—were obtained using the Princeton GO Term Mapper (go.princeton.edu/cgi-bin/GOTermMapper) and repeats were eliminated. Lists of proteins annotated as extracellular, comprising ECM (GO:0031012), extracellular region (GO:0005576), extracellular region part (GO:0044421), extracellular space (GO:0005615), and proteinaceous ECM (GO:0005578), were also obtained using the Princeton GO Term Mapper, and repeats were eliminated. These lists were further curated via comparison with the UniProt database. Proteins annotated as “Secreted” in the UniProt database were retained and denoted as “Secretory Cargo.” To quantify the fractional abundance of a particular subcellular organelle in the whole cell lysate or subcellular fractions isolated using our protocols, we used the method previously described by Gilchrist et al. (10Gilchrist A. Au C.E. Hiding J. Bell A.W. Fernandez-Rodriguez J. Lesimple S. Nagaya H. Roy L. Gosline S.J. Hallett M. Paiement J. Kearney R.E. Nilsson T. Bergeron J.J. Quantitative proteomics analysis of the secretory pathway.Cell. 2006; 127: 1265-1281Abstract Full Text Full Text PDF PubMed Scopus (385) Google Scholar). Briefly, for each sample analyzed, we obtained a list of all nonredundant peptides identified in MS analysis and the corresponding spectral count data. The fractional abundance of peptides associated with a particular organelle i (Fi) in a given sample was estimated as follows: peptides that map to proteins annotated to the specific organelle i were identified, and this set of peptides was denoted by Si. Subsequently, Fi was estimated as Ei=Spectral Counts due to peptides in SiTotal Spectral Counts in MS analysis of the sample(Eq.2)EQ. 2 Fi was used as a metric to quantify the fractional abundance of organelle i in a given sample. Note that Fi accounts for the abundance of all identified peptides associated with a particular organelle. Subsequently, the fold-enrichment of organelle i in subcellular fractions was calculated as Ei=Fi in subcellular fractionFi in whole cell lysate(Eq.3)EQ. 3 The two-tailed Fisher's exact test was used to calculate the p value associated with Ei. A fold-enrichment value greater than 1 indicates that the organelle is enriched in the subcellular fraction isolated. Conversely, a value of Ei less than 1 shows depletion of the organelle during subcellular fractionation. The secretory pathway comprises the ER, the Golgi apparatus, and the associated transport vesicles that transport proteins from ER to Golgi and finally from Golgi to the plasma membrane and the extracellular space. Protocols for the extraction of smooth ER, rough ER, cis-Golgi, trans-Golgi, and the transport vesicles have been worked out (10Gilchrist A. Au C.E. Hiding J. Bell A.W. Fernandez-Rodriguez J. Lesimpl DA - 2012/12// PY - 2012/12// DO - 10.1074/mcp.m112.020503 VL - 11 IS - 12 SP - 1829-1839 SN - 1535-9484 ER - TY - CONF TI - Moisture vapor barrier properties of biopolymers for packaging materials AU - Grewal, R. AU - Sweesy, W. AU - Jur, J. S. AU - Willoughby, J. AB - We present a review of current research focused on the use of biopolymers as viable packaging materials. We discuss polysaccharides, proteins, lipids, materials systems comprising edible coatings, and inorganic surface modification processes as they impact moisture barrier permeability properties. We give an overview of the fundamental factors that affect moisture vapor permeability (MVP), provide an overview of barrier properties for typical packaging materials on a common unit basis, and the MVP improvements made with evolving techniques. We explore some challenges and unknowns with surface modifications specific to altering the barrier properties of polymers derived from renewable resources. We provide some of the future directions in our own work to improve materials with inherently poor moisture vapor properties using the insights from this review as a road map. C2 - 2012/// C3 - Functional materials from renewable sources DA - 2012/// DO - 10.1021/bk-2012-1107.ch015 VL - 1107 SP - 271-296 ER - TY - JOUR TI - Fabrication of Environmentally Biodegradable Lignin Nanoparticles AU - Frangville, Camille AU - Rutkevicius, Marius AU - Richter, Alexander P. AU - Velev, Orlin D. AU - Stoyanov, Simeon D. AU - Paunov, Vesselin N. T2 - CHEMPHYSCHEM AB - Abstract We developed a method for the fabrication of novel biodegradable nanoparticles (NPs) from lignin which are apparently non‐toxic for microalgae and yeast. We compare two alternative methods for the synthesis of lignin NPs which result in particles of very different stability upon change of pH. The first method is based on precipitation of low‐sulfonated lignin from an ethylene glycol solution by using diluted acidic aqueous solutions, which yields lignin NPs that are stable over a wide range of pH. The second approach is based on the acidic precipitation of lignin from a high‐pH aqueous solution which produces NPs stable only at low pH. Our study reveals that lignin NPs from the ethylene glycol‐based precipitation contain densely packed lignin domains which explain the stability of the NPs even at high pH. We characterised the properties of the produced lignin NPs and determined their loading capacities with hydrophilic actives. The results suggest that these NPs are highly porous and consist of smaller lignin domains. Tests with microalgae like Chlamydomonas reinhardtii and yeast incubated in lignin NP dispersions indicated that these NPs lack measurable effect on the viability of these microorganisms. Such biodegradable and environmentally compatible NPs can find applications as drug delivery vehicles, stabilisers of cosmetic and pharmaceutical formulations, or in other areas where they may replace more expensive and potentially toxic nanomaterials. DA - 2012/12/21/ PY - 2012/12/21/ DO - 10.1002/cphc.201200537 VL - 13 IS - 18 SP - 4235-4243 SN - 1439-7641 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84872833784&partnerID=MN8TOARS KW - biodegradable KW - lignin KW - nanoparticles KW - pH dependence KW - porosity ER - TY - JOUR TI - Temperature and Exposure Dependence of Hybrid Organic-Inorganic Layer Formation by Sequential Vapor Infiltration into Polymer Fibers AU - Akyildiz, Halil I. AU - Padbury, Richard P. AU - Parsons, Gregory N. AU - Jur, Jesse S. T2 - LANGMUIR AB - The characteristic processing behavior for growth of a conformal nanoscale hybrid organic–inorganic modification to polyamide 6 (PA6) by sequential vapor infiltration (SVI) is demonstrated. The SVI process is a materials growth technique by which exposure of organometallic vapors to a polymeric material promotes the formation of a hybrid organic–inorganic modification at the near surface region of the polymer. This work investigates the SVI exposure temperature and cycling times of sequential exposures of trimethylaluminum (TMA) on PA6 fiber mats. The result of TMA exposure is the preferential subsurface organic–inorganic growth by diffusion into the polymer and reaction with the carbonyl in PA6. Mass gain, infrared spectroscopy, and transmission electron microscopy analysis indicate enhanced materials growth and uniformity at lower processing temperatures. The inverse relationship between mass gain and exposure temperature is explained by the formation of a hybrid layer that prevents the diffusion of TMA into the polymer to react with the PA6 upon subsequent exposure cycles. As few as 10 SVI exposure cycles are observed to saturate the growth, yielding a modified thickness of ∼75 nm and mass increase of ∼14 wt %. Removal of the inherent PA6 moisture content reduces the mass gain by ∼4 wt % at low temperature exposures. The ability to understand the characteristic growth process is critical for the development of the hybrid materials fabrication and modification techniques. DA - 2012/11/6/ PY - 2012/11/6/ DO - 10.1021/la302991c VL - 28 IS - 44 SP - 15697-15704 SN - 0743-7463 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000310664300032&KeyUID=WOS:000310664300032 ER - TY - JOUR TI - Surface Functionalized Nanofibrillar Cellulose (NFC) Film as a Platform for Immunoassays and Diagnostics AU - Orelma, Hannes AU - Filpponen, Ilari AU - Johansson, Leena-Sisko AU - Osterberg, Monika AU - Rojas, Orlando J. AU - Laine, Janne T2 - BIOINTERPHASES AB - We introduce a new method to modify films of nanofibrillated cellulose (NFC) to produce non-porous, water-resistant substrates for diagnostics. First, water resistant NFC films were prepared from mechanically disintegrated NFC hydrogel, and then their surfaces were carboxylated via TEMPO-mediated oxidation. Next, the topologically functionalized film was activated via EDS/NHS chemistry, and its reactivity verified with bovine serum albumin and antihuman IgG. The surface carboxylation, EDC/NHS activation and the protein attachment were confirmed using quartz crystal microbalance with dissipation, contact angle measurements, conductometric titrations, X-ray photoelectron spectroscopy and fluorescence microscopy. The surface morphology of the prepared films was investigated using confocal laser scanning microscopy and atomic force microscopy. Finally, we demonstrate that antihuman IgG can be immobilized on the activated NFC surface using commercial piezoelectric inkjet printing. DA - 2012/12// PY - 2012/12// DO - 10.1007/s13758-012-0061-7 VL - 7 IS - 1-4 SP - SN - 1559-4106 ER - TY - CONF TI - Solvent-LiBF4 phase diagrams, ionic association and solubility - cyclic carbonates and lactones AU - Allen, J. L. AU - Seo, D. M. AU - Ly, Q. D. AU - Boyle, P. D. AU - Henderson, W. A. C2 - 2012/// C3 - Rechargeable lithium and lithium ion batteries DA - 2012/// VL - 41 SP - 41-45 M1 - 41 ER - TY - CONF TI - Delving into the properties and solution structure of nitrile-lithium difluoro(oxalato)borate (LiDFOB) electrolytes for Li-ion batteries AU - Han, S. D. AU - Allen, J. L. AU - Boyle, P. D. AU - Henderson, W. A. C2 - 2012/// C3 - Rechargeable lithium and lithium ion batteries DA - 2012/// VL - 41 SP - 47-51 M1 - 41 ER - TY - CONF TI - A "Looking Glass" into electrolyte properties: Cyclic carbonate and ester-LiClO4 mixtures AU - Seo, D. M. AU - Afroz, T. AU - Ly, Q. AU - O'Connell, M. AU - Boyle, P. D. AU - Henderson, W. A. C2 - 2012/// C3 - Rechargeable lithium and lithium ion batteries DA - 2012/// VL - 41 SP - 11-15 M1 - 41 ER - TY - JOUR TI - Electrochemical Performance of Carbon Nanofibers Containing an Enhanced Dispersion of Silicon Nanoparticles for Lithium-Ion Batteries by Employing Surfactants AU - Li, Ying AU - Lin, Zhan AU - Xu, Guanjie AU - Yao, Yingfang AU - Zhang, Shu AU - Toprakci, Ozan AU - Alcoutlabi, Mataz AU - Zhang, Xiangwu T2 - ECS ELECTROCHEMISTRY LETTERS AB - Si/C composite nanofibers were prepared by electrospinning and carbonization. Two surfactants: cetyl trimethyl ammonium bromide (CTAB) and sodium dodecanoate (SD), were used to improve the dispersion of Si nanoparticles and the electrochemical performance. Results show that after 50 cycles, the discharge capacity of Si/C nanofibers does not have significant change after the addition of CTAB surfactant, however, the discharge capacity of Si/C nanofibers with SD surfactant is more than 20% higher than that without surfactant. It is demonstrated that employing SD surfactant is a simple and effective way to obtain Si/C nanofibers with large capacities and good cycling stability. DA - 2012/// PY - 2012/// DO - 10.1149/2.002202eel VL - 1 IS - 2 SP - A31-A33 SN - 2162-8734 UR - https://publons.com/publon/674390/ ER - TY - JOUR TI - Ternary Phase Behavior of a Triblock Copolymer in the Presence of an Endblock-Selective Homopolymer and a Midblock-Selective Oil AU - Krishnan, Arjun S. AU - Smith, Steven D. AU - Spontak, Richard J. T2 - MACROMOLECULES AB - Bicomponent block copolymers are known to exhibit rich phase behavior in systems containing one or two block-selective homopolymers or solvents. In this study, we combine these efforts by investigating ternary blends composed of an ABA triblock copolymer, an A-selective homopolymer and a B-selective oil. A styrenic thermoplastic elastomer is selected here because of its ability to form a physical network upon microphase separation and thus impart significant elasticity and toughness to such blends. Synchrotron small-angle X-ray scattering is employed to classify the nanostructures of blends varying in composition, homopolymer molecular weight, and oil type, and the results are used to construct ternary morphology diagrams that reveal the phases present at the glass transition temperature of the styrenic endblocks. Of all the classical and complex morphologies commonly observed in binary copolymer blends and solutions, only the bicontinuous gyroid consisting of styrenic channels in a mixed midblock/oil matrix is consistently absent. Variations in nanostructural dimensions with blend composition are provided for selected morphologies. DA - 2012/8/14/ PY - 2012/8/14/ DO - 10.1021/ma300417u VL - 45 IS - 15 SP - 6056-6067 SN - 1520-5835 ER - TY - JOUR TI - Surface-Bound Gradients for Studies of Soft Materials Behavior AU - Genzer, Jan T2 - ANNUAL REVIEW OF MATERIALS RESEARCH, VOL 42 AB - We provide a succinct account of surface-bound gradient structures created from soft materials or those facilitating the study of soft materials behavior. We commence by classifying the chief attributes of gradient structures and offer a few examples of fabrication methods employed to generate such structures. We then illustrate the versatility of gradient assemblies in functioning as recording media for monitoring a physico-chemical process, facilitating fast screening of physico-chemical phenomena, and playing an important part in the design and fabrication of surface-anchored molecular and macromolecular engines for the directed transport of soft materials. DA - 2012/// PY - 2012/// DO - 10.1146/annurev-matsci-070511-155050 VL - 42 SP - 435-468 SN - 1531-7331 KW - self-assembly KW - grafted polymer KW - polymer brush KW - screening KW - directed motion KW - combinatorial materials science KW - high throughput KW - soft materials ER - TY - JOUR TI - Stable anatase TiO2 coating on quartz fibers by atomic layer deposition for photoactive light-scattering in dye-sensitized solar cells AU - Kim, Do Han AU - Koo, Hyung-Jun AU - Jur, Jesse S. AU - Woodroof, Mariah AU - Kalanyan, Berc AU - Lee, Kyoungmi AU - Devine, Christina K. AU - Parsons, Gregory N. T2 - NANOSCALE AB - Quartz fibers provide a unique high surface-area substrate suitable for conformal coating using atomic layer deposition (ALD), and are compatible with high temperature annealing. This paper shows that the quartz fiber composition stabilizes ALD TiO(2) in the anatase phase through TiO(2)-SiO(2) interface formation, even after annealing at 1050 °C. When integrated into a dye-sensitized solar cell, the TiO(2)-coated quartz fiber mat improves light scattering performance. Results also confirm that annealing at high temperature is necessary for better photoactivity of ALD TiO(2), which highlights the significance of quartz fibers as a substrate. The ALD TiO(2) coating on quartz fibers also boosts dye adsorption and photocurrent response, pushing the overall efficiency of the dye-cells from 6.5 to 7.4%. The mechanisms for improved cell performance are confirmed using wavelength-dependent incident photon to current efficiency and diffuse light scattering results. The combination of ALD and thermal processing on quartz fibers may enable other device structures for energy conversion and catalytic reaction applications. DA - 2012/// PY - 2012/// DO - 10.1039/c2nr30939d VL - 4 IS - 15 SP - 4731-4738 SN - 2040-3372 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000306324000056&KeyUID=WOS:000306324000056 ER - TY - JOUR TI - ReaxFF molecular dynamics simulation of thermal stability of a Cu3(BTC)2 metal–organic framework AU - Huang, Liangliang AU - Joshi, Kaushik L. AU - Duin, Adri C. T. van AU - Bandosz, Teresa J. AU - Gubbins, Keith E. T2 - Physical Chemistry Chemical Physics AB - The thermal stability of a dehydrated Cu(3)(BTC)(2) (copper(II) benzene 1,3,5-tricarboxylate) metal-organic framework was studied by molecular dynamics simulation with a ReaxFF reactive force field. The results show that Cu(3)(BTC)(2) is thermally stable up to 565 K. When the temperature increases between 600 K and 700 K, the framework starts to partially collapse. The RDF analysis shows that the long range correlations between Cu dimers disappear, indicating the loss of the main channels of Cu(3)(BTC)(2). When the temperature is above 800 K, we find the decomposition of the Cu(3)(BTC)(2) framework. CO is the major product, and we also observe the release of CO(2), O(2), 1,3,5-benzenetricarboxylate (C(6)H(3)(CO(2))(3), BTC) and glassy carbon. The Cu dimer is stable up to 1100 K, but we find the formation of new copper oxide clusters at 1100 K. These results are consistent with experimental findings, and provide valuable information for future theoretical investigations of Cu(3)(BTC)(2) and its application in adsorption, separation and catalytic processes. DA - 2012/// PY - 2012/// DO - 10.1039/c2cp41511a VL - 14 IS - 32 SP - 11327 J2 - Phys. Chem. Chem. Phys. LA - en OP - SN - 1463-9076 1463-9084 UR - http://dx.doi.org/10.1039/C2CP41511A DB - Crossref ER - TY - JOUR TI - Oil Spills Abatement: Factors Affecting Oil Uptake by Cellulosic Fibers AU - Payne, Katharine C. AU - Jackson, Colby D. AU - Aizpurua, Carlos E. AU - Rojas, Orlando J. AU - Hubbe, Martin A. T2 - ENVIRONMENTAL SCIENCE & TECHNOLOGY AB - Wood-derived cellulosic fibers prepared in different ways were successfully employed to absorb simulated crude oil, demonstrating their possible use as absorbents in the case of oil spills. When dry fibers were used, the highest sorption capacity (six parts of oil per unit mass of fiber) was shown by bleached softwood kraft fibers, compared to hardwood bleached kraft and softwood chemithermomechanical pulp(CTMP) fibers. Increased refining of CTMP fibers decreased their oil uptake capacity. When the fibers were soaked in water before exposure to the oil, the ability of the unmodified kraft fibers to sorb oil was markedly reduced, whereas the wet CTMP fibers were generally more effective than the wet kraft fibers. Predeposition of lignin onto the surfaces of the bleached kraft fibers improved their ability to take up oil when wet. Superior ability to sorb oil in the wet state was achieved by pretreating the kraft fibers with a hydrophobic sizing agent, alkenylsuccinic anhydride (ASA). Contact angle tests on a model cellulose surface showed that some of the sorption results onto wetted fibers could be attributed to the more hydrophobic nature of the fibers after treatment with either lignin or ASA. DA - 2012/7/17/ PY - 2012/7/17/ DO - 10.1021/es3015524 VL - 46 IS - 14 SP - 7725-7730 SN - 1520-5851 ER - TY - JOUR TI - Mesoporous Metal Oxides by Vapor Infiltration and Atomic Layer Deposition on Ordered Surfactant Polymer Films AU - Gong, Bo AU - Kim, Do Han AU - Parsons, Gregory N. T2 - LANGMUIR AB - Catalysis, chemical separations, and energy conversion devices often depend on well-defined mesoporous materials as supports or active component elements. Herein, we show that ordered assembled organic surfactant films can directly template porous inorganic solids with surface area exceeding 1000 m(2)/g by infusing the polymers with reactive inorganic vapors, followed by anneal. The specific surface area, pore size, chemical composition, and overall shape of the product material are tuned by choice of the polymer and precursor materials as well as the influsion and postinfusion treatment conditions. X-ray diffraction, infrared spectroscopy, and electron microscopy show that vapor infusion changes both the physical and chemical structure of the starting ordered polymer films, consistent with quantified trends in specific surface area and pore size distribution measured by nitrogen adsorption after film annealing. This method yields porous TiO(2) films, for example, that function as an anode layer in a dye-sensitized solar cell. DA - 2012/8/14/ PY - 2012/8/14/ DO - 10.1021/la302027b VL - 28 IS - 32 SP - 11915-11922 SN - 0743-7463 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000307479000029&KeyUID=WOS:000307479000029 ER - TY - JOUR TI - Li+ cation coordination by acetonitrile-insights from crystallography AU - Seo, Daniel M. AU - Boyle, Paul D. AU - Borodin, Oleg AU - Henderson, Wesley A. T2 - RSC ADVANCES AB - Solvation is a critical factor for determining the properties of electrolytes and lithium reagents, but only limited information is available about the coordination number for Li+ cations in solution with different solvents. The present manuscript examines the manner in which acetonitrile (AN) fully solvates Li+ cations. The results are also likely pertinent to other nitrile and dinitrile solvents. In particular, the crystal structure for a (AN)6:LiPF6 solvate is reported—this is the first 6/1 AN/Li solvate structure to be determined. The structure consists of Li+ cations fully solvated by four AN molecules (i.e., [(AN)4Li]+ species), uncoordinated PF6− anions and uncoordinated AN molecules (two per Li+ cation). This structure validates, in part, density functional theory (DFT) calculations which predict that there is little to no energetic benefit to coordinating Li+ cations with more than four AN solvent molecules. DA - 2012/// PY - 2012/// DO - 10.1039/c2ra21290k VL - 2 IS - 21 SP - 8014-8019 SN - 2046-2069 ER - TY - JOUR TI - Influence of temperature on formation of perfect tau fragment fibrils using PRIME20/DMD simulations AU - Cheon, Mookyung AU - Chang, Iksoo AU - Hall, Carol K. T2 - PROTEIN SCIENCE AB - We investigate the fibrillization process for amyloid tau fragment peptides (VQIVYK) by applying the discontinuous molecular dynamics method to a system of 48 VQIVYK peptides modeled using a new protein model/force field, PRIME20. The aim of the article is to ascertain which factors are most important in determining whether or not a peptide system forms perfect coherent fibrillar structures. Two different directional criteria are used to determine when a hydrogen bond occurs: the original H-bond constraints and a parallel preference H-bond constraint that imparts a slight bias towards the formation of parallel versus antiparallel strands in a β-sheet. Under the original H-bond constraints, the resulting fibrillar structures contain a mixture of parallel and antiparallel pairs of strands within each β-sheet over the whole fibrillization temperature range. Under the parallel preference H-bond constraints, the β-sheets within the fibrillar structures are more likely to be parallel and indeed become perfectly parallel, consistent with X-ray crystallography, at a high temperature slightly below the fibrillization temperature. The high temperature environment encourages the formation of perfect fibril structures by providing enough time and space for peptides to rearrange during the aggregation process. There are two different kinetic mechanisms, template assembly with monomer addition at high temperature and merging/rearrangement without monomer addition at low temperature, which lead to significant differences in the final fibrillar structure. This suggests that the diverse fibril morphologies generally observed in vitro depend more on environmental conditions than has heretofore been appreciated. DA - 2012/10// PY - 2012/10// DO - 10.1002/pro.2141 VL - 21 IS - 10 SP - 1514-1527 SN - 1469-896X KW - amyloid tau-fragment KW - protein aggregation KW - steric-zipper interface KW - coarse-grained model KW - discontinuous molecular dynamics ER - TY - JOUR TI - Increasing the electrochemically available active sites for heat-treated hemin catalysts supported on carbon black AU - Jiang, R. Z. AU - Tran, D. T. AU - McClure, J. P. AU - Chu, D. T2 - Electrochimica Acta DA - 2012/// PY - 2012/// VL - 75 SP - 185-190 ER - TY - JOUR TI - High-capacity Li2Mn0.8Fe0.2SiO4/carbon composite nanofiber cathodes for lithium-ion batteries AU - Zhang, Shu AU - Li, Ying AU - Xu, Guanjie AU - Li, Shuli AU - Lu, Yao AU - Toprakci, Ozan AU - Zhang, Xiangwu T2 - JOURNAL OF POWER SOURCES AB - Li2MnSiO4 has been considered as a promising cathode material with an extremely high theoretically capacity of 332 mAh g−1. However, due to its low intrinsic conductivity and poor structural stability, only about half of the theoretical capacity has been realized in practice and the capacity decays rapidly during cycling. To realize the high capacity and improve the cycling performance, Li2Mn0.8Fe0.2SiO4/carbon composite nanofibers were prepared by the combination of iron doping and electrospinning. X-ray diffraction, scanning electron microscope, and transmission electronic microscope were applied to characterize the Li2Mn0.8Fe0.2SiO4/carbon nanofibers. It was found that Li2Mn0.8Fe0.2SiO4 nanoparticles were embedded into continuous carbon nanofiber matrices, which formed free-standing porous mats that could be used as binder-free cathodes. The iron doping improved the conductivity and purity of the active material, and the carbon nanofiber matrix facilitated ion transfer and charge diffusion. As a result, Li2Mn0.8Fe0.2SiO4/carbon nanofiber cathodes showed promising improvement on reversible capacity and cycling performance. DA - 2012/9/1/ PY - 2012/9/1/ DO - 10.1016/j.jpowsour.2012.04.011 VL - 213 SP - 10-15 SN - 1873-2755 UR - https://publons.com/publon/674394/ KW - Li2MnSiO4 KW - Iron doping KW - Cathode KW - Electrospinning KW - Carbon nanofibers ER - TY - JOUR TI - Epimerase (Msed_0639) and Mutase (Msed_0638 and Msed_2055) Convert (S)-Methylmalonyl-Coenzyme A (CoA) to Succinyl-CoA in the Metallosphaera sedula 3-Hydroxypropionate/4-Hydroxybutyrate Cycle AU - Han, Yejun AU - Hawkins, Aaron S. AU - Adams, Michael W. W. AU - Kelly, Robert M. T2 - APPLIED AND ENVIRONMENTAL MICROBIOLOGY AB - ABSTRACT Crenarchaeotal genomes encode the 3-hydroxypropionate/4-hydroxybutyrate (3-HP/4-HB) cycle for carbon dioxide fixation. Of the 13 enzymes putatively comprising the cycle, several of them, including methylmalonyl-coenzyme A (CoA) epimerase (MCE) and methylmalonyl-CoA mutase (MCM), which convert ( S )-methylmalonyl-CoA to succinyl-CoA, have not been confirmed and characterized biochemically. In the genome of Metallosphaera sedula (optimal temperature [ T opt ], 73°C), the gene encoding MCE (Msed_0639) is adjacent to that encoding the catalytic subunit of MCM-α (Msed_0638), while the gene for the coenzyme B 12 -binding subunit of MCM (MCM-β) is located remotely (Msed_2055). The expression of all three genes was significantly upregulated under autotrophic compared to heterotrophic growth conditions, implying a role in CO 2 fixation. Recombinant forms of MCE and MCM were produced in Escherichia coli ; soluble, active MCM was produced only if MCM-α and MCM-β were coexpressed. MCE is a homodimer and MCM is a heterotetramer (α 2 β 2 ) with specific activities of 218 and 2.2 μmol/min/mg, respectively, at 75°C. The heterotetrameric MCM differs from the homo- or heterodimeric orthologs in other organisms. MCE was activated by divalent cations (Ni 2+ , Co 2+ , and Mg 2+ ), and the predicted metal binding/active sites were identified through sequence alignments with less-thermophilic MCEs. The conserved coenzyme B 12 -binding motif ( DXHXXG -SXL-GG) was identified in M. sedula MCM-β. The two enzymes together catalyzed the two-step conversion of ( S )-methylmalonyl-CoA to succinyl-CoA, consistent with their proposed role in the 3-HP/4-HB cycle. Based on the highly conserved occurrence of single copies of MCE and MCM in Sulfolobaceae genomes, the M. sedula enzymes are likely to be representatives of these enzymes in the 3-HP/4-HB cycle in crenarchaeal thermoacidophiles. DA - 2012/9// PY - 2012/9// DO - 10.1128/aem.01312-12 VL - 78 IS - 17 SP - 6194-6202 SN - 1098-5336 ER - TY - JOUR TI - Engineering nanomedicines using stimuli-responsive biomaterials AU - Wang, Yapei AU - Byrne, James D. AU - Napier, Mary E. AU - DeSimone, Joseph M. T2 - ADVANCED DRUG DELIVERY REVIEWS AB - The ability to engineer particles has the potential to shift the paradigm in the creation of new medicines and diagnostics. Complete control over particle characteristics, such as size, shape, mechanical property, and surface chemistry, can enable rapid translation and facilitate the US Food and Drug Administration (FDA) approval of particle technologies for the treatment of cancer, infectious diseases, diabetes, and a host of other major illnesses. The incorporation of natural and artificial external stimuli to trigger the release of drugs enables exquisite control over the release profiles of drugs in a given environment. In this article, we examine several readily scalable top–down methods for the fabrication of shape-specific particles that utilize stimuli-responsive biomaterials for controlled drug delivery. Special attention is given to Particle Replication In Nonwetting Templates (PRINT®) technology and the application of novel triggered-release synthetic and natural polymers. DA - 2012/8// PY - 2012/8// DO - 10.1016/j.addr.2012.01.003 VL - 64 IS - 11 SP - 1021-1030 SN - 1872-8294 KW - Top-down KW - Trigger-release KW - Microfluidic KW - Photolithography KW - PRINT ER - TY - JOUR TI - Diffusivity Maximum in a Reentrant Nematic Phase AU - Stieger, Tillmann AU - Mazza, Marco G. AU - Schoen, Martin T2 - INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES AB - We report molecular dynamics simulations of confined liquid crystals using the Gay-Berne-Kihara model. Upon isobaric cooling, the standard sequence of isotropic-nematic-smectic A phase transitions is found. Upon further cooling a reentrant nematic phase occurs. We investigate the temperature dependence of the self-diffusion coefficient of the fluid in the nematic, smectic and reentrant nematic phases. We find a maximum in diffusivity upon isobaric cooling. Diffusion increases dramatically in the reentrant phase due to the high orientational molecular order. As the temperature is lowered, the diffusion coefficient follows an Arrhenius behavior. The activation energy of the reentrant phase is found in reasonable agreement with the reported experimental data. We discuss how repulsive interactions may be the underlying mechanism that could explain the occurrence of reentrant nematic behavior for polar and non-polar molecules. DA - 2012/6// PY - 2012/6// DO - 10.3390/ijms13067854 VL - 13 IS - 6 SP - 7854-7871 SN - 1422-0067 KW - reentrant phase KW - nematic KW - dynamics KW - diffusion ER - TY - JOUR TI - Transport properties of proton- and hydroxide-exchange membranes for fuel cells AU - Wang, Xuhai AU - McClure, Joshua P. AU - Fedkiw, Peter S. T2 - ELECTROCHIMICA ACTA AB - The electro-osmotic drag coefficients (ξ) of water-vapor equilibrated Nafion® 117, a proton conductor, and Tokuyama® A201, a hydroxide conductor were determined from the steady-state voltage of a water concentration cell. The ξ values are reported, along with water uptake, ion-exchange capacity, ionic conductivity, and methanol permeability of these membranes. The room-temperature ξ of Nafion® 117 and Tokuyama® A201 is 0.99 (±0.07) and 0.61 (±0.12), respectively, and is relatively independent of water content over the relative humidity range of 14–96%. The time to steady potential in the water concentration cell was longer for the Tokuyama® A201 membrane than the Nafion® 117 membrane, which is tentatively attributed to the lower mobility of hydrated hydroxide (or carbonate from absorption of adventitious carbon dioxide) in comparison to hydronium ion. DA - 2012/9/30/ PY - 2012/9/30/ DO - 10.1016/j.electacta.2012.06.098 VL - 79 SP - 126-132 SN - 0013-4686 KW - Electro-osmotic drag coefficient KW - Concentration cell KW - Anion exchange membrane KW - Proton exchange membrane ER - TY - JOUR TI - The effect of pH on gel structures produced using protein-polysaccharide phase separation and network inversion AU - Cakir, Esra AU - Khan, Saad A. AU - Foegeding, E. Allen T2 - INTERNATIONAL DAIRY JOURNAL AB - Forming heat-induced gels through combined effects of micro-phase separation of whey protein isolate (WPI; 5%, w/v, 100 mm NaCl) by pH change (5.5, 6.0, and 6.5), and addition of κ-carrageenan (0–0.3%, w/w), were evaluated. The microstructure of WPI gels was homogeneous at pH 6.0 and 6.5 and micro-phase separated at pH 5.5. Addition of 0.075% κ-carrageenan to WPI solutions caused the microstructure of the gel to switch from homogeneous (pH 6.0 and 6.5) to micro-phase separated; and higher concentrations led to inversion of the continuous network from protein to κ-carrageenan. Protein solutions containing 0.075% (w/w) κ-carrageenan produced gels with increased storage modulus (G′) at pH 6.5 and decreased G′ at pH 5.5. All gels containing 0.3% (w/w) κ-carrageenan had κ-carrageenan-continuous networks. It was shown that microstructural and rheological changes were different in WPI and κ-carrageenan mixed gels when micro-phase separation was caused by pH rather than ionic strength. DA - 2012/12// PY - 2012/12// DO - 10.1016/j.idairyj.2012.03.013 VL - 27 IS - 1-2 SP - 99-102 SN - 0958-6946 ER - TY - JOUR TI - Templating Quantum Dot to Phase-Transformed Electrospun TiO2 Nanofibers for Enhanced Photo-Excited Electron Injection AU - Aykut, Yakup AU - Saquing, Carl D. AU - Pourdeyhimi, Behnam AU - Parsons, Gregory N. AU - Khan, Saad A. T2 - ACS APPLIED MATERIALS & INTERFACES AB - We report on the microstructural crystal phase transformation of electrospun TiO2 nanofibers generated via sol–gel electrospinning technique, and the incorporation of as-synthesized CdSe quantum dots (QDs) to different phases of TiO2 nanofibers (NFs) via bifunctional surface modification. The effect of different phases of TiO2 on photo-excited electron injection from CdSe QDs to TiO2 NFs, as measured by photoluminescence spectroscopy (PL) is also discussed. Nanofiber diameter and crystal structures are dramatically affected by different calcination temperatures due to removal of polymer carrier, conversion of ceramic precursor into ceramic nanofibers, and formation of different TiO2 phases in the fibers. At a low calcination temperature of 400 oC only anatase TiO2 nanofiber are obtained; with increasing calcination temperature (up to 500 oC) these anatase crystals became larger. Crystal transformation from the anatase to the rutile phase is observed above 500oC, with most of the crystals transforming into the rutile phase at 800oC. Bi-functional surface modification of calcined TiO2 nanofibers with 3-mercaptopropionic acid (3-MPA) is used to incorporate as-synthesized CdSe QD nanoparticles on to TiO2 nanofibers. Evidence of formation of CdSe/TiO2 composite nanofibers is obtained from elemental analysis using Energy Dispersive X-ray spectroscopy (EDS) and TEM microscopy that reveal templated quantum dots on TiO2 nanofibers. Photoluminescence emission intensities increase considerably with the addition of QDs to all TiO2 nanofiber samples, with fibers containing small amount of rutile crystals with anatase crystals showing the most enhanced effect. DA - 2012/8// PY - 2012/8// DO - 10.1021/am300524a VL - 4 IS - 8 SP - 3837-3845 SN - 1944-8252 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000307698600011&KeyUID=WOS:000307698600011 KW - quantum dot KW - sol-gel electrospinning KW - nanofibers KW - photoluminescence ER - TY - JOUR TI - Stochastic dynamics of membrane protrusion mediated by the DOCK180/Rac pathway in migrating cells (vol 3, pg 30, 2010) AU - Welf, E. S. AU - Haugh, J. M. T2 - Cellular and Molecular Bioengineering DA - 2012/// PY - 2012/// VL - 5 IS - 4 SP - 514-516 ER - TY - JOUR TI - Oxygen Reduction on Metal-Free Nitrogen-Doped Carbon Nanowall Electrodes AU - McClure, Joshua P. AU - Thornton, Jackson D. AU - Jiang, Rongzhong AU - Chu, Deryn AU - Cuomo, Jerome J. AU - Fedkiw, Peter S. T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - A plasma-enhanced chemical vapor deposition (PECVD) process using a CH4:H2 gas mixture creates vertically aligned carbon nanowalls (CNWs) on glassy carbon (GC) and Si substrates. Metal catalysts are not required for the nucleation and growth of CNWs on the substrates. The PECVD deposition temperatures and reaction times alter the morphology and thickness of the resulting CNW layer. A low-pressure, post-processing N2:Ar plasma treatment dopes the CNWs with nitrogen, and X-ray photoelectron spectroscopy measurements demonstrate that nitrogen is present at 4–20 atomic% with varying CNx bonding configurations dependent upon processing conditions. Raman spectroscopy shows relatively high intensity disorder bands (ID) compared to lower intensity graphitic bands (IG) indicating small crystalline domains. Rotating disk electrode voltammetry results show that the number of electrons (n) and kinetic current density (jk) of the oxygen reduction reaction both increase with nitrogen content. In addition, n and jk increase with thickness of the nitrogen-containing CNW deposit. The results indicate that nitrogen-doped CNWs have higher electrochemical reactivity than their non-doped counterparts. DA - 2012/// PY - 2012/// DO - 10.1149/2.056211jes VL - 159 IS - 11 SP - F733-F742 SN - 1945-7111 ER - TY - JOUR TI - On-chip latex agglutination immunoassay readout by electrochemical impedance spectroscopy AU - Gupta, S. AU - Kilpatrick, P.K. AU - Melvin, E. AU - Velev, Orlin T2 - Lab on a Chip - Miniaturisation for Chemistry and Biology AB - We describe a new class of impedance-based lab-on-chip immunosensors in which the immunoagglutination of latex is monitored by electrochemical impedance spectroscopy (EIS). Antibody-coated latex microspheres agglutinated in the presence of target antigens are precipitated from solution between interdigitated microsized electrodes on a chip. Impedance spectra are reproducibly measured in the 0.1-1 MHz frequency range within several minutes and are shown to be dependent on the aggregate morphology and the sedimentation rates of the agglutinated particles. An equivalent circuit model of the system suggests that the impedance is governed primarily by the electric double layer interactions close to the electrode surface. The effects of sedimentation time, particle type, particle size, and concentration are characterized. The readout method holds promise for developing sensitive miniaturized sensors for rapid immunotesting. DA - 2012/// PY - 2012/// DO - 10.1039/c2lc40127d VL - 12 IS - 21 SP - 4279-4286 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84867289203&partnerID=MN8TOARS ER - TY - JOUR TI - Low Modulus Biomimetic Microgel Particles with High Loading of Hemoglobin AU - Chen, Kai AU - Merkel, Timothy J. AU - Pandya, Ashish AU - Napier, Mary E. AU - Luft, J. Christopher AU - Daniel, Will AU - Sheiko, Sergei AU - DeSimone, Joseph M. T2 - BIOMACROMOLECULES AB - We synthesized extremely deformable red blood cell-like microgel particles and loaded them with bovine hemoglobin (Hb) to potentiate oxygen transport. With similar shape and size as red blood cells (RBCs), the particles were fabricated using the PRINT (particle replication in nonwetting templates) technique. Low cross-linking of the hydrogel resulted in very low mesh density for these particles, allowing passive diffusion of hemoglobin throughout the particles. Hb was secured in the particles through covalent conjugation of the lysine groups of Hb to carboxyl groups in the particles via EDC/NHS coupling. Confocal microscopy of particles bound to fluorescent dye-labeled Hb confirmed the uniform distribution of Hb throughout the particle interior, as opposed to the surface conjugation only. High loading ratios, up to 5 times the amount of Hb to polymer by weight, were obtained without a significant effect on particle stability and shape, though particle diameter decreased slightly with Hb conjugation. Analysis of the protein by circular dichroism (CD) spectroscopy showed that the secondary structure of Hb was unperturbed by conjugation to the particles. Methemoglobin in the particles could be maintained at a low level and the loaded Hb could still bind oxygen, as studied by UV–vis spectroscopy. Hb-loaded particles with moderate loading ratios demonstrated excellent deformability in microfluidic devices, easily deforming to pass through restricted pores half as wide as the diameter of the particles. The suspension of concentrated particles with a Hb concentration of 5.2 g/dL showed comparable viscosity to that of mouse blood, and the particles remained intact even after being sheared at a constant high rate (1000 1/s) for 10 min. Armed with the ability to control size, shape, deformability, and loading of Hb into RBC mimics, we will discuss the implications for artificial blood. DA - 2012/9// PY - 2012/9// DO - 10.1021/bm3007242 VL - 13 IS - 9 SP - 2748-2759 SN - 1526-4602 ER - TY - JOUR TI - Generic Method for Attaching Biomolecules via Avidin-Biotin Complexes Immobilized on Films of Regenerated and Nanofibrillar Cellulose AU - Orelma, Hannes AU - Johansson, Leena-sisko AU - Filpponen, Ilari AU - Rojas, Orlando J. AU - Laine, Janne T2 - BIOMACROMOLECULES AB - We investigated the adsorption and chemical conjugation of avidin and its deglycosylated form, neutravidin, on films of regenerated and nanofibrillar cellulose. The dynamics and extent of biomolecular attachment were monitored in situ by quartz crystal microbalance microgravimetry and ex situ via surface analyses with atomic force microscopy and X-ray photoelectron spectroscopy. The installation of carboxyl groups on cellulose after modification with carboxymethylated cellulose (CMC) or TEMPO-oxidation significantly increases physisorption of avidins, which can be then covalently conjugated by using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride/N-hydroxysuccinimide (EDS/NHS) coupling chemistries. The developed cellulose–avidin biointerfaces are able to scavenge biotinylated molecules from solution as demonstrated by successful surface complexation of biotinylated bovine serum albumin (Biotin-BSA) and antihuman immunoglobulin G (Biotin-anti-hIgG). Finally, we show that cellulose substrates carrying immobilized anti-hIgG are effective in detecting human immunoglobulin G (hIgG) from fluid matrices. DA - 2012/9// PY - 2012/9// DO - 10.1021/bm300781k VL - 13 IS - 9 SP - 2802-2810 SN - 1526-4602 ER - TY - JOUR TI - Electrolyte Solvation and Ionic Association II. Acetonitrile-Lithium Salt Mixtures: Highly Dissociated Salts AU - Seo, Daniel M. AU - Borodin, Oleg AU - Han, Sang-Don AU - Boyle, Paul D. AU - Henderson, Wesley A. T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - The electrolyte solution structure for acetonitrile (AN)-lithium salt mixtures has been examined for highly dissociated salts. Phase diagrams are reported for (AN)n-LiN(SO2CF3)2 (LiTFSI) and -LiPF6 electrolytes. Single crystal structures and Raman spectroscopy have been utilized to provide information regarding the solvate species present in the solid-state and liquid phases, as well as the average solvation number variation with salt concentration. Molecular dynamics (MD) simulations of the mixtures have been correlated with the experimental data to provide additional insight into the molecular-level interactions. Quantum chemistry (QC) calculations were performed on (AN)n-Li-(anion)m clusters to validate the ability of the developed many-body polarizable force field (used for the simulations) to accurately describe cluster stability (ionic association). The combination of these techniques provides tremendous insight into the solution structure within these electrolyte mixtures. DA - 2012/// PY - 2012/// DO - 10.1149/2.035209jes VL - 159 IS - 9 SP - A1489-A1500 SN - 1945-7111 ER - TY - JOUR TI - Designing Energy-Storage Devices from Textile Materials AU - Zhang, Xiangwu AU - Ji, Liwen AU - Lin, Zhan AU - Li, Ying AU - Shao, JH AU - Fan, QG T2 - ECO-DYEING, FINISHING AND GREEN CHEMISTRY AB - Research and development in textiles have gone beyond the conventional applications as clothing and furnishing materials; for example, the convergence of textiles, nanotechnologies, and energy science opens up the opportunity to take on one of the major challenges in the 21st century energy. This presentation addresses the development of high-energy lithium-ion batteries using electrospun nanofibers. DA - 2012/// PY - 2012/// DO - 10.4028/www.scientific.net/amr.441.231 VL - 441 SP - 231-234 SN - 1022-6680 UR - https://publons.com/publon/6540103/ KW - Fibers KW - Electrospinning KW - Energy Storage KW - Lithium-Ion Battery ER - TY - JOUR TI - Design and demonstration of a novel micro-Coulter counter utilizing liquid metal electrodes AU - Richards, A. L. AU - Dickey, M. D. AU - Kennedy, A. S. AU - Buckner, G. D. T2 - JOURNAL OF MICROMECHANICS AND MICROENGINEERING AB - This paper describes the design and demonstration of a novel, easily fabricated micro-Coulter counter utilizing liquid metal electrodes. Fluid and electrode channels were fabricated simultaneously in a single lithographic patterning step. Eutectic gallium–indium (EGaIn) was injected into the device to form functional electrodes in a cross-channel parallel configuration. Functionality of the device was demonstrated at an ac excitation frequency of 5 kHz using a polymer microsphere suspension and simple post-processing techniques. The device successfully detected particles, exhibiting an output response proportional to particle size. EGaIn was demonstrated to be an effective micro-fluidic electrode material and provided a novel approach for the fabrication of a functional micro-Coulter counter. DA - 2012/11// PY - 2012/11// DO - 10.1088/0960-1317/22/11/115012 VL - 22 IS - 11 SP - SN - 0960-1317 ER - TY - JOUR TI - Clustering and mobility of hard rods in a quasicrystalline substrate potential AU - Kaehlitz, Philipp AU - Schoen, Martin AU - Stark, Holger T2 - JOURNAL OF CHEMICAL PHYSICS AB - Recently, we have studied the self-assembly of hard needles in a quasicrystalline substrate potential with decagonal symmetry [P. Kählitz and H. Stark, J. Chem. Phys. 136, 174705 (2012)10.1063/1.4711086]. We have identified new structure formation using Monte Carlo simulations. However, hard needles have a zero width. To investigate how the excluded volume of rod-shaped particles influences their phase ordering, we extend here our studies to spherocylinders. We determine phase diagrams and plot them in the relevant variables, strength of substrate potential versus area fraction. At increasing area fraction η short rods form clusters that ultimately destroy directional ordering along the decagonal symmetry directions while surface-induced positional order exists for all η. In contrast, long rods show directional order in the whole density range. However, at high area fractions they assemble into compact clusters which destroy positional ordering. Finally, we also study the rod mobility using the kinetic Monte Carlo method and discuss an unexpected mobility enhancement with increasing density. All these features crucially depend on the non-zero excluded volume of the spherocylinders. DA - 2012/12/14/ PY - 2012/12/14/ DO - 10.1063/1.4769839 VL - 137 IS - 22 SP - SN - 0021-9606 ER - TY - JOUR TI - A study of the production and reversible stability of EGaIn liquid metal microspheres using flow focusing AU - Thelen, Jacob AU - Dickey, Michael D. AU - Ward, Thomas T2 - LAB ON A CHIP AB - This manuscript describes an experimental study of the production of micro-scale droplets of the room-temperature liquid alloy eutectic gallium indium (EGaIn) formed using a microfluidic flow-focusing device. The EGaIn surface oxidizes readily to form a passivating oxide “skin” that imparts some mechanical stability to the resulting microspheres, but does not appear to affect the dynamics of droplet formation. EGaIn has an interfacial tension nearly an order of magnitude larger than typical water-in-oil systems that are used to study droplet production in microfluidic flow-focusing devices. The size of the microdroplets increase as the ratio of the flow rates of the dispersed and continuous-phase increase for both EGaIn-in-glycerol and water-in-oil systems; however, these fluid pairs form droplets through different dispersing modes at otherwise identical flow conditions (i.e., flow rate ratios and capillary numbers). Consequently, the EGaIn droplets are larger than the water droplets. The difference in dispersing modes and droplet size are attributed to the relatively larger interfacial and inertial forces of the EGaIn system compared to the water-in-oil system. The addition of polyvinyl alcohol (PVA), which is known to bind to oxide surfaces, to the continuous phase yields stable, monodisperse emulsions of liquid metal. These emulsions can be destabilized on demand by changing the solution pH, allowing the liquid metal to be recovered. The ability of the PVA to bind to the liquid metal also influences droplet production by changing the shape of the liquid as it approaches the orifice of the flow focusing device, which results in droplets with smaller diameters relative to those formed without PVA. DA - 2012/// PY - 2012/// DO - 10.1039/c2lc40492c VL - 12 IS - 20 SP - 3961-3967 SN - 1473-0197 ER - TY - JOUR TI - Synthesis of cross-linked, partially neutralized poly(acrylic acid) by suspension polymerization in supercritical carbon dioxide AU - Hussain, Y. A. AU - Liu, T. AU - Roberts, G. W. T2 - Industrial & Engineering Chemistry Research DA - 2012/// PY - 2012/// VL - 51 IS - 35 SP - 11401-11408 ER - TY - JOUR TI - Heat-treated hemin supported on graphene nanoplatelets for the oxygen reduction reaction AU - Jiang, R. Z. AU - Tran, D. T. AU - McClure, J. AU - Chu, D. T2 - Electrochemistry Communications DA - 2012/// PY - 2012/// VL - 19 SP - 73-76 ER - TY - JOUR TI - Effect of residual lignin and heteropolysaccharides in nanofibrillar cellulose and nanopaper from wood fibers AU - Ferrer, Ana AU - Quintana, Elisabet AU - Filpponen, Ilari AU - Solala, Iina AU - Vidal, Teresa AU - Rodriguez, Alejandro AU - Laine, Janne AU - Rojas, Orlando J. T2 - CELLULOSE DA - 2012/12// PY - 2012/12// DO - 10.1007/s10570-012-9788-z VL - 19 IS - 6 SP - 2179-2193 SN - 1572-882X KW - Nanofibrillated cellulose (NFC) KW - Nanopaper KW - Birch fibers KW - NFC films KW - Heteropolysaccharides KW - Hemicellulose KW - Water interactions KW - Mechanical properties KW - Mechanoradicals KW - Water interactions KW - Nanopaper strength KW - Microfluidization ER - TY - JOUR TI - A versatile method for preparation of hydrated microbial-latex biocatalytic coatings for gas absorption and gas evolution AU - Gosse, Jimmy L. AU - Chinn, Mari S. AU - Grunden, Amy M. AU - Bernal, Oscar I. AU - Jenkins, Jessica S. AU - Yeager, Chris AU - Kosourov, Sergey AU - Seibert, Michael AU - Flickinger, Michael C. T2 - JOURNAL OF INDUSTRIAL MICROBIOLOGY & BIOTECHNOLOGY AB - Abstract We describe a latex wet coalescence method for gas-phase immobilization of microorganisms on paper which does not require drying for adhesion. This method reduces drying stresses to the microbes. It is applicable for microorganisms that do not tolerate desiccation stress during latex drying even in the presence of carbohydrates. Small surface area, 10–65 μm thick coatings were generated on chromatography paper strips and placed in the head-space of vertical sealed tubes containing liquid to hydrate the paper. These gas-phase microbial coatings hydrated by liquid in the paper pore space demonstrated absorption or evolution of H2, CO, CO2 or O2. The microbial products produced, ethanol and acetate, diffuse into the hydrated paper pores and accumulate in the liquid at the bottom of the tube. The paper provides hydration to the back side of the coating and also separates the biocatalyst from the products. Coating reactivity was demonstrated for Chlamydomonas reinhardtii CC124, which consumed CO2 and produced 10.2 ± 0.2 mmol O2 m−2 h−1, Rhodopseudomonas palustris CGA009, which consumed acetate and produced 0.47 ± 0.04 mmol H2 m−2 h−1, Clostridium ljungdahlii OTA1, which consumed 6 mmol CO m−2 h−1, and Synechococcus sp. PCC7002, which consumed CO2 and produced 5.00 ± 0.25 mmol O2 m−2 h−1. Coating thickness and microstructure were related to microbe size as determined by digital micrometry, profilometry, and confocal microscopy. The immobilization of different microorganisms in thin adhesive films in the gas phase demonstrates the utility of this method for evaluating genetically optimized microorganisms for gas absorption and gas evolution. DA - 2012/9// PY - 2012/9// DO - 10.1007/s10295-012-1135-8 VL - 39 IS - 9 SP - 1269-1278 SN - 1476-5535 KW - Latex coating immobilization on chromatography paper KW - Chlamydomonas KW - Rhodopseudomonas KW - Clostridium KW - Synechococcus ER - TY - JOUR TI - Valorization of residual Empty Palm Fruit Bunch Fibers (EPFBF) by microfluidization: Production of nanofibrillated cellulose and EPFBF nanopaper AU - Ferrer, Ana AU - Filpponen, Ilari AU - Rodriguez, Alejandro AU - Laine, Janne AU - Rojas, Orlando J. T2 - BIORESOURCE TECHNOLOGY AB - Different cellulose pulps were produced from sulfur-free chemical treatments of Empty Palm Fruit Bunch Fibers (EPFBF), a by-product from palm oil processing. The pulps were microfluidized for deconstruction into nanofibrillated cellulose (NFC) and nanopaper was manufactured by using an overpressure device. The morphological and structural features of the obtained NFCs were characterized via atomic force and scanning electron microscopies. The physical properties as well as the interactions with water of sheets from three different pulps were compared with those of nanopaper obtained from the corresponding NFC. Distinctive chemical and morphological characteristics and ensuing nanopaper properties were generated by the EPFBF fibers. The NFC grades obtained compared favorably with associated materials typically produced from bleached wood fibers. Lower water absorption, higher tensile strengths (107–137 MPa) and elastic modulus (12–18 GPa) were measured, which opens the possibility for valorization of such widely available bioresource. DA - 2012/12// PY - 2012/12// DO - 10.1016/j.biortech.2012.08.108 VL - 125 SP - 249-255 SN - 1873-2976 KW - Empty Palm Fruit Bunch Fibers (EPFBF) KW - Nanofibrillated cellulose (NFC) KW - Film strength KW - Water interactions KW - Nanopaper ER - TY - JOUR TI - Uranium extremophily is an adaptive, rather than intrinsic, feature for extremely thermoacidophilic Metallosphaera species AU - Mukherjee, Arpan AU - Wheaton, Garrett H. AU - Blum, Paul H. AU - Kelly, Robert M. T2 - PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA AB - Thermoacidophilic archaea are found in heavy metal-rich environments, and, in some cases, these microorganisms are causative agents of metal mobilization through cellular processes related to their bioenergetics. Given the nature of their habitats, these microorganisms must deal with the potentially toxic effect of heavy metals. Here, we show that two thermoacidophilic Metallosphaera species with nearly identical (99.99%) genomes differed significantly in their sensitivity and reactivity to uranium (U). Metallosphaera prunae, isolated from a smoldering heap on a uranium mine in Thüringen, Germany, could be viewed as a "spontaneous mutant" of Metallosphaera sedula, an isolate from Pisciarelli Solfatara near Naples. Metallosphaera prunae tolerated triuranium octaoxide (U(3)O(8)) and soluble uranium [U(VI)] to a much greater extent than M. sedula. Within 15 min following exposure to "U(VI) shock," M. sedula, and not M. prunae, exhibited transcriptomic features associated with severe stress response. Furthermore, within 15 min post-U(VI) shock, M. prunae, and not M. sedula, showed evidence of substantial degradation of cellular RNA, suggesting that transcriptional and translational processes were aborted as a dynamic mechanism for resisting U toxicity; by 60 min post-U(VI) shock, RNA integrity in M. prunae recovered, and known modes for heavy metal resistance were activated. In addition, M. sedula rapidly oxidized solid U(3)O(8) to soluble U(VI) for bioenergetic purposes, a chemolithoautotrophic feature not previously reported. M. prunae, however, did not solubilize solid U(3)O(8) to any significant extent, thereby not exacerbating U(VI) toxicity. These results point to uranium extremophily as an adaptive, rather than intrinsic, feature for Metallosphaera species, driven by environmental factors. DA - 2012/10/9/ PY - 2012/10/9/ DO - 10.1073/pnas.1210904109 VL - 109 IS - 41 SP - 16702-16707 SN - 0027-8424 KW - uranium oxidation KW - uranium resistance KW - chemolithotrophy KW - terminal oxidases ER - TY - JOUR TI - The effect of confinement on thermal frontal polymerization AU - Datta, Preeta AU - Efimenko, Kirill AU - Genzer, Jan T2 - POLYMER CHEMISTRY AB - In thermal frontal polymerization, the interplay between heat diffusion and Arrhenius type reaction kinetics gives rise to a propagating reactive front that is effectively sustained through a system positive feedback mechanism. We seek to understand how spatial confinement affects the system dynamics and overall polymerization kinetics. We find that with increasing confinement of the system, the front propagation velocity decreases and the nearly “parabolic” front profile flattens out. While in bulk or unconfined systems the convective heat and mass transfer effects are responsible for higher heat generation rates and higher temperature gradients, leading to faster front propagation, the convection is significantly suppressed in highly confined systems. Consequently, a smaller number of radicals are generated, resulting in a slower propagation step and long polymer chains. DA - 2012/12// PY - 2012/12// DO - 10.1039/c2py20640d VL - 3 IS - 12 SP - 3243-3246 SN - 1759-9954 ER - TY - JOUR TI - Systemic Perturbation of the ERK Signaling Pathway by the Proteasome Inhibitor, MG132 AU - Cirit, Murat AU - Grant, Kyle G. AU - Haugh, Jason M. T2 - PLOS ONE AB - Inhibition of the ubiquitin-proteasome protein degradation pathway has been identified as a viable strategy for anti-tumor therapy based on its broad effects on cell proliferation. By the same token, the variety of elicited effects confounds the interpretation of cell-based experiments using proteasome inhibitors such as MG132. It has been proposed that MG132 treatment reduces growth factor-stimulated phosphorylation of extracellular signal-regulated kinases (ERKs), at least in part through upregulation of dual specificity phosphatases (DUSPs). Here, we show that the effects of MG132 treatment on ERK signaling are more widespread, leading to a reduction in activation of the upstream kinase MEK. This suggests that MG132 systemically perturbs the intracellular phosphoproteome, impacting ERK signaling by reducing phosphorylation status at multiple levels of the kinase cascade. DA - 2012/11/30/ PY - 2012/11/30/ DO - 10.1371/journal.pone.0050975 VL - 7 IS - 11 SP - SN - 1932-6203 ER - TY - JOUR TI - Modeling the influence of slurry concentration on Saccharomyces cerevisiae cake porosity and resistance during microfiltration AU - Mota, Manuel AU - Flickinger, Michael C. T2 - BIOTECHNOLOGY PROGRESS AB - Abstract Filtration of an isotonic suspension of baker's yeast through a 0.45‐μm membrane was studied at two different pressures, 40 and 80 kPa, for yeast concentrations ranging from 0.14 to 51 kg/m 3 (dry weight). For a yeast volume fraction above 0.06 (∼21.8 kg/m 3 ), the porosity of the yeast cake is less dependent on the suspension concentration. For highly diluted suspensions, the specific cake resistance approaches a minimum that depends on the filtration pressure. Correlation functions of cake porosity and specific cake resistance were obtained for the concentration range investigated showing that the Kozeny–Carman coefficient increases when the applied pressure increases. Both filtration pressure and slurry concentration can be process controlled. In the range of moderate yeast concentration, the filtrate flux may be increased by manipulating the filtration pressure and the slurry concentration, thereby improving the overall process efficiency. The complex behavior of yeast cakes at high slurry concentration can be described by a conventional model as long as part of yeast cells are assumed to form aggregates, which behave as single bigger particles. The aggregation effect may be accounted for using a binary mixture model. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012 DA - 2012/// PY - 2012/// DO - 10.1002/btpr.1636 VL - 28 IS - 6 SP - 1534-1541 SN - 8756-7938 KW - microfiltration KW - cake resistance KW - concentration KW - yeast KW - porosity ER - TY - JOUR TI - Microfluidic elastomer composites with switchable vis-IR transmittance AU - Ucar, A. B. AU - Velev, O. D. T2 - Soft Matter DA - 2012/// PY - 2012/// VL - 8 IS - 44 SP - 11232-11235 ER - TY - JOUR TI - LiF/Fe/C nanofibres as a high-capacity cathode material for Li-ion batteries AU - Zhang, Shu AU - Lu, Yao AU - Xu, Guanjie AU - Li, Ying AU - Zhang, Xiangwu T2 - JOURNAL OF PHYSICS D-APPLIED PHYSICS AB - Abstract LiF/Fe/C composite nanofibres with different morphologies were prepared by electrospinning and heat treatment of LiF/ferrocene/polyacrylonitrile (PAN) precursors. X-ray diffraction and scanning electron microscopy were employed to study the structural variations of these composite nanofibres. It was found that Fe nanoparticles and carbon nanofibres were obtained from the thermal decomposition of ferrocene and PAN precursors, respectively. The electrochemical performance was evaluated using the prepared composite nanofibres as the cathode material in lithium half-cells. With uniformly embedded active particles in the carbon nanofibre matrix, the resultant cathode materials presented highly reversible discharge capacities of over 472 mA h g −1 . DA - 2012/10/3/ PY - 2012/10/3/ DO - 10.1088/0022-3727/45/39/395301 VL - 45 IS - 39 SP - SN - 1361-6463 UR - https://publons.com/publon/7178351/ ER - TY - JOUR TI - Imprinting substrate structures onto a nematic liquid crystal AU - Greschek, Manuel AU - Gubbins, Keith E. AU - Schoen, Martin T2 - JOURNAL OF CHEMICAL PHYSICS AB - By means of Monte Carlo simulations in the grand canonical ensemble we study the morphology of the nematic phase of a simple model liquid crystal interacting with an alternating sequence of chemically different stripes. The stripes anchor molecules such that their orientation is either parallel or perpendicular with the substrate plane. The different molecular orientations are realized through anchoring functions that cause an energetic penalty for molecules oriented in an undesired fashion. We consider combinations of monostable and degenerate anchoring fields. The nature of the nematic phase is characterized through both the local nematic order parameter and the associated local director field. We observe states of uniaxial or biaxial symmetry depending on the ratio of stripe widths and the range of fluid-substrate attraction. In some cases the specific substrate pattern causes regions of biaxial symmetry to coexist with a bulk-like regime sufficiently far away from the substrates in which the local director field indicates a (homogeneous) bent state of the nematic liquid crystal. DA - 2012/10/14/ PY - 2012/10/14/ DO - 10.1063/1.4757391 VL - 137 IS - 14 SP - SN - 1089-7690 KW - molecular orientation KW - Monte Carlo methods KW - nematic liquid crystals ER - TY - JOUR TI - Design of pH Sensitive Binding Proteins from the Hyperthermophilic Sso7d Scaffold AU - Gera, Nimish AU - Hill, Andrew B. AU - White, Dalon P. AU - Carbonell, Ruben G. AU - Rao, Balaji M. T2 - PLOS ONE AB - We have engineered pH sensitive binding proteins for the Fc portion of human immunoglobulin G (hIgG) (hFc) using two different strategies - histidine scanning and random mutagenesis. We obtained an hFc-binding protein, Sso7d-hFc, through mutagenesis of the Sso7d protein from the hyperthermophilic archaeon Sulfolobus solfataricus; Sso7d-hFc was isolated from a combinatorial library of Sso7d mutants using yeast surface display. Subsequently, we identified a pH sensitive mutant, Sso7d-his-hFc, through systematic evaluation of Sso7d-hFc mutants containing single histidine substitutions. In parallel, we also developed a yeast display screening strategy to isolate a different pH sensitive hFc binder, Sso7d-ev-hFc, from a library of mutants obtained by random mutagenesis of a pool of hFc binders. In contrast to Sso7d-hFc, both Sso7d-his-hFc and Sso7d-ev-hFc have a higher binding affinity for hFc at pH 7.4 than at pH 4.5. The Sso7d-mutant hFc binders can be recombinantly expressed at high yield in E. coli and are monomeric in solution. They bind an epitope in the CH3 domain of hFc that has high sequence homology in all four hIgG isotypes (hIgG(1-4)), and recognize hIgG(1-4) as well as deglycosylated hIgG in western blotting assays. pH sensitive hFc binders are attractive candidates for use in chromatography, to achieve elution of IgG under milder pH conditions. However, the surface density of immobilized hFc binders, as well as the avidity effect arising from the multivalent interaction of dimeric hFc with the capture surface, influences the pH dependence of dissociation from the capture surface. Therefore, further studies are needed to evaluate if the Sso7d mutants identified in this study are indeed useful as affinity ligands in chromatography. DA - 2012/11/7/ PY - 2012/11/7/ DO - 10.1371/journal.pone.0048928 VL - 7 IS - 11 SP - SN - 1932-6203 ER - TY - JOUR TI - Crystal structure of the ionic liquid EtNH3NO3-Insights into the thermal phase behavior of protic ionic liquids AU - Henderson, W. A. AU - Fylstra, P. AU - De Long, H. C. AU - Trulove, P. C. AU - Parsons, S. T2 - Physical Chemistry Chemical Physics DA - 2012/// PY - 2012/// VL - 14 IS - 46 SP - 16041-16046 ER - TY - JOUR TI - The Role of the Distal Histidine in H2O2 Activation and Heme Protection in both Peroxidase and Globin Functions AU - Zhao, Junjie AU - Serrano, Vesna AU - Dumarieh, Rania AU - Thompson, Matt AU - Ghiladi, Reza A. AU - Franzen, Stefan T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - The distal histidine mutations of dehaloperoxidase-hemoglobin A (DHP A) to aspartate (H55D) and asparagine (H55N) have been prepared to study the role played by the distal histidine in both activation and protection against oxidation by radicals in heme proteins. The H55D and H55N mutants of DHP A have ∼6-fold and ∼11-fold lower peroxidase activities than wild type enzyme toward the oxidation of 2,4,6-trichlorophenol (TCP) to yield 2,6-dichloroquinone (DCQ) in the presence of H2O2. The origin of the lower rate constants may be the solvent-exposed conformations of distal D55 and N55, which would have the dual effect of destabilizing the binding of H2O2 to the heme iron, and of removing the acid–base catalyst necessary for the heterolytic O–O bond cleavage of heme-bound H2O2 (i.e., compound 0). The partial peroxidase activity of H55D can be explained if one considers that there are two conformations of the distal aspartate (open and closed) by analogy with the distal histidine. We hypothesize that the distal aspartate has an active conformation in the distal pocket (closed). Although the open form is observed in the low-temperature X-ray crystal structure of ferric H55D, the closed form is observed in the FTIR spectrum of the carbonmonoxy form of the H55D mutant. Consistent with this model, the H55D mutant also shows inhibition of TCP oxidation by 4-bromophenol (4-BP). Consistent with the protection hypothesis, compound ES, the tyrosyl radical-containing ferryl intermediate observed in WT DHP A, was not observed in H55D. DA - 2012/10/11/ PY - 2012/10/11/ DO - 10.1021/jp300014b VL - 116 IS - 40 SP - 12065-12077 SN - 1520-5207 ER - TY - JOUR TI - Reconfigurable liquid metal circuits by Laplace pressure shaping AU - Cumby, Brad L. AU - Hayes, Gerard J. AU - Dickey, Michael D. AU - Justice, Ryan S. AU - Tabor, Christopher E. AU - Heikenfeld, Jason C. T2 - APPLIED PHYSICS LETTERS AB - We report reconfigurable circuits formed by liquid metal shaping with &lt;10 pounds per square inch (psi) Laplace and vacuum pressures. Laplace pressure drives liquid metals into microreplicated trenches, and upon release of vacuum, the liquid metal dewets into droplets that are compacted to 10–100× less area than when in the channel. Experimental validation includes measurements of actuation speeds exceeding 30 cm/s, simple erasable resistive networks, and switchable 4.5 GHz antennas. Such capability may be of value for next generation of simple electronic switches, tunable antennas, adaptive reflectors, and switchable metamaterials. DA - 2012/10/22/ PY - 2012/10/22/ DO - 10.1063/1.4764020 VL - 101 IS - 17 SP - SN - 1077-3118 ER - TY - JOUR TI - Purification of human immunoglobulins A, G and M from Cohn fraction II/III by small peptide affinity chromatography AU - Liu, Zhuo AU - Gurgel, Patrick V. AU - Carbonell, Ruben G. T2 - JOURNAL OF CHROMATOGRAPHY A AB - This work describes attempts to purify human IgG, IgA and IgM from Cohn fraction II/III using HWRGWV affinity peptide resin. The effects of peptide density and different elution additives on recovery of the three antibodies were investigated. At low peptide density, salting-in salts such as magnesium chloride and calcium chloride facilitated antibody elution. Ethylene glycol, urea and arginine also facilitated elution because of their ability to decrease hydrophobic interactions, hydrogen bonding and electrostatic interactions. However, at high peptide density, no recovery improvements were observed because of increased non-specific hydrophobic interactions. The final elution conditions for each antibody were chosen based on the resulting yields and purities when a 10:2:1 mg/mL mixture of human IgG, IgA and IgM was used as starting material. Different pretreatment methods were employed in order to improve the purity of antibodies from Cohn fraction II/III. After pretreatment with caprylic acid precipitation or combination of caprylic acid and polyethylene glycol precipitation, purities over 95% and yields of about 60% were obtained for hIgG, which are comparable to current chromatographic purification methods involving two chromatography steps when hIgG is isolated from plasma fractions. A hIgA-enriched fraction with 42% hIgA and 56% hIgG, as well as a hIgM enriched fraction with 46% hIgM, 28% hIgA and 24% hIgG, were obtained as the by-products. DA - 2012/11/2/ PY - 2012/11/2/ DO - 10.1016/j.chroma.2012.09.026 VL - 1262 SP - 169-179 SN - 1873-3778 KW - Hexamer peptide KW - IVIG KW - Cohn fraction KW - Elution additive KW - PEG KW - Ammonium sulfate ER - TY - JOUR TI - Process for purification of monoclonal antibody expressed in transgenic Lemna plant extract using dextran-coated charcoal and hexamer peptide affinity resin AU - Naik, A. D. AU - Menegatti, S. AU - Reese, H. R. AU - Gurgel, P. V. AU - Carbonell, R. G. T2 - Journal of Chromatography A AB - The production of therapeutic proteins using transgenic plants offers several advantages, including low production cost, absence of human pathogens, presence of glycosylation mechanisms, and the ability to fold complex therapeutic proteins into their proper conformation. However, impurities such as phenolic compounds and pigments encountered during purification are quite different from those faced during purification from mammalian cell culture supernatants. This paper deals with the development of a pretreatment and affinity separation process for the purification of a monoclonal antibody from transgenic Lemna plant extract. A pretreatment step is described using dextran-coated charcoal for the removal of pigments and phenolic compounds without reducing the antibody concentration. Then, the peptide affinity ligand HWRGWV coupled to a commercial polymethacrylate resin is used for the capture and purification of MAb from the pretreated plant extract. The final yield and purity of the MAb obtained were 90% and 96% respectively. The performance of the hexamer peptide resin after the pretreatment step was found to be similar to that obtained with a commercial Protein A resin. DA - 2012/// PY - 2012/// DO - 10.1016/j.chroma.2012.08.043 VL - 1260 SP - 61–66 KW - Dextran-coated charcoal KW - Transgenic plants KW - Hexapeptide ligand KW - IgG purification KW - Monoclonal antibody KW - Phenolics KW - Lemna minor ER - TY - JOUR TI - Piezoelectric Effect of Cellulose Nanocrystals Thin Films AU - Csoka, Levente AU - Hoeger, Ingrid C. AU - Rojas, Orlando J. AU - Peszlen, Ilona AU - Pawlak, Joel J. AU - Peralta, Perry N. T2 - ACS MACRO LETTERS AB - Ultrathin films of aligned cellulose nanocrystals (CNCs) were assembled on mica supports by using electric field-assisted shear. The relationship between polarization gradients and strain mechanics of the obtained films was examined by monitoring their deflection with an atomic force microscope operated in contact mode. The piezoelectric response of the films was ascribed to the collective contribution of the asymmetric crystalline structure of the cellulose crystals. The magnitude of the effective shear piezoelectric constant (d25) of highly ordered CNC films was determined to be 2.1 Å/V, which is comparable to that of a reference film of a piezoelectric metal oxide. DA - 2012/7// PY - 2012/7// DO - 10.1021/mz300234a VL - 1 IS - 7 SP - 867-870 SN - 2161-1653 ER - TY - JOUR TI - PEGylated PRINT Nanoparticles: The Impact of PEG Density on Protein Binding, Macrophage Association, Biodistribution, and Pharmacokinetics AU - Perry, Jillian L. AU - Reuter, Kevin G. AU - Kai, Marc P. AU - Herlihy, Kevin P. AU - Jones, Stephen W. AU - Luft, J. Chris AU - Napier, Mary AU - Bear, James E. AU - DeSimone, Joseph M. T2 - NANO LETTERS AB - In this account, we varied PEGylation density on the surface of hydrogel PRINT nanoparticles and systematically observed the effects on protein adsorption, macrophage uptake, and circulation time. Interestingly, the density of PEGylation necessary to promote a long-circulating particle was dramatically less than what has been previously reported. Overall, our methodology provides a rapid screening technique to predict particle behavior in vivo and our results deliver further insight to what PEG density is necessary to facilitate long-circulation. DA - 2012/10// PY - 2012/10// DO - 10.1021/nl302638g VL - 12 IS - 10 SP - 5304-5310 SN - 1530-6992 KW - PRINT KW - nanoparticle KW - PEGylation KW - protein adsorption KW - macrophage association KW - pharmacokinetics ER - TY - JOUR TI - In Situ TEM Study of Lithiation Behavior of Silicon Nanoparticles Attached to and Embedded in a Carbon Matrix AU - Gu, Meng AU - Li, Ying AU - Li, Xiaolin AU - Hu, Shenyang AU - Zhang, Xiangwu AU - Xu, Wu AU - Thevuthasan, Suntharampillai AU - Baer, Donald R. AU - Zhang, Ji-Guang AU - Liu, Jun AU - Wang, Chongmin T2 - ACS NANO AB - Rational design of silicon and carbon nanocomposite with a special topological feature has been demonstrated to be a feasible way for mitigating the capacity fading associated with the large volume change of silicon anode in lithium ion batteries. Although the lithiation behavior of silicon and carbon as individual components has been well understood, lithium ion transport behavior across a network of silicon and carbon is still lacking. In this paper, we probe the lithiation behavior of silicon nanoparticles attached to and embedded in a carbon nanofiber using in situ TEM and continuum mechanical calculation. We found that aggregated silicon nanoparticles show contact flattening upon initial lithiation, which is characteristically analogous to the classic sintering of powder particles by a neck-growth mechanism. As compared with the surface-attached silicon particles, particles embedded in the carbon matrix show delayed lithiation. Depending on the strength of the carbon matrix, lithiation of the embedded silicon nanoparticles can lead to the fracture of the carbon fiber. These observations provide insights on lithium ion transport in the network-structured composite of silicon and carbon and ultimately provide fundamental guidance for mitigating the failure of batteries due to the large volume change of silicon anodes. DA - 2012/9// PY - 2012/9// DO - 10.1021/nn303312m VL - 6 IS - 9 SP - 8439-8447 SN - 1936-086X UR - https://publons.com/publon/7178349/ KW - Si nanoparticle KW - carbon fiber KW - Li-ion battery KW - in situ TEM KW - lithiation KW - fracture ER - TY - JOUR TI - Exploring formation pathways of aromatic compounds in laboratory-based model flames of aliphatic fuels AU - Hansen, N. AU - Miller, J. A. AU - Klippenstein, S. J. AU - Westmoreland, P. R. AU - Kohse-Hoeinghaus, K. T2 - COMBUSTION EXPLOSION AND SHOCK WAVES DA - 2012/9// PY - 2012/9// DO - 10.1134/s0010508212050024 VL - 48 IS - 5 SP - 508-515 SN - 1573-8345 KW - formation of polycyclic aromatic hydrocarbons and soot KW - resonance-stabilized free radicals KW - hydrocarbon flames KW - identification of species in flames KW - molecular-beam mass spectrometry KW - photoionization by vacuum ultraviolet ER - TY - JOUR TI - Electromechanical instabilities of thermoplastics: Theory and in situ observation AU - Wang, Qiming AU - Niu, Xiaofan AU - Pei, Qibing AU - Dickey, Michael D. AU - Zhao, Xuanhe T2 - APPLIED PHYSICS LETTERS AB - Thermoplastics under voltages are used in diverse applications ranging from insulating cables to organic capacitors. Electromechanical instabilities have been proposed as a mechanism that causes electrical breakdown of thermoplastics. However, existing experiments cannot provide direct observations of the instability process, and existing theories for the instabilities generally assume thermoplastics are mechanically unconstrained. Here, we report in situ observations of electromechanical instabilities in various thermoplastics. A theory is formulated for electromechanical instabilities of thermoplastics under different mechanical constraints. We find that the instabilities generally occur in thermoplastics when temperature is above their glass transition temperatures and electric field reaches a critical value. The critical electric field for the instabilities scales with square root of yield stress of the thermoplastic and depends on its Young's modulus and hardening property. DA - 2012/10/1/ PY - 2012/10/1/ DO - 10.1063/1.4757867 VL - 101 IS - 14 SP - SN - 1077-3118 ER - TY - JOUR TI - Directed inorganic modification of bi-component polymer fibers by selective vapor reaction and atomic layer deposition AU - Gong, Bo AU - Spagnola, Joseph C. AU - Arvidson, Sara A. AU - Khan, Saad A. AU - Parsons, Gregory N. T2 - POLYMER AB - Abstract Nanocomposite organic/inorganic materials with spatially-controlled composition can be formed using vapor-phase atomic layer deposition (ALD) on bi-component polymer fibers. The ALD process promotes selective precursor infusion into the inner core of a core/shell polymer fiber, yielding nanoparticles encapsulated within the core. Likewise, choosing alternate precursors or reaction conditions yield particles or films on the outer polymer shell. In-situ infrared spectroscopy and transmission electron microscopy show that infusion yields selective dispersion of aluminum oxide in different polymer regions, forming fine nanoparticle dispersions or films. Selective inclusion of metal oxide materials during atomic layer deposition on polymers can create unique organic/inorganic composite structures for many advanced uses. DA - 2012/9/28/ PY - 2012/9/28/ DO - 10.1016/j.polymer.2012.08.018 VL - 53 IS - 21 SP - 4631-4636 SN - 1873-2291 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000309377400009&KeyUID=WOS:000309377400009 KW - Atomic layer deposition KW - Bi-component fibers KW - Vapor infiltration ER - TY - JOUR TI - Determining the Polydispersity in Chemical Composition and Monomer Sequence Distribution in Random Copolymers Prepared by Postpolymerization Modification of Homopolymers AU - Powers, Wayne AU - Ryu, Chang Y. AU - Jhon, Young K. AU - Strickland, Lawrence A. AU - Hall, Carol K. AU - Genzer, Jan T2 - ACS MACRO LETTERS AB - We report on establishing the polydispersity in chemical composition (PCC) and polydispersity in monomer sequence distribution (PMSD) in random copolymers of poly(styrene-co-4-bromostyrene) (PBrxS), where x = (0.385 ± 0.035) is the mole fraction of the 4-bromostyrene units (4-BrS), prepared by electrophilic substitution of bromine in the para-position of the phenyl ring of the parent polystyrene. Upon fixing the total number of repeating units, we tune the distribution of styrene and 4-BrS segments in PBrxS by carrying out the bromination reaction on polystyrene homopolymers in different solvents. While PBrxS with relatively random comonomer distribution is prepared in 1-chlorodecane, random-blocky sequences of 4-BrS in PBrxS are achieved by carrying out the bromination reaction in 1-chlorododecane. The PCC in both copolymers is established by fractionating both polymers using interaction chromatography (IC) and determining the chemical composition of the individual fractions by neutron activation analysis (NAA). The NAA data along with IC experiments reveal that the random-blocky sample possesses a narrowed PCC relative to a specimen with a more random comonomer sequence distribution. The full width at half-maximum (fwhm) in the chemical composition profile from IC is used to quantify PCC; the random mother sample possessed a 25% fwhm, while the random blocky mother sample has a fwhm equal to 8.7%. The change in the adsorption enthalpy per brominated segment due to adsorption is determined to be ≈1.5 times greater for the random-blocky than the relatively random sample, proving that more pronounced cooperative adsorption occurs in the case of the random-blocky sample relative to the random copolymer sample. Computer simulation employing the discontinuous molecular dynamic scheme further reveals that the distribution of comonomer sequences, that is, PMSD, in the random-blocky copolymer is narrower than that in the copolymer with a random distribution of both monomers. DA - 2012/9// PY - 2012/9// DO - 10.1021/mz300386g VL - 1 IS - 9 SP - 1128-1133 SN - 2161-1653 ER - TY - JOUR TI - Concerted Reactions and Mechanism of Glucose Pyrolysis and Implications for Cellulose Kinetics AU - Seshadri, Vikram AU - Westmoreland, Phillip R. T2 - The Journal of Physical Chemistry A AB - Concerted reactions are proposed to be keys to understanding thermal decomposition of glucose in the absence of ionic chemistry, including molecular catalysis by ROH molecules such as H2O, other glucose molecules, and most of the intermediates and products. Concerted transition states, elementary-reaction pathways, and rate coefficients are computed for pyrolysis of β-d-glucose (β-d-glucopyranose), the monomer of cellulose, and for related molecules, giving an improved and elementary-reaction interpretation of the reaction network proposed by Sanders et al. (J. Anal. Appl. Pyrolysis, 2003, 66, 29–50). Reactions for ring-opening and formation, ring contraction, retro-aldol condensation, keto–enol tautomerization, and dehydration are included. The dehydration reactions are focused on bicyclic ring formations that lead to levoglucosan and 1,6-β-d-anhydrousglucofuranose. The bimolecular ROH-assisted reactions are found to have lower activation energy compared to the unimolecular reactions. The same dehydration reaction to levoglucosan should occur for cellulose going to cellosan (e.g., cellotriosan) plus a shortened cellulose chain, a hypothesis supported by the very similar activation energies computed when alternate groups were substituted at the C1 glycosidic oxygen. The principles of Sanders et al. that distinguish d-glucose, d-fructose, sucrose, and cellulose pyrolysis prove useful in providing qualitative insights into cellulose pyrolysis. DA - 2012/11/9/ PY - 2012/11/9/ DO - 10.1021/jp3085099 VL - 116 IS - 49 SP - 11997-12013 J2 - J. Phys. Chem. A LA - en OP - SN - 1089-5639 1520-5215 UR - http://dx.doi.org/10.1021/jp3085099 DB - Crossref ER - TY - JOUR TI - Co-assembly of oppositely charged particles into linear clusters and chains of controllable length AU - Bharti, B. AU - Findenegg, G.H. AU - Velev, Orlin T2 - Scientific Reports AB - Colloidal particles with strongly attractive interactions snap on contact and form permanent, but disordered aggregates. In contrast, AC electric fields allow directional assembly of chains or crystals from repulsive particles by dielectrophoresis (DEP), but these structures fall apart once the field is switched off. We demonstrate how well-organized, permanent clusters and chains of micron-sized particles can be assembled by applying DEP to mixtures of oppositely charged microspheres. We found that the length of the formed chains depends on size ratio as well as the number ratio of the two species and formulated a statistical model for this assembly mechanism, which is in excellent agreement with the experimental results. The assembly rules resulting from this study form a basis for tailoring new classes of permanent supracolloidal clusters and gels. DA - 2012/// PY - 2012/// DO - 10.1038/srep01004 VL - 2 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84871752021&partnerID=MN8TOARS ER - TY - JOUR TI - Caldicellulosiruptor Core and Pangenomes Reveal Determinants for Noncellulosomal Thermophilic Deconstruction of Plant Biomass AU - Blumer-Schuette, Sara E. AU - Giannone, Richard J. AU - Zurawski, Jeffrey V. AU - Ozdemir, Inci AU - Ma, Qin AU - Yin, Yanbin AU - Xu, Ying AU - Kataeva, Irina AU - Poole, Farris L., II AU - Adams, Michael W. W. AU - Hamilton-Brehm, Scott D. AU - Elkins, James G. AU - Larimer, Frank W. AU - Land, Miriam L. AU - Hauser, Loren J. AU - Cottingham, Robert W. AU - Hettich, Robert L. AU - Kelly, Robert M. T2 - JOURNAL OF BACTERIOLOGY AB - Extremely thermophilic bacteria of the genus Caldicellulosiruptor utilize carbohydrate components of plant cell walls, including cellulose and hemicellulose, facilitated by a diverse set of glycoside hydrolases (GHs). From a biofuel perspective, this capability is crucial for deconstruction of plant biomass into fermentable sugars. While all species from the genus grow on xylan and acid-pretreated switchgrass, growth on crystalline cellulose is variable. The basis for this variability was examined using microbiological, genomic, and proteomic analyses of eight globally diverse Caldicellulosiruptor species. The open Caldicellulosiruptor pangenome (4,009 open reading frames [ORFs]) encodes 106 GHs, representing 43 GH families, but only 26 GHs from 17 families are included in the core (noncellulosic) genome (1,543 ORFs). Differentiating the strongly cellulolytic Caldicellulosiruptor species from the others is a specific genomic locus that encodes multidomain cellulases from GH families 9 and 48, which are associated with cellulose-binding modules. This locus also encodes a novel adhesin associated with type IV pili, which was identified in the exoproteome bound to crystalline cellulose. Taking into account the core genomes, pangenomes, and individual genomes, the ancestral Caldicellulosiruptor was likely cellulolytic and evolved, in some cases, into species that lost the ability to degrade crystalline cellulose while maintaining the capacity to hydrolyze amorphous cellulose and hemicellulose. DA - 2012/8// PY - 2012/8// DO - 10.1128/jb.00266-12 VL - 194 IS - 15 SP - 4015-4028 SN - 1098-5530 ER - TY - JOUR TI - Bicomponent Lignocellulose Thin Films to Study the Role of Surface Lignin in Cellulolytic Reactions AU - Hoeger, Ingrid C. AU - Filpponen, Ilari AU - Martin-Sampedro, Raquel AU - Johansson, Leena-Sisko AU - Osterberg, Monika AU - Laine, Janne AU - Kelley, Stephen AU - Rojas, Orlando J. T2 - BIOMACROMOLECULES AB - Ultrathin bicomponent films of cellulose and lignin derivatives were deposited on silica supports by spin coating, and after conversion into the respective polymer precursor, they were used as a model system to investigate interfacial phenomena relevant to lignocellulose biocatalysis. Film morphology, surface chemical composition, and wettability were determined by atomic force microscopy, X-ray photoelectron spectroscopy, and water contact angle, respectively. Phase separation of cellulose and lignin produced structures that resembled the cell wall of fibers and were used to monitor enzyme binding and cellulolytic reactions via quartz crystal microgravimetry. The rate and extent of hydrolysis was quantified by using kinetic models that indicated the role of the surface lignin domains in enzyme inhibition. Hydrophobic interactions between cellulases and the substrates and their critical role on irreversible adsorption were elucidated by using acetylated lignin films with different degrees of substitution. Overall, it is concluded that sensors based on the proposed ultrathin films of lignocellulose can facilitate a better understanding of the complex events that occur during bioconversion of cellulosic biomass. DA - 2012/10// PY - 2012/10// DO - 10.1021/bm301001q VL - 13 IS - 10 SP - 3228-3240 SN - 1526-4602 ER - TY - JOUR TI - Applications of surface-grafted macromolecules derived from post-polymerization modification reactions AU - Galvin, Casey J. AU - Genzer, Jan T2 - PROGRESS IN POLYMER SCIENCE AB - The formation of functional polymers by implementing small-molecule organic chemistry reactions to homopolymers has attracted great attention lately due to an increasing number of novel potential applications. This post-polymerization modification (PPM) approach circumvents a number of problems associated with direct polymer synthesis and enables the creation of polymeric systems that are difficult or impossible to produce otherwise. This holds especially true in the field of polymer brushes where the tethering of the polymer chains to a surface complicates direct polymerization of bulky monomers. The advantages of PPM reactions do not stop with polymer synthesis. This review highlights a variety of innovations that stem directly from this approach. A selection of these applications includes modified barrier properties, catalysis, surface patterning, separations, and biologically active substrates. DA - 2012/7// PY - 2012/7// DO - 10.1016/j.progpolymsci.2011.12.001 VL - 37 IS - 7 SP - 871-906 SN - 1873-1619 KW - Surface-anchored polymers KW - Post-polymerization modification KW - Polymer analogous reactions KW - Functional polymer layer KW - Polymer nanocomposites KW - Biomaterials ER - TY - CONF TI - Application of plagiarism screening software in the chemical engineering curriculum AU - Cooper, M. AU - Bullard, L. AU - Peretti, S. AU - Ollis, D. C2 - 2012/// C3 - ASEE Annual Conference Proceedings DA - 2012/// ER - TY - JOUR TI - All-Cellulose Composite Fibers Obtained by Electrospinning Dispersions of Cellulose Acetate and Cellulose Nanocrystals AU - Vallejos, Maria E. AU - Peresin, Maria S. AU - Rojas, Orlando J. T2 - JOURNAL OF POLYMERS AND THE ENVIRONMENT AB - All-cellulose composite fibers were produced by electrospinning dispersions containing cellulose acetate (CA) and cellulose nanocrystals (CNCs). Precursor polymer matrices were obtained after dispersion of CA with different degrees of substitution in a binary mixture of organic solvents. The obtained fibers of CA loaded with CNCs had typical widths in the nano- and micro-scale and presented a glass transition temperature of 145 °C. The CA component was converted to cellulose by using alkaline hydrolysis to yield all-cellulose composite fibers that preserved the original morphology of the precursor system. Together with Fourier Transform Infrared Spectroscopy fingerprints the thermal behavior of the all-cellulose composite fibers indicated complete conversion of cellulose acetate to regenerated cellulose. Noticeable changes in the thermal, surface and chemical properties were observed upon deacetylation. Not only the thermal transitions of cellulose acetate disappeared but the initial water contact angle of the web was reduced drastically. Overall, we propose a simple method to produce all-cellulose composite fibers which are expected to display improved thermo-mechanical properties while keeping the unique features of the cellulose polymer. DA - 2012/12// PY - 2012/12// DO - 10.1007/s10924-012-0499-1 VL - 20 IS - 4 SP - 1075-1083 SN - 1572-8919 KW - Cellulose acetate KW - Cellulose KW - All-cellulose composite KW - Nanofibers KW - Cellulose nanocrystals KW - Deacetylation KW - Electrospinning ER - TY - JOUR TI - Survey of Soy Protein Flour as a Novel Dry Strength Agent for Papermaking Furnishes AU - Jin, Haoyu AU - Lucia, Lucian A. AU - Rojas, Orlando J. AU - Hubbe, Martin A. AU - Pawlak, Joel J. T2 - JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY AB - A series of experiments were conducted on recycled pulp samples for the novel purpose of determining the efficacy of employing soy protein flour to increase the strength of dry paper. Values of short span compression and tensile strength were the prime criteria for comparison based on industrial considerations. Various conditions were considered to uncover effective schemes for applying the soy proteins under industrial-like papermaking conditions including alkaline versus acidic as well as high or low ionic content papermaking conditions. A hybrid system of starch, a dry strength additive currently used in paper furnishes, and soy protein was considered to study the possible existence of any synergistic chemical effects. Results indicated that a 1 part (by mass) soy protein to 3 parts cationic starch hybrid system resulted in the highest strength increase in comparison to solely either the soy protein or the cationic starch as dry strength additives. DA - 2012/10/3/ PY - 2012/10/3/ DO - 10.1021/jf303023j VL - 60 IS - 39 SP - 9828-9833 SN - 1520-5118 KW - soybean protein KW - papermaking KW - dry strength KW - mechanical properties ER - TY - CONF TI - Stochastic models of cell protrusion arising from spatiotemporal signaling and adhesion dynamics AU - Welf, E. S. AU - Haugh, J. M. C2 - 2012/// C3 - Methods in cell biology, vol 110: computational methods in cell biology DA - 2012/// VL - 110 SP - 223-241 ER - TY - JOUR TI - Self-assembly of model amphiphilic Janus particles AU - Rosenthal, Gerald AU - Gubbins, Keith E. AU - Klapp, Sabine H. L. T2 - JOURNAL OF CHEMICAL PHYSICS AB - We apply molecular dynamics simulations to investigate the structure formation of amphiphilic Janus particles in the bulk phase. The Janus particles are modeled as (soft) spheres composed of a hydrophilic and hydrophobic part. Their orientation is described by a vector representing an internal degree of freedom. Investigating energy fluctuations and cluster size distributions, we determine the aggregation line in a temperature-density-diagram, where the reduced temperature is an inverse measure for the anisotropic coupling. Below this aggregation line clusters of various sizes depending on density and reduced temperature are found. For low densities in the range ρ* ⩽ 0.3, the cluster size distribution has a broad maximum, indicating simultaneous existence of various cluster sizes between 5 and 10. We find no hint of a condensation transition of these clustered systems. In the case of higher densities (ρ* = 0.5 and 0.6), the cluster size distribution shows an extremely narrow peak at clusters of size 13. In these icosahedrons, the particles are arranged in a closed-packed manner, thereby maximizing the number of bonds. Analyzing the translational mean-square displacement we also observe indications of hindered diffusion due to aggregation. DA - 2012/5/7/ PY - 2012/5/7/ DO - 10.1063/1.4707954 VL - 136 IS - 17 SP - SN - 0021-9606 ER - TY - JOUR TI - Quantitative in situ infrared analysis of reactions between trimethylaluminum and polymers during Al2O3 atomic layer deposition AU - Gong, Bo AU - Parsons, Gregory N. T2 - JOURNAL OF MATERIALS CHEMISTRY AB - The reactions of trimethylaluminum (TMA) toward substrates during the Al2O3 atomic layer deposition (ALD) on a variety of polymers were studied by in situ Fourier transform infrared spectroscopy (FTIR). The experiments demonstrate that TMA reacts with certain nucleophilic functional groups on the polymer surface during the first several ALD cycles. For some polymer substrates, TMA vapor penetrates into the polymer and reacts in the polymer bulk. In both cases, the initial reaction plays an important role in the nucleation and growth of Al2O3. For chemically inert polymers, such as polypropylene, nucleation of Al2O3 ALD is relative slow at the initial stage due to the lack of reactive groups on the substrate. However, polyester, polyamide and polyether are more reactive, and in situ FTIR spectra showed a larger extent of reaction with TMA, facilitating the nucleation of ALD film on these polymers. By comparing FTIR spectra, we quantitatively estimate the extent of TMA reaction towards different polymers, and confirmed the results using X-ray photoelectron spectroscopy and scanning electron microscopy. Results give insight into the importance of the polymer structure in determining the nature and extent of the reaction during ALD film processing on polymer substrates. DA - 2012/// PY - 2012/// DO - 10.1039/c2jm32343e VL - 22 IS - 31 SP - 15672-15682 SN - 1364-5501 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000306479600031&KeyUID=WOS:000306479600031 ER - TY - JOUR TI - Prestrain-Free Dielectric Elastomers Based on Acrylic Thermoplastic Elastomer Gels: A Morphological and (Electro)Mechanical Property Study AU - Vargantwar, Pruthesh H. AU - Oezcam, A. Evren AU - Ghosh, Tushar K. AU - Spontak, Richard J. T2 - ADVANCED FUNCTIONAL MATERIALS AB - Abstract Recent efforts have established that thermoplastic elastomer gels (TPEGs) composed of styrenic triblock copolymers swollen with a midblock‐selective solvent exhibit remarkable electromechanical properties as high‐performance dielectric elastomers. This class of electroactive polymers typically requires high electric fields for actuation, and a shortcoming that continues to thwart the widespread commercialization of such materials in general is the need to apply mechanical prestrain prior to electroactuation to decrease film thickness and, thus, the electric potential required to promote actuation. To alleviate this requirement, TPEGs consisting of acrylic triblock copolymers differing in molecular weight and composition, and swollen with a high dielectric, midblock‐selective solvent are investigated. Synchrotron small‐angle x‐ray scattering is used to probe the nanoscale morphologies of the resultant materials, and analysis of quasi‐static and cyclic tensile properties provides additional insight into both blend morphologies and electroactuation efficacy. Actuation strains measured in the absence of mechanical prestrain exceed 100% on an area basis, and electric fields capable of inducing actuation are as low as ∼20 kV/mm. Failure occurs by either electromechanical instability or dielectric breakdown, depending on the copolymer and TPEG composition employed. The electromechanical properties of these acrylic‐based TPEGs match or exceed those of skeletal muscle, in which case they constitute an attractive and unexplored alternative to existing dielectric elastomers. DA - 2012/5/23/ PY - 2012/5/23/ DO - 10.1002/adfm.201101985 VL - 22 IS - 10 SP - 2100-2113 SN - 1616-301X ER - TY - JOUR TI - Plasma-Electrospinning Hybrid Process and Plasma Pretreatment to Improve Adhesive Properties of Nanofibers on Fabric Surface AU - Vitchuli, Narendiran AU - Shi, Quan AU - Nowak, Joshua AU - Nawalakhe, Rupesh AU - Sieber, Michael AU - Bourham, Mohamed AU - McCord, Marian AU - Zhang, Xiangwu T2 - PLASMA CHEMISTRY AND PLASMA PROCESSING DA - 2012/4// PY - 2012/4// DO - 10.1007/s11090-011-9341-0 VL - 32 IS - 2 SP - 275-291 SN - 1572-8986 UR - https://publons.com/publon/7178354/ KW - Adhesion KW - Plasma KW - Electrospinning KW - Surface KW - Nanofibers ER - TY - JOUR TI - Pickering emulsions stabilized by cellulose nanocrystals grafted with thermo-responsive polymer brushes AU - Zoppe, Justin O. AU - Venditti, Richard A. AU - Rojas, Orlando J. T2 - JOURNAL OF COLLOID AND INTERFACE SCIENCE AB - Cellulose nanocrystals (CNCs) from ramie fibers are studied as stabilizers of oil-in-water emulsions. The phase behavior of heptane and water systems is studied, and emulsions stabilized by CNCs are analyzed by using drop sizing (light scattering) and optical, scanning, and freeze-fracture electron microscopies. Water-continuous Pickering emulsions are produced with cellulose nanocrystals (0.05-0.5 wt%) grafted with thermo-responsive poly(NIPAM) brushes (poly(NIPAM)-g-CNCs). They are observed to be stable during the time of observation of 4 months. In contrast, unmodified CNCs are unable to stabilize heptane-in-water emulsions. After emulsification, poly(NIPAM)-g-CNCs are observed to form aligned, layered structures at the oil-water interface. The emulsions stabilized by poly(NIPAM)-g-CNCs break after heating at a temperature above the LCST of poly(NIPAM), which is taken as indication of the temperature responsiveness of the brushes installed on the particles and thus the responsiveness of the Pickering emulsions. This phenomenon is further elucidated via rheological measurements, in which viscosities of the Pickering emulsions increase on approach of the low critical solution temperature of poly(NIPAM). The effect of temperature can be counterbalanced with the addition of salt which is explained by the reduction of electrostatic and steric interactions of poly(NIPAM)-g-CNCs at the oil-water interface. DA - 2012/3/1/ PY - 2012/3/1/ DO - 10.1016/j.jcis.2011.12.011 VL - 369 SP - 202-209 SN - 1095-7103 KW - Pickering emulsions KW - Oil-in-water emulsions KW - Cellulose nanoparticles KW - Cellulose nanocrystals KW - Thermo-responsive emulsions KW - Poly(N-isopropylacrylamide) KW - LCST KW - Grafts KW - Surface-initiated single-electron transfer KW - living radical polymerization ER - TY - JOUR TI - Oligomer Orientation in Vapor-Molecular-Layer-Deposited Alkyl-Aromatic Polyamide Films AU - Peng, Qing AU - Efimenko, Kirill AU - Genzer, Jan AU - Parsons, Gregory N. T2 - LANGMUIR AB - The surface-limited molecular-layer deposition of alkyl-aromatic polyamide films using sequential doses of 1,4-butane diamine (BDA) and terephthaloyl dichloride (TDC) is characterized using in situ quartz crystal microbalance and ex situ spectroscopy analysis. For the first time, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is used to offer insight into molecular orientation in films deposited via molecular-layer deposition (MLD). The results show that the oligomer units are lying nearly parallel to the surface, which differs from the linear vertical growth mode often used to illustrate film growth. DA - 2012/7/17/ PY - 2012/7/17/ DO - 10.1021/la3017936 VL - 28 IS - 28 SP - 10464-10470 SN - 0743-7463 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000306441100019&KeyUID=WOS:000306441100019 ER - TY - JOUR TI - Nanoscale ceramic surface modification of textiles by atomic layer deposition AU - Jur, Jesse S. AU - Parsons, Gregory N. T2 - American Ceramic Society Bulletin DA - 2012/// PY - 2012/// VL - 91 IS - 6 SP - 24-27 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000307316900013&KeyUID=WOS:000307316900013 ER - TY - JOUR TI - Lignin-Based Electrospun Nanofibers Reinforced with Cellulose Nanocrystals AU - Ago, Mariko AU - Okajima, Kunihiko AU - Jakes, Joseph E. AU - Park, Sunkyu AU - Rojas, Orlando J. T2 - BIOMACROMOLECULES AB - Lignin-based fibers were produced by electrospinning aqueous dispersions of lignin, poly(vinyl alcohol) (PVA), and cellulose nanocrystals (CNCs). Defect-free nanofibers with up to 90 wt % lignin and 15% CNCs were achieved. The properties of the aqueous dispersions, including viscosity, electrical conductivity, and surface tension, were examined and correlated to the electrospinnability and resulting morphology of the composite fibers. A ternary lignin–PVA–water phase diagram was constructed as a tool to rationalize the effect of mixing ratios on the dispersion electrospinability and morphology of the resulting fibers. The influence of reinforcing CNCs on the thermal properties of the multicomponent fibers was investigated by using thermal gravimetric analysis and differential scanning calorimetry. The thermal stability of the system was observed to increase owing to a strong interaction of the lignin–PVA matrix with the dispersed CNCs, mainly via hydrogen bonding, as observed in Fourier transform infrared spectroscopy experiments. DA - 2012/3// PY - 2012/3// DO - 10.1021/bm201828g VL - 13 IS - 3 SP - 918-926 SN - 1526-4602 ER - TY - JOUR TI - LiFePO4 nanoparticles encapsulated in graphene-containing carbon nanofibers for use as energy storage materials AU - Toprakci, Ozan AU - Toprakci, Hatice A. K. AU - Ji, Liwen AU - Lin, Zhan AU - Gu, Renpeng AU - Zhang, Xiangwu T2 - JOURNAL OF RENEWABLE AND SUSTAINABLE ENERGY AB - LiFePO4/graphene/C composite nanofibers, in which LiFePO4 nanoparticles were encapsulated in graphene-containing carbon nanofiber matrix, were synthesized by using a combination of electrospinning and sol-gel techniques. Polyacrylonitrile (PAN) was used as the electrospinning media and the carbon source. Graphene was incorporated in order to increase the conductivity of the composite. PAN was dissolved in N,N–dimethylformamide (DMF). LiFePO4 precursor and graphene were dispersed in DMF separately and were mixed with PAN solution before electrospinning. Electrospun fibers were heat-treated to obtain LiFePO4/graphene/C composite nanofibers. The structure of LiFePO4/graphene/C composite nanofibers was determined by X–ray diffraction analysis. The surface morphology and microstructure of LiFePO4/graphene/C composite nanofibers were characterized using scanning electron microscopy and transmission electron microscopy. Electrochemical performance of LiFePO4/graphene/C composite nanofibers was evaluated in coin-type cells. Graphene flakes were found to be well-dispersed in the carbonaceous matrix and increased the electrochemical performance of the composite nanofibers. As a result, cells containing LiFePO4/graphene/C composite nanofiber cathodes showed good electrochemical performance, in terms of capacity, cycle life, and rate capability. DA - 2012/1/1/ PY - 2012/1/1/ DO - 10.1063/1.3690936 VL - 4 IS - 1 SP - SN - 1941-7012 UR - https://publons.com/publon/674392/ KW - crystal microstructure KW - electrical conductivity KW - electrochemistry KW - electrospinning KW - graphene KW - iron compounds KW - lithium compounds KW - nanocomposites KW - nanofabrication KW - nanofibres KW - nanoparticles KW - scanning electron microscopy KW - sol-gel processing KW - surface morphology KW - transmission electron microscopy KW - X-ray diffraction ER - TY - JOUR TI - Incorporation and Controlled Release of Silyl Ether Prodrugs from PRINT Nanoparticles AU - Parrott, Matthew C. AU - Finniss, Mathew AU - Luft, J. Chris AU - Pandya, Ashish AU - Gullapalli, Anuradha AU - Napier, Mary E. AU - Desimone, Joseph M. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Asymmetric bifunctional silyl ether (ABS) prodrugs of chemotherapeutics were synthesized and incorporated within 200 nm × 200 nm particles. ABS prodrugs of gemcitabine were selected as model compounds because of the difficulty to encapsulate a water-soluble drug within a hydrogel. The resulting drug delivery systems were degraded under acidic conditions and were found to release only the parent or active drug. Furthermore, changing the steric bulk of the alkyl substituents on the silicon atom could regulate the rate of drug release and, therefore, the intracellular toxicity of the gemcitabine-loaded particles. This yielded a family of novel nanoparticles that could be tuned to release drug over the course of hours, days, or months. DA - 2012/5/9/ PY - 2012/5/9/ DO - 10.1021/ja301710z VL - 134 IS - 18 SP - 7978-7982 SN - 0002-7863 ER - TY - JOUR TI - Generation of Functional Coatings on Hydrophobic Surfaces through Deposition of Denatured Proteins Followed by Grafting from Polymerization AU - Goli, Kiran K. AU - Rojas, Orlando J. AU - Oezcam, A. Evren AU - Genzer, Jan T2 - BIOMACROMOLECULES AB - Hydrophilic coatings were produced on flat hydrophobic substrates featuring n-octadecyltrichlorosilane (ODTS) and synthetic polypropylene (PP) nonwoven surfaces through the adsorption of denatured proteins. Specifically, physisorption from aqueous solutions of α-lactalbumin, lysozyme, fibrinogen, and two soy globulin proteins (glycinin and β-conglycinin) after chemical (urea) and thermal denaturation endowed the hydrophobic surfaces with amino and hydroxyl functionalities, yielding enhanced wettability. Proteins adsorbed strongly onto ODTS and PP through nonspecific interactions. The thickness of adsorbed heat-denatured proteins was adjusted by varying the pH, protein concentration in solution, and adsorption time. In addition, the stability of the immobilized protein layer was improved significantly after interfacial cross-linking with glutaraldehyde in the presence of sodium borohydride. The amino and hydroxyl groups present on the protein-modified surfaces served as reactive sites for the attachment of polymerization initiators from which polymer brushes were grown by surface-initiated atom-transfer radical polymerization of 2-hydroxyethyl methacrylate. Protein denaturation and adsorption as well as the grafting of polymeric brushes were characterized by circular dichroism, ellipsometry, contact angle, and Fourier transform infrared spectroscopy in the attenuated total reflection mode. DA - 2012/5// PY - 2012/5// DO - 10.1021/bm300075u VL - 13 IS - 5 SP - 1371-1382 SN - 1525-7797 ER - TY - JOUR TI - Flexible Liquid Metal Alloy (EGaIn) Microstrip Patch Antenna AU - Hayes, Gerard J. AU - So, Ju-Hee AU - Qusba, Amit AU - Dickey, Michael D. AU - Lazzi, Gianluca T2 - IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION AB - This paper describes a flexible microstrip patch antenna that incorporates a novel multi-layer construction consisting of a liquid metal (eutectic gallium indium) encased in an elastomer. The combined properties of the fluid and the elastomeric substrate result in a flexible and durable antenna that is well suited for conformal antenna applications. Injecting the metal into microfluidic channels provides a simple way to define the shape of the liquid, which is stabilized mechanically by a thin oxide skin that forms spontaneously on its surface. This approach has proven sufficient for forming simple, single layer antenna geometries, such as dipoles. More complex fluidic antennas, particularly those featuring large, co-planar sheet-like geometries, require additional design considerations to achieve the desired shape of the metal. Here, a multi-layer patch antenna is fabricated using specially designed serpentine channels that take advantage of the unique rheological properties of the liquid metal alloy. The flexibility of the resulting antennas is demonstrated and the antenna parameters are characterized through simulation and measurement in both the relaxed and flexed states. DA - 2012/5// PY - 2012/5// DO - 10.1109/tap.2012.2189698 VL - 60 IS - 5 SP - 2151-2156 SN - 0018-926X KW - EGaIn antenna KW - flexible microstrip patch antenna KW - liquid metal antenna KW - multi-layer KW - polydimethylsiloxane (PDMS) ER - TY - JOUR TI - Deposition of composite coatings from particle–particle and particle–yeast blends by convective-sedimentation assembly AU - Jenkins, Jessica S. AU - Flickinger, Michael C. AU - Velev, Orlin D. T2 - Journal of Colloid and Interface Science AB - The structures resulting from convective-sedimentation assembly (CSA) of bimodal suspensions (4.1–10% solids) of strongly charged sulfate latex microspheres (zeta potential −55.9 ± 1.8 mV at pH 8.0) and weakly charged Saccharomyces cerevisiae (zeta potential −18.7 ± 0.71 mV at pH 8.0) on glass, polyester, polypropylene, and aluminum foil substrates was evaluated. This study shows how substrate wettability, suspension composition, particle size ratio and surface charge affect the deposition process and resulting coating microstructure (particle ordering and void space). Size ratio and charge influence deposition, convective mixing or demixing and relative particle locations. Substrate wettability and suspension composition influence coating microstructure by controlling suspension delivery and spreading across the substrate. S. cerevisiae behave like negatively-charged colloidal particles during CSA. CSA of particle–yeast blends result in open-packed structures (15–45% mean void space), instead of tightly packed coatings attainable with single component systems, confirming the existence of significant polymer particle–yeast interactions and formation of particle aggregates that disrupt coating microstructure during deposition. Further optimization of the process should allow void space reduction and deposition of cells plus adhesive polymer particles into tightly packed adhesive monolayer coatings for biosensors, biophotoabsorbers, energy applications, and highly reactive microbial absorbers. DA - 2012/8// PY - 2012/8// DO - 10.1016/j.jcis.2012.04.060 VL - 380 IS - 1 SP - 192-200 J2 - Journal of Colloid and Interface Science LA - en OP - SN - 0021-9797 UR - http://dx.doi.org/10.1016/j.jcis.2012.04.060 DB - Crossref KW - Colloidal coatings KW - Size-selective segregation KW - Bimodal blends KW - Convective assembly of biocomposite yeast blends ER - TY - JOUR TI - Defect topologies in a nematic liquid crystal near a patchy colloid AU - Melle, Michael AU - Schlotthauer, Sergej AU - Mazza, Marco G. AU - Klapp, Sabine H. L. AU - Schoen, Martin T2 - JOURNAL OF CHEMICAL PHYSICS AB - Using isothermal-isobaric Monte Carlo simulations we investigate defect topologies due to a spherical colloidal particle immersed in a nematic liquid crystal. Defects arise because of the competition between the preferential orientation at the colloid's surface and the far-field director ̂n(0). Considering a chemically homogeneous colloid as a special case we observe the well-known surface and saturn ring defect topologies for weak and strong perpendicular anchoring, respectively; for homogeneous, strong parallel anchoring we find a boojum defect topology that has been seen experimentally [see P. Poulin and D. A. Weitz, Phys. Rev. E 57, 626 (1998)] but not in computer simulations. We also consider a heterogeneous, patchy colloid where the liquid-crystal molecules anchor either preferentially planar or perpendicular at the surface of the colloid. For a patchy colloid we observe a boojum ring defect topology in agreement with recent experimental studies [see M. Conradi, M. Ravnik, M. Bele, M. Zorko, S. Žumer, and I. Muševič, Soft Matter 5, 3905 (2009)]. We also observe two other novel defect topologies that have not been reported thus far neither experimentally nor theoretically. DA - 2012/5/21/ PY - 2012/5/21/ DO - 10.1063/1.4717619 VL - 136 IS - 19 SP - SN - 1089-7690 ER - TY - JOUR TI - Coal-Direct Chemical Looping Gasification for Hydrogen Production: Reactor Modeling and Process Simulation AU - Zeng, Liang AU - He, Feng AU - Li, Fanxing AU - Fan, Liang-Shih T2 - Energy & Fuels AB - A novel process scheme for hydrogen production from coal with in situ CO2 capture, known as the coal-direct chemical looping (CDCL) gasification process, is discussed in this article. The CDCL process utilizes an iron oxide based oxygen carrier as a chemical looping medium to indirectly gasify coal into separate streams of H2 and CO2. ASPEN Plus reactor simulation models based on both thermodynamic equilibrium limitations and kinetic limitations are developed to analyze individual CDCL reactors. Process simulations are subsequently performed to estimate the performance of the CDCL process under various mass and energy management schemes. Reactor modeling results indicate that a moving bed reducer can effectively convert coal while reducing the oxygen carrier. The reduced oxygen carrier can in turn be oxidized by steam to produce hydrogen in a moving bed oxidizer. The fates of pollutants as well as the effects of various process operating parameters such as carbon and iron oxide conversions are also evaluated. Process simulation indicates that, even under a set of conservative assumptions, the CDCL process has the potential to convert coal to hydrogen at a thermal efficiency of nearly 78% (HHV) while capturing >90% CO2, which is 30% higher, on a relative basis, than conventional hydrogen generation processes. DA - 2012/5/23/ PY - 2012/5/23/ DO - 10.1021/ef3003685 VL - 26 IS - 6 SP - 3680-3690 J2 - Energy Fuels LA - en OP - SN - 0887-0624 1520-5029 UR - http://dx.doi.org/10.1021/ef3003685 DB - Crossref ER - TY - JOUR TI - Capillary flooding of wood with microemulsions from Winsor I systems AU - Carrillo, Carlos A. AU - Saloni, Daniel AU - Lucia, Lucian A. AU - Hubbe, Martin A. AU - Rojas, Orlando J. T2 - JOURNAL OF COLLOID AND INTERFACE SCIENCE AB - A new approach based on microemulsions formulated with at least 85% water and minority components consisting of oil (limonene) and surfactant (anionic and nonionic) is demonstrated for the first time to be effective for flooding wood’s complex capillary structure. The formulation of the microemulsion was based on phase behavior scans of Surfactant–Oil–Water systems (SOWs) and the construction of pseudo-ternary diagrams to localize thermodynamically stable one-phase emulsion systems with different composition, salinity and water-to-oil ratios. Wicking and fluid penetration isotherms followed different kinetic regimes and indicated enhanced performance relative to that of the base fluids (water, oil or surfactant solutions). The key properties of microemulsions to effectively penetrate the solid structure are discussed; microemulsion formulation and resultant viscosity are found to have a determining effect in the extent of fluid uptake. The solubilization of cell wall components is observed after microemulsion impregnation. Thus, the microemulsion can be tuned not only to effectively penetrate the void spaces but also to solubilize hydrophobic and hydrophilic components. The concept proposed in this research is expected to open opportunities in fluid sorption in fiber systems for biomass pretreatment, and delivery of hydrophilic or lipophilic moieties in porous, lignocellulosics. DA - 2012/9/1/ PY - 2012/9/1/ DO - 10.1016/j.jcis.2012.05.032 VL - 381 SP - 171-179 SN - 0021-9797 KW - Microemulsions KW - Flooding KW - Surfactants KW - Capillary structure KW - Biomass KW - Wood impregnation KW - Extraction ER - TY - JOUR TI - Analytical solution for electrolyte concentration distribution in lithium-ion batteries AU - Guduru, A. AU - Northrop, P. W. C. AU - Jain, S. AU - Crothers, A. C. AU - Marchant, T. R. AU - Subramanian, V. R. T2 - Journal of Applied Electrochemistry DA - 2012/// PY - 2012/// VL - 42 IS - 4 SP - 189-199 ER - TY - JOUR TI - RESOURCE-FOCUSED TOOLCHAIN FOR RAPID PROTOTYPING OF EMBEDDED SYSTEMS AU - Peng, Shaolin AU - Parsons, Gregory AU - Dean, Alexander G. T2 - JOURNAL OF CIRCUITS SYSTEMS AND COMPUTERS AB - This paper introduces the RaPTEX toolchain and its use for rapid prototyping and evaluation of embedded communication systems. This toolchain is unique for several reasons. First, by using static code analysis techniques, it is able to predict both the typical case and bounds for resource usage, such as computational, memory (both static and dynamic), and energy requirements. Second, it provides a graphical user interface with configurable software building blocks which allows easy creation and customization of protocol stacks. Third, it targets low-cost, low-energy hardware, allowing the creation of low-cost systems. We demonstrate the RaPTEX toolchain by evaluating different design options for an experimental ultrasonic communication system for biotelemetry in extremely shallow waters. The power, size, mass, and cost constraints of this application make it critical to pack as much processing into the available resources as possible. The RaPTEX toolchain analyzes resource use, enabling the system to safely operate closer to the edge of the resource envelope. The toolchain also helps users with the rapid prototyping of communication protocols by providing users with quick feedback on resource requirements. We demonstrate the use and output of the toolchain. We compare the accuracy of its predictions against measurements of the real hardware. DA - 2012/4// PY - 2012/4// DO - 10.1142/s0218126612400038 VL - 21 IS - 2 SP - SN - 1793-6454 KW - RaPTEX KW - static timing analysis KW - code generation KW - optimization ER - TY - JOUR TI - Migrating fibroblasts reorient directionality by a metastable, PI3K-dependent mechanism AU - Welf, Erik S. AU - Ahmed, Shoeb AU - Johnson, Heath E. AU - Melvin, Adam T. AU - Haugh, Jason M. T2 - JOURNAL OF CELL BIOLOGY AB - Mesenchymal cell migration as exhibited by fibroblasts is distinct from amoeboid cell migration and is characterized by dynamic competition among multiple protrusions, which determines directional persistence and responses to spatial cues. Localization of phosphoinositide 3-kinase (PI3K) signaling is thought to play a broadly important role in cell motility, yet the context-dependent functions of this pathway have not been adequately elucidated. By mapping the spatiotemporal dynamics of cell protrusion/retraction and PI3K signaling monitored by total internal reflection fluorescence microscopy, we show that randomly migrating fibroblasts reorient polarity through PI3K-dependent branching and pivoting of protrusions. PI3K inhibition did not affect the initiation of newly branched protrusions, nor did it prevent protrusion induced by photoactivation of Rac. Rather, PI3K signaling increased after, not before, the onset of local protrusion and was required for the lateral spreading and stabilization of nascent branches. During chemotaxis, the branch experiencing the higher chemoattractant concentration was favored, and, thus, the cell reoriented so as to align with the external gradient. DA - 2012/4/2/ PY - 2012/4/2/ DO - 10.1083/jcb.201108152 VL - 197 IS - 1 SP - 105-114 SN - 1540-8140 ER - TY - JOUR TI - Genetically encoded norbornene directs site-specific cellular protein labelling via a rapid bioorthogonal reaction AU - Lang, Kathrin AU - Davis, Lloyd AU - Torres-Kolbus, Jessica AU - Chou, Chungjung AU - Deiters, Alexander AU - Chin, Jason W. T2 - NATURE CHEMISTRY AB - The site-specific incorporation of bioorthogonal groups via genetic code expansion provides a powerful general strategy for site-specifically labelling proteins with any probe. However, the slow reactivity of the bioorthogonal functional groups that can be encoded genetically limits the utility of this strategy. We demonstrate the genetic encoding of a norbornene amino acid using the pyrrolysyl tRNA synthetase/tRNACUA pair in Escherichia coli and mammalian cells. We developed a series of tetrazine-based probes that exhibit ‘turn-on’ fluorescence on their rapid reaction with norbornenes. We demonstrate that the labelling of an encoded norbornene is specific with respect to the entire soluble E. coli proteome and thousands of times faster than established encodable bioorthogonal reactions. We show explicitly the advantages of this approach over state-of-the-art bioorthogonal reactions for protein labelling in vitro and on mammalian cells, and demonstrate the rapid bioorthogonal site-specific labelling of a protein on the mammalian cell surface. The site-specific incorporation of a norbornene amino acid into proteins via genetic code expansion, together with the synthesis of a series of tetrazine-based probes that exhibit turn-on fluorescence on their fast cycloaddition with norbornene, enables rapid protein labelling on mammalian cells. DA - 2012/4// PY - 2012/4// DO - 10.1038/nchem.1250 VL - 4 IS - 4 SP - 298-304 SN - 1755-4330 ER - TY - JOUR TI - Effect of Aspect Ratio and Deformability on Nanoparticle Extravasation through Nanopores AU - Kersey, Farrell R. AU - Merkel, Timothy J. AU - Perry, Jillian L. AU - Napier, Mary E. AU - DeSimone, Joseph M. T2 - LANGMUIR AB - We describe the fabrication of filamentous hydrogel nanoparticles using a unique soft lithography based particle molding process referred to as PRINT (particle replication in nonwetting templates). The nanoparticles possess a constant width of 80 nm, and we varied their lengths ranging from 180 to 5000 nm. In addition to varying the aspect ratio of the particles, the deformability of the particles was tuned by varying the cross-link density within the particle matrix. Size characteristics such as hydrodynamic diameter and persistence length of the particles were analyzed using dynamic light scattering and electron microscopy techniques, respectively, while particle deformability was assessed by atomic force microscopy. Additionally, the ability of the particles to pass through membranes containing 0.2 μm pores was assessed by means of a simple filtration technique, and particle recovery was determined using fluorescence spectroscopy. The results show that particle recovery is mostly independent of aspect ratio at all cross-linker concentrations utilized, with the exception of 96 wt % PEG diacrylate 80 × 5000 nm particles, which showed the lowest percent recovery. DA - 2012/6/12/ PY - 2012/6/12/ DO - 10.1021/la301279v VL - 28 IS - 23 SP - 8773-8781 SN - 0743-7463 ER - TY - JOUR TI - Dorsal-Ventral Gene Expression in the Drosophila Embryo Reflects the Dynamics and Precision of the Dorsal Nuclear Gradient AU - Reeves, Gregory T. AU - Trisnadi, Nathanie AU - Truong, Thai V. AU - Nahmad, Marcos AU - Katz, Sophie AU - Stathopoulos, Angelike T2 - Developmental Cell AB - Patterning of the dorsal-ventral axis in the early Drosophila embryo depends on the nuclear distribution of the Dorsal transcription factor. Using live two-photon light-sheet microscopy, we quantified the nuclear Dorsal gradient in space and time and found that its amplitude and basal levels display oscillations throughout early embryonic development. These dynamics raise questions regarding how cells can reproducibly establish patterns of gene expression from a rapidly varying signal. We therefore quantified domains of Dorsal target genes, discovering their expression patterns are also dynamic. Computational modeling of this system reveals a correlation between Dorsal gradient dynamics and changes in target gene expression and suggests that these dynamics, together with time averaging of noise, results in the formation of graded gene expression borders in regions where the gradient is nearly flat. We propose that mRNA levels remain plastic during transient signaling events, allowing tissues to refine patterns in the face of genetic or environmental variation. DA - 2012/3// PY - 2012/3// DO - 10.1016/j.devcel.2011.12.007 VL - 22 IS - 3 SP - 544-557 J2 - Developmental Cell LA - en OP - SN - 1534-5807 UR - http://dx.doi.org/10.1016/j.devcel.2011.12.007 DB - Crossref ER - TY - JOUR TI - Chemical looping technology and its applications in fossil fuel conversion and CO2 capture AU - Liang, Z. AU - Feng, H. AU - Li, F. AU - Fan, L.-S. T2 - Science China Chemistry DA - 2012/// PY - 2012/// VL - 743 IS - 2 SP - 260-281 ER - TY - JOUR TI - Carbon Nanotube-Loaded Electrospun LiFePO4/Carbon Composite Nanofibers As Stable and Binder-Free Cathodes for Rechargeable Lithium-Ion Batteries AU - Toprakci, Ozan AU - Toprakci, Hatice A. K. AU - Ji, Liwen AU - Xu, Guanjie AU - Lin, Zhan AU - Zhang, Xiangwu T2 - ACS APPLIED MATERIALS & INTERFACES AB - LiFePO4/CNT/C composite nanofibers were synthesized by using a combination of electrospinning and sol–gel techniques. Polyacrylonitrile (PAN) was used as the electrospinning media and carbon source. Functionalized CNTs were used to increase the conductivity of the composite. LiFePO4 precursor materials, PAN and functionalized CNTs were dissolved or dispersed in N,N–dimethylformamide separately and they were mixed before electrospinning. LiFePO4 precursor/CNT/PAN composite nanofibers were then heat-treated to obtain LiFePO4/CNT/C composite nanofibers. Fourier transform infrared spectroscopy measurements were done to demonstrate the functionalization of CNTs. The structure of LiFePO4/CNT/C composite nanofibers was determined by X–ray diffraction analysis. The surface morphology and microstructure of LiFePO4/CNT/C composite nanofibers were characterized using scanning electron microscopy and transmission electron microscopy. Electrochemical performance of LiFePO4/CNT/C composite nanofibers was evaluated in coin-type cells. Functionalized CNTs were found to be well-dispersed in the carbonaceous matrix and increased the electrochemical performance of the composite nanofibers. As a result, cells using LiFePO4/CNT/C composite nanofibers have good performance, in terms of large capacity, extended cycle life, and good rate capability. DA - 2012/3// PY - 2012/3// DO - 10.1021/am201527r VL - 4 IS - 3 SP - 1273-1280 SN - 1944-8252 UR - https://publons.com/publon/674388/ KW - lithium-ion batteries KW - cathodes KW - LiFePO4 KW - carbon nanofibers KW - carbon nanotubes ER - TY - JOUR TI - Under pressure: Quasi-high pressure effects in nanopores AU - Long, Yun AU - Palmer, Jeremy C. AU - Coasne, Benoit AU - Sliwinska-Bartkowiak, Malgorzata AU - Gubbins, Keith E. T2 - MICROPOROUS AND MESOPOROUS MATERIALS AB - Phenomena that occur only at high pressures in bulk phases are often observed in nanopores, suggesting that the pressure in such confined phases is large. We develop two models to study the pressure tensor of an argon nanophase confined in carbon micropores by molecular simulation, and show that the in-pore tangential pressure is positive and on the order of 104 bar, while the normal pressure can be positive or negative depending on pore width, with a magnitude of ∼103 bar at ambient bulk pressure. We find that the in-pore tangential pressure is very sensitive to the bulk pressure, suggesting that it should be possible to control the former over wide ranges in laboratory experiments. We also report results for porous materials other than carbon, and show that the pressure enhancement is smaller for pores with weakly attractive walls (e.g. silica and oxides), but larger for more strongly attractive walls (e.g. mica). DA - 2012/5/15/ PY - 2012/5/15/ DO - 10.1016/j.micromeso.2011.07.017 VL - 154 SP - 19-23 SN - 1873-3093 KW - Molecular simulation KW - Pressure tensor KW - Adsorption KW - Pressure enhancement ER - TY - JOUR TI - Surface-Initiated Polymerization by Means of Novel, Stable, Non-Ester-Based Radical Initiator AU - Bain, Erich D. AU - Dawes, Keith AU - Oezcam, A. Evren AU - Hu, Xinfang AU - Gorman, Christopher B. AU - Srogl, Jiri AU - Genzer, Jan T2 - MACROMOLECULES AB - A novel, ester-free initiator for surface-initiated free radical polymerization has been synthesized and tested. The structurally non-symmetrical azo-based initiator features a chemically stable alkane linker between the initiating group and the silane anchoring group, setting it apart from the majority of surface initiators that are linked by hydrolyzable moieties, such as esters. The novel design of the initiator is bolstered by an original synthetic approach, leading to a greater yield and a dramatic reduction in cyanide usage relative to previous methods. Here we demonstrate the capability of this novel initiator for surface-initiated free radical polymerization (SI-FRP), reverse ATRP, and RAFT, noting that Arrhenius behavior of SI-FRP differs significantly from that of FRP in the bulk. Furthermore, we show that polymer brushes formed from the novel initiator are more stable than those formed from ester-based initiators. DA - 2012/5/8/ PY - 2012/5/8/ DO - 10.1021/ma300491e VL - 45 IS - 9 SP - 3802-3815 SN - 1520-5835 ER - TY - JOUR TI - Structural transitions and oligomerization along polyalanine fibril formation pathways from computer simulations AU - Phelps, E. M. AU - Hall, Carol T2 - Proteins AB - Abstract The results of a computer simulation study of the aggregation kinetics of a large system of model peptides with particular focus on the formation of intermediates are presented. Discontinuous molecular dynamic simulations were used in combination with our intermediate‐resolution protein model, PRIME, to simulate the aggregation of a system of 192 polyalanine (KA 14 K) peptides at a concentration of 5 m M and a reduced temperature of T * = 0.13 starting from a random configuration and ending in the assembly of a fibrillar structure. The population of various structures, including free monomers, beta sheets, amorphous aggregates, hybrid aggregates, and fibrils, and the transitions between the structures were tracked over the course of 30 independent simulations and averaged together. The aggregation pathway for this system starts with the association of free monomers into small amorphous aggregates that then grow to moderate size by incorporating other free monomers or merging with other small amorphous aggregates. These then rearrange into either small beta sheets or hybrid aggregates formed by association between unstructured chains and beta sheets, both of which grow in size by adding free monomer chains or other small aggregates, one at a time. Fibrillar structures are formed initially either by the stacking of beta sheets, rearrangement of hybrid aggregates or association between beta sheets and hybrid aggregates. They grow by the addition of beta sheets, hybrid aggregates, and other small fibrillar structures. The rearrangement of amorphous aggregates into beta sheets is a critical and necessary step in the fibril formation pathway. Proteins 2012. © 2012 Wiley Periodicals, Inc. DA - 2012/// PY - 2012/// DO - 10.1002/prot.24052 VL - 80 IS - 6 SP - 1582–1597 ER - TY - JOUR TI - Structural analysis of water and carbon tetrachloride adsorbed in activated carbon fibres AU - Śliwińska-Bartkowiak, Małgorzata AU - Drozdowski, Henryk AU - Kempiński, Mateusz AU - Jażdżewska, Monika AU - Long, Yun AU - Palmer, Jeremy C. AU - Gubbins, Keith E. T2 - Physical Chemistry Chemical Physics AB - We report X-ray diffraction studies of water and carbon tetrachloride adsorbed in nanoporous activated carbon fibres. The fibres are built of turbostratic nanoparticles separated by quasi two-dimensional voids, forming narrow slit-shaped pores. In order to determine the structure of water within the pores and its influence on the fibres' structure, mean interatomic and intermolecular distances have been estimated from the positions of the maxima of the normalized angular distribution functions obtained by X-ray diffraction. We observe a cluster arrangement of the water molecules, as well as significant changes in the interlayer distance of the carbon nanoparticles upon adsorption of both water and carbon tetrachloride. The results suggest that very high pressures arise within the pores, as has been observed in molecular simulations, and this may give rise to the large change in electronic properties of the fibres after adsorption of guest molecules. The in-pore pressure normal to the pore walls is estimated from the experimental data, and is found to be positive and of the order 4000 bar. Molecular simulation results for the normal pressure component are presented for both water and carbon tetrachloride in carbon slit pores, and are in general agreement with the experiments. For both fluids the normal pressure is an oscillating function of pore width. DA - 2012/// PY - 2012/// DO - 10.1039/c2cp22111j VL - 14 IS - 19 SP - 7145 J2 - Phys. Chem. Chem. Phys. LA - en OP - SN - 1463-9076 1463-9084 UR - http://dx.doi.org/10.1039/C2CP22111J DB - Crossref ER - TY - JOUR TI - Rendering Protein-Based Particles Transiently Insoluble for Therapeutic Applications AU - Xu, Jing AU - Wang, Jin J. AU - Luft, J. Christopher AU - Tian, Shaomin AU - Owens, Gary, Jr. AU - Pandya, Ashish A. AU - Bergund, Peter AU - Pohlhaus, Patrick AU - Maynor, Benjamin W. AU - Smith, Jonathan AU - Hubby, Bolyn AU - Napier, Mary E. AU - DeSimone, Joseph M. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Herein, we report the fabrication of protein (bovine serum albumin, BSA) particles which were rendered transiently insoluble using a novel, reductively labile disulfide-based cross-linker. After being cross-linked, the protein particles retain their integrity in aqueous solution and dissolve preferentially under a reducing environment. Our data demonstrates that cleavage of the cross-linker leaves no chemical residue on the reactive amino group. Delivery of a self-replicating RNA was achieved via the transiently insoluble PRINT protein particles. These protein particles can provide new opportunities for drug and gene delivery. DA - 2012/5/30/ PY - 2012/5/30/ DO - 10.1021/ja302363r VL - 134 IS - 21 SP - 8774-8777 SN - 0002-7863 ER - TY - JOUR TI - Live-Cell Fluorescence Microscopy with Molecular Biosensors: What Are We Really Measuring? AU - Haugh, Jason M. T2 - BIOPHYSICAL JOURNAL AB - Engineered protein biosensors, such as those based on Förster resonance energy transfer, membrane translocation, or solvatochromic shift, are being used in combination with live-cell fluorescence microscopy to reveal kinetics and spatial localization of intracellular processes as they occur. Progress in the application of this approach has been steady, yet its general suitability for quantitative measurements remains unclear. To address the pitfalls of the biosensor approach in quantitative terms, simple reaction-diffusion models were analyzed. The analysis shows that although high-affinity molecular recognition allows robust detection of the fluorescence readout, either of two detrimental effects is fostered. Binding of an intramolecular biosensor or of a relatively abundant intermolecular biosensor introduces observer effects in which the dynamics of the target molecule under study are significantly perturbed, whereas binding of a sparingly expressed intermolecular biosensor is subject to a saturation effect, where the pool of unbound biosensor is significantly depleted. The analysis explores how these effects are manifest in the kinetics and spatial gradients of the biosensor-target complex. A sobering insight emerges: the observer or saturation effect is always significant; the question is whether or not it can be tolerated or accounted for. The challenge in managing the adverse effects is that specification of the biosensor-target affinity to within a certain order of magnitude is required. DA - 2012/5/2/ PY - 2012/5/2/ DO - 10.1016/j.bpj.2012.03.055 VL - 102 IS - 9 SP - 2003-2011 SN - 0006-3495 ER - TY - CHAP TI - Electrolytes for Lithium-Ion Battery Materials AU - Lex-Balducci A., Henderson W. A. AU - S., Passerini T2 - Lithium Ion Batteries: Advanced Materials and Technologies A2 - Yuan, Y. A2 - Liu, H. A2 - J., Zhang. PY - 2012/// PB - Boca Raton : CRC Press SN - 9781439841280 ER - TY - JOUR TI - Durable hydrophobic cotton surfaces prepared using silica nanoparticles and multifunctional silanes AU - Roe, Barry AU - Kotek, Richard AU - Zhang, Xiangwu T2 - JOURNAL OF THE TEXTILE INSTITUTE AB - Durable non-fluorine hydrophobic cotton surfaces were obtained by treating woven cotton fabrics using combinations of silica nanoparticles and multifunctional silanes. Both the hydrophobicity and durability of treated cotton surfaces were controlled by selectively adjusting the alkyl chain length of silane hydrophobes and the surface chemistry, surface area, and content of silica nanoparticles. It was found that with an increase in the alkyl chain length of the silane hydrophobes, the hydrophobicity of treated cotton surfaces increased: the maximum surface durability was obtained at an alkyl chain length of 12 carbon atoms. Hydrophilic silica nanoparticles significantly improved the hydrophobicity and durability of treated cotton surfaces, whereas the hydrophobic silica nanoparticles were found to reduce them. The surface area of the silica nanoparticles did not have a significant impact on the cotton fabric hydrophobicity, however, a larger silica surface area resulted in better durability. The highest hydrophobicity (a contact angle of 142°) and the best durability (a 95.7% recovery of contact angle after heavy-duty industrial laundering) were achieved when treating cotton surfaces with the silane tetramethoxysilane crosslink enhancer, silane n-dodecyltrimethoxysilane hydrophobe (alkyl chain length = 12 carbon atoms), and 0.2% hydrophilic silica nanoparticles with a diameter of 12 nm. DA - 2012/// PY - 2012/// DO - 10.1080/00405000.2011.580540 VL - 103 IS - 4 SP - 385-393 SN - 0040-5000 UR - https://publons.com/publon/7178356/ KW - cotton KW - silica nanoparticles KW - silane KW - surface treatment KW - hydrophobicity ER - TY - JOUR TI - Atomistic models for disordered nanoporous carbons using reactive force fields AU - Palmer, Jeremy C. AU - Gubbins, Keith E. T2 - MICROPOROUS AND MESOPOROUS MATERIALS AB - Optimization of disordered nanoporous carbons (DNCs) for specific applications remains a challenge due to the difficulty in accurately characterizing their nanostructures with current experimental methods. We describe how atomistic simulation techniques can be used to build structural models of DNCs and subsequently elucidate the structure–function relationship in these complex porous materials. In particular, two state-of-the-art approaches that use methods based in statistical mechanics to predict the structure of DNCs are described. The quench molecular dynamics method is a pseudo-mimetic approach that captures the effect of synthesis temperature on the structural morphology of disordered carbons, while the hybrid reverse Monte Carlo method is a reconstruction approach that builds realistic replicas of DNCs from experimental diffraction data. Both of these methods use reactive force fields to capture the formation and disassociation of chemical bonds during the simulations, allowing for the structural and porous features of DNCs to be predicted. We describe the principles behind these methods and provide illustrative examples that demonstrate their utility in modeling DNCs. Finally, we also discuss their current limitations and future avenues for improving their predictive capabilities. DA - 2012/5/15/ PY - 2012/5/15/ DO - 10.1016/j.micromeso.2011.08.017 VL - 154 SP - 24-37 SN - 1873-3093 KW - Nanoporous carbon KW - Adsorption KW - Molecular simulation KW - Molecular dynamics KW - Monte Carlo ER - TY - JOUR TI - Reductively Responsive siRNA-Conjugated Hydrogel Nanoparticles for Gene Silencing AU - Dunn, Stuart S. AU - Tian, Shaomin AU - Blake, Steven AU - Wang, Jin AU - Galloway, Ashley L. AU - Murphy, Andrew AU - Pohlhaus, Patrick D. AU - Rolland, Jason P. AU - Napier, Mary E. AU - DeSimone, Joseph M. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - A critical need still remains for effective delivery of RNA interference (RNAi) therapeutics to target tissues and cells. Self-assembled lipid- and polymer-based systems have been most extensively explored for transfection with small interfering RNA (siRNA) in liver and cancer therapies. Safety and compatibility of materials implemented in delivery systems must be ensured to maximize therapeutic indices. Hydrogel nanoparticles of defined dimensions and compositions, prepared via a particle molding process that is a unique off-shoot of soft lithography known as particle replication in nonwetting templates (PRINT), were explored in these studies as delivery vectors. Initially, siRNA was encapsulated in particles through electrostatic association and physical entrapment. Dose-dependent gene silencing was elicited by PEGylated hydrogels at low siRNA doses without cytotoxicity. To prevent disassociation of cargo from particles after systemic administration or during postfabrication processing for surface functionalization, a polymerizable siRNA pro-drug conjugate with a degradable, disulfide linkage was prepared. Triggered release of siRNA from the pro-drug hydrogels was observed under a reducing environment while cargo retention and integrity were maintained under physiological conditions. Gene silencing efficiency and cytocompatibility were optimized by screening the amine content of the particles. When appropriate control siRNA cargos were loaded into hydrogels, gene knockdown was only encountered for hydrogels containing releasable, target-specific siRNAs, accompanied by minimal cell death. Further investigation into shape, size, and surface decoration of siRNA-conjugated hydrogels should enable efficacious targeted in vivo RNAi therapies. DA - 2012/5/2/ PY - 2012/5/2/ DO - 10.1021/ja300174v VL - 134 IS - 17 SP - 7423-7430 SN - 1520-5126 ER - TY - JOUR TI - Porcine parvovirus removal using trimer and biased hexamer peptides AU - Heldt, Caryn L. AU - Gurgel, Patrick V. AU - Jaykus, Lee-Ann AU - Carbonell, Ruben G. T2 - BIOTECHNOLOGY JOURNAL AB - Abstract Assuring the microbiological safety of biological therapeutics remains an important concern. Our group has recently reported small trimeric peptides that have the ability to bind and remove a model nonenveloped virus, porcine parvovirus (PPV), from complex solutions containing human blood plasma. In an effort to improve the removal efficiency of these small peptides, we created a biased library of hexamer peptides that contains two previously reported trimeric peptides designated WRW and KYY. This library was screened and several hexamer peptides were discovered that also removed PPV from solution, but there was no marked improvement in removal efficiency when compared to the trimeric peptides. Based on simulated docking experiments, it appeared that hexamer peptide binding is dictated more by secondary structure, whereas the binding of trimeric peptides is dominated by charge and hydrophobicity. This study demonstrates that trimeric and hexameric peptides may have different, matrix‐specific roles to play in virus removal applications. In general, the hexamer ligand may perform better for binding of specific viruses, whereas the trimer ligand may have more broadly reactive virus‐binding properties. DA - 2012/4// PY - 2012/4// DO - 10.1002/biot.201000397 VL - 7 IS - 4 SP - 558-565 SN - 1860-6768 KW - Affinity adsorption KW - Biosafety KW - Bioseparation KW - Ligand KW - Virus removal ER - TY - JOUR TI - Phase behavior of gradient copolymer solutions: a Monte Carlo simulation study AU - Pandav, Gunja AU - Pryamitsyn, Victor AU - Gallow, Keith C. AU - Loo, Yueh-Lin AU - Genzer, Jan AU - Ganesan, Venkat T2 - SOFT MATTER AB - We use computer simulations to study the phase separation behavior of amphiphilic linear gradient copolymer solution under poor solvent conditions. Using the bond fluctuation model and parallel tempering algorithm, we explore the influence of the gradient strength (the largest difference in the instantaneous composition along the copolymer) upon the phase separation characteristics. Under poor solvent conditions, the chains collapse to form micelle-like aggregates. We find that the critical temperature for this transition exhibits a linear dependence on the gradient strength of the copolymers. A systematic quantification of the cluster characteristics formed during the phase separation also reveals a strong dependence of aggregation numbers and the bridging statistics upon the gradient strength of the copolymers. Analysis of our results reveals that the critical parameter determining the thermodynamic behavior of gradient copolymers is in fact the average length of the hydrophobic sequences in the gradient copolymers. We demonstrate that the latter provides a useful measure to quantitatively predict the critical transition temperature of the gradient copolymer solution. We also present a few results from the framework of an annealed representation of the sequences of the gradient copolymer to demonstrate the limitations arising from such a model representation. DA - 2012/// PY - 2012/// DO - 10.1039/c2sm25577d VL - 8 IS - 24 SP - 6471-6482 SN - 1744-6848 ER - TY - JOUR TI - Palladium Catalysts for Fatty Acid Deoxygenation: Influence of the Support and Fatty Acid Chain Length on Decarboxylation Kinetics AU - Ford, Jeffrey P. AU - Immer, Jeremy G. AU - Lamb, H. Henry T2 - TOPICS IN CATALYSIS DA - 2012/5// PY - 2012/5// DO - 10.1007/s11244-012-9786-2 VL - 55 IS - 3-4 SP - 175-184 SN - 1572-9028 KW - Fatty acid alkyl chain length KW - Biofuels KW - Palladium KW - Activated carbon KW - Silica KW - Alumina ER - TY - JOUR TI - Interfacial stabilization of bilayered nanolaminates by asymmetric block copolymers AU - Gozen, Arif O. AU - Genzer, Jan AU - Spontak, Richard J. T2 - APPLIED PHYSICS LETTERS AB - Block copolymers are macromolecular surfactants that self-assemble into a variety of nanostructural elements or reduce the interfacial tension between incompatible polymers. Here, we examine the ability of diblock copolymers differing in composition to stabilize bilayered homopolymer nanolaminates on flat solid supports. In this arrangement, self-assembly competes with interfacial modification and, in one case, promotes destabilization of the top film. To discern the corresponding mechanism, we investigate nanolaminates with a thin copolymer layer positioned between the homopolymer layers. Stabilization commences when this middle layer is sufficiently thick so that the block that is miscible with the top layer forms a brush. DA - 2012/3/5/ PY - 2012/3/5/ DO - 10.1063/1.3692102 VL - 100 IS - 10 SP - SN - 0003-6951 ER - TY - JOUR TI - Influence of polymer chain length and chains ends on polyelectrolyte solvate structure and melting point AU - Henderson, W. A. T2 - Solid State Ionics DA - 2012/// PY - 2012/// VL - 217 SP - 1-5 ER - TY - JOUR TI - Gel-Based Self-Propelling Particles Get Programmed To Dance AU - Sharma, Rachita AU - Chang, Suk Tai AU - Velev, Orlin D. T2 - LANGMUIR AB - We present a class of gel-based self-propelling particles moving by the Marangoni effect in an oscillatory mode. The particles are made of an ethanol-infused polyacrylamide hydrogel contained in plastic tubing. These gel boats floating on the water surface exhibit periodic propulsion for several hours. The release of ethanol from the hydrogel takes place beneath the liquid surface. The released ethanol rises to the air–water interface by buoyancy and generates a self-sustained cycle of surface tension gradient driven motion. The disruption of the ethanol flux to the surface by the bulk flows around the moving particle results in their pulsating motion. The pulse interval and the distance propelled in a pulse by these gel floaters were measured and approximated by simple expressions based on the rate of ethanol mass-transfer through and out of the hydrogel. This allowed us to design a multitude of particles performing periodic steps in different directions or at different angles of rotation, traveling in complex preprogrammed trajectories on the surface of the liquid. Similar gel-based self-propelling floaters can find applications as mixers and cargo carriers in lab-on-a-chip devices, and in various platforms for sensing and processing at the microscale. DA - 2012/6/3/ PY - 2012/6/3/ DO - 10.1021/la301437f VL - 28 IS - 26 SP - 10128-10135 SN - 0743-7463 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84863471809&partnerID=MN8TOARS ER - TY - JOUR TI - Fibrillization Propensity for Short Designed Hexapeptides Predicted by Computer Simulation AU - Wagoner, Victoria A. AU - Cheon, Mookyung AU - Chang, Iksoo AU - Hall, Carol K. T2 - JOURNAL OF MOLECULAR BIOLOGY AB - Assembly of normally soluble proteins into ordered aggregates, known as amyloid fibrils, is a cause or associated symptom of numerous human disorders, including Alzheimer's and the prion diseases. Here, we test the ability of discontinuous molecular dynamics (DMD) simulations based on PRIME20, a new intermediate-resolution protein force field, to predict which designed hexapeptide sequences will form fibrils, which will not, and how this depends on temperature and concentration. Simulations were performed on 48-peptide systems containing STVIIE, STVIFE, STVIVE, STAIIE, STVIAE, STVIGE, and STVIEE starting from random-coil configurations. By the end of the simulations, STVIIE and STVIFE (which form fibrils in vitro) form fibrils over a range of temperatures, STVIEE (which does not form fibrils in vitro) does not form fibrils, and STVIVE, STAIIE, STVIAE, and STVIGE (which do not form fibrils in vitro) form fibrils at lower temperatures but stop forming fibrils at higher temperatures. At the highest temperatures simulated, the results on the fibrillization propensity of the seven short de novo designed peptides all agree with the experiments of López de la Paz and Serrano. Our results suggest that the fibrillization temperature (temperature above which fibrils cease to form) is a measure of fibril stability and that by rank ordering the fibrillization temperatures of various sequences, PRIME20/DMD simulations could be used to ascertain their relative fibrillization propensities. A phase diagram showing regions in the temperature-concentration plane where fibrils are formed in our simulations is presented. DA - 2012/3/2/ PY - 2012/3/2/ DO - 10.1016/j.jmb.2011.12.038 VL - 416 IS - 4 SP - 598-609 SN - 0022-2836 KW - fibrils KW - fibrillization propensity KW - fibril stability KW - coarse-grained model KW - discontinuous molecular dynamics ER - TY - JOUR TI - Chevreul Medal for Uwe T. Bornscheuer AU - DeSimone, J. M. AU - Goodenough, J. B. AU - Groves, J. T. AU - Bornscheuer, U. T. T2 - ANGEWANDTE CHEMIE-INTERNATIONAL EDITION AB - Angewandte Chemie International EditionVolume 51, Issue 27 p. 6563-6563 News New Members of the National Academy of Sciences / Chevreul Medal: U. T. Bornscheuer First published: 13 June 2012 https://doi.org/10.1002/anie.201204166Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Graphical Abstract References 1aAngew. Chem. 2011, 123, 10194; Angew. Chem. Int. Ed. 2011, 50, 10018; 1bAngew. Chem. 2012, 5892; Angew. Chem. Int. Ed. 2012, 51, 5792; 1cAngew. Chem. 2011, 123, 7357; Angew. Chem. Int. Ed. 2011, 50, 7219. 2aJ. Wang, J. D. Byrne, M. E. Napier, J. M. DeSimone, Small 2011, 7, 1919; 2bM. J. Hampton, S. S. Williams, Z. Zhou, J. Nunes, D.-H. Ko, J. L. Templeton, E. T. Samulski, J. M. DeSimone, Adv. Mater. 2008, 20, 2667. 3J. B. Goodenough, Z. Anorg. Allg. Chem. 2012, DOI: . 4aR. N. Austin, K. Luddy, K. Erickson, M. Pender-Cudlip, E. Bertrand, D. Deng, R. S. Buzdygon, J. B. van Beilen, J. T. Groves, Angew. Chem. 2008, 120, 5310; Angew. Chem. Int. Ed. 2008, 47, 5232; 4bT. P. Umile, J. T. Groves, Angew. Chem. 2011, 123, 721; Angew. Chem. Int. Ed. 2011, 50, 695. 5aE. Fernández-Álvaro, R. Snajdrova, H. Jochens, T. Davids, D. Böttcher, U. T. Bornscheuer, Angew. Chem. 2011, 123, 8742; Angew. Chem. Int. Ed. 2011, 50, 8584; 5bH. B. Brundiek, A. S. Evitt, R. Kourist, U. T. Bornscheuer, Angew. Chem. 2012, 124, 425; Angew. Chem. Int. Ed. 2012, 51, 412. Volume51, Issue27July 2, 2012Pages 6563-6563 ReferencesRelatedInformation DA - 2012/// PY - 2012/// DO - 10.1002/anie.201204166 VL - 51 IS - 27 SP - 6563-6563 SN - 1433-7851 ER - TY - JOUR TI - Cell regulation: A time to signal, a time to respond (Comment on DOI 10.1002/bies.201100172) AU - Haugh, Jason M. T2 - BIOESSAYS AB - The behaviours of living cells are normally controlled by growth factors, cytokines, and other molecular cues in vivo, affecting cell division, migration, differentiation, and survival. Specific receptors on the cell surface recognize these cues and mobilize signal transduction networks, which constitute the intracellular machinery responsible for actuating and regulating functional responses. In cancer, certain proteins (oncogenes) are mutated so as to render the cell autonomous from external cues. Consequently, intracellular signalling is robust and uncontrolled, and thus so are cell proliferation, survival, and movement. It is therefore of paramount importance to understand the intricate mechanisms by which signal transduction networks are governed, but the problem is the daunting complexity at the molecular level. Even when considering a single pathway, one must wade through a morass of protein components and post-translational modifications to figure out how it is regulated. The encouraging news is that considerable progress over the past 20 years or so has resulted in a mature understanding of many signalling pathways. At least conceptually, this simplifies the problem by allowing us to treat pathways as modules, each responsible for the activation of a critical node in the network. Such ‘master regulators’ would include mitogen-activated protein kinases (MAPKs) and other important protein kinases such as Akt. Hence, the notion is that we can reduce the complexity of the problem by splitting it into two parts: one, the convergence of receptor-mediated pathways resulting in activation of a handful of master regulators, and two, the influences of those regulators on cell behaviour. With this paradigm, we can tackle each of the two parts independently and develop quantitative frameworks in which measurements are compared with mathematical models 1. Thus, it is envisioned that we will be able to predict the effects of molecular interventions in both normal and transformed cells, a prospect that is not lost on forward-thinking drug companies 2. In this issue of BioEssays, Schneider et al. 3 highlight an important fundamental gap in the paradigm outlined above: at some point, one must make the jump from molecules to phenotype. Whereas the molecular world can be described purely mechanistically, i.e. according to physicochemical principles, it is prohibitively difficult to go from signalling to response that way. For example, a mechanistic model of cell growth would need to wholly incorporate gene expression and cell metabolism. The only recourse is a correlative approach 4. Signalling readouts (focused on presumed master regulators) are measured along with cell responses, and then a mathematical relationship between the two may be constructed. But what relationship do we choose? A linear regression is arguably the simplest approach; is that good enough? To a certain extent, the answer has proven to be yes, although the relationships that have been identified incorporate multiple signalling readouts 5; as one might expect, measurement of a single pathway does not adequately predict the outcome across all stimulation/intervention conditions. Schneider et al. 3 add a new wrinkle to this discussion, which is the temporal aspect of cell signalling. Activation of a signalling network is dynamic, subject to receptor downregulation and other forms of negative feedback adaptation. Thus, the magnitude of pathway activation typically peaks early before reaching a quasi-steady plateau. Negative feedback in signalling networks has been sucessfully characterized through quantitative measurements and models 6, but then linking the temporal output of such models to cell responses requires hard assumptions about how the cell makes decisions. As articulated by Marshall 7, is it the steady state that matters most, or the peak? If the entire time course is important, how should one weight the signalling magnitudes at different times? Schneider et al. 3 discuss the merits of mathematically representing the kinetics as a time integral, calculated numerically. They explain that a primary challenge with this approach is that one must assume when the integration should be truncated, i.e. when the cell's decision is final. This sort of conjecture highlights the fundamental difficulties we face when trying to simplify complex biology using mathematics. DA - 2012/7// PY - 2012/7// DO - 10.1002/bies.201200077 VL - 34 IS - 7 SP - 528-529 SN - 0265-9247 ER - TY - JOUR TI - Alkaline-stable peptide ligand affinity adsorbents for the purification of biomolecules AU - Menegatti, S. AU - Naik, A. D. AU - Gurgel, P. V. AU - Carbonell, R. G. T2 - Journal of Chromatography A AB - A strategy of modification of resin surface chemistry is presented to produce hydrophilic peptide-based alkaline-stable affinity adsorbents for the purification of biopharmaceuticals from complex media. In this work, the peptide-based affinity adsorbent HWRGWV-Toyopearl resin for the purification of IgG is presented as an example. When prepared by direct peptide synthesis on the chromatographic matrix, the peptide-based resin showed lability under alkaline conditions. In fact, the regeneration with aqueous 0.1 M NaOH caused the leaching of 40% of the peptide ligand, resulting in a decrease of IgG yield from 85% to 23%. It was found that the ligand leaching was caused by the coupling of a significant amount of peptide by alkaline-labile ester bonds. A method was designed to prevent the formation of ester bonds and allow the synthesis of the ligand exclusively on alkaline-stable bonds. The method consists in activating the hydrophilic base resin, blocking the hydroxyl groups responsible for alkaline lability and performing the peptide synthesis exclusively via alkaline-stable amide bonds. Repeated cycles of IgG purification from a cell culture medium were performed, each followed by cleaning with aqueous NaOH (0.1 M, 0.5 M and 1 M). The IgG yield decreased from 91% to 85% after 200 purification cycles with 0.1 M NaOH. However, the IgG purity remained almost constant at around 95% based on SDS-PAGE analysis. The procedure presented is rapid, efficient and inexpensive and does not require any equipment other than the conventional instrumentation for peptide synthesis. The method also has a broad application since it is valid for any peptide ligand identified for the purification of a biopharmaceutical target. DA - 2012/7/6/ PY - 2012/7/6/ DO - 10.1016/j.chroma.2012.04.072 VL - 1245 SP - 55–64 KW - Peptide ligand KW - Affinity adsorbent KW - NaOH stability KW - Modification of surface chemistry KW - Solid-phase peptide synthesis KW - Cleaning-in-place ER - TY - JOUR TI - alpha-Fe2O3 Nanoparticle-Loaded Carbon Nanofibers as Stable and High-Capacity Anodes for Rechargeable Lithium-Ion Batteries AU - Ji, Liwen AU - Toprakci, Ozan AU - Alcoutlabi, Mataz AU - Yao, Yingfang AU - Li, Ying AU - Zhang, Shu AU - Guo, Bingkun AU - Lin, Zhan AU - Zhang, Xiangwu T2 - ACS APPLIED MATERIALS & INTERFACES AB - α-Fe(2)O(3) nanoparticle-loaded carbon nanofiber composites were fabricated via electrospinning FeCl(3)·6H(2)O salt-polyacrylonitrile precursors in N,N-dimethylformamide solvent and the subsequent carbonization in inert gas. Scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and elemental analysis were used to study the morphology and composition of α-Fe(2)O(3)-carbon nanofiber composites. It was indicated that α-Fe(2)O(3) nanoparticles with an average size of about 20 nm have a homogeneous dispersion along the carbon nanofiber surface. The resultant α-Fe(2)O(3)-carbon nanofiber composites were used directly as the anode material in rechargeable lithium half cells, and their electrochemical performance was evaluated. The results indicated that these α-Fe(2)O(3)-carbon nanofiber composites have high reversible capacity, good capacity retention, and acceptable rate capability when used as anode materials for rechargeable lithium-ion batteries. DA - 2012/5// PY - 2012/5// DO - 10.1021/am300333s VL - 4 IS - 5 SP - 2672-2679 SN - 1944-8244 UR - https://publons.com/publon/674393/ KW - lithium-ion batteries KW - anodes KW - nanofibers KW - carbon KW - alpha-Fe2O3 ER - TY - JOUR TI - Tuning Multiphase Amphiphilic Rods to Direct Self-Assembly AU - Wang, Jie-Yu AU - Wang, Yapei AU - Sheiko, Sergei S. AU - Betts, Douglas E. AU - DeSimone, Joseph M. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - New methods to direct the self-assembly of particles are highly sought after for multiple applications, including photonics, electronics, and drug delivery. Most techniques, however, are limited to chemical patterning on spherical particles, limiting the range of possible structures. We developed a lithographic technique for fabrication of chemically anisotropic rod-like particles in which we can specify both the size and shape of particles and implement multiple diverse materials to control interfacial interactions. Multiphase rod-like particles, including amphiphilic diblock, triblock, and multiblock were fabricated in the same template mold having a tunable hydrophilic/hydrophobic ratio. Self-assembly of diblock or triblock rods at a water/oil interface led to the formation of bilayer or ribbon-like structures. DA - 2012/4/4/ PY - 2012/4/4/ DO - 10.1021/ja2066187 VL - 134 IS - 13 SP - 5801-5806 SN - 0002-7863 ER - TY - JOUR TI - Magnetic field-induced alignment of nanoparticles in electrospun microfibers AU - Roskov, Kristen E. AU - Atkinson, Jessie E. AU - Bronstein, Lyudmila M. AU - Spontak, Richard J. T2 - RSC ADVANCES AB - We report on the facile and switchable alignment of superparamagnetic iron oxide nanoparticles measuring ∼18 nm in diameter in electrospun microfibers. Application of a magnetic field perpendicular to the electric field employed during electrospinning yields polymeric microfibers with nanoparticles aligned in one-dimensional arrays, thereby providing control over when and where the nanoparticles align. According to electron microscopy, the length over which alignment is desired can be judiciously selected, thereby making these nanomaterials excellent candidates for nanotechnologies requiring nanoscale alignment on-demand. Concurrent alignment of the electrospun fibers using established procedures provides a viable route to organic/inorganic materials possessing anisotropic properties that reflect multiscale alignment. DA - 2012/// PY - 2012/// DO - 10.1039/c2ra20489d VL - 2 IS - 11 SP - 4603-4607 SN - 2046-2069 ER - TY - JOUR TI - Boundary Lubrication of PEO-PPO-PEO Triblock Copolymer Physisorbed on Polypropylene, Polyethylene, and Cellulose Surfaces AU - Li, Y. AU - Rojas, O. J. AU - Hinestroza, J. P. T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - In situ lateral force microscopy (LFM) and X-ray photoelectron spectroscopy (XPS) were used to probe the lubrication behavior of an aqueous solution of poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) (PEO-PPO-PEO) symmetric triblock copolymer on thin films of polypropylene (PP), polyethylene (PE), and cellulose. LFM experiments were carried out while the substrates were immersed in water and in solutions of the copolymer. The friction coefficient on PP and PE was reduced after adsorption from the PEO-PPO-PEO aqueous solution while the opposite effect was observed for cellulose surfaces. A critical normal loading force, at which the friction coefficient of the lubricated and unlubricated surfaces is equal, was identified and related to the affinity of the polymer with the substrate. Further experiments were performed to mimic practical operations involving lubricant addition during manufacturing and postprocessing removal. XPS was used to verify the presence of the lubricant on the polymeric substrates and to evaluate its removal by water washing. The lubricant layer was easily removed by water from the PP and cellulose surfaces while a durable layer was found on PE. The XPS results were in agreement with the highest critical normal loading force measured for PE (52 nN for PE in contrast to a minimum of 10 nN for cellulose). While several reports exist on lubrication on hard surfaces, friction behavior on soft surfaces is still not well documented as the substrates usually deform under loading pressure. Therefore, we also propose a simple lubrication model for PP, PE, and cellulose and the use of critical normal loading force as a parameter to predict lubricity and durability of adsorbed nonionic block copolymers. DA - 2012/2/22/ PY - 2012/2/22/ DO - 10.1021/ie202292r VL - 51 IS - 7 SP - 2931-2940 SN - 0888-5885 ER - TY - JOUR TI - Bicomponent fibre mats with adhesive ultra-hydrophobicity tailored with cellulose derivatives AU - Taajamaa, Laura AU - Kontturi, Eero AU - Laine, Janne AU - Rojas, Orlando J. T2 - JOURNAL OF MATERIALS CHEMISTRY AB - Morphologies featured in bicomponent 2D ultrathin films were reproduced on 3D non-woven microfibre structures. Fibre networks were constructed by electrospinning hydrophobised cellulose derivatives, trimethylsilyl cellulose (TMSC) and cellulose triacetate (CTA), dissolved in a common solvent. Diverse morphologies were obtained depending on the polymer blend ratio: electrospinning of TMSC produced non-continuous micron fibres with shallow dints, TMSC/CTA 5 : 1 flat micron fibres with regular pore arrays, TMSC/CTA 1 : 1 wrinkled micron fibres decorated with shallow dints and occasional larger pores, TMSC/CTA 1 : 5 flat micron fibres with ellipsoidal porous structures and finally, CTA that led to smooth micron and submicron fibres. The fibre mats were ultra-hydrophobic with characteristic water contact angles of ca. 150 degrees. In addition, they were characterised by high contact angle hysteresis, and water droplets adhered to the substrate even after tilting the system upside down. Through conversion of the respective components to cellulose, chemical and adsorption properties of the fibre networks could be tuned without significantly altering the large-scale network morphology. DA - 2012/// PY - 2012/// DO - 10.1039/c2jm30572k VL - 22 IS - 24 SP - 12072-12082 SN - 1364-5501 ER - TY - JOUR TI - Tuning Binary Ionic Liquid Mixtures: Linking Alkyl Chain Length to Phase Behavior and Ionic Conductivity AU - Fox, Eric T. AU - Weaver, Joshua E. F. AU - Henderson, Wesley A. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - The use of mixed salts to generate new composite ionic liquids (ILs) provides a facile means of readily tuning or tailoring the desired properties of ionic media. Despite this, very little information is available about how the structure of the selected ions and composition impacts the properties of salt mixtures. To explore this, six binary IL1–IL2 mixtures based on N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide salts have been characterized. The physicochemical properties (density, viscosity, and ionic conductivity) and phase behavior of these mixtures are reported. The variation of the alkyl chains lengths on the cations plays a significant role in determining both the phase behavior and the physicochemical properties of the mixtures. Notably, the “tunability” of the properties of the IL mixtures is much easier to control than is found by simply making small structural changes to the ions in a given salt. DA - 2012/3/1/ PY - 2012/3/1/ DO - 10.1021/jp300667h VL - 116 IS - 8 SP - 5271-5275 SN - 1932-7447 ER - TY - JOUR TI - Time Dependence of Lysozyme Adsorption on End-Grafted Polymer Layers of Variable Grafting Density and Length AU - Genzer, Jan AU - Arifuzzaman, Shafi AU - Bhat, Rajendra R. AU - Efimenko, Kirill AU - Ren, Chun-lai AU - Szleifer, Igal T2 - LANGMUIR AB - A combined experimental and theoretical approach establishes the long-lived nature of protein adsorption on surfaces coated with chemically grafted macromolecules. Specifically, we monitor the time dependence of adsorption of lysozyme on surfaces comprising polymer assemblies made of poly(2-hydroxyethyl methacrylate) brushes grafted onto flat silica surfaces such that they produce patterns featuring orthogonal and gradual variation of the chain length (N) and grafting density (σ). We show that in the kinetically controlled regime, the amount of adsorbed protein scales universally with the product σN, while at equilibrium the amount of adsorbed protein is governed solely by σ. Surprisingly, for moderate concentrations of protein in solution, adsorption takes more than 72 h to reach an equilibrium, or steady state. Our experimental findings are corroborated with predictions using molecular theory that provides further insight into the protein adsorption phenomenon. The theory predicts that the universal behavior observed experimentally should be applicable to polymers in poor and theta solvents and to a limited extent also to good solvent conditions. Our combined experimental and theoretical findings reveal that protein adsorption is a long-lived phenomenon, much longer than generally assumed. Our studies confirm the previously predicted important differences in behavior for the kinetic versus thermodynamic control of protein adsorption. DA - 2012/1/31/ PY - 2012/1/31/ DO - 10.1021/la2038747 VL - 28 IS - 4 SP - 2122-2130 SN - 0743-7463 ER - TY - JOUR TI - Self-folding of polymer sheets using local light absorption AU - Liu, Ying AU - Boyles, Julie K. AU - Genzer, Jan AU - Dickey, Michael D. T2 - SOFT MATTER AB - This paper demonstrates experimentally and models computationally a novel and simple approach for self-folding of thin sheets of polymer using unfocused light. The sheets are made of optically transparent, pre-strained polystyrene (also known as Shrinky-Dinks) that shrink in-plane if heated uniformly. Black ink patterned on either side of the polymer sheet provides localized absorption of light, which heats the underlying polymer to temperatures above its glass transition. At these temperatures, the predefined inked regions (i.e., hinges) relax and shrink, and thereby cause the planar sheet to fold into a three-dimensional object. Self-folding is therefore achieved in a simple manner without the use of multiple fabrication steps and converts a uniform external stimulus (i.e., unfocused light) on an otherwise compositionally homogenous substrate into a hinging response. Modeling captures effectively the experimental folding trends as a function of the hinge width and support temperature and suggests that the hinged region must exceed the glass transition temperature of the sheet for folding to occur. DA - 2012/// PY - 2012/// DO - 10.1039/c1sm06564e VL - 8 IS - 6 SP - 1764-1769 SN - 1744-6848 ER - TY - JOUR TI - Responsive PET Nano/Microfibers via Surface-Initiated Polymerization AU - Ozcam, A. Evren AU - Roskov, Kristen E. AU - Genzer, Jan AU - Spontak, Richard J. T2 - ACS APPLIED MATERIALS & INTERFACES AB - Poly(ethylene terephthalate) (PET) is one of the most important thermoplastics in ubiquitous use today because of its mechanical properties, clarity, solvent resistance, and recyclability. In this work, we functionalize the surface of electrospun PET microfibers by growing poly(N-isopropylacrylamide) (PNIPAAm) brushes through a chemical sequence that avoids PET degradation to generate thermoresponsive microfibers that remain mechanically robust. Amidation of deposited 3-aminopropyltriethoxysilane, followed by hydrolysis, yields silanol groups that permit surface attachment of initiator molecules, which can be used to grow PNIPAAm via "grafting from" atom-transfer radical polymerization. Spectroscopic analyses performed after each step confirm the expected reaction and the ultimate growth of PNIPAAm brushes. Water contact-angle measurements conducted at temperatures below and above the lower critical solution temperature of PNIPAAm, coupled with adsorption of Au nanoparticles from aqueous suspension, demonstrate that the brushes retain their reversible thermoresponsive nature, thereby making PNIPAAm-functionalized PET microfibers suitable for filtration media, tissue scaffolds, delivery vehicles, and sensors requiring robust microfibers. DA - 2012/1// PY - 2012/1// DO - 10.1021/am201559f VL - 4 IS - 1 SP - 59-64 SN - 1944-8252 KW - electrospinning KW - polymer brush KW - poly(ethylene terephthalate) KW - responsive polymer KW - surface functionalization ER - TY - JOUR TI - Physical and electrochemical properties of binary ionic liquid mixtures: (1-x) PYR14TFSI-(x) PYR14IM14 AU - Montanino, M. AU - Moreno, M. AU - Alessandrini, F. AU - Appetecchi, G. B. AU - Passerini, S. AU - Zhou, Q. AU - Henderson, W. A. T2 - Electrochimica Acta DA - 2012/// PY - 2012/// VL - 60 SP - 163-169 ER - TY - JOUR TI - Mesoscopic Simulations of the Phase Behavior of Aqueous EO19PO29EO19 Solutions Confined and Sheared by Hydrophobic and Hydrophilic Surfaces AU - Liu, Hongyi AU - Li, Yan AU - Krause, Wendy E. AU - Pasquinelli, Melissa A. AU - Rojas, Orlando J. T2 - ACS APPLIED MATERIALS & INTERFACES AB - The MesoDyn method is used to investigate associative structures in aqueous solution of a nonionic triblock copolymer consisting of poly(propylene oxide) capped on both ends with poly(ethylene oxide) chains. The effect of adsorbing (hydrophobic) and nonadsorbing (hydrophilic) solid surfaces in contact with aqueous solutions of the polymer is elucidated. The macromolecules form self-assembled structures in solution. Confinement under shear forces is investigated in terms of interfacial behavior and association. The formation of micelles under confinement between hydrophilic surfaces occurs faster than in bulk aqueous solution while layered structures assemble when the polymers are confined between hydrophobic surfaces. Micelles are deformed under shear rates of 1 μs(-1) and eventually break to form persistent, adsorbed layered structures. As a result, surface damage under frictional forces is prevented. Overall, this study indicates that aqueous triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) (Pluronics, EO(m)PO(n)EO(m)) act as a boundary lubricant for hydrophobic surfaces but not for hydrophilic ones. DA - 2012/1// PY - 2012/1// DO - 10.1021/am200917h VL - 4 IS - 1 SP - 87-95 SN - 1944-8252 KW - triblock nonionic polymers KW - pluronics KW - MesoDyn KW - lubrication KW - boundary layer KW - spherical micelles KW - cylindrical micelles KW - wormlike micelles ER - TY - JOUR TI - Electrospun carbon nanofibers decorated with various amounts of electrochemically-inert nickel nanoparticles for use as high-performance energy storage materials AU - Ji, Liwen AU - Lin, Zhan AU - Alcoutlabi, Mataz AU - Toprakci, Ozan AU - Yao, Yingfang AU - Xu, Guanjie AU - Li, Shuli AU - Zhang, Xiangwu T2 - RSC ADVANCES AB - Carbon nanofibers decorated with various amounts of electrochemically-inert metallic nickel nanoparticles are synthesized through electrospinning and carbonization processes. The morphology and composition of Ni nanoparticles in carbon nanofibers are controlled by preparing different nanofiber precursors. The lithium-ion battery performance evaluations indicated that the content of electrochemically-inert Ni nanoparticles in carbon nanofibers has a great influence on the final electrochemical performance. For example, at certain Ni contents, these composite nanofibers display excellent electrochemical performance, such as high reversible capacities, good capacity retention, and excellent rate performance, when directly used as binder-free anodes for rechargeable lithium-ion batteries. However, when the Ni content is too low or too high, the corresponding electrodes show low reversible capacities although they still have good reversibility and rate performance. DA - 2012/// PY - 2012/// DO - 10.1039/c1ra00676b VL - 2 IS - 1 SP - 192-198 SN - 2046-2069 UR - https://publons.com/publon/674391/ ER - TY - JOUR TI - Data-driven modelling of receptor tyrosine kinase signalling networks quantifies receptor-specific potencies of PI3K-and Ras-dependent ERK activation AU - Cirit, Murat AU - Haugh, Jason M. T2 - BIOCHEMICAL JOURNAL AB - Signal transduction networks in mammalian cells, comprising a limited set of interacting biochemical pathways, are accessed by various growth factor and cytokine receptors to elicit distinct cell responses. This raises the question as to how specificity of the stimulus-response relationship is encoded at the molecular level. It has been proposed that specificity arises not only from the activation of unique signalling pathways, but also from quantitative differences in the activation and regulation of shared receptor-proximal signalling proteins. To address such hypotheses, data sets with greater precision and coverage of experimental conditions will need to be acquired, and rigorous frameworks that codify and parameterize the inherently non-linear relationships among signalling activities will need to be developed. In the present study we apply a systematic approach combining quantitative measurements and mathematical modelling to compare the signalling networks accessed by FGF (fibroblast growth factor) and PDGF (platelet-derived growth factor) receptors in mouse fibroblasts, in which the ERK (extracellular-signal-regulated kinase) cascade is activated by Ras- and PI3K (phosphoinositide 3-kinase)-dependent pathways. We show that, whereas the FGF stimulation of PI3K signalling is relatively weak, this deficiency is compensated for by a more potent Ras-dependent activation of ERK. Thus, as the modelling would predict, the ERK pathway is activated to a greater extent in cells co-stimulated with FGF and PDGF, relative to the saturated levels achieved with either ligand alone. It is envisaged that similar approaches will prove valuable in the elucidation of quantitative differences among other closely related receptor signalling networks. DA - 2012/1/1/ PY - 2012/1/1/ DO - 10.1042/bj20110833 VL - 441 IS - 1 SP - 77-85 SN - 0264-6021 KW - computational biology KW - cross-talk KW - growth factor KW - kinetic analysis KW - mitogen-activated protein kinase (MAPK) KW - receptor tyrosine kinase ER - TY - JOUR TI - Computer Simulation of Concurrent Bulk- and Surface-Initiated Living Polymerization AU - Turgman-Cohen, Salomon AU - Genzer, Jan T2 - MACROMOLECULES AB - We use Monte Carlo simulation implementing the bond fluctuation model formalism in the canonical (NVT) ensemble to study living polymerization initiated concurrently in bulk and on flat substrates. Our results reveal that the molecular weights and molecular weight distributions of both classes of polymers depend on the grafting density of the surface-bound polymers (σ) and the fraction of polymers on the surface (η) relative to that in bulk. In general, polymer grafts on the surface possess lower molecular weight and higher polydispersity index compared to their bulk counterparts. The difference between the molecular weight of the two populations of polymers decreases with decreasing σ and increasing η. Our work provides evidence that the common practice of using the molecular weight of bulk-initiated polymers in estimating the grafting density of polymeric anchors on flat substrates is not generally valid. DA - 2012/2/28/ PY - 2012/2/28/ DO - 10.1021/ma202679r VL - 45 IS - 4 SP - 2128-2137 SN - 0024-9297 ER - TY - JOUR TI - Wetting properties induced in nano-composite POSS-MA polymer films by atomic layer deposited oxides AU - Vasquez, Kyle A. AU - Vincent-Johnson, Anita J. AU - Hughes, W. Christopher AU - Augustine, Brian H. AU - Lee, Kyoungmi AU - Parsons, Gregory N. AU - Scarel, Giovanna T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Due to their unique properties, nano-composite polyhedral oligomeric silsequioxane (POSS) copolymer films are attractive for various applications. Here we show that their natural hydrophobic character can become hydrophilic when the films are modified by a thin oxide layer, up to 8 nm thick, prepared using atomic layer deposition. A proper choice of the deposition temperature and thickness of the oxide layer are required to achieve this goal. Unlike other polymeric systems, a marked transition to a hydrophilic state is observed with oxide layers deposited at increasing temperatures up to the glass transition temperature (∼110 °C) of the POSS copolymer film. The hydrophilic state is monitored through the water contact angle of the POSS film. Infrared absorbance spectra indicate that, in hydrophilic samples, the integral of peaks corresponding to surface Al–O (hydrophilic) is significantly larger than that of peaks linked to hydrophobic species. DA - 2012/1// PY - 2012/1// DO - 10.1116/1.3639134 VL - 30 IS - 1 SP - SN - 0734-2101 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298992800005&KeyUID=WOS:000298992800005 ER - TY - JOUR TI - The subcellular proteome of undifferentiated human embryonic stem cells AU - Sarkar, Prasenjit AU - Collier, Timothy S. AU - Randall, Shan M. AU - Muddiman, David C. AU - Rao, Balaji M. T2 - PROTEOMICS AB - Abstract We have characterized the subcellular proteome of human embryonic stem cells (hESCs) through MS analysis of the membrane, cytosolic, and nuclear fractions, isolated from the same sample of undifferentiated hESCs. Strikingly, 74% of all proteins identified were detected in a single subcellular fraction; we also carried out immunofluorescence studies to validate the subcellular localization suggested by proteomic analysis, for a subset of proteins. Our approach resulted in deeper proteome coverage – peptides mapping to 893, 2475, and 1185 proteins were identified in the nuclear, cytosolic, and membrane fractions, respectively. Additionally, we used spectral counting to estimate the relative abundance of all cytosolic proteins. A large number of proteins relevant to hESC biology, including growth factor receptors, cell junction proteins, transcription factors, chromatin remodeling proteins, and histone modifying enzymes were identified. Our analysis shows that components of a large number of interacting signaling pathways are expressed in hESCs. Finally, we show that proteomic analysis of the endoplasmic reticulum (ER) and Golgi compartments is a powerful alternative approach to identify secreted proteins since these are synthesized in the ER and transit through the Golgi. Taken together, our results show that systematic subcellular proteomic analysis is a valuable tool for studying hESC biology. DA - 2012/2// PY - 2012/2// DO - 10.1002/pmic.201100507 VL - 12 IS - 3 SP - 421-430 SN - 1615-9853 KW - Cell biology KW - Extracellular proteins KW - Human embryonic stem cells KW - Subcellular fractionation KW - Subcellular proteomics ER - TY - JOUR TI - Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition AU - Poodt, Paul AU - Cameron, David C. AU - Dickey, Eric AU - George, Steven M. AU - Kuznetsov, Vladimir AU - Parsons, Gregory N. AU - Roozeboom, Fred AU - Sundaram, Ganesh AU - Vermeer, Ad T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Atomic layer deposition (ALD) is a technique capable of producing ultrathin conformal films with atomic level control over thickness. A major drawback of ALD is its low deposition rate, making ALD less attractive for applications that require high throughput processing. An approach to overcome this drawback is spatial ALD, i.e., an ALD mode where the half-reactions are separated spatially instead of through the use of purge steps. This allows for high deposition rate and high throughput ALD without compromising the typical ALD assets. This paper gives a perspective of past and current developments in spatial ALD. The technology is discussed and the main players are identified. Furthermore, this overview highlights current as well as new applications for spatial ALD, with a focus on photovoltaics and flexible electronics. DA - 2012/1// PY - 2012/1// DO - 10.1116/1.3670745 VL - 30 IS - 1 SP - SN - 1520-8559 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298992800066&KeyUID=WOS:000298992800066 ER - TY - JOUR TI - S-Layer Homology Domain Proteins Csac_0678 and Csac_2722 Are Implicated in Plant Polysaccharide Deconstruction by the Extremely Thermophilic Bacterium Caldicellulosiruptor saccharolyticus AU - Ozdemir, Inci AU - Blumer-Schuette, Sara E. AU - Kelly, Robert M. T2 - APPLIED AND ENVIRONMENTAL MICROBIOLOGY AB - ABSTRACT The genus Caldicellulosiruptor contains extremely thermophilic bacteria that grow on plant polysaccharides. The genomes of Caldicellulosiruptor species reveal certain surface layer homology (SLH) domain proteins that have distinguishing features, pointing to a role in lignocellulose deconstruction. Two of these proteins in Caldicellulosiruptor saccharolyticus (Csac_0678 and Csac_2722) were examined from this perspective. In addition to three contiguous SLH domains, the Csac_0678 gene encodes a glycoside hydrolase family 5 (GH5) catalytic domain and a family 28 carbohydrate-binding module (CBM); orthologs to Csac_0678 could be identified in all genome-sequenced Caldicellulosiruptor species. Recombinant Csac_0678 was optimally active at 75°C and pH 5.0, exhibiting both endoglucanase and xylanase activities. SLH domain removal did not impact Csac_0678 GH activity, but deletion of the CBM28 domain eliminated binding to crystalline cellulose and rendered the enzyme inactive on this substrate. Csac_2722 is the largest open reading frame (ORF) in the C. saccharolyticus genome (predicted molecular mass of 286,516 kDa) and contains two putative sugar-binding domains, two Big4 domains (bacterial domains with an immunoglobulin [Ig]-like fold), and a cadherin-like (Cd) domain. Recombinant Csac_2722, lacking the SLH and Cd domains, bound to cellulose and had detectable carboxymethylcellulose (CMC) hydrolytic activity. Antibodies directed against Csac_0678 and Csac_2722 confirmed that these proteins bound to the C. saccharolyticus S-layer. Their cellular localization and functional biochemical properties indicate roles for Csac_0678 and Csac_2722 in recruitment and hydrolysis of complex polysaccharides and the deconstruction of lignocellulosic biomass. Furthermore, these results suggest that related SLH domain proteins in other Caldicellulosiruptor genomes may also be important contributors to plant biomass utilization. DA - 2012/2// PY - 2012/2// DO - 10.1128/aem.07031-11 VL - 78 IS - 3 SP - 768-777 SN - 1098-5336 ER - TY - JOUR TI - Paper deacidification and UV protection using ZnO atomic layer deposition AU - Hanson, C. A. AU - Oldham, C. J. AU - Parsons, G. N. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Acid degradation of cellulosic paper in archival books, periodicals, and historic documents is a serious and widespread problem. Using acidic page samples from ∼40 year old books, we demonstrate that atomic layer deposition (ALD) ZnO can adjust and controllably neutralize the paper acid content. The paper samples were collected and analyzed in accordance with recognized Technical Association of the Pulp and Paper Industry (TAPPI) test standards. The average pH of the starting paper was 3.7 ± 0.4 and 4.4 ± 0.1 as determined using the TAPPI surface probe and cold water extraction methods, respectively. After 50 ALD ZnO cycles, the same tests on the coated paper produced an average pH of 7.39 ± 0.08 and 7.3 ± 0.4, respectively. Scanning electron microscopy confirmed that the cellulose structure remained intact during ALD. Additional tests of recently printed newspaper samples coated with ALD ZnO also show that ALD can effectively prevent paper discoloration and embrittlement caused by UV sunlight photoexposure. While there are many known methods for paper preservation, including others using diethyl zinc, the control afforded by ALD provides attractive advantages over other known approaches for preservation of archival paper and other natural fibrous materials. DA - 2012/1// PY - 2012/1// DO - 10.1116/1.3656251 VL - 30 IS - 1 SP - SN - 1520-8559 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298992800017&KeyUID=WOS:000298992800017 ER - TY - JOUR TI - Modification of Melt-Spun Isotactic Polypropylene and Poly(lactic acid) Bicomponent Filaments with a Premade Block Copolymer AU - Arvidson, Sara A. AU - Roskov, Kristen E. AU - Pate, Jaimin J. AU - Spontak, Richard J. AU - Khan, Saad A. AU - Gorga, Russell E. T2 - MACROMOLECULES AB - While numerous studies have investigated the effect of adding a block copolymer as a macromolecular surfactant to immiscible polymer blends, no such efforts have sought to alter the properties of melt-spun bicomponent core–sheath filaments with a nonreactive compatibilizing agent. In this study, we examine the effect of adding poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) triblock copolymer to core–sheath filaments consisting of isotactic polypropylene (iPP) and poly(lactic acid) (PLA). Incorporation of the copolymer into blends of iPP/PLA is observed to reduce the size scale of phase separation. Interfacial slip between molten iPP and PLA layers is evaluated by rheology under steady-shear conditions. Addition of SEBS to the PLA sheath during filament formation reduces the tendency of PLA sheaths to crack prior to iPP core failure during tensile testing. In reversed filament configurations, the copolymer does not hinder the development of molecular orientation, related to fiber strength, during fiber spinning. Electron microscopy reveals that the copolymer molecules form unique, highly nonequilibrium morphologies under the spinning conditions employed here. DA - 2012/1/24/ PY - 2012/1/24/ DO - 10.1021/ma202246h VL - 45 IS - 2 SP - 913-925 SN - 1520-5835 ER - TY - JOUR TI - Mechanisms for hydrophilic/hydrophobic wetting transitions on cellulose cotton fibers coated using Al2O3 atomic layer deposition AU - Lee, Kyoungmi AU - Jur, Jesse S. AU - Kim, Do Han AU - Parsons, Gregory N. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - This report explores reactions that proceed during the first few cycles of inorganic film atomic layer deposition (ALD) on natural cellulose cotton fibers, and how surface reactions can explain the previously observed transitions in surface wetting upon ALD on cotton fibers. Atomic layer deposition of aluminum oxide and zinc oxide onto natural cotton cellulose produces a transition from hydrophilic to hydrophobic, then from hydrophobic back to hydrophilic, and we describe here the main factors that bring about. Interestingly, we show that air exposure and related adventitious carbon adsorption also affects the subsequent reactions and wetting properties obtained after subsequent ALD cycles. X-ray photoelectron spectroscopy and in situ Fourier transform infrared spectroscopy data indicate Al-(O-C-)3 bonding units form when trimethylaluminum interacts with surface –OH units during the first precursor doses, producing a hydrophobic finish on the cotton that remains for only a few ALD cycles. Also, field-emission scanning electron microscopy results show that some surface roughening may occur in the first few ALD cycles, and the roughening of the hydrophobic-finished surface can also promote an increase in measured hydrophobicity. DA - 2012/1// PY - 2012/1// DO - 10.1116/1.3671942 VL - 30 IS - 1 SP - SN - 0734-2101 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298992800063&KeyUID=WOS:000298992800063 ER - TY - JOUR TI - Hydrophilic mechanical buffer layers and stable hydrophilic finishes on polydimethylsiloxane using combined sequential vapor infiltration and atomic/molecular layer deposition AU - Gong, Bo AU - Spagnola, Joseph C. AU - Parsons, Gregory N. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Polydimethylsiloxane (PDMS) is an important polymer material widely used for microfluidic device fabrication, microcontact lithography, and surface morphology molding. However, the hydrophobic surface limits its functionality. Low temperature atomic layer deposition (ALD) has recently been used to functionalize a wide range of polymer surfaces. In previous research, the authors were able to produce a uniform hydrophilic alumina film coating on PDMS using trimethyl aluminum/water ALD. However, the surface recovered its hydrophobicity after 24–48 h in ambient air or under inert gas storage, which was ascribed to organic species outdiffusion through the ALD layer. This paper reports a stable hydrophilic ALD surface modification on the PDMS. The PDMS substrate was first sequentially exposed to trimethylaluminum and water vapor, allowing the vapors to infiltrate and react to create a mechanical and diffusion buffer layer in the PDMS surface region. This buffer layer helps to nucleate a cohesive hydrophilic ALD or molecular layer deposition (MLD) coating and also helps prevent organic outdiffusion that typically leads to PDMS hydrophobic recovery. The results provide valuable insight into reliable surface energy and mechanical modification of PDMS using vapor-phase precursor/polymer reactions. In addition, molecular layer deposition of “alucone” coatings was also investigated to modify the PDMS surface. The experiment result showed the vapor infiltration and MLD coatings produce a viable and stable hydrophilic surface on PDMS. DA - 2012/1// PY - 2012/1// DO - 10.1116/1.3670963 VL - 30 IS - 1 SP - SN - 0734-2101 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298992800056&KeyUID=WOS:000298992800056 ER - TY - JOUR TI - Enhanced Biomimetic Performance of Ionic Polymer-Metal Composite Actuators Prepared with Nanostructured Block Ionomers AU - Vargantwar, Pruthesh H. AU - Roskov, Kristen E. AU - Ghosh, Tushar K. AU - Spontak, Richard J. T2 - MACROMOLECULAR RAPID COMMUNICATIONS AB - Abstract Ionic polymer–metal composites (IPMCs) represent an important class of stimuli‐responsive polymers that are capable of bending upon application of an electric potential. Conventional IPMCs, prepared with Nafion and related polyelectrolytes, often suffer from processing challenges, relatively low actuation levels and back relaxation during actuation. In this study, we examine and compare the effects of fabrication and solvent on the actuation behavior of a block ionomer with a sulfonated midblock and glassy endblocks that are capable of self‐organizing and thus stabilizing a molecular network in the presence of a polar solvent. Unlike Nafion, this material can be readily dissolved and cast from solution to yield films that vary in thickness and exhibit enormous solvent uptake. Cycling the initial chemical deposition of Pt on the surfaces of swollen films (the compositing process) increases the extent to which the electrodes penetrate the films, thereby improving contact along the polymer/electrode interface. The maximum bending actuation measured from IPMCs prepared with different solvents is at least comparable, but is often superior, to that reported for conventional IPMCs, without evidence of back relaxation. An unexpected characteristic observed here is that the actuation direction can be solvent regulated. Our results confirm that this block ionomer constitutes an attractive alternative for use in IPMCs and their associated applications. DA - 2012/1/16/ PY - 2012/1/16/ DO - 10.1002/marc.201100535 VL - 33 IS - 1 SP - 61-68 SN - 1022-1336 KW - block ionomer KW - electroactive polymer KW - ionic polymer-metal composite KW - ion transport KW - polyelectrolyte KW - stimulti-responsive polymer ER - TY - JOUR TI - Effect of temperature and gas velocity on growth per cycle during Al2O3 and ZnO atomic layer deposition at atmospheric pressure AU - Mousa, Moataz Bellah M. AU - Oldham, Christopher J. AU - Jur, Jesse S. AU - Parsons, Gregory N. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - The growth per cycle as a function of temperature during atomic layer deposition (ALD) of Al2O3 and ZnO at atmospheric pressure follows very closely the trend measured at typical (∼2 Torr) process pressure. However, the overall growth rate is found to be nearly 2 × larger at higher pressure and the magnitude of the growth increase can be adjusted by controlling the gas velocity near the growth surface. The growth increase at high pressure is approximately independent of process temperature at T < 200 °C for Al2O3 and ZnO, but the effect begins to become less pronounced at T > 150 °C, especially for Al2O3. The relatively high growth/cycle measured at 760 Torr and T < 150 °C suggests that excess physisorbed water remains on the alumina or zinc oxide surface after the water purge step. Increasing the gas velocity in the growth zone reduces the growth rate, consistent with more efficient removal of excess water. To better understand the observed trends, we present analytical expressions for the boundary layer thickness and species diffusivity and describe how these parameters are affected by reactor pressure and bulk gas velocity in the low temperature regime. To optimize ALD films and products, new ALD schemes at ambient pressure will need to understand the interaction between reactor pressure, gas velocity near the growth surface, fluid boundary layer thickness, and product desorption and diffusivity to achieve controlled growth. DA - 2012/1// PY - 2012/1// DO - 10.1116/1.3670961 VL - 30 IS - 1 SP - SN - 1520-8559 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298992800055&KeyUID=WOS:000298992800055 ER - TY - JOUR TI - Atomic layer deposition of Ru onto organic monolayers: Shifting metal effective work function using monolayer structure AU - Park, Kie Jin AU - Parsons, Gregory N. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Organic thin films are integrated with metal atomic layer deposition metallization to adjust and tune the electronic properties of metal/dielectric junctions. Specifically, 3-aminopropyltriethoxysilane (APTES) and undecenyltrichlorosilane (UDTS) self-assembled monolayers on hafnia-based dielectrics produce a shift in the effective work function of ruthenium metal deposited by atomic layer deposition at 325 °C onto the monolayer/oxide heterostructure. Based on infrared analysis, the molecular monolayer is relatively stable upon heating above 300 °C. The effective work function extracted from measurements of flat band voltage versus oxide thickness shift by +0.1 and −0.6 V when the metal is deposited on APTES and UDTS, respectively, consistent with expected organic interface dipoles on the dielectric surface. Results suggest various nucleation mechanisms for ALD growth on organic monolayers, and demonstrate that low temperature ALD is useful for metallization of organic modified surfaces for a range of applications. DA - 2012/1// PY - 2012/1// DO - 10.1116/1.3671938 VL - 30 IS - 1 SP - SN - 1520-8559 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298992800062&KeyUID=WOS:000298992800062 ER - TY - JOUR TI - Atomic layer deposition for electrochemical energy generation and storage systems AU - Peng, Qing AU - Lewis, Jay S. AU - Hoertz, Paul G. AU - Glass, Jeffrey T. AU - Parsons, Gregory N. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Clean renewable energy sources (e.g., solar, wind, and hydro) offers the most promising solution to energy and environmental sustainability. On the other hand, owing to the spatial and temporal variations of renewable energy sources, and transportation and mobility needs, high density energy storage and efficient energy distribution to points of use is also critical. Moreover, it is challenging to scale up those processes in a cost-effective way. Electrochemical processes, including photoelectrochemical devices, batteries, fuel cells, super capacitors, and others, have shown promise for addressing many of the abovementioned challenges. Materials with designer properties, especially the interfacial properties, play critical role for the performance of those devices. Atomic layer deposition is capable of precise engineering material properties on atomic scale. In this review, we focus on the current state of knowledge of the applications, perspective and challenges of atomic layer deposition process on the electrochemical energy generation and storage devices and processes. DA - 2012/1// PY - 2012/1// DO - 10.1116/1.3672027 VL - 30 IS - 1 SP - SN - 0734-2101 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298992800067&KeyUID=WOS:000298992800067 ER - TY - JOUR TI - Analysis of EIS Technique and Nafion 117 Conductivity as a Function of Temperature and Relative Humidity AU - Yadav, Rameshwar AU - Fedkiw, Peter S. T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - This work presents an analysis of electrochemical impedance spectroscopy (EIS) technique and conductivity of Nafion 117 membrane at relative humidities of 10–100% and at temperatures 25–80°C. A correlation is presented to calculate the conductivity of Nafion 117 over the temperature and water vapor activity range measured. The correlation also captures the effect of water vapor activity on the activation energy for proton transport. The two-probe EIS technique was employed to measure the in-plane membrane resistance and the effect of platinum electrode dimension was investigated. An equivalent circuit that captures the impedance spectra was used to resolve the ionic resistance. The capacitive behavior of Nafion 117 with water-uptake was observed and analyzed. The two- and four-probe methods are compared and yield essentially identical Nafion 117 conductivities (two-probe 79 ± 1% mS cm−1, four-probe 82 ± 1% mS cm−1) in room-temperature liquid water. DA - 2012/// PY - 2012/// DO - 10.1149/2.104203jes VL - 159 IS - 3 SP - B340-B346 SN - 1945-7111 ER - TY - JOUR TI - The Soft-Confined Method for Creating Molecular Models of Amorphous Polymer Surfaces AU - Liu, Hongyi AU - Li, Yan AU - Krause, Wendy E. AU - Rojas, Orlando J. AU - Pasquinelli, Melissa A. T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - The goal of this work was to use molecular dynamics (MD) simulations to build amorphous surface layers of polypropylene (PP) and cellulose and to inspect their physical and interfacial properties. A new method to produce molecular models for these surfaces was developed, which involved the use of a "soft" confining layer comprised of a xenon crystal. This method compacts the polymers into a density distribution and a degree of molecular surface roughness that corresponds well to experimental values. In addition, calculated properties such as density, cohesive energy density, coefficient of thermal expansion, and the surface energy agree with experimental values and thus validate the use of soft confining layers. The method can be applied to polymers with a linear backbone such as PP as well as those whose backbones contain rings, such as cellulose. The developed PP and cellulose surfaces were characterized by their interactions with water. It was found that a water nanodroplet spreads on the amorphous cellulose surfaces, but there was no significant change in the dimension of the droplet on the PP surface; the resulting MD water contact angles on PP and amorphous cellulose surfaces were determined to be 106 and 33°, respectively. DA - 2012/2/9/ PY - 2012/2/9/ DO - 10.1021/jp209024r VL - 116 IS - 5 SP - 1570-1578 SN - 1520-6106 ER - TY - JOUR TI - High-rate capability of LiFePO4 cathode materials containing Fe2P and trace carbon AU - Yin, Yuehui AU - Gao, Mingxia AU - Pan, Hongge AU - Shen, Lukai AU - Ye, Xin AU - Liu, Yongfeng AU - Fedkiw, Peter S. AU - Zhang, Xiangwu T2 - JOURNAL OF POWER SOURCES AB - Carbon coating and nano-scale particle size are two impactful factors in improving the rate capability of LiFePO4 cathode materials for lithium-ion batteries. However, both factors decrease the tap density of the materials and are possibly causing unfavorable effect on the volumetric capacity of the cathode materials and thus the batteries, which is undesirable in commercial application. In the present study, LiFePO4 materials with moderate particle size of sub-micron and trace carbon content (0.5–0.9 wt.%) are synthesized by a mechanical activation method. High-electronic conductivity iron phosphides (Fe2P/FeP) are in situ introduced into the LiFePO4 materials and the amount is modified by the calcination temperature. Electrochemical testing shows that Fe2P/FeP plays an important role in improving the high-rate capability of LiFePO4 with moderate particle size. The product calcined at 700 °C, which has a high-tap density of 1.37 g cm−3 correlating to a specific surface area approximately of 4 m2 g−1, possesses discharge capacities of 110 and 100 mAh g−1 at discharge rates of 5 C and 10 C, respectively. The introduction of Fe2P/FeP in an amount of ca. 5 wt.% rather than carbon coating and the moderate particle size of LiFePO4 are promising approaches to obtain LiFePO4 cathode material of high-rate capability without unduly compromising its volumetric capacity. DA - 2012/2/1/ PY - 2012/2/1/ DO - 10.1016/j.jpowsour.2011.10.042 VL - 199 SP - 256-262 SN - 0378-7753 UR - https://publons.com/publon/4984276/ KW - Lithium-ion battery KW - Lithium iron phosphate KW - Particle size KW - Rate capability KW - Mechanical activation ER - TY - JOUR TI - Diffusion coefficients from 13C PGSE NMR measurements--Fluorine-free ionic liquids with the DCTA- anion AU - Herriot, C. AU - Khatun, S. AU - Fox, E. T. AU - Judeinstein, P. AU - Armand, M. AU - Henderson, W. A. AU - Greenbaum, S. T2 - The Journal of Physical Chemistry Letters DA - 2012/// PY - 2012/// VL - 3 IS - 3 SP - 441-444 ER - TY - JOUR TI - Adsorption of Glycinin and beta-Conglycinin on Silica and Cellulose: Surface Interactions as a Function of Denaturation, pH, and Electrolytes AU - Salas, Carlos AU - Rojas, Orlando J. AU - Lucia, Lucian A. AU - Hubbe, Martin A. AU - Genzer, Jan T2 - BIOMACROMOLECULES AB - Soybean proteins have found uses in different nonfood applications due to their interesting properties. We report on the kinetics and extent of adsorption on silica and cellulose surfaces of glycinin and β-conglycinin, the main proteins present in soy. Quartz crystal microgravimetry (QCM) experiments indicate that soy protein adsorption is strongly affected by changes in the physicochemical environment. The affinity of glycinin and the mass adsorbed on silica and cellulose increases (by ca. 13 and 89%, respectively) with solution ionic strength (as it increases from 0 to 100 mM NaCl) due to screening of electrostatic interactions. In contrast, β-conglycinin adsorbs on the same substrates to a lower extent and the addition of electrolyte reduces adsorption (by 25 and 57%, respectively). The addition of 10 mM 2-mercaptoethanol, a denaturing agent, reduces the adsorption of both proteins with a significant effect for glycinin. This observation is explained by the cleavage of disulfide bonds which allows unfolding of the molecules and promotes dissociation into subunits that favors more compact adsorbed layer structures. In addition, adsorption of glycinin onto cellulose decreases with lowering the pH from neutral to pH 3 due to dissociation of the macromolecules, resulting in flatter adsorbed layers. The respective adsorption isotherms fit a Langmuir model and QCM shifts in energy dissipation and frequency reveal multiple-step kinetic processes indicative of changes in adlayer structure. DA - 2012/2// PY - 2012/2// DO - 10.1021/bm2014153 VL - 13 IS - 2 SP - 387-396 SN - 1526-4602 ER - TY - JOUR TI - Selective Permeation of Cross-Linked Polyelectrolyte and Polyelectrolyte-Filled Nonwoven Membranes AU - Jung, Kyung-Hye AU - Pourdeyhimi, Behnam AU - Zhang, Xiangwu T2 - JOURNAL OF APPLIED POLYMER SCIENCE AB - Abstract Selective permeation, driven by ionic attraction, is one of the most important properties of polyelectrolyte membranes. In this study, selective permeation behaviors of different polyelectrolytes, poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPS), poly(styrene sulfonic acid) (PSS), and poly(methacrylic acid) (PMA), were studied via solution‐diffusion mechanism. Among these three polyelectrolytes, PSS membranes showed the highest permeabilities for both water and dimethyl methylphophonate vapors due to their high diffusion coefficients caused by the high flexibility of PSS chains. It was also found that the cross‐linking of polymer chains increased membrane permeabilities by weakening the physical network formed by ionic attraction. However, the type and cross‐linking of polyelectrolytes did not have significant effect on the membrane selectivities. Nonwoven fabric was employed to control the selective permeation of polyelectrolyte membranes. It was found that filling the nonwoven fabric with polyelectrolytes led to composite membranes with reduced permeabilities and increased selectivities. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011. DA - 2012/1/5/ PY - 2012/1/5/ DO - 10.1002/app.34453 VL - 123 IS - 1 SP - 227-233 SN - 0021-8995 UR - https://publons.com/publon/7178357/ KW - membranes KW - crosslinking KW - diffusion ER - TY - JOUR TI - Pretreatment of corn stover by combining ionic liquid dissolution with alkali extraction AU - Geng, X. L. AU - Henderson, W. A. T2 - Biotechnology and Bioengineering DA - 2012/// PY - 2012/// VL - 109 IS - 1 SP - 84-91 ER - TY - JOUR TI - Finite-size scaling analysis of isotropic-polar phase transitions in an amphiphilic fluid AU - Melle, Michael AU - Giura, Stefano AU - Schlotthauer, Sergej AU - Schoen, Martin T2 - JOURNAL OF PHYSICS-CONDENSED MATTER AB - We present Monte Carlo simulations of the isotropic-polar (IP) phase transition in an amphiphilic fluid carried out in the isothermal-isobaric ensemble. Our model consists of Lennard-Jones spheres where the attractive part of the potential is modified by an orientation-dependent function. This function gives rise to an angle dependence of the intermolecular attractions corresponding to that characteristic of point dipoles. Our data show a substantial system-size dependence of the dipolar order parameter. We analyze the system-size dependence in terms of the order-parameter distribution and a cumulant involving its first and second moments. The order parameter, its distribution, and susceptibility observe the scaling behavior characteristic of the 3D Ising universality class. Because of this scaling behavior and because all cumulants have a common intersection irrespective of system size we conclude that the IP phase transition is continuous. Considering pressures 1.3 ≤ P ≤ 3.0 we demonstrate that a line of continuous phase transitions exists which is analogous to the Curie line in systems exhibiting a ferroelectric transition. Our results are qualitatively consistent with Landau's theory of continuous phase transitions. DA - 2012/1/25/ PY - 2012/1/25/ DO - 10.1088/0953-8984/24/3/035103 VL - 24 IS - 3 SP - SN - 0953-8984 ER - TY - JOUR TI - Structure, molecular orientation, and resultant mechanical properties in core/sheath poly(lactic acid)/polypropylene composites AU - Arvidson, Sara A. AU - Wong, Ka C. AU - Gorga, Russell E. AU - Khan, Saad A. T2 - POLYMER AB - We study the coaxial spinning of poly(lactic acid) (PLA) with polypropylene (PP) in a core/sheath configuration. PPcore/PLAsheath and PLAcore/PPsheath fibers maintain the high breaking strength that PP and PLA exhibit individually, showing marked improvement in strength over previous reports of PP/PLA blend fibers. Crystalline morphologies are greatly affected by the location within the fiber (i.e., core, sheath, or spun individually), and hence, co-spinning provides a route to tailor the morphology and fiber diameter beyond that available with single component fibers. A new approach to estimate molecular orientation of core sheath fibers based on the tensile response of the fiber is developed, and indicates that co-spinning PP with PLA results in a synergistic effect with increases in the molecular orientation above that which is possible with spinning either PP or PLA individually. DA - 2012/2// PY - 2012/2// DO - 10.1016/j.polymer.2011.12.042 VL - 53 IS - 3 SP - 791-800 SN - 0032-3861 KW - Polypropylene KW - Poly(lactic acid) KW - Core/sheath fiber ER - TY - JOUR TI - Phase diagram of two-dimensional systems of dipole-like colloids AU - Schmidle, Heiko AU - Hall, Carol K. AU - Velev, Orlin D. AU - Klapp, Sabine H. L. T2 - SOFT MATTER AB - Based on Discontinuous Molecular Dynamics (DMD) simulations we present a phase diagram of two-dimensional nano-particles with dipole-like short-ranged interactions. Similar to systems with true, long-ranged dipolar interactions the present system undergoes a transition from an isotropic fluid phase into a polymer-like fluid, characterized by an association of most particles into clusters. Further decrease of the temperature leads to a percolated system which, moreover, displays dynamical properties reminiscent of a gel. Specifically, we find a plateau in the mean-squared displacement and a non-gaussian behavior of the self-part of the van Hove correlation function. In the high density region we observe crystallization from the isotropic fluid into a solid phase with hexagonal order. Surprisingly, the crystallization is accompanied by a global parallel ordering of the dipole moments, i.e., a ferroelectric phase. This behavior is in marked contrast to what is found in 2D systems with long-ranged dipolar interactions. Our results allow insights into the design of gel-like or highly ordered structures at interfaces, shells around droplets and bubbles and new-sheet like materials. DA - 2012/// PY - 2012/// DO - 10.1039/c1sm06576a VL - 8 IS - 5 SP - 1521-1531 SN - 1744-6848 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84855679881&partnerID=MN8TOARS ER - TY - JOUR TI - Ionic Current Rectification in Soft-Matter Diodes with Liquid-Metal Electrodes AU - So, Ju-Hee AU - Koo, Hyung-Jun AU - Dickey, Michael D. AU - Velev, Orlin D. T2 - ADVANCED FUNCTIONAL MATERIALS AB - Abstract A soft‐matter‐based diode composed of hydrogel and liquid metal (eutectic gallium indium, EGaIn) is presented. The ability to control the thickness, and thus resistivity, of an oxide skin on the metal enables rectification. First, a simple model system with liquid‐metal/electrolyte‐solution/Pt interfaces is characterized. The electrically insulating oxide skin on the EGaIn electrode is reduced or oxidized further depending on the direction of the bias, thereby allowing unidirectional ionic current. The forward current of the diode increases as the conductivity of the electrolyte increases, whereas backward current depends on the pH of the medium in contact with the insulating oxide layer on the EGaIn electrode. As a result, the diode shows a higher rectification ratio (defined as the ratio of forward to backward current measured at the same absolute bias) with more conductive electrolyte at neutral pH. Replacement of the liquid electrolyte solution with a hydrogel improves the structural stability of the soft diode. The rectification performance also improves due to the increased ionic conductivity by the gel. Finally, a diode composed entirely of soft materials by replacing the platinum electrode with a second liquid‐metal electrode is presented. Contacting each liquid metal with a polyelectrolyte gel featuring different pH values provided asymmetry in the device, which is necessary for rectification. A hydrogel layer infused with a strong basic polyelectrolyte removes the insulating oxide layer, allowing one interface with the EGaIn electrode to be conductive regardless of the direction of bias. Thus, the oxide layer at the other interface rectifies the current. DA - 2012/2/8/ PY - 2012/2/8/ DO - 10.1002/adfm.201101967 VL - 22 IS - 3 SP - 625-631 SN - 1616-301X UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84856758970&partnerID=MN8TOARS KW - hydrogels KW - liquid metal KW - ionic current rectification KW - polyelectrolytes KW - soft matter KW - soft electronics KW - electrochemical diodes ER - TY - JOUR TI - Influence of gradient strength and composition profile on the onset of the cloud point transition in hydroxyethyl methacrylate/dimethylaminoethyl methacrylate gradient copolymers AU - Gallow, Keith C. AU - Jhon, Young K. AU - Genzer, Jan AU - Loo, Yueh-Lin T2 - POLYMER AB - We examined the onset of the cloud point in dilute aqueous solutions of gradient copolymers of 2-hydroxyethyl methacrylate and dimethylaminoethyl methacrylate. Dynamic Light Scattering (DLS) and transmittance measurements both indicate that the copolymer solution cloud point decreases with increasing copolymer gradient strength, defined as the largest difference in the instantaneous composition along the copolymer. While transmittance measurements suggest that macroscopic clouding does not set in until 30% of the polymer chain becomes insoluble, DLS experiments, which are more sensitive to the onset of aggregation, indicate that the onset of aggregation occurs at the point where the least soluble polymer chain end becomes insoluble. Collectively, our data indicate that the macroscopic cloud point transition is highly sensitive to co-monomer sequence distribution of the copolymers, with its onset and transition breadth tunable through copolymer gradient strength. DA - 2012/2/28/ PY - 2012/2/28/ DO - 10.1016/j.polymer.2012.01.027 VL - 53 IS - 5 SP - 1131-1137 SN - 1873-2291 KW - Gradient Copolymers KW - Composition Profile KW - Cloud Point ER - TY - JOUR TI - Generation of functional PET microfibers through surface-initiated polymerization AU - Oezcam, A. Evren AU - Roskov, Kristen E. AU - Spontak, Richard J. AU - Genzer, Jan T2 - JOURNAL OF MATERIALS CHEMISTRY AB - In this study, we report on a facile and robust method by which poly(ethylene terephthalate) (PET) surfaces can be chemically modified with functional polymer brushes while avoiding chemical degradation. The surface of electrospun PET microfibers has been functionalized by growing poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and poly(2-hydroxyethyl methacrylate) (PHEMA) brushes through a multi-step chemical sequence that ensures retention of mechanically robust microfibers. Polymer brushes are grown via “grafting from” atom-transfer radical polymerization after activation of the PET surface with 3-aminopropyltriethoxysilane. Spectroscopic analyses confirm the expected reactions at each reaction step, as well as the ultimate growth of brushes on the PET microfibers. Post-polymerization modification reactions have likewise been conducted to further functionalize the brushes and impart surface properties of biomedical interest on the PET microfibers. Antibacterial activity and protein resistance of PET microfibers functionalized with PDMAEMA and PHEMA brushes, respectively, are demonstrated, thereby making these surface-modified PET microfibers suitable for filtration media, tissue scaffolds, delivery vehicles, and sensors requiring mechanically robust support media. DA - 2012/// PY - 2012/// DO - 10.1039/c2jm16017j VL - 22 IS - 12 SP - 5855-5864 SN - 1364-5501 ER - TY - JOUR TI - Factors affecting time-composition equivalence in ternary block copolymer/cosolvent systems AU - Krishnan, Arjun S. AU - Spontak, Richard J. T2 - SOFT MATTER AB - Time–temperature rheological equivalence is one of the most important and broadly used concepts developed with regard to the viscoelastic behavior of polymers. In this study, we explore the generality of an analogous relationship, time–composition equivalence, in several series of ternary block copolymer/cosolvent systems at ambient temperature. Of particular interest are triblock copolymers solvated with a miscible mixture of midblock-selective solvents to yield physical gels. Such gels, consisting of a midblock-rich network stabilized by glassy endblock-rich microdomains, exhibit remarkable elasticity. The copolymers employed here are styrenic thermoplastic elastomers, whereas the solvents include an aliphatic/alicyclic mineral oil and several different tackifying resins varying in molecular weight and, hence, viscosity. Despite changes in solvent properties, time–composition superpositioning (tCS) yields master curves wherein the composition shift factors consistently scale with cosolvent zero-shear viscosity. Corresponding scaling exponents vary linearly with copolymer concentration and change slope at a morphological transition. Failure of tCS at low frequencies can be largely avoided by implementing copolymers with high-molecular-weight endblocks. DA - 2012/// PY - 2012/// DO - 10.1039/c1sm06672b VL - 8 IS - 5 SP - 1334-1343 SN - 1744-6848 ER - TY - JOUR TI - Electric-Field-Controlled Flow in Nanoscale-Thin Wetting Films AU - Kleinert, Jairus AU - Kim, Sejong AU - Velev, Orlin D. T2 - LANGMUIR AB - A novel nanofluidic system based on electroosmotic flow in nanoscale-thin aqueous wetting films is reported. The water films formed spontaneously on mica substrates in a saturation humidity environment. The film thickness was determined to be a few tens of nanometers by optical interference and fluorescence intensity measurements and was consistent with a theoretical evaluation of the thickness of a film based on the competing forces of electrostatic repulsion and capillary pressure. Lateral flow was induced by applying a dc electric field tangential to the film and characterized by tracking the position of a fluorescent probe. The mobilities of the thin fluid layer and the flow marker were lower than the predictions of the electrokinetic theory, which may be a result of adsorption of the fluorescent molecules to the mica. Confinement of the film to two-dimensional “channels” was achieved by microcontact printing of patterned hydrophobic monolayers onto the substrate. This system has the advantage of simple and inexpensive fabrication in comparison to nanofluidic devices made by traditional lithography techniques. DA - 2012/2/7/ PY - 2012/2/7/ DO - 10.1021/la204774s VL - 28 IS - 5 SP - 3037-3044 SN - 0743-7463 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84863050366&partnerID=MN8TOARS ER - TY - JOUR TI - Delivery of Multiple siRNAs Using Lipid-Coated PLGA Nanoparticles for Treatment of Prostate Cancer AU - Hasan, Warefta AU - Chu, Kevin AU - Gullapalli, Anuradha AU - Dunn, Stuart S. AU - Enlow, Elizabeth M. AU - Luft, J. Christopher AU - Tian, Shaomin AU - Napier, Mary E. AU - Pohlhaus, Patrick D. AU - Rolland, Jason P. AU - DeSimone, Joseph M. T2 - NANO LETTERS AB - Nanotechnology can provide a critical advantage in developing strategies for cancer management and treatment by helping to improve the safety and efficacy of novel therapeutic delivery vehicles. This paper reports the fabrication of poly(lactic acid-co-glycolic acid)/siRNA nanoparticles coated with lipids for use as prostate cancer therapeutics made via a unique soft lithography particle molding process called Particle Replication In Nonwetting Templates (PRINT). The PRINT process enables high encapsulation efficiency of siRNA into neutral and monodisperse PLGA particles (32–46% encapsulation efficiency). Lipid-coated PLGA/siRNA PRINT particles were used to deliver therapeutic siRNA in vitro to knockdown genes relevant to prostate cancer. DA - 2012/1// PY - 2012/1// DO - 10.1021/nl2035354 VL - 12 IS - 1 SP - 287-292 SN - 1530-6992 KW - Soft lithography KW - siRNA delivery KW - PLGA KW - lipids KW - PRINT KW - prostate cancer ER - TY - JOUR TI - Activation of water on the TiO2 (110) surface: The case of Ti adatoms AU - Miao, Meng AU - Liu, Yingchun AU - Wang, Qi AU - Wu, Tao AU - Huang, Liping AU - Gubbins, Keith E. AU - Nardelli, Marco Buongiorno T2 - JOURNAL OF CHEMICAL PHYSICS AB - Using first-principles calculations we have studied the reactions of water over Ti adatoms on the (110) surface of rutile TiO2. Our results provide fundamental insights into the microscopic mechanisms that drive this reaction at the atomic level and assess the possibility of using this system to activate the water dissociation reaction. In particular, we show that a single water molecule dissociates exothermically with a small energy barrier of 0.17 eV. After dissociation, both H+ and OH− ions bind strongly to the Ti adatom, which serves as an effective reactive center on the TiO2 surface. Finally, clustering of Ti adatoms does not improve the redox activity of the system and results in a slightly higher energy barrier for water dissociation. DA - 2012/2/14/ PY - 2012/2/14/ DO - 10.1063/1.3682781 VL - 136 IS - 6 SP - SN - 0021-9606 ER -