TY - JOUR TI - Probing inducible nitric oxide synthase with a pterin-ruthenium(II) sensitizer wire AU - Glazer, E.C. AU - Le Nguyen, Y.H. AU - Gray, H.B. AU - Goodin, D.B. T2 - Angewandte Chemie - International Edition AB - Binding by the light: A photoactive ruthenium(II)–pterin wire designed to target the tetrahydrobiopterin (H4B) binding site of inducible nitric oxide synthase (iNOSheme) binds to iNOSheme in a competitive fashion with the natural cofactor and other small molecules; thus it can be used to screen potential inhibitors. Rapid charge injection to the heme occurs upon 450-nm excitation of an iNOSheme/wire conjugate. DA - 2008/// PY - 2008/// DO - 10.1002/anie.200703743 VL - 47 IS - 5 SP - 898-901 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-38549093580&partnerID=MN8TOARS ER - TY - RPRT TI - Azapeptides as CD36 Binding Compounds AU - Ong, Huy AU - Chemtob, Sylvain AU - Lubell, William D. AU - Boeglin, Damien AU - Proulx, Caroline AU - Sabatino, David AU - Sajjadi, Zohreh DA - 2008/6/18/ PY - 2008/6/18/ M1 - PCT/CA2008/001162 M3 - Patent SN - PCT/CA2008/001162 ER - TY - CONF TI - Elucidation of structural and conformational requirements for GHRP-6 binding to the GHSR-1a and CD36 receptors using aza-peptides AU - Proulx, C. AU - Boeglin, D. AU - Chemtob, S. AU - Ong, H. AU - Lubell, W.D. T2 - Québec-Ontario Minisymposium on Bio-Organic and Synthetic Chemistry (QOMSBOC) meeting C2 - 2008/11// CY - Toronto, Ontario DA - 2008/11// PY - 2008/11// ER - TY - CONF TI - Aza-peptide analogs of GHRP-6 with selective receptor affinity for CD36 versus GHS-R1a” AU - Proulx, C. AU - Boeglin, D. AU - Chemtob, S. AU - Ong, H. AU - Lubell, W.D. T2 - American Chemical Society (ACS) meeting C2 - 2008/8/17/ CY - Philadelphia, Pennsylvania DA - 2008/8/17/ PY - 2008/8/17/ ER - TY - JOUR TI - SERS as a bioassay platform: fundamentals, design, and applications AU - Porter, Marc D. AU - Lipert, Robert J. AU - Siperko, Lorraine M. AU - Wang, Gufeng AU - Narayanan, Radha T2 - Chemical Society Reviews AB - Bioanalytical science is experiencing a period of unprecedented growth. Drivers behind this growth include the need to detect markers central to human and veterinary diagnostics at ever-lower levels and greater speeds. A set of parallel arguments applies to pathogens with respect to bioterrorism prevention and food and water safety. This tutorial review outlines our recent explorations on the use of surface enhanced Raman scattering (SERS) for detection of proteins, viruses, and microorganisms in heterogeneous immunoassays. It will detail the design and fabrication of the assay platform, including the capture substrate and nanoparticle-based labels. The latter, which is the cornerstone of our strategy, relies on the construction of gold nanoparticles modified with both an intrinsically strong Raman scatterer and an antibody. This labelling motif, referred to as extrinsic Raman labels (ERLs), takes advantage of the well-established signal enhancement of scatterers when coated on nanometre-sized gold particles, whereas the antibody imparts antigenic specificity. We will also examine the role of plasmon coupling between the ERLs and capture substrate, and challenges related to particle stability, nonspecific adsorption, and assay speed. DA - 2008/// PY - 2008/// DO - 10.1039/b708461g VL - 37 IS - 5 SP - 1001 J2 - Chem. Soc. Rev. LA - en OP - SN - 0306-0012 1460-4744 UR - http://dx.doi.org/10.1039/b708461g DB - Crossref ER - TY - CONF TI - The Development of a Nano-LC Mass Spectrometric Method for Profiling Glycans in Epithelial Ovarian Cancer (EOC) and Control Plasma AU - Bereman, M.S. AU - Williams, T.Islam AU - Muddiman, D.C. T2 - Triangle Chromatography Symposium and Instrument Exhibit C2 - 2008/// CY - Raleigh, NC DA - 2008/// PY - 2008/// ER - TY - CONF TI - Analysis of O-linked Glycans Derived from Normal and Diseased EOC Plasma by Nano LC-ESI-FTICR Mass Spectrometry AU - Bereman, M.S. AU - Williams, T.Islam AU - Hawkridge, A.M. AU - Muddiman, D.C. T2 - American Society for Mass Spectrometry C2 - 2008/// CY - Denver, CO DA - 2008/// PY - 2008/// ER - TY - CONF TI - Innovative Technology Development Directed at the Elucidation of Biomarkers for the Detection of Early-Stage Ovarian Cancer AU - Williams, T.Islam AU - Bereman, M.S. AU - Williams, D.Keith AU - Muddiman, D.C. T2 - Meeting for the Innovative Molecular Analysis Technologies (IMAT) Program of the National Cancer Institute C2 - 2008/// CY - Cambridge, MA DA - 2008/// PY - 2008/// ER - TY - CONF TI - In Search of Epithelial Ovarian Cancer Molecular Markers by MALDI-FT-ICR-MS and NANO-LC-LTQ-ORBITRAP-MS AU - Williams, T.Islam AU - Bereman, M.S. AU - Nielsen, D.M. AU - Kalli, K.R. AU - Cliby, W.A. AU - Muddiman, D.C. T2 - Mass Spectrometry Applications to the Clinical Laboratory C2 - 2008/// CY - University of California - San Diego, San Diego, CA DA - 2008/// PY - 2008/// ER - TY - CONF TI - Glycan Profiling in Plasma: Fundamentals and Applications to Ovarian Cancer AU - Williams, T.Islam AU - Muddiman, D.C. T2 - Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy C2 - 2008/// CY - New Orleans, LA DA - 2008/// PY - 2008/// ER - TY - SOUND TI - Applications of Carbohydrate Profiling in Ovarian Cancer Plasma Glycoproteins AU - Williams, T.Islam AU - Muddiman, D.C. DA - 2008/// PY - 2008/// ER - TY - CONF TI - Epithelial Ovarian Cancer Detection by Glycan Profiling in Blood AU - Williams, T.Islam AU - Muddiman, D.C. T2 - North Carolina State University C2 - 2008/// CY - Raleigh, NC DA - 2008/// PY - 2008/// ER - TY - CONF TI - Mining the Plasma Glycome for Epithelial Ovarian Cancer Biomarker Discovery AU - Williams, T.Islam AU - Nielsen, D.M. AU - Cliby, W.A. AU - Kalli, K.R. AU - Muddiman, D.C. T2 - American Society for Mass Spectrometry C2 - 2008/// CY - Denver, CO DA - 2008/// PY - 2008/// ER - TY - CONF TI - A Combinatorial Approach: The Use of MALDI-MS and Nano LC-MS for Glycan Biomarker Discovery AU - Williams, T.Islam AU - Bereman, M.S. AU - Nielsen, D.M. AU - Kalli, K.R. AU - Cliby, W.A. AU - Muddiman, D.C. T2 - Protein Biomarkers Meeting C2 - 2008/// CY - Philadelphia, PA DA - 2008/// PY - 2008/// ER - TY - CONF TI - Glycan Analysis by Nano LC-MS: Applications for Biomarker Discovery in Epithelial Ovarian Cancer (EOC) AU - Bereman, M.S. AU - Williams, T.Islam AU - Kalli, K.R. AU - Cliby, W.A. AU - Muddiman, D.C. T2 - Atlanta Athens Mass Spectrometry Discussion Group Symposium C2 - 2008/// CY - University of Georgia, Athens, GA DA - 2008/// PY - 2008/// ER - TY - JOUR TI - The Use of Size-Selective Excitation To Study Photocurrent through Junctions Containing Single-Size and Multi-Size Arrays of Colloidal CdSe Quantum Dots AU - Weiss, Emily A. AU - Porter, Venda J. AU - Chiechi, Ryan C. AU - Geyer, Scott M. AU - Bell, David C. AU - Bawendi, Moungi G. AU - Whitesides, George M. T2 - J. Am. Chem. Soc. AB - This paper describes a study of the generation and flow of photocurrent through junctions containing three-dimensional arrays of colloidal CdSe quantum dots (QDs) of either a single size or multiple sizes. The electrodes were indium tin oxide (ITO) covered with a thin layer of poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS) and a eutectic alloy of Ga and In (EGaIn). We measured the current-voltage characteristics of the junctions in the dark and under illumination, with various sources and wavelengths of excitation, and their photocurrent action spectra. Size-selective photoexcitation of the arrays of multiple sizes of QDs helped to determine (i) the location of the interface at which photoinduced separation of charge occurred, (ii) whether the energy absorbed by the QDs was redistributed before separation of charge, and (iii) the dependence of the photovoltage on the locations of various sizes of QDs within the junction. This research is a step toward the use of QDs for harvesting light and for transporting energy and charge in devices-for example, solar cells and photodetectors-that operate at zero bias. DA - 2008/1// PY - 2008/1// DO - 10.1021/ja076439+ VL - 130 IS - 1 SP - 83-92 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-38349070351&partnerID=MN8TOARS ER - TY - JOUR TI - Size-Dependent Charge Collection in Junctions Containing Single-Size and Multi-Size Arrays of Colloidal CdSe Quantum Dots AU - Weiss, Emily A. AU - Chiechi, Ryan C. AU - Geyer, Scott M. AU - Porter, Venda J. AU - Bell, David C. AU - Bawendi, Moungi G. AU - Whitesides, George M. T2 - J. Am. Chem. Soc. AB - This paper describes the electrical characteristics of junctions composed of three-dimensional arrays of colloidal CdSe quantum dots (QDs) with tin-doped indium oxide (ITO)/poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS) and eutectic Ga−In (EGaIn) electrodes. It focuses on a comparison of junctions containing QDs of one size to those of arrays containing QDs of multiple sizes. This comparison makes it possible to estimate the relative contributions of transport across various interfaces (e.g., between the QDs and between the QDs and the electrodes) to the observed electrical characteristics of the junction and to evaluate the dependence of these contributions on the locations of various sizes of QDs within the junction. The junctions were diodes, and their turn-on voltage depended on the size of the QDs next to the PEDOT:PSS. We describe this dependence using a Marcus model to estimate the barrier for charge transfer induced by the difference in energies between the orbitals of the QDs and the valence band of PEDOT:PSS. DA - 2008/1// PY - 2008/1// DO - 10.1021/ja076438h VL - 130 IS - 1 SP - 74-82 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-38349043778&partnerID=MN8TOARS ER - TY - JOUR TI - Eutectic Gallium-Indium (EGaIn): A Liquid Metal Alloy for the Formation of Stable Structures in Microchannels at Room Temperature AU - Dickey, Michael D. AU - Chiechi, Ryan C. AU - Larsen, Ryan J. AU - Weiss, Emily A. AU - Weitz, David A. AU - Whitesides, George M. T2 - Adv. Funct. Mater. AB - Abstract This paper describes the rheological behavior of the liquid metal eutectic gallium‐indium (EGaIn) as it is injected into microfluidic channels to form stable microstructures of liquid metal. EGaIn is well‐ ;suited for this application because of its rheological properties at room temperature: it behaves like an elastic material until it experiences a critical surface stress, at which point it yields and flows readily. These properties allow EGaIn to fill microchannels rapidly when sufficient pressure is applied to the inlet of the channels, yet maintain structural stability within the channels once ambient pressure is restored. Experiments conducted in microfluidic channels, and in a parallel‐plate rheometer, suggest that EGaIn's behavior is dictated by the properties of its surface (predominantly gallium oxide, as determined by Auger measurement s); these two experiments both yield approximately the same number for the critical surface stress required to induce EGaIn to flow (∼0 .5 N/m). This analysis–which shows that the pressure that must be exceeded for EGaIn to flow through a microchannel is inversely proportional to the critical (i.e., smallest) dimension of the channel–is useful to guide future fabrication of microfluidic channels to mold EGaIn into functional microstructures. DA - 2008/4/11/ PY - 2008/4/11/ DO - 10.1002/adfm.200701216 VL - 18 IS - 7 SP - 1097-1104 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-42549111682&partnerID=MN8TOARS ER - TY - JOUR TI - Laterally Ordered Bulk Heterojunction of Conjugated Polymers: Nanoskiving a Jelly Roll AU - Lipomi, Darren J. AU - Chiechi, Ryan C. AU - Reus, William F. AU - Whitesides, George M. T2 - Adv. Funct. Mater. AB - Abstract This paper describes the fabrication of a nanostructured heterojunction of two conjugated polymers by a three‐step process: i) spin‐coating a multilayered film of the two polymers, ii) rolling the film into a cylinder (a “jelly roll”) and iii) sectioning the film perpendicular to the axis of the roll with an ultramicrotome (nanoskiving). The conjugated polymers are poly(benzimidazobenzophenanthroline ladder) (BBL, n‐type) and poly(2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene) (MEH‐PPV, p‐type). The procedure produces sections with an interdigitated junction of the two polymers. The spacing between the phases is determined by spin‐coating (∼15 nm to 100 nm) and the thickness of each section is determined by the ultramicrotome (100 to 1000 nm). The minimum width of the MEH‐PPV layers accessible with this technique (∼15 nm) is close to reported exciton diffusion lengths for the polymer. When placed in a junction between two electrodes with asymmetric work functions (tin‐doped indium oxide (ITO) coated with poly(3,4‐ethylenedioxythiophene:poly(styrenesulfonate) (PEDOT:PSS), and eutectic gallium‐indium, EGaIn) the heterostructures exhibit a photovoltaic response under white light, although the efficiency of conversion of optical to electrical energy is low. Selective excitation of BBL with red light confirms that the photovoltaic effect is the result of photoinduced charge transfer between BBL and MEH‐PPV. DA - 2008/11/10/ PY - 2008/11/10/ DO - 10.1002/adfm.200800578 VL - 18 IS - 21 SP - 3469-3477 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-55849150529&partnerID=MN8TOARS ER - TY - JOUR TI - Fabrication of Conjugated Polymer Nanowires by Edge Lithography AU - Lipomi, Darren J. AU - Chiechi, Ryan C. AU - Dickey, Michael D. AU - Whitesides, George M. T2 - Nano Lett. AB - This paper describes the fabrication of conjugated polymer nanowires by a three stage process: (i) spin-coating a composite film comprising alternating layers of a conjugated polymer and a sacrificial material, (ii) embedding the film in an epoxy matrix and sectioning it with an ultramicrotome (nanoskiving), and (iii) etching the sacrificial material to reveal nanowires of the conjugated polymer. A free-standing, 100-layer film of two conjugated polymers was spin-coated from orthogonal solvents: poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) from chloroform and poly(benzimidazobenzophenanthroline ladder) (BBL) from methanesulfonic acid. After sectioning the multilayer film, dissolution of the BBL with methanesulfonic acid yielded uniaxially aligned MEH-PPV nanowires with rectangular cross sections, and etching MEH-PPV with an oxygen plasma yielded BBL nanowires. The conductivity of MEH-PPV nanowires changed rapidly and reversibly by >103 upon exposure to I2 vapor. The result suggests that this technique could be used to fabricate high-surface-area structures of conducting organic nanowires for possible applications in sensing and in other fields where a high surface area in a small volume is desirable. DA - 2008/7// PY - 2008/7// DO - 10.1021/nl8009318 VL - 8 IS - 7 SP - 2100-2105 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-53149142545&partnerID=MN8TOARS ER - TY - JOUR TI - Eutectic Gallium–Indium (EGaIn): A Moldable Liquid Metal for Electrical Characterization of Self-Assembled Monolayers AU - Chiechi, Ryan C. AU - Weiss, Emily A. AU - Dickey, Michael D. AU - Whitesides, George M. T2 - Angew. Chem. Int. Ed. AB - A great GaIn: Micrometer-sized conformal electrodes formed from the title compound are shown to be ideal for measuring the electrical properties of self-assembled monolayers. The image shows the bifurcation of the EGaIn between a metal needle and an Ag surface (not shown) at the point indicated by the two white arrows. The portion above the arrows will form the EGaIn electrode. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z703642_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2008/1// PY - 2008/1// DO - 10.1002/anie.200703642 VL - 47 IS - 1 SP - 142-144 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-37549043162&partnerID=MN8TOARS KW - electrodes KW - gallium KW - indium KW - monolayers KW - tunnel junctions ER - TY - JOUR TI - Eutectic Gallium–Indium (EGaIn): A Moldable Liquid Metal for Electrical Characterization of Self-Assembled Monolayers AU - Chiechi, Ryan C. AU - Weiss, Emily A. AU - Dickey, Michael D. AU - Whitesides, George M. T2 - Angew. Chem. AB - Angewandte ChemieVolume 120, Issue 1 p. 148-150 Zuschrift Eutectic Gallium–Indium (EGaIn): A Moldable Liquid Metal for Electrical Characterization of Self-Assembled Monolayers† Ryan C. Chiechi Dr., Ryan C. Chiechi Dr. Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA, Fax: (+1) 617-495-9857Search for more papers by this authorEmily A. Weiss Dr., Emily A. Weiss Dr. Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA, Fax: (+1) 617-495-9857Search for more papers by this authorMichael D. Dickey Dr., Michael D. Dickey Dr. Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA, Fax: (+1) 617-495-9857Search for more papers by this authorGeorge M. Whitesides Prof., George M. Whitesides Prof. [email protected] Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA, Fax: (+1) 617-495-9857Search for more papers by this author Ryan C. Chiechi Dr., Ryan C. Chiechi Dr. Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA, Fax: (+1) 617-495-9857Search for more papers by this authorEmily A. Weiss Dr., Emily A. Weiss Dr. Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA, Fax: (+1) 617-495-9857Search for more papers by this authorMichael D. Dickey Dr., Michael D. Dickey Dr. Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA, Fax: (+1) 617-495-9857Search for more papers by this authorGeorge M. Whitesides Prof., George M. Whitesides Prof. [email protected] Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA, Fax: (+1) 617-495-9857Search for more papers by this author First published: 13 December 2007 https://doi.org/10.1002/ange.200703642Citations: 125 † We acknowledge funding from NSF CHE-0518055, and the shared facilities supported by the NSF under NSEC (PHY-0117795), and MRSEC (DMR-0213805). E.A.W. thanks the Petroleum Research Fund of the American Chemical Society for a fellowship (PRF 43083-AEF). Read the full textAboutPDF ToolsRequest permissionAdd to favorites 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 Mikroelektroden aus der Titelverbindung erweisen sich als ideal für die Messung der elektrischen Eigenschaften selbstorganisierter Monoschichten. Im Bild ist gezeigt, wie sich das EGaIn zwischen einer Metallnadel und einer Ag-Oberfläche (nicht erkennbar) teilt. Aus dem Teil oberhalb der weißen Pfeile wird später die EGaIn-Elektrode. Supporting Information Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2008/z703642_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. References 1S. J. French, D. J. Saunders, G. W. Ingle, J. Phys. Chem. 1938, 42, 265. 10.1021/j100897a011 CASWeb of Science®Google Scholar 2D. Zrnic, D. S. Swatik, J. Less-Common Met. 1969, 18, 67. 10.1016/0022-5088(69)90121-0 CASWeb of Science®Google Scholar 3A. D. Pasquier, S. Miller, M. Chhowalla, Solar Energy Mater. Solar Cells 2006, 90, 1828. 10.1016/j.solmat.2005.11.003 CASWeb of Science®Google Scholar 4E. J. Lous, P. W. M. Blom, L. W. Molenkamp, D. M. d. Leeuw, J. Appl. Phys. 1997, 81. 10.1063/1.364990 CASPubMedWeb of Science®Google Scholar 5C. P. Rhodes, J. W. Long, M. S. 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Larsen, E. A. Weiss, D. A. Weitz, G. M. Whitesides, Adv. Funct. Mater., unpublished results. Google Scholar 17The surface energy of γ-Al2O3 is 560 dynes cm−1: A. Bondi, Chem. Rev. 1953, 52, 417. 10.1021/cr60162a002 CASWeb of Science®Google Scholar 18The origin of the sudden change in the shape of the J–V trace in Figure 2 a between V=±0.05 is probably a switch from the “low-bias regime” (e V≪Φ) to the “intermediate-bias regime” (e V<Φ), whereby Φ is the height of the tunneling barrier imposed by the organic monolayer (within the often-used Simmons model). In the low-bias regime, J depends only linearly on V, but, in the intermediate bias regime, J depends exponentially on V as a result of the so-called “barrier-lowering effect” of the applied bias. We did not acquire data in small enough intervals of V to capture the shape of the J–V response in this region; the transition from low- to intermediate-bias regimes therefore appears as a discontinuity in the plot in Figure 2 a; see: Chen et al. in Molecular Nanoelectronics (Eds.: ), American Scientific Publishers, Valencia, 2003, pp. 1–76. Google Scholar 19E. A. Weiss, R. C. Chiechi, S. M. Geyer, V. J. Porter, D. C. Bell, M. G. Bawendi, G. M. Whitesides, J. Am. Chem. Soc., in press. Google Scholar Citing Literature Volume120, Issue1December 17, 2007Pages 148-150 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. ReferencesRelatedInformation DA - 2008/1// PY - 2008/1// DO - 10.1002/ange.200703642 VL - 120 IS - 1 SP - 148-150 ER - TY - JOUR TI - Visible and Near-Infrared Absorbing, Low Band Gap Conjugated Oligomers Based on Cyclopentadieneones AU - Walker, Wesley AU - Veldman, Brittnee AU - Chiechi, Ryan AU - Patil, Satish AU - Bendikov, Michael AU - Wudl, Fred T2 - Macromolecules AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTVisible and Near-Infrared Absorbing, Low Band Gap Conjugated Oligomers Based on CyclopentadieneonesWesley Walker†, Brittnee Veldman‡, Ryan Chiechi†§, Satish Patil†∥, Michael Bendikov⊥, and Fred Wudl*†‡View Author Information Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Box 951569, Los Angeles, California 90095-1569, and Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106-9510* Corresponding author. E-mail: [email protected]†University of California, Los Angeles.‡University of California, Santa Barbara.§Current address: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138.∥Current address: Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India 560012.⊥Current address: Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel.Cite this: Macromolecules 2008, 41, 20, 7278–7280Publication Date (Web):September 25, 2008Publication History Received4 March 2008Revised14 August 2008Published online25 September 2008Published inissue 28 October 2008https://doi.org/10.1021/ma8004873Copyright © 2008 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views2484Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. 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Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (152 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Absorption,Conjugated polymers,Electrical conductivity,Monomers,Polymers Get e-Alerts DA - 2008/10// PY - 2008/10// DO - 10.1021/ma8004873 VL - 41 IS - 20 SP - 7278-7280 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-55649115790&partnerID=MN8TOARS ER - TY - JOUR TI - Fabrication of Arrays of Metal and Metal Oxide Nanotubes by Shadow Evaporation AU - Dickey, Michael D. AU - Weiss, Emily A. AU - Smythe, Elizabeth J. AU - Chiechi, Ryan C. AU - Capasso, Federico AU - Whitesides, George M. T2 - ACS Nano AB - This paper describes a simple technique for fabricating uniform arrays of metal and metal oxide nanotubes with controlled heights and diameters. The technique involves depositing material onto an anodized aluminum oxide (AAO) membrane template using a collimated electron beam evaporation source. The evaporating material enters the porous openings of the AAO membrane and deposits onto the walls of the pores. The membrane is tilted with respect to the column of evaporating material, so the shadows cast by the openings of the pores onto the inside walls of the pores define the geometry of the tubes. Rotation of the membrane during evaporation ensures uniform deposition inside the pores. After evaporation, dissolution of the AAO in base easily removes the template to yield an array of nanotubes connected by a thin backing of the same metal or metal oxide. The diameter of the pores dictates the diameter of the tubes, and the incident angle of evaporation determines the height of the tubes. Tubes up to approximately 1.5 mum in height and 20-200 nm in diameter were fabricated. This method is adaptable to any material that can be vapor-deposited, including indium-tin oxide (ITO), a conductive, transparent material that is useful for many opto-electronic applications. An array of gold nanotubes produced by this technique served as a substrate for surface-enhanced Raman spectroscopy: the Raman signal (per molecule) from a monolayer of benzenethiolate was a factor of approximately 5 x 10(5) greater than that obtained using bulk liquid benzenethiol. DA - 2008/4// PY - 2008/4// DO - 10.1021/nn800036r VL - 2 IS - 4 SP - 800-808 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-46849115799&partnerID=MN8TOARS KW - shadow evaporation KW - nanotube arrays KW - SERS (surface-enhanced Raman spectroscopy) KW - templated fabrication KW - ITO (indium-tin oxide) KW - AAO (anodized aluminum oxide) KW - nanofabrication KW - line-of-sight deposition ER - TY - JOUR TI - Visible−Near Infrared Absorbing Dithienylcyclopentadienone−Thiophene Copolymers for Organic Thin-Film Transistors AU - Yang, Changduk AU - Cho, Shinuk AU - Chiechi, Ryan C. AU - Walker, Wesley AU - Coates, Nelson E. AU - Moses, Daniel AU - Heeger, Alan J. AU - Wudl, Fred T2 - Journal of the American Chemical Society AB - Structural design, synthesis, and characterization of a series of organic semiconductors consisting exclusively of dithienylcyclopentadienone subunits within a polythiophene backbone are described as the first example for organic electronic devices. The donor (thiophene)-alt-acceptor (cyclopentadienone) copolymers exhibit a substantial p-carrier mobility in OFET but an unexpected noncorrelation between absorption and photoconductivity. DA - 2008/// PY - 2008/// DO - 10.1021/ja806784e VL - 130 IS - 49 SP - 16524-16526 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-57549097793&partnerID=MN8TOARS ER - TY - CONF TI - The Use of Multi-Size Arrays of Colloidal Quantum Dots to Study Energy and Electron Transport in QD Junctions AU - Weiss, Emily AU - Chiechi, Ryan AU - Porter, Venda AU - Geyer, Scott AU - Bawendi, Moungi AU - Whitesides, George C2 - 2008/// C3 - Materials Research Society Symposium Proceedings DA - 2008/// DO - 10.1557/proc-1121-n04-01 PB - Cambridge University Press (CUP) ER - TY - CONF TI - Relaxation and structural assembly control the mechanism of crystal growth in condensed matter AU - Martin, James T2 - 235th National American Chemical Society (ACS) Meeting C2 - 2008/4/6/ CY - New Orleans, LA DA - 2008/4/6/ PY - 2008/4/6/ ER - TY - SOUND TI - A Chemist Becomes Chair of the Faculty: Using Science Demos as Object Lessons for Good University Policy AU - Martin, James DA - 2008/7// PY - 2008/7// ER - TY - JOUR TI - Having Our Say AU - Spires, Hiller A. AU - Lee, John K. AU - Turner, Kimberly A. AU - Johnson, Janet T2 - Journal of Research on Technology in Education AB - Growing consensus among policy makers and educators alike suggests that our education system must be transformed to address the needs of a global society as well as the needs of the 21st century student. Often overlooked as a resource, students can contribute a valuable perspective on education. The purpose of this study, therefore, was to learn from middle grades students, through surveys and focus groups, what engages them to achieve in school. The findings, which centered on student perspectives of school, uses of technologies in and out of school, and academic engagement, are viewed within the context of global changes and the new demands that this trend places on education. DA - 2008/6// PY - 2008/6// DO - 10.1080/15391523.2008.10782518 VL - 40 IS - 4 SP - 497-515 J2 - Journal of Research on Technology in Education LA - en OP - SN - 1539-1523 1945-0818 UR - http://dx.doi.org/10.1080/15391523.2008.10782518 DB - Crossref KW - technologies KW - academic engagement KW - middle grades KW - student perspectives ER - TY - JOUR TI - Optimization of Electrochemical Aptamer-Based Sensors via Optimization of Probe Packing Density and Surface Chemistry AU - White, Ryan J. AU - Phares, Noelle AU - Lubin, Arica A. AU - Xiao, Yi AU - Plaxco, Kevin W. T2 - Langmuir AB - Electrochemical, aptamer-based (E-AB) sensors, which are comprised of an electrode modified with surface immobilized, redox-tagged DNA aptamers, have emerged as a promising new biosensor platform. In order to further improve this technology we have systematically studied the effects of probe (aptamer) packing density, the AC frequency used to interrogate the sensor, and the nature of the self-assembled monolayer (SAM) used to passivate the electrode on the performance of representative E-AB sensors directed against the small molecule cocaine and the protein thrombin. We find that, by controlling the concentration of aptamer employed during sensor fabrication, we can control the density of probe DNA molecules on the electrode surface over an order of magnitude range. Over this range, the gain of the cocaine sensor varies from 60% to 200%, with maximum gain observed near the lowest probe densities. In contrast, over a similar range, the signal change of the thrombin sensor varies from 16% to 42% and optimal signaling is observed at intermediate densities. Above cut-offs at low hertz frequencies, neither sensor displays any significant dependence on the frequency of the alternating potential employed in their interrogation. Finally, we find that E-AB signal gain is sensitive to the nature of the alkanethiol SAM employed to passivate the interrogating electrode; while thinner SAMs lead to higher absolute sensor currents, reducing the length of the SAM from 6-carbons to 2-carbons reduces the observed signal gain of our cocaine sensor 10-fold. We demonstrate that fabrication and operational parameters can be varied to achieve optimal sensor performance and that these can serve as a basic outline for future sensor fabrication. DA - 2008/8/9/ PY - 2008/8/9/ DO - 10.1021/la800801v VL - 24 IS - 18 SP - 10513-10518 J2 - Langmuir LA - en OP - SN - 0743-7463 1520-5827 UR - http://dx.doi.org/10.1021/la800801v DB - Crossref ER - TY - JOUR TI - Optimization of a Reusable, DNA Pseudoknot-Based Electrochemical Sensor for Sequence-Specific DNA Detection in Blood Serum AU - Cash, Kevin J. AU - Heeger, Alan J. AU - Plaxco, Kevin W. AU - Xiao, Yi T2 - Analytical Chemistry AB - We describe in detail a new electrochemical DNA (E-DNA) sensing platform based on target-induced conformation changes in an electrode-bound DNA pseudoknot. The pseudoknot, a DNA structure containing two stem-loops in which the first stem’s loop forms part of the second stem, is modified with a methylene blue redox tag at its 3′ terminus and covalently attached to a gold electrode via the 5′ terminus. In the absence of a target, the structure of the pseudoknot probe minimizes collisions between the redox tag and the electrode, thus reducing faradaic current. Target binding disrupts the pseudoknot structure, liberating a flexible, single-stranded element that can strike the electrode and efficiently transfer electrons. In this article we report further characterization and optimization of this new E-DNA architecture. We find that optimal signaling is obtained at an intermediate probe density (∼1.8 × 1013 molecules/cm2 apparent density), which presumably represents a balance between steric and electrostatic blocking at high probe densities and increased background currents arising from transfer from the pseudoknot probe at lower densities. We also find that optimal 3′ stem length, which appears to be 7 base pairs, represents a balance between pseudoknot structural stability and target affinity. Finally, a 3′ loop comprised of poly(A) exhibits better mismatch discrimination than the equivalent poly(T) loop, but at the cost of decreased gain. Optimization over this parameter space significantly improves the signaling of the pseudoknot-based E-DNA architecture, leading to the ability to sensitively and specifically detect DNA targets even when challenged in complex, multicomponent samples such as blood serum. DA - 2008/12/18/ PY - 2008/12/18/ DO - 10.1021/ac802011d VL - 81 IS - 2 SP - 656-661 J2 - Anal. Chem. LA - en OP - SN - 0003-2700 1520-6882 UR - http://dx.doi.org/10.1021/ac802011d DB - Crossref ER - TY - CONF TI - The Physical Organic Chemistry of Electron Spin Exchange Coupling AU - Schultz, D T2 - 32nd Reaction Mechanisms Conference C2 - 2008/// CY - University of North Carolina at Chapel Hill DA - 2008/// PY - 2008/6/28/ ER - TY - JOUR TI - Effect of Plasma Protein Depletion on BNP-32 Recovery AU - Hawkridge, A.M. AU - Muddiman, D.C. AU - Hebulein, D.M. AU - Cataliotti, A AU - Burnett, J.C., Jr T2 - Clinical Chemistry AB - Depletion of abundant proteins from plasma and serum is an important initial step in many biomarker discovery platforms(1). Decreasing the concentrations of highly abundant proteins (e.g., albumin, IgG, and antitrypsin) facilitates the use of contemporary proteomics technologies, such as gel electrophoresis and mass spectrometry, for detection and identification of low-abundant proteins. Furthermore, decreasing abundant protein concentrations may also improve immunoprecipitation recovery efficiencies for targeted low-abundant species by decreasing nonspecific binding (i.e., shielding the antigen-binding domain) to the antibody and/or solid supports. A notable pitfall to depletion strategies is the potential for unintentionally removing low-abundant plasma or serum proteins. These low-abundant species may be bound specifically or nonspecifically to the depletion ligand, depletion target protein (e.g., carrier proteins), or the solid support(s). Thus, it is important to critically evaluate the effectiveness of abundant plasma protein depletion for enhancing the study of low-abundant protein biomarker(s). We have been actively developing a targeted biomarker discovery platform for characterizing the circulating forms of B-type natriuretic peptide (BNP) that includes protein depletion strategies, immunoprecipitation, gel electrophoresis, isotope dilution (absolute quantification), and nanoflow liquid chromatography coupled to high-performance hybrid Fourier transform mass … DA - 2008/5/1/ PY - 2008/5/1/ DO - https://doi.org/10.1373/clinchem.2007.098038 VL - 54 IS - 5 SP - 933–934 ER - TY - JOUR TI - Donor-Acceptor Biradicals: From Analogs of Photoinduced Charge-Separated Excited States to Nanoscale Electron Correlation AU - Schultz, D DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Reversibility Effects on the Stereoselectivity of Pt(II)-Mediated Cascade Poly-ene Cyclizations AU - Feducia, Jeremiah A. AU - Gagné, Michel R. T2 - Journal of the American Chemical Society AB - Cyclization of 1,5-dienes bearing nucleophilic traps with electrophilic trisphosphine pincer ligated Pt(II) complexes results in the formation of a polycyclic Pt-alkyl via a Pt(eta2-alkene) intermediate. With electron-rich triphosphine ligands, an equilibrium between the Pt(eta2-alkene) and Pt-alkyl was observed. The position of the equilibrium was sensitive to ligand basicity, conjugate acid strength, solvent polarity, and ring size. In cases where the ligand was electron poor and did not promote retrocyclization, the kinetic products adhering to the Stork-Eschenmoser postulate were observed (E-alkenes give trans-ring junctions). When retrocyclization was rapid, alternative thermodynamic products resulting from multistep rearrangements were observed (cis-[6,5]-bicycles). Under both kinetic and thermodynamic conditions, remote methyl substituents led to highly diastereoselective reactions. In the case of trienol substrates, long-range asymmetric induction from a C-ring substituent was considerably attenuated and only modest diastereoselectivity was observed (approximately 2:1). The data suggest that for a tricyclization, the long-range stereocontrol results from diastereo-selecting interactions that develop during the organization of the nascent rings. In contrast, the bicyclization diastereoselectivities result from reversible cascade cyclization. DA - 2008/1// PY - 2008/1// DO - 10.1021/ja075518i VL - 130 IS - 2 SP - 592-599 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja075518i DB - Crossref ER - TY - JOUR TI - Report from the third workshop on future directions of solid-state chemistry: The status of solid-state chemistry and its impact in the physical sciences AU - Kanatzidis, M.G. AU - Poeppelmeier, K.R. AU - Bobev, S. AU - Guloy, A.M. AU - Hwu, S.-J. AU - Lachgar, A. AU - Latturner, S.E. AU - Raymond AU - Schaak, E. AU - Seo, D.-K. AU - Sevov, S.C. AU - Stein, A. AU - Dabrowski, B. AU - Greedan, J.E. AU - Greenblatt, M. AU - Grey, C.P. AU - Jacobson, A.J. AU - Keszler, D.A. AU - Li, J. AU - Subramanian, M.A. AU - Xia, Y. AU - Cagin, T. AU - Häussermann, U. AU - Hughbanks, T. AU - Mahanti, S.D. AU - Morgan, D. AU - Seo, D.-K. AU - Spaldin, N.A. AU - Buhro, W.E. AU - Giammar, D.E. AU - Hollingsworth, J.A. AU - Johnson, D.C. AU - Nozik, A.J. AU - Peng, X. AU - Bedard, R.L. AU - Brese, N.E. AU - Cao, G. AU - Dhingra, S.S. AU - Kagan, C.R. AU - Mitzi, D.B. AU - Geselbracht, M.J. AU - Lisensky, G.C. AU - Lufaso, M.W. AU - Maggard, P.A. AU - Michael, O. AU - Wilkinson, A.P. AU - Loye, H.-C. AU - Egami, T. AU - Greedan, J.E. AU - Hodges, J.P. AU - Martin, J.D. AU - Parise, J.B. AU - Toby, B.H. AU - Vanderah, T.A. AU - Burns, P.C. AU - Chan, J.Y. AU - Meyer, A.E. AU - Murray, C.B. AU - Ramirez, A.P. AU - Ward, M.D. AU - Yu, L. AU - Alario-Franco, M.A. AU - Battle, P.D. AU - Bein, T. AU - Cahill, C.L. AU - Halasyamani, P.S. AU - Maignan, A. AU - Seshadri, R. T2 - Progress in Solid State Chemistry AB - Public awareness of solid-state chemistry, or more broadly solid-state science and technology rapidly grew along with the transistor revolution and the development of the integrated circuit. We are now at the half-way point in the solid state century [Scientific American The Solid-State Century 1997;8(1) [special issue]], a period of the last 50 years when the term “solid state electronics” was in general vernacular and “solid state” was prominently stamped on consumer electronics appliances, almost as a synonym for “advanced” or “modern.” Clearly without the Bell Labs discovery of the first transistor, which boosted an electrical signal a 100-fold, our personal computers would not be possible, and the information age it spawned would never have happened. It is clear with hindsight that those individuals, companies, regions and nations that have embraced the new information technology have flourished. At the present time the solid-state age does not show any sign of stopping. In this the second half of the century, we have chips with 10 million transistors, solar photovoltaics and all—solid-state lighting, cell phones, displays, data storage, the insulated gate bipolar transistor (IGBT) revolutionizing power electronics, and enthusiasm is high for quantum-optical devices which may begin to dominate new technology. The goal of the Solid State Chemistry Workshop was to assess the current state of solid-state chemistry and explore its impact on allied disciplines as well as industry. In this report we articulate the solid-state chemistry community's sense of the future opportunities and directions and make several recommendations. The findings of this workshop could act as a vehicle for informing the solid-state chemistry community of programs and opportunities for support at NSF and elsewhere. This report aims to identify research directions in solid-state chemistry closely aligned with emerging or potential technologies, as well as areas of original research that could lead to new advances in materials science, solid-state physics and the solid-state sciences in general. Of course, judgment must be exercised to distinguish which of such efforts have true fundamental value, and sufficient patience must be accorded for fundamental research to ultimately bring about new technologies. A major societal impact of the solid state and materials chemistry community is the education of students who are able to excel in multidisciplinary areas crucial to the competitiveness of American industry. Solid state and materials chemistry by its nature, with its interdisciplinary history, has the ability to prepare and educate its graduates to excel in a wide variety of industries including the fields of energy, pharmaceuticals, optical materials and all manner of electronic devices, and nano and biotechnology. Since by their nature emerging technologies depend on the discovery of new materials and their properties, individuals with training in solid-state chemistry are key members of research teams and companies developing these technologies. Which scientific disciplines are affected most by what goes on in solid-state chemistry? The focus of the proposed workshop was two-fold, we sought a close look at the discipline of solid-state chemistry in the beginning of the third millennium and explored its continued impact and relationship with allied disciplines in the physical sciences and also industry. This report highlights a number of accomplishments, emerging research directions and areas requiring increased effort but is not meant to be all inclusive and it is certain that we have left out a number of important aspects. An assessment of how solid-state chemistry is impacting the physical sciences, through continuing advances and the many ways of interacting across disciplinary boundaries, could help the National Science Foundation and the scientific community better appreciate its value and contributions in the greater scientific and societal context. The report also includes discussions of existing and new modes for educating students, and the development and use of national facilities for performing state-of-the-art research in our field. A critical enabler of this societal benefit has been funding from the NSF and other agencies in this area, in particular our nation's premier national user facilities. 1. There is great interest in developing methodologies for synthesis of materials with intended functionalities. To continue the pace of progress solid-state chemistry has enjoyed in the past we recommend sustained support for exploratory synthesis and directed synthesis aimed at new materials' discoveries and the development of methodological and design principles. Syntheses assisted by theory and modeling are only still emerging and should be encouraged. 2. Structure–property relationships are the fundamental underpinning of solid-state sciences. Be they experimental or theoretical, efforts and ideas that will make advances in this area should be supported with sustained funding from the Foundation. 3. The Foundation should encourage and support outreach ideas aimed at explaining, promoting and projecting the place and significance of solid-state chemistry to society. This could be done under the umbrella of Centers or smaller special projects. 4. Fundamental research and materials discovery emanating from NSF and other agency support of solid-state chemistry in academia ultimately affects the strength of industry and therefore the economy. Where appropriate, the NSF should seek the advice of industrial experts in solid-state chemistry as a development tool in formulating potential research directions. In addition existing programs aimed at supporting academic–industry collaborations leveraging industry resources and providing graduate students with goal-driven perspectives are viewed favorably. 5. Solid state and materials chemistry research will extract maximum benefit from NSF funding of personnel and support activities in national facilities. These often unique facilities enable the solution of important problems in solid-state chemistry. Greater utilization of these facilities is limited by lack of expertise on the use of these techniques amongst solid-state chemists and limited user support from the facilities. The NSF has an important role to play as an advocate for the needs of solid-state chemistry to the facilities. 6. The NSF should consider and implement mechanisms for supporting collaborative research between the solid-state sciences and investigators in far-ranging fields, which may require creative funding mechanisms involving other agencies. 7. Programs within NSF that foster collaborative research with international PIs, groups or Institutes such as the Materials World Network should be supported. Also recommended is funding for short term overseas career development ‘sabbaticals’ for faculty and increases in the number of US postdoctoral fellowships for positions abroad with a well-defined NSF affiliation. DA - 2008/// PY - 2008/// DO - 10.1016/j.progsolidstchem.2007.02.002 VL - 36 IS - 1-2 SP - 1-133 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-36148951787&partnerID=MN8TOARS ER - TY - BOOK TI - Book Review of Organic Synthesis with Enzymes in Non-Aqueous Media AU - Ghiladi, Reza A. AU - Carrea, Giacomo AU - Riva, Sergio AB - ADVERTISEMENT RETURN TO ISSUEPREVBook ReviewNEXTBook Review of Organic Synthesis with Enzymes in Non-Aqueous MediaReza A. GhiladiView Author Information North Carolina State UniversityCite this: J. Am. Chem. Soc. 2008, 130, 45, 15218–15219Publication Date (Web):October 15, 2008Publication History Received3 October 2008Published online15 October 2008Published inissue 12 November 2008https://doi.org/10.1021/ja807826gCopyright © 2008 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views254Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (71 KB) Get e-AlertsSUBJECTS:Biocatalysis,Organic synthesis,Peptides and proteins,Solvents,Stereoselectivity Get e-Alerts DA - 2008/11/12/ PY - 2008/11/12/ DO - 10.1021/ja807826g VL - 130 PB - American Chemical Society (ACS) SE - 15218–15219 UR - http://dx.doi.org/10.1021/ja807826g ER - TY - JOUR TI - Coupled molecular dynamics/continuum simulations of Joule heating and melting of isolated copper–aluminum asperity contacts AU - Irving, D L AU - Padgett, C W AU - Brenner, D W T2 - Modelling and Simulation in Materials Science and Engineering AB - Atomic-level dynamics of Joule heating, melting and plastic dynamics at loaded nanometer-scale Cu and Al asperity contacts are modeled using an ad hoc coupling between a numerical solution to a heat transport equation, a virtual resistor network for describing electric current flow and a molecular dynamics simulation using the embedded atom method. Under constant voltage conditions the simulations demonstrate the formation of an Al melt that removes faceting from a Cu asperity via surface disordering at the melt–solid interface. Constant current simulations demonstrate initial disordering of both copper and aluminum at the interface. Flow from the aluminum melt increases the contact area, which lowers the resistance and drops the voltage to below that needed for melting. For the system with a loaded copper asperity, the interface recrystallizes and the dynamics transition from molten flow to plastic damage via dislocation emission. For an aluminum asperity, the asperity remains disordered after the voltage drop and no dislocation emission occurs into the copper or aluminum substrate. DA - 2008/11/18/ PY - 2008/11/18/ DO - 10.1088/0965-0393/17/1/015004 VL - 17 IS - 1 SP - 015004 J2 - Modelling Simul. Mater. Sci. Eng. OP - SN - 0965-0393 1361-651X UR - http://dx.doi.org/10.1088/0965-0393/17/1/015004 DB - Crossref ER - TY - JOUR TI - PLP Labeling in ESR Spectroscopic Analysis of Secondary and Tertiary Acrylate Propagating Radicals AU - Buback, Michael AU - Hesse, Pascal AU - Junkers, Thomas AU - Sergeeva, Tatiana AU - Theis, Thomas T2 - Macromolecules AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTPLP Labeling in ESR Spectroscopic Analysis of Secondary and Tertiary Acrylate Propagating RadicalsMichael Buback*Michael BubackInstitut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstr. 6, D-37077 Göttingen, Germany Corresponding author: e-mail [email protected], phone +49-551-393141, fax + 49-551-393144.More by Michael Buback, Pascal HessePascal HesseInstitut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstr. 6, D-37077 Göttingen, Germany More by Pascal Hesse, Tanja JunkersTanja JunkersInstitut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstr. 6, D-37077 Göttingen, Germany More by Tanja Junkers, Tatiana SergeevaTatiana SergeevaInstitut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstr. 6, D-37077 Göttingen, Germany More by Tatiana Sergeeva, and Thomas TheisThomas TheisInstitut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstr. 6, D-37077 Göttingen, Germany More by Thomas TheisCite this: Macromolecules 2008, 41, 2, 288–291Publication Date (Web):December 29, 2007Publication History Received6 September 2007Revised6 December 2007Published online29 December 2007Published inissue 1 January 2008https://doi.org/10.1021/ma702011qCopyright © 2008 American Chemical SocietyRequest reuse permissionsArticle Views355Altmetric-Citations56LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (142 KB) Get e-AlertscloseSUBJECTS:Aromatic compounds,Electron paramagnetic resonance spectroscopy,Lasers,Organic compounds,Surface plasmon resonance spectroscopy Get e-Alerts DA - 2008/1// PY - 2008/1// DO - 10.1021/ma702011q VL - 41 IS - 2 SP - 288-291 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-38949156525&partnerID=MN8TOARS ER - TY - JOUR TI - Purification and Characterization of the Epoxidase Catalyzing the Formation of Fosfomycin from Pseudomonas syringae AU - Munos, Jeffrey W. AU - Moon, Sung-Ju AU - Mansoorabadi, Steven O. AU - Chang, Weichen AU - Hong, Lin AU - Yan, Feng AU - Liu, Aimin AU - Liu, Hung-wen T2 - Biochemistry AB - The final step in the biosynthesis of fosfomycin in Streptomyces wedmorensis is catalyzed by ( S)-2-hydroxypropylphosphonic acid (HPP) epoxidase ( Sw-HppE). A homologous enzyme from Pseudomonas syringae whose encoding gene ( orf3) shares a relatively low degree of sequence homology with the corresponding Sw-HppE gene has recently been isolated. This purified P. syringae protein was determined to catalyze the epoxidation of ( S)-HPP to fosfomycin and the oxidation of ( R)-HPP to 2-oxopropylphosphonic acid under the same conditions as Sw-HppE. Therefore, this protein is indeed a true HPP epoxidase and is termed Ps-HppE. Like Sw-HppE, Ps-HppE was determined to be post-translationally modified by the hydroxylation of a putative active site tyrosine (Tyr95). Analysis of the Fe(II) center by EPR spectroscopy using NO as a spin probe and molecular oxygen surrogate reveals that Ps-HppE's metal center is similar, but not identical, to that of Sw-HppE. The identity of the rate-determining step for the ( S)-HPP and ( R)-HPP reactions was determined by measuring primary deuterium kinetic effects, and the outcome of these results was correlated with density functional theory calculations. Interestingly, the reaction using the nonphysiological substrate ( R)-HPP was 1.9 times faster than that with ( S)-HPP for both Ps-HppE and Sw-HppE. This is likely due to the difference in bond dissociation energy of the abstracted hydrogen atom for each respective reaction. Thus, despite the low level of amino acid sequence identity, Ps-HppE is a close mimic of Sw-HppE, representing a second example of a non-heme iron-dependent enzyme capable of catalyzing dehydrogenation of a secondary alcohol to form a new C-O bond. DA - 2008/8// PY - 2008/8// DO - 10.1021/bi800877v VL - 47 IS - 33 SP - 8726–8735 SN - 0006-2960 1520-4995 UR - http://dx.doi.org/10.1021/bi800877v ER - TY - JOUR TI - Evidence for the Involvement of Acid/Base Chemistry in the Reaction Catalyzed by the Type II Isopentenyl Diphosphate/Dimethylallyl Diphosphate Isomerase fromStaphylococcus aureus AU - Thibodeaux, Christopher J. AU - Mansoorabadi, Steven O. AU - Kittleman, William AU - Chang, Wei-chen AU - Liu, Hung-wen T2 - Biochemistry AB - The type II isopentenyl diphosphate/dimethylallyl diphosphate isomerase (IDI-2) is a flavin mononucleotide (FMN)-dependent enzyme that catalyzes the reversible isomerization of isopentenyl pyrophosphate (IPP) to dimethylallyl pyrophosphate (DMAPP), a reaction with no net change in redox state of the coenzyme or substrate. Here, UV-vis spectral analysis of the IDI-2 reaction revealed the accumulation of a reduced neutral dihydroflavin intermediate when the reduced enzyme was incubated with IPP or DMAPP. When IDI-2 was reconstituted with 1-deazaFMN and 5-deazaFMN, similar reduced neutral forms of the deazaflavin analogues were observed in the presence of IPP. Single turnover stopped-flow absorbance experiments indicated that this flavin intermediate formed and decayed at kinetically competent rates in the pre-steady-state and, thus, most likely represents a true intermediate in the catalytic cycle. UV-vis spectra of the reaction mixtures reveal trace amounts of a neutral semiquinone, but evidence for the presence of IPP-based radicals could not be obtained by EPR spectroscopy. Rapid-mix chemical quench experiments show no burst in DMAPP formation, suggesting that the rate determining step in the forward direction (IPP to DMAPP) occurs prior to DMAPP formation. A solvent deuterium kinetic isotope effect (D2OVmax = 1.5) was measured on vo in steady-state kinetic experiments at saturating substrate concentrations. A substrate deuterium kinetic isotope effect was also measured on the initital velocity (DVmax = 1.8) and on the decay rate of the flavin intermediate (Dks = 2.3) in single-turnover stopped-flow experiments using (R)-[2-2H]-IPP. Taken together, these data suggest that the C2-H bond of IPP is cleaved in the rate determining step and that general acid/base catalysis may be involved during turnover. Possible mechanisms for the IDI-2 catalyzed reaction are presented and discussed in terms of the available X-ray crystal structures. DA - 2008/2// PY - 2008/2// DO - 10.1021/bi701467g VL - 47 IS - 8 SP - 2547–2558 SN - 0006-2960 1520-4995 UR - http://dx.doi.org/10.1021/bi701467g ER - TY - ER - TY - JOUR TI - Synthesis of Hydroxylated Bicyclic Amino Acids from l-Tyrosine: Octahydro-1 H-indole Carboxylates AU - Pierce, Joshua G. AU - Kasi, Dhanalakshmi AU - Fushimi, Makoto AU - Cuzzupe, Anthony AU - Wipf, Peter T2 - The Journal of Organic Chemistry AB - A stereoselective approach to polyhydroxylated l-Choi derivatives has been developed. The oxidative cyclization of l-tyrosine was optimized to avoid partial racemization and to allow a more efficient scale-up. DA - 2008/10/3/ PY - 2008/10/3/ DO - 10.1021/jo801552j VL - 73 IS - 19 SP - 7807–7810 SN - 0022-3263 1520-6904 UR - http://dx.doi.org/10.1021/jo801552j ER - TY - JOUR TI - A high-throughput fluorescence-based glycosyltransferase screen and its application in directed evolution AU - Williams, Gavin J AU - Thorson, Jon S T2 - Nature Protocols DA - 2008/2/14/ PY - 2008/2/14/ DO - 10.1038/nprot.2007.538 VL - 3 IS - 3 SP - 357-362 J2 - Nat Protoc LA - en OP - SN - 1754-2189 1750-2799 UR - http://dx.doi.org/10.1038/nprot.2007.538 DB - Crossref ER - TY - JOUR TI - Optimizing Glycosyltransferase Specificity via “Hot Spot” Saturation Mutagenesis Presents a Catalyst for Novobiocin Glycorandomization AU - Williams, Gavin J. AU - Goff, Randal D. AU - Zhang, Changsheng AU - Thorson, Jon S. T2 - Chemistry & Biology AB - A comprehensive two-phase "hot spot" saturation mutagenesis strategy for the rapid evolution of glycosyltransferase (GT) specificity for nonnatural acceptors is described. Specifically, the application of a high-throughput screen (based on the fluorescent acceptor umbelliferone) was used to identify key amino acid hot spots that contribute to GT proficiency and/or promiscuity. Saturation mutagenesis of the corresponding hot spots facilitated the utilization of a lower-throughput screen to provide OleD prodigy capable of efficiently glycosylating the nonnatural acceptor novobiocic acid with an array of unique sugars. Incredibly, even in the absence of a high-throughput screen for novobiocic acid glycosylation, this approach rapidly led to improvements in the desired catalytic activity of several hundred-fold. DA - 2008/4// PY - 2008/4// DO - 10.1016/j.chembiol.2008.02.017 VL - 15 IS - 4 SP - 393-401 J2 - Chemistry & Biology LA - en OP - SN - 1074-5521 UR - http://dx.doi.org/10.1016/j.chembiol.2008.02.017 DB - Crossref ER - TY - JOUR TI - The impact of enzyme engineering upon natural product glycodiversification AU - Williams, Gavin J AU - Gantt, Richard W AU - Thorson, Jon S T2 - Current Opinion in Chemical Biology AB - Glycodiversification of natural products is an effective strategy for small molecule drug development. Recently, improved methods for chemo-enzymatic synthesis of glycosyl donors has spurred the characterization of natural product glycosyltransferases (GTs), revealing that the substrate specificity of many naturally occurring GTs as too stringent for use in glycodiversification. Protein engineering of natural product GTs has emerged as an attractive approach to overcome this limitation. This review highlights recent progress in the engineering/evolution of enzymes relevant to natural product glycodiversification with a particular focus upon GTs. DA - 2008/10// PY - 2008/10// DO - 10.1016/j.cbpa.2008.07.013 VL - 12 IS - 5 SP - 556-564 J2 - Current Opinion in Chemical Biology LA - en OP - SN - 1367-5931 UR - http://dx.doi.org/10.1016/j.cbpa.2008.07.013 DB - Crossref ER - TY - JOUR TI - Probing the Aglycon Promiscuity of an Engineered Glycosyltransferase AU - Gantt, Richard W. AU - Goff, Randal D. AU - Williams, Gavin J. AU - Thorson, Jon S. T2 - Angewandte Chemie International Edition AB - A sweet library: Two variants (wild-type (WT) and a triple mutant) of glycosyltransferase (GT) OleD have been shown to catalyze glycosylation of over 70 substrates, formation of O-, S- and N-glycosidic bonds, and iterative glycosylation (see scheme). Identified substrates include nucleophiles not previously known to act in GT reactions and span numerous natural product and therapeutic drug classes. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2008/11/3/ PY - 2008/11/3/ DO - 10.1002/anie.200803508 VL - 47 IS - 46 SP - 8889-8892 J2 - Angew. Chem. Int. Ed. LA - en OP - SN - 1433-7851 1521-3773 UR - http://dx.doi.org/10.1002/anie.200803508 DB - Crossref KW - carbohydrates KW - enzymes KW - glycosides KW - glycosylation KW - natural products ER - TY - JOUR TI - Measurement of the mixing state, mass, and optical size of individual black carbon particles in urban and biomass burning emissions AU - Schwarz, J. P. AU - Gao, R. S. AU - Spackman, J. R. AU - Watts, L. A. AU - Thomson, D. S. AU - Fahey, D. W. AU - Ryerson, T. B. AU - Peischl, J. AU - Holloway, J. S. AU - Trainer, M. AU - Frost, G. J. AU - Baynard, T. AU - Lack, D. A. AU - de Gouw, J. A. AU - Warneke, C. AU - Del Negro, L. A. T2 - Geophysical Research Letters AB - In situ measurements of the mass, mixing state, and optical size of individual black‐carbon (BC) particles in the fine mode (90–600 nm) have been made in fresh emissions from urban and biomass burning sources with an airborne single‐particle soot photometer. Contrasts between the two sources are significant and consistent. Urban BC tends to smaller sizes, fewer coated particles, thinner coatings, and less absorption per unit mass than biomass‐burning BC. This suggests that urban BC may have a longer lifetime in the atmosphere and a different impact on BC radiative forcing in the first indirect effect than biomass‐burning BC. These measurements bound the likely variability in the microphysical state of BC emissions from typical continental processes, and provide direct measurements of the size distribution and coating state of fine‐mode BC for use in constraining climate and aerosol models. These results highlight the need for the integration of source‐specific information into such models. DA - 2008/7/9/ PY - 2008/7/9/ DO - 10.1029/2008gl033968 VL - 35 IS - 13 J2 - Geophys. Res. Lett. LA - en OP - SN - 0094-8276 UR - http://dx.doi.org/10.1029/2008GL033968 DB - Crossref ER - TY - JOUR TI - Visible-Light Induced Water Detoxification Catalyzed by PtII Dye Sensitized Titania AU - Zhao, Wei AU - Sun, Yali AU - Castellano, Felix N. T2 - Journal of the American Chemical Society AB - A new dye sensitization system incorporating Pt(dcbpy)Cl2 on Degussa P-25 TiO2 for the photomineralization of aqueous organic pollutants under visible light irradiation is described. The representative wastewater pollutant, 4-chlorophenol (4-CP), is readily oxidized (ultimately to CO2) when the PtII dye sensitized TiO2 is exposed to visible light in the presence of dissolved O2, and the reaction is accelerated when the solution is purged with O2 gas at 1 atm. The sensitizer is regenerated during the photocatalysis; therefore, 4-CP effectively reduces the oxidized form of the surface bound dye. The experimental data are consistent with parallel oxidative decomposition pathways for 4-CP, one which operates using conduction band electrons to produce hydroxyl radicals and another where the oxidized sensitizer irreversibly oxidizes 4-CP. DA - 2008/9/24/ PY - 2008/9/24/ DO - 10.1021/ja803522v VL - 130 IS - 38 SP - 12566–12567 SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja803522v ER - TY - JOUR TI - Photophysics of the Platinum(II) Terpyridyl Terpyridylacetylide Platform and the Influence of FeII and ZnII Coordination AU - Muro, Maria L. AU - Diring, Stéphane AU - Wang, Xianghuai AU - Ziessel, Raymond AU - Castellano, Felix N. T2 - Inorganic Chemistry AB - The synthesis, structural characterization, and photoluminescence (PL) properties of the square-planar terpyridylplatinum(II) complex [tBu3tpyPtCCtpy]+ (1) and the octahedral trinuclear FeII and ZnII analogues [Fe(tBu3tpyPtCCtpy)2]4+ (2) and [Zn(tBu3tpyPtCCtpy)2]4+ (3) are described. The photophysical properties of the mononuclear PtII complex 1 are consistent with a charge-transfer excited-state parentage producing a large Stokes shift with a concomitant broad, structureless emission profile. The Fe-based ligand-field states in 2 provide an efficient nonradiative deactivation pathway for excited-state decay, resulting in a nonemissive compound at room temperature. Interestingly, upon chelation of 1 with ZnII, a higher energy charge-transfer emission with a low-energy shoulder and a 215 ns excited-state lifetime is produced in 3. A spectroscopically identical species relative to 3 was produced in control experiments when 1 was reacted with excess protons (HClO4) as ascertained by UV−vis and static PL spectra measured at room temperature and 77 K. Therefore, the chelation of ZnII to 1 is acid−base in nature, and its Lewis acidity renders the highest occupied molecular orbital level in 1 much less electron-rich, which induces a blue shift in both the absorption and emission spectra. At 77 K, complexes 1, 3, and protonated 1 display at least one prevalent vibronic component in the emission profile (1360 cm−1) resembling PL emanating from a ligand-localized excited-state, indicating that these emitting states are inverted relative to room temperature. These results are qualitatively confirmed by the application of time-dependent theory using only the 1360 cm−1 mode to reproduce the low-temperature emission spectra. DA - 2008/8// PY - 2008/8// DO - 10.1021/ic800316x VL - 47 IS - 15 SP - 6796–6803 SN - 0020-1669 1520-510X UR - http://dx.doi.org/10.1021/ic800316x ER - TY - JOUR TI - Slow Cation Transfer Follows Sensitizer Regeneration at Anatase TiO2 Interfaces AU - Staniszewski, Aaron AU - Ardo, Shane AU - Sun, Yali AU - Castellano, Felix N. AU - Meyer, Gerald J. T2 - Journal of the American Chemical Society AB - After rapid photoinduced electron injection into TiO2 and regeneration by a donor, D, such as iodide or phenothiazine, sensitizers are present in an environment distinctly different from that prior to light absorption. Significantly, the absorption spectrum of the Ru(II) sensitizer in this new environment is one that is known to be less favorable for excited-state electron injection. The transient absorption features were found to report on photoinduced variations in the local electronic environment of the Ru(II) sensitizer−TiO2 interface that were induced by ion transfer. The data demonstrate that slow (μs to ms) cation transfer follows regeneration to yield the sensitizer that was initially photoexcited. DA - 2008/9/3/ PY - 2008/9/3/ DO - 10.1021/ja803668z VL - 130 IS - 35 SP - 11586–11587 SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja803668z ER - TY - CONF TI - Low-power upconversion in solid polymer films AU - Islangulov, R.R. AU - Singh, T. AU - Lott, J. AU - Weder, C. AU - Castellano, F.N. C2 - 2008/// C3 - American Chemical Society, Polymer Preprints, Division of Polymer Chemistry DA - 2008/// VL - 49 SP - 1028-1029 M1 - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-51849130452&partnerID=MN8TOARS ER - TY - JOUR TI - A Water-Soluble Luminescence Oxygen Sensor AU - Castellano, Felix N. AU - Lakowicz, Joseph R. T2 - Photochemistry and Photobiology AB - ABSTRACT We developed a water‐soluble luminescent probe for dissolved oxygen. This probe is based on (Ru[dpp(SO 3 Na) 2 ] 3 ) Cl 2 , which is a sulfonated analogue of the well‐known oxygen probe (Ru[dpp] 3 )Cl 2 . The compound dpp is 4,7‐diphenyl‐1,10‐phenanthroline and dpp(SO 3 Na) 2 is a disulfonated derivative of the same ligand. In aqueous solution in the absence of oxygen (Ru[dpp(SO 3 Na) 2 ] 3 )Cl 2 displays a lifetime of 3.7 μs that decreases to 930 ns on equilibrium with air and 227 ns on equilibrium with 100% oxygen. The Stern–Vohner quenching constant is 11330 M −1 . This high oxygen‐quenching constant means that the photoluminescence of Ru(dpp[SO 3 Na] 2 ) 3 Cl 2 is 10% quenched at an oxygen concentration of 8.8 x 10 −6 M , or equilibration with 5.4 torr of oxygen. The oxygen probe dissolved in water displays minimal interactions with lipid vesicles composed of dipalmityl‐L‐α‐phosphatidyl glycerol but does appear to interact with human serum albumin. The absorption maximum near 480 nm, long lifetime and large Stokes’shift allow this probe to be used with simple instrumentation based on a light‐emitting diode light source, allowing low‐cost oxygen sensing in aqueous solutions. To the best of our knowledge this is the first practical water‐soluble oxygen sensor. DA - 2008/1/2/ PY - 2008/1/2/ DO - 10.1111/j.1751-1097.1998.tb05184.x VL - 67 IS - 2 SP - 179-183 ER - TY - JOUR TI - New methods in asymmetric catalysis based on new hemi-labile bidentate ligands AU - Charette, A. B. AU - Côté, A. AU - Desrosiers, J.-N. AU - Bonnaventure, I. AU - Lindsay, V.N.G. AU - Lauzon, C. AU - Tannous, J. AU - Boezio, A.A. T2 - Pure and Applied Chemistry AB - Abstract Chiral bidentate hemi-labile bis(phosphine) monoxide ligands were shown to be quite effective in various copper-catalyzed transformations. Among them, the nucleophilic addition to imines, the conjugate addition to α,β-unsaturated nitro derivatives, and the conjugate reduction of α,β-unsaturated sulfones generally gave good to excellent yields and high enantiomeric excesses. DA - 2008/// PY - 2008/// DO - 10.1351/pac200880050881 VL - 80 IS - 5 SP - 881-890 UR - http://dx.doi.org/10.1351/pac200880050881 KW - bis(phosphine) monoxide KW - hemi-labile bidentate ligands KW - organozinc KW - conjugate addition KW - chiral amines ER - TY - JOUR TI - Triplet spin resonance of the Haldane magnet Pb Ni2 V2 O8 with interchain coupling AU - Smirnov, A.I. AU - Glazkov, V.N. AU - Kashiwagi, T. AU - Kimura, S. AU - Hagiwara, M. AU - Kindo, K. AU - Shapiro, A.Ya. AU - Demianets, L.N. T2 - Physical Review B - Condensed Matter and Materials Physics AB - Spin resonance of the triplet excitations is studied experimentally in the Haldane magnet $\mathrm{Pb}{\mathrm{Ni}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{8}$. The absorption spectrum has features of spin $S=1$ resonance in a crystal field, with all three components, corresponding to transitions $\ensuremath{\mid}\ifmmode\pm\else\textpm\fi{}1⟩\ensuremath{\leftrightarrows}\ensuremath{\mid}0⟩$ and $\ensuremath{\mid}\ensuremath{-}1⟩\ensuremath{\leftrightarrows}\ensuremath{\mid}1⟩$, being observable. The resonance field is temperature dependent, indicating the renormalization of excitation spectrum in the interaction between the triplets. Magnetic resonance frequencies and critical fields of the magnetization are consistent with a boson version of the macroscopic field theory [J. Affleck, Phys. Rev. B 46, 9002 (1992); A. M. Farutin and V. I. Marchenko, Zh. Eksp. Teor. Fiz. 131, 860 (2007)] [JETP 104, 751 (2007)] while they contradict the fermion version and the previously used approach of noninteracting spin chains. DA - 2008/// PY - 2008/// DO - 10.1103/PhysRevB.77.100401 VL - 77 IS - 10 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-41449105978&partnerID=MN8TOARS ER - TY - BOOK TI - Recent Advances in ESR Techniques and Methods Employed in Nitroxide Experiments AU - Smirnov, A.I. AB - This chapter contains sections titled: Introduction Macromolecular Distance Constraints from Spin-Labeling Magnetic Resonance Experiments Continuous Wave ESR of Nitroxide–Nitroxide Pairs Continuous Wave ESR of Nitroxide–Metal Ion Pairs Time Domain Magnetic Resonance of Spin Pairs Nitroxide Spin Labels in Protein Structure Determination by NMR Electronic Relaxation Enhancement in Spin Pairs Pulsed Double Electron-Electron Resonance ESR Double Quantum Coherence Experiments Distance and Angular Constraints by ESR of Spin Pairs at High Magnetic Fields Multiquantum ESR Spin-Labeling ESR of Macroscopically Aligned Lipid Bilayers and Membrane Proteins Mechanical Alignment of Lipid Bilayers on Planar Surfaces Alignment of Discoidal Bilayered Micelles by Magnetic Forces Nanopore-Confined Cylindrical Bilayers Spin-labeling ESR at High Magnetic Fields Spin-Labeling HF and Multifrequency ESR in Studying Molecular Dynamics Stochastic Liouville Theory of Slow Motion ESR Spectra Simulations Molecular Dynamics Simulation Methods High Field ESR in Studying Nitroxide Microenvironment Probing Local Polarity and Proticity of Membrane and Proteins Site-Directed pH-Sensitive Spin-labeling: Differentiating Local pK and Polarity Effects by High-Field ESR Perspectives DA - 2008/// PY - 2008/// DO - 10.1002/9783527621743.ch4 SE - 121-159 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84889425865&partnerID=MN8TOARS ER - TY - JOUR TI - Nitroxides. Applications in Chemistry, Biomedicine, and Materials Science. Von Gertz L. Likhtenshtein, Jun Yamauchi, Shin'ichi Nakatsuji, Alex I. Smirnov und Rui Tamura. AU - Turro, Nicholas J. AU - Chen, Judy Y.-C. T2 - Angew. Chem. AB - Angewandte ChemieVolume 120, Issue 50 p. 9739-9740 Buchbesprechung Nitroxides. Applications in Chemistry, Biomedicine, and Materials Science. Von Gertz L. Likhtenshtein, Jun Yamauchi, Shin'ichi Nakatsuji, Alex I. Smirnov und Rui Tamura. Nicholas J. Turro, Nicholas J. Turro Department of Chemistry, University of Columbia, New York (USA)Search for more papers by this authorJudy Y.-C. Chen, Judy Y.-C. Chen Department of Chemistry, University of Columbia, New York (USA)Search for more papers by this author Nicholas J. Turro, Nicholas J. Turro Department of Chemistry, University of Columbia, New York (USA)Search for more papers by this authorJudy Y.-C. Chen, Judy Y.-C. Chen Department of Chemistry, University of Columbia, New York (USA)Search for more papers by this author First published: 26 November 2008 https://doi.org/10.1002/ange.200885605Read the full textAboutPDF ToolsRequest permissionAdd to favorites 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 onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume120, Issue50December 1, 2008Pages 9739-9740 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. RelatedInformation DA - 2008/// PY - 2008/// DO - 10.1002/ange.200885605 VL - 120 IS - 50 SP - 9739-9740 ER - TY - BOOK TI - Nitroxides AU - Likhtenshtein, Gertz I. AU - Yamauchi, Jun AU - Nakatsuji, Shin'ichi AU - Smirnov, Alex I. AU - Tamura, Rui DA - 2008/2// PY - 2008/2// DO - 10.1002/9783527621743 PB - Wiley-Blackwell SE - 1-419 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-62949108328&partnerID=MN8TOARS ER - TY - JOUR TI - An Accurate and Transferable Intermolecular Diatomic Hydrogen Potential for Condensed Phase Simulation AU - Belof, Jonathan L. AU - Stern, Abraham C. AU - Space, Brian T2 - Journal of Chemical Theory and Computation AB - An anisotropic many-body H2 potential energy function has been developed for use in heterogeneous systems. The intermolecular potential has been derived from first principles and expressed in a form that is readily transferred to exogenous systems, e.g. in modeling H2 sorption in solid-state materials. Explicit many-body polarization effects, known to be important in simulating hydrogen at high density, are incorporated. The analytic form of the potential energy function is suitable for methods of statistical physics, such as Monte Carlo or Molecular Dynamics simulation. The model has been validated on dense supercritical hydrogen and demonstrated to reproduce the experimental data with high accuracy. DA - 2008/7/17/ PY - 2008/7/17/ DO - 10.1021/ct800155q VL - 4 IS - 8 SP - 1332-1337 J2 - J. Chem. Theory Comput. LA - en OP - SN - 1549-9618 1549-9626 UR - http://dx.doi.org/10.1021/ct800155q DB - Crossref ER - TY - JOUR TI - Photophysical Studies of the Trans to Cis Isomerization of the Push−Pull Molecule: 1-(Pyridin-4-yl)-2-(N-methylpyrrol-2-yl)ethene (mepepy) AU - Mokdad, Audrey AU - Belof, Jonathan L. AU - Yi, Sung Wook AU - Shuler, Stephen E. AU - McLaughlin, Mark L. AU - Space, Brian AU - Larsen, Randy W. T2 - The Journal of Physical Chemistry A AB - Organic molecules possessing intramolecular charge-transfer properties (D−π−A type molecules) are of key interest particularly in the development of new optoelectronic materials as well as photoinduced magnetism. One such class of D−π−A molecules that is of particular interest contains photoswitchable intramolecular charge-transfer states via a photoisomerizable π-system linking the donor and acceptor groups. Here we report the photophysical and electronic properties of the trans to cis isomerization of 1-(pyridin-4-yl)-2-(N-methylpyrrol-2-yl)ethene ligand (mepepy) in aqueous solution using photoacoustic calorimetry (PAC) and theoretical methods. Density functional theory (DFT) calculations demonstrate a global energy difference between cis and trans isomers of mepepy to be 8 kcal mol−1, while a slightly lower energy is observed between the local minima for the trans and cis isomers (7 kcal mol−1). Interestingly, the trans isomer appears to exhibit two ground-state minima separated by an energy barrier of ∼9 kcal mol−1. Results from the PAC studies indicate that the trans to cis isomerization results in a negligible volume change (0.9 ± 0.4 mL mol−1) and an enthalpy change of 18 ± 3 kcal mol−1. The fact that the acoustic waves associated with the trans to cis transition of mepepy overlap in frequency with those of a calorimetric reference implies that the conformational transition occurs faster than the ∼50 ns response time of the acoustic detector. Comparison of the experimental results with theoretical studies provide evidence for a mechanism in which the trans to cis isomerization of mepepy results in the loss of a hydrogen bond between a water molecule and the pyridine ring of mepepy. DA - 2008/9/11/ PY - 2008/9/11/ DO - 10.1021/jp803268r VL - 112 IS - 36 SP - 8310-8315 J2 - J. Phys. Chem. A LA - en OP - SN - 1089-5639 1520-5215 UR - http://dx.doi.org/10.1021/jp803268r DB - Crossref ER - TY - JOUR TI - Making a life in the physical sciences AU - Space, Brian T2 - Journal of Organizational Behavior AB - Abstract As a practicing physical chemist, I argue that the challenges faced by the physical sciences have more parallels with organization science than it might first appear. While the physical sciences do represent a strong paradigm endeavor, many of the same issues that were raised in the article “Making a life in the field of organizational science” arise in physical sciences. An essential difference between the physical sciences and organization science is the essentially capital intensive nature of our research. Ironically, the constant pursuit of the requisite research dollars leads to substantial similarity between the fields. The state of academic physical sciences is analyzed in this context informed by the current state of research funding in the United States. Copyright © 2008 John Wiley & Sons, Ltd. DA - 2008/5/16/ PY - 2008/5/16/ DO - 10.1002/job.534 VL - 29 IS - 6 SP - 755-759 J2 - J. Organiz. Behav. LA - en OP - SN - 0894-3796 UR - http://dx.doi.org/10.1002/job.534 DB - Crossref ER - TY - JOUR TI - COLL 465-Synthesis and characterization of nanoparticle assemblies for electronic applications AU - Ayres, Jennifer A. AU - Chandra, Kusum L. AU - Gorman, Christopher B. T2 - Abstracts of Papers of the American Chemical Society DA - 2008/// PY - 2008/// VL - 235 ER - TY - JOUR TI - Critical Assessment of QSAR Models of Environmental Toxicity against Tetrahymena pyriformis: Focusing on Applicability Domain and Overfitting by Variable Selection AU - Tetko, Igor V. AU - Sushko, Iurii AU - Pandey, Anil Kumar AU - Zhu, Hao AU - Tropsha, Alexander AU - Papa, Ester AU - Öberg, Tomas AU - Todeschini, Roberto AU - Fourches, Denis AU - Varnek, Alexandre T2 - Journal of Chemical Information and Modeling AB - The estimation of the accuracy of predictions is a critical problem in QSAR modeling. The “distance to model” can be defined as a metric that defines the similarity between the training set molecules and the test set compound for the given property in the context of a specific model. It could be expressed in many different ways, e.g., using Tanimoto coefficient, leverage, correlation in space of models, etc. In this paper we have used mixtures of Gaussian distributions as well as statistical tests to evaluate six types of distances to models with respect to their ability to discriminate compounds with small and large prediction errors. The analysis was performed for twelve QSAR models of aqueous toxicity against T. pyriformis obtained with different machine-learning methods and various types of descriptors. The distances to model based on standard deviation of predicted toxicity calculated from the ensemble of models afforded the best results. This distance also successfully discriminated molecules with low and large prediction errors for a mechanism-based model developed using log P and the Maximum Acceptor Superdelocalizability descriptors. Thus, the distance to model metric could also be used to augment mechanistic QSAR models by estimating their prediction errors. Moreover, the accuracy of prediction is mainly determined by the training set data distribution in the chemistry and activity spaces but not by QSAR approaches used to develop the models. We have shown that incorrect validation of a model may result in the wrong estimation of its performance and suggested how this problem could be circumvented. The toxicity of 3182 and 48774 molecules from the EPA High Production Volume (HPV) Challenge Program and EINECS (European chemical Substances Information System), respectively, was predicted, and the accuracy of prediction was estimated. The developed models are available online at http://www.qspr.org site. DA - 2008/8/26/ PY - 2008/8/26/ DO - 10.1021/ci800151m VL - 48 IS - 9 SP - 1733-1746 J2 - J. Chem. Inf. Model. LA - en OP - SN - 1549-9596 1549-960X UR - http://dx.doi.org/10.1021/ci800151m DB - Crossref ER - TY - JOUR TI - Combinatorial QSAR Modeling of Chemical Toxicants Tested against Tetrahymena pyriformis AU - Zhu, Hao AU - Tropsha, Alexander AU - Fourches, Denis AU - Varnek, Alexandre AU - Papa, Ester AU - Gramatica, Paola AU - Öberg, Tomas AU - Dao, Phuong AU - Cherkasov, Artem AU - Tetko, Igor V. T2 - Journal of Chemical Information and Modeling AB - Selecting most rigorous quantitative structure-activity relationship (QSAR) approaches is of great importance in the development of robust and predictive models of chemical toxicity. To address this issue in a systematic way, we have formed an international virtual collaboratory consisting of six independent groups with shared interests in computational chemical toxicology. We have compiled an aqueous toxicity data set containing 983 unique compounds tested in the same laboratory over a decade against Tetrahymena pyriformis. A modeling set including 644 compounds was selected randomly from the original set and distributed to all groups that used their own QSAR tools for model development. The remaining 339 compounds in the original set (external set I) as well as 110 additional compounds (external set II) published recently by the same laboratory (after this computational study was already in progress) were used as two independent validation sets to assess the external predictive power of individual models. In total, our virtual collaboratory has developed 15 different types of QSAR models of aquatic toxicity for the training set. The internal prediction accuracy for the modeling set ranged from 0.76 to 0.93 as measured by the leave-one-out cross-validation correlation coefficient ( Q abs2). The prediction accuracy for the external validation sets I and II ranged from 0.71 to 0.85 (linear regression coefficient R absI2) and from 0.38 to 0.83 (linear regression coefficient R absII2), respectively. The use of an applicability domain threshold implemented in most models generally improved the external prediction accuracy but at the same time led to a decrease in chemical space coverage. Finally, several consensus models were developed by averaging the predicted aquatic toxicity for every compound using all 15 models, with or without taking into account their respective applicability domains. We find that consensus models afford higher prediction accuracy for the external validation data sets with the highest space coverage as compared to individual constituent models. Our studies prove the power of a collaborative and consensual approach to QSAR model development. The best validated models of aquatic toxicity developed by our collaboratory (both individual and consensus) can be used as reliable computational predictors of aquatic toxicity and are available from any of the participating laboratories. DA - 2008/3// PY - 2008/3// DO - 10.1021/ci700443v VL - 48 IS - 4 SP - 766-784 J2 - J. Chem. Inf. Model. LA - en OP - SN - 1549-9596 1549-960X UR - http://dx.doi.org/10.1021/ci700443v DB - Crossref ER - TY - JOUR TI - Microarray pattern recognition based on PtII terpyridyl chloride complexes: vapochromic and vapoluminescent response AU - Muro, Maria L. AU - Daws, Charles A. AU - Castellano, Felix N. T2 - Chemical Communications AB - Eighteen distinct PtII terpyridyl chloride cross-reactive sensor elements incorporated into microarrays with 1000 × 250 μm well dimensions generate distinctive colorimetric and luminometric responses upon exposure to a variety of volatile organic compounds (VOCs). DA - 2008/// PY - 2008/// DO - 10.1039/b812634h IS - 46 SP - 6134 J2 - Chem. Commun. LA - en OP - SN - 1359-7345 1364-548X UR - http://dx.doi.org/10.1039/b812634h DB - Crossref ER - TY - JOUR TI - Solvent-induced configuration mixing and triplet excited state inversion exemplified in a Pt(ii) complex AU - Goeb, Sébastien AU - Rachford, Aaron A. AU - Castellano, Felix N. T2 - Chem. Commun. AB - The present study provides clear-cut experimental evidence for solvent-induced configuration mixing and complete triplet state inversion at room temperature in a Pt(ii) charge transfer complex bearing a combination of energetically proximate charge transfer and intraligand triplet excited states. DA - 2008/// PY - 2008/// DO - 10.1039/b713285a IS - 7 SP - 814-816 J2 - Chem. Commun. LA - en OP - SN - 1359-7345 1364-548X UR - http://dx.doi.org/10.1039/b713285a DB - Crossref ER - TY - JOUR TI - Photochemical Upconversion Approach to Broad-Band Visible Light Generation AU - Singh-Rachford, Tanya N. AU - Islangulov, Radiy R. AU - Castellano, Felix N. T2 - The Journal of Physical Chemistry A AB - The sensitized triplet−triplet annihilation (TTA) of 9,10-dimethylanthracene (DMA) upon selective excitation of [Ru(dmb)3]2+ (dmb = 4,4‘-dimethyl-2,2‘-bipyridine) at 514.5 nm in dimethylformamide (DMF) resulted in upconverted and downconverted DMA excimer photoluminescence. The triplet excited state of [Ru(dmb)3]2+ is efficiently quenched by 11 mM DMA in DMF resulting in photon upconversion but no excimer formation. The bimolecular quenching constant of the dynamic quenching process is 1.4 × 109 M-1 s-1. At 90 mM DMA, both upconversion and downconversion processes are readily observed in aerated DMF solutions. The TTA process was confirmed by the quadratic dependence of the upconverted and downconverted emission emanating from the entire integrated photoluminescence profile (400−800 nm) of DMA measured with respect to incident light power. Time-resolved emission spectra of [Ru(dmb)3]2+ and 90 mM DMA in both aerated and deaerated DMF clearly illustrates the time-delayed nature of both types of singlet-state emission, which interestingly shows similar decay kinetics on the order of 14 μs. The emission quantum yields (Φ) measured using relative actinometry increased with increasing DMA concentrations, reaching a plateau at 3.0 mM DMA (Φ = 4.0%), while at 90 mM DMA, the overall quantum yield diminished to 0.5%. The dominant process occurring at 3.0 mM DMA is upconversion from the singlet excited state of DMA, whereas at 90 mM DMA, both upconversion and excimeric emission are observed in almost equal portions, thereby resulting in an overall broad-band visible light-emission profile. DA - 2008/5// PY - 2008/5// DO - 10.1021/jp712165h VL - 112 IS - 17 SP - 3906-3910 J2 - J. Phys. Chem. A LA - en OP - SN - 1089-5639 1520-5215 UR - http://dx.doi.org/10.1021/jp712165h DB - Crossref ER - TY - JOUR TI - Pd(II) Phthalocyanine-Sensitized Triplet−Triplet Annihilation from Rubrene AU - Singh-Rachford, Tanya N. AU - Castellano, Felix N. T2 - The Journal of Physical Chemistry A AB - Upconverted yellow singlet fluorescence from rubrene (5,6,11,12-tetraphenylnapthacene) was generated from selective excitation (lambdaex = 725 nm) of the red light absorbing triplet sensitizer palladium(II) octabutoxyphthalocyanine, PdPc(OBu)8, in vacuum degassed toluene solutions using a Nd:YAG/OPO laser system in concert with gated iCCD detection. The data are consistent with upconversion proceeding from triplet-triplet annihilation (TTA) of rubrene acceptor molecules. The TTA process was confirmed by the quadratic dependence of the upconverted delayed fluorescence intensity with respect to incident light, measured by integrating the corresponding kinetic traces as a function of the incident excitation power. In vacuum degassed toluene solutions, the red-to-yellow upconversion process is stable under continuous long wavelength irradiation and is readily visualized by the naked eye even at modest laser fluence (0.6 mJ/pulse). In aerated solutions, however, selective excitation of the phthalocyanine sensitizer leads to rapid decomposition of rubrene into its corresponding endoperoxide as evidenced by UV-vis (in toluene), 1H NMR (in d6-benzene), and MALDI-TOF mass spectrometry, consistent with the established reactivity of rubrene with singlet dioxygen. The upconversion process in this triplet sensitizer/acceptor-annihilator combination was preliminarily investigated in solid polymer films composed of a 50:50 mixture of an ethyleneoxide/epichlorohydrin copolymer, P(EO/EP). Films that were prepared under an argon atmosphere and maintained under this inert environment successfully achieve the anticipated quadratic incident power dependence, whereas air exposure causes the film to deviate somewhat from this dependence. To the best of our knowledge, the current study represents the first example of photon upconversion using a phthalocyanine triplet sensitizer, furthering the notion that anti-Stokes light-producing sensitized TTA appears to be a general phenomenon as long as proper energy criteria are met. DA - 2008/4// PY - 2008/4// DO - 10.1021/jp7111878 VL - 112 IS - 16 SP - 3550-3556 J2 - J. Phys. Chem. A LA - en OP - SN - 1089-5639 1520-5215 UR - http://dx.doi.org/10.1021/jp7111878 DB - Crossref ER - TY - JOUR TI - Boron Dipyrromethene Chromophores: Next Generation Triplet Acceptors/Annihilators for Low Power Upconversion Schemes AU - Singh-Rachford, Tanya N. AU - Haefele, Alexandre AU - Ziessel, Raymond AU - Castellano, Felix N. T2 - Journal of the American Chemical Society AB - In the present study, the red-light absorbing platinum(II) tetraphenyltetrabenzoporphyrin (PtTPBP) was used as a triplet sensitizer in conjunction with two distinct iodophenyl-bearing BODIPY derivatives independently serving as triplet acceptors/annihilators poised for photon upconversion based on triplet-triplet annihilation. In deaerated benzene solutions, extremely stable and high quantum efficiency green (Phi(UC) = 0.0313 +/- 0.0005) and yellow (Phi(UC) = 0.0753 +/- 0.0036) upconverted emissions were observed from selective red excitation of the PtTPBP sensitizer at 635 +/- 5 nm. The current systems represent the first examples of photon upconversion where aromatic hydrocarbons do not serve the role of triplet acceptor/annihilator. Notably, the nature of the current chromophore compositions permitted highly reproducible upconversion quantum efficiency determinations while permitting the evaluation of the triplet-triplet annihilation quantum yields in both instances. DA - 2008/12/3/ PY - 2008/12/3/ DO - 10.1021/ja807056a VL - 130 IS - 48 SP - 16164-16165 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja807056a DB - Crossref ER - TY - JOUR TI - Accessing the Triplet Excited State in Perylenediimides AU - Rachford, Aaron A. AU - Goeb, Sébastien AU - Castellano, Felix N. T2 - Journal of the American Chemical Society AB - Here, we present a strategy designed to permit access to the PDI triplet manifold that preserves the desirable colorfastness and visible light-absorption properties associated with these dyes. To this end, three new Pt(II) complexes each bearing two PDI moieties tethered to the metal center via acetylide linkages emanating from one of the PDI bay positions have been synthesized, structurally characterized, and thoroughly examined by nanosecond laser flash photolysis. Upon ligation, the bright singlet-state fluorescence of the PDI chromophore is quantitatively quenched, and no long wavelength photoluminescence is observed from the Pt(II)-PDI complexes in deaerated solutions. In each of the Pt-PDI chromophores, quantitatively similar transient absorption difference spectra were obtained; the only distinguishing characteristic is in their single-exponential lifetimes (tau = 246 ns, 1.0 micros, and 710 ns). Triplet-state sensitization experiments of "free" PDI-CCH using thioxanthone confirmed the PDI triplet state assignments in each of the Pt-PDI structures. DA - 2008/3// PY - 2008/3// DO - 10.1021/ja800333y VL - 130 IS - 9 SP - 2766-2767 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja800333y DB - Crossref ER - TY - JOUR TI - Bi- and Terpyridyl Platinum(II) Chloro Complexes: Molecular Catalysts for the Photogeneration of Hydrogen from Water or Simply Precursors for Colloidal Platinum? AU - Du, Pingwu AU - Schneider, Jacob AU - Li, Fan AU - Zhao, Wei AU - Patel, Upali AU - Castellano, Felix N. AU - Eisenberg, Richard T2 - Journal of the American Chemical Society AB - Platinum(II) bi- and terpyridyl chloro complexes, Pt(dcbpy)Cl2 and [Pt(ttpy)Cl]+, where dcbpy = 4,4′-dicarboxyl-2,2′-bipyridine and ttpy = 4-tolyl-2,2′:6′,2″-terpyridine, are used to investigate the nature of the active catalyst for the photocatalytic production of hydrogen from water. In a Pt(II) chloro system that contains a sacrificial electron donor, either MeOH or triethanolamine (TEOA), and titanium dioxide (TiO2) as an electron relay, sizable amounts of H2 can be observed upon UV bandgap irradiation. The quantity of H2 can be significantly reduced in the presence of mercury under the same conditions. Using a known sensitizer, [Pt(ttpy)(phenylacetylide)]+ (1), combined with a Pt(II) chloro complex in a similar system, there is a substantial induction period until the evolution of H2, under visible light (λ > 410 nm) irradiation. It is suggested that the Pt(II) chloro complexes are simply acting as precursors to Pt colloids that function as the H2 generating catalyst DA - 2008/4// PY - 2008/4// DO - 10.1021/ja711090w VL - 130 IS - 15 SP - 5056-5058 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja711090w DB - Crossref ER - TY - JOUR TI - Ultrafast Excited State Dynamics of Pt(II) Chromophores Bearing Multiple Infrared Absorbers AU - Glik, Elena A. AU - Kinayyigit, Solen AU - Ronayne, Kate L. AU - Towrie, Michael AU - Sazanovich, Igor V. AU - Weinstein, Julia A. AU - Castellano, Felix N. T2 - Inorganic Chemistry AB - The paper reports the synthesis, structural characterization, electrochemistry, ultrafast time-resolved infrared (TRIR) and transient absorption (TA) spectroscopy associated with two independent d (8) square planar Pt(II) diimine chromophores, Pt(dnpebpy)Cl 2 ( 1) and Pt(dnpebpy)(C[triple bond]Cnaph) 2 ( 2), where dnpebpy = 4,4'-(CO 2CH 2- (t) Bu) 2-2,2'-bipyridine and CCnaph = naphthylacetylide. The neopentyl ester substitutions provided markedly improved complex solubility relative to the corresponding ethyl ester which facilitates synthetic elaboration as well as spectroscopic investigations. Following 400 nm pulsed laser excitation in CH 2Cl 2, the 23 cm (-1) red shift in the nu C=O vibrations in 1 are representative of a complex displaying a lowest charge-transfer-to-diimine (CT) excited state. The decay kinetics in 1 are composed of two time constants assigned to vibrational cooling of the (3)CT excited-state concomitant with its decay to the ground state (tau = 2.2 +/- 0.4 ps), and to cooling of the formed vibrationally hot ground electronic state (tau = 15.5 +/- 4.0 ps); we note that an assignment of the latter to a ligand field state cannot be excluded. Ultrafast TA data quantitatively support these assignments yielding an excited-state lifetime of 2.7 +/- 0.4 ps for the (3)CT excited-state of 1 and could not detect any longer-lived species. The primary intention of this study was to develop a Pt (II) complex ( 2) bearing dual infrared spectroscopic tags (C[triple bond]C attached to the metal and CO (ester) attached to the diimine ligand) to independently track the movement of charge density in different segments of the molecule following pulsed light excitation. Femtosecond laser excitation of 2 in CH 2Cl 2 at 400 nm simultaneously induces a red-shift in both the nu C=O (-30 cm (-1)) and the nu C[triple bond]C (-61 cm (-1)) vibrations. The TRIR data in 2 are consistent with a charge transfer assignment, and the significant decrease of the energy of the nu C[triple bond]C vibration suggests a considerable contribution from the acetylide ligands in the highest occupied molecular orbital. Therefore, we assign the lowest energy optical transitions in 2 as a combination of metal-to-ligand and ligand-to-ligand charge transfers. The excited-state of 2 is emissive at RT, with an emission maximum at 715 nm, quantum yield of 0.0012, and lifetime of 23 ns. DA - 2008/8// PY - 2008/8// DO - 10.1021/ic800578h VL - 47 IS - 15 SP - 6974-6983 J2 - Inorg. Chem. LA - en OP - SN - 0020-1669 1520-510X UR - http://dx.doi.org/10.1021/ic800578h DB - Crossref ER - TY - JOUR TI - Ligand Localized Triplet Excited States in Platinum(II) Bipyridyl and Terpyridyl Peryleneacetylides AU - Rachford, Aaron A. AU - Goeb, Sébastien AU - Ziessel, Raymond AU - Castellano, Felix N. T2 - Inorganic Chemistry AB - An investigation of the photophysics of two complexes, [Pt((t)Bu3tpy)(C triple bond C-perylene)]BF4 (1) and Pt((t)Bu2bpy)(C triple bond C-perylene)2 (2), where (t)Bu3tpy is 4,4',4''-tri( tert-butyl)-2,2':6',2''-terpyridine, (t)Bu2bpy is 4,4'-di( tert-butyl)-2,2'-bipyridine, and C triple bond C-perylene is 3-ethynylperylene, reveals that they both exhibit perylene-centered ligand localized excited triplet states ((3)IL) upon excitation with visible light. These complexes do not display any significant photoluminescence at room temperature but readily sensitize (1)O2 in aerated CH2Cl2 solutions, as evidenced by its characteristic emission near 1270 nm. The transient absorption difference spectra were compared to bi- and tridentate phosphine peryleneacetylides intended to model the (3)IL peryleneacetylide excited states in addition to the related phenylacetylide-bearing polyimine analogues, with the latter model being the respective triplet charge-transfer ((3)CT) excited states. The transient difference spectra of the two title compounds display excited-state absorptions largely attributable to perylene localized (3)IL states yet exhibit somewhat attenuated excited-state lifetimes relative to those of the phosphine model chromophores. The abbreviated lifetimes in 1 and 2 may suggest the involvement of the energetically proximate (3)CT triplet state exerting an influence on excited-state decay, and the effect appears to be stronger in 1 relative to 2, consistent with the energies of their respective (3)CT states. DA - 2008/5// PY - 2008/5// DO - 10.1021/ic702454k VL - 47 IS - 10 SP - 4348-4355 J2 - Inorg. Chem. LA - en OP - SN - 0020-1669 1520-510X UR - http://dx.doi.org/10.1021/ic702454k DB - Crossref ER - TY - JOUR TI - The Mitochondrial Targeted GS-Nitroxide JP4-039 is Radioprotective In Vitro and In Vivo AU - Epperly, M.W. AU - Pierce, J.G. AU - Dixon, T. AU - Franicola, D. AU - Wipf, P. AU - Greenberger, J.S. T2 - International Journal of Radiation Oncology*Biology*Physics AB - Nitroxides are very efficient scavengers of free radicals and have been proposed for use as radioprotective agents. One disadvantage is the need for high concentrations for an in vivo effect. Stabilization of the mitochondria following irradiation has been demonstrated to be important to prevent ionizing irradiation-induced apoptosis. Attaching a hemi-gramicidin linker to nitroxide was evaluated as an approach to getting mitochondrial localization at lower systemic drug concentration. We report here that hemi-gramicidin linked nitroxide efficiently prevents irradiation-induced apoptosis of hematopoietic cells. Irradiation survival curves were performed by incubating 32D cl 3 murine hematopoietic progenitor cells in JP4-039 or non-mitochondrial localized tempol (1 μM) for 1 hr. The cells were then irradiated to doses ranging from 0 to 8 Gy, suspending in methylcellulose-containing media, incubating for 7 days at 37oC, and colonies of greater than 50 cells were scored. The data was analyzed using linear quadratic and single-hit, multi-target models. In vivo survival analysis was performed by injecting intraperitoneally JP4-039 or tempol (1 mg/kg) 10 min before irradiation of female C57BL/6NHsd mice to the LD 75/30 dose of 9.75 Gy. Mice were followed for survival. Those moribund from the hematopoietic syndrome were sacrificed. Incubation of 32D cl 3 cells in JP4-039 for 1 hour prior to irradiation resulted in a significant increase in Do of 2.25 ± 0.11 Gy compared to 1.19 ± 0.13 Gy for 32D cl 3 cells alone or 1.32 ± 0.09 Gy for 32D cl 3 cells incubated in tempol (p = 0.0042 or p = 0.0073, respectively). C57BL/6NHsd female mice injected with 1 mg/kg JP4-039 before irradiation had a significant increase in survival of 80% compared to 20% for control irradiated mice (p = 0.0005) or 60% for tempol treated mice (p = 0.2252). JP4-039, a mitochondrial targeted nitroxide, is an effective radioprotector. Further studies are required to optimize the schedule of drug delivery for potential translation to clinical use. DA - 2008/9// PY - 2008/9// DO - 10.1016/j.ijrobp.2008.06.952 VL - 72 IS - 1 SP - S82 J2 - International Journal of Radiation Oncology*Biology*Physics LA - en OP - SN - 0360-3016 UR - http://dx.doi.org/10.1016/j.ijrobp.2008.06.952 DB - Crossref ER - TY - JOUR TI - Reactions of Sulfur Dioxide with Neutral Vanadium Oxide Clusters in the Gas Phase. II. Experimental Study Employing Single-Photon Ionization AU - He, Sheng-Gui AU - Xie, Yan AU - Dong, Feng AU - Heinbuch, Scott AU - Jakubikova, Elena AU - Rocca, J. J. AU - Bernstein, Elliot R. T2 - The Journal of Physical Chemistry A AB - Single-photon ionization through vacuum ultraviolet (VUV, 10.5 eV) and soft X-ray (extreme ultraviolet, EUV, 26.5 eV) laser radiation is successfully employed for the study of the reactions of neutral vanadium oxide clusters (V(m)O(n)) with sulfur dioxide (SO2) in the gas phase. V(m)O(n) clusters are generated by reaction of a laser-generated vanadium plasma with O2 in a supersonic expansion. The clusters are cooled in the expansion and are reacted with SO2 in a fast-flow reactor. Detection of neutral clusters and products is through ionization employing VUV and EUV laser radiation and time-of-flight mass spectrometry. Many association reaction intermediates [V(m)O(n)SO2 and V2O4(SO2)2] are observed. Isolated SO is also observed, as a product as predicted by theoretical studies presented in part I (J. Phys. Chem. A 2007, 111, 13339). A weak feature at the SO3 mass channel (80 amu) is suggested to be present in the product mass spectra. Further reactions of the intermediates with O2 are positively identified for VO2SO2, V3O7SO2, and V5O10SO2. Reaction mechanisms are interpreted on the basis of the observations and preliminary theoretical calculations. Molecular level reaction mechanisms for oxidation of SO2 to SO3 facilitated by condensed-phase vanadium oxides as catalysts are suggested. DA - 2008/11/6/ PY - 2008/11/6/ DO - 10.1021/jp805744g VL - 112 IS - 44 SP - 11067-11077 J2 - J. Phys. Chem. A LA - en OP - SN - 1089-5639 1520-5215 UR - http://dx.doi.org/10.1021/jp805744g DB - Crossref ER - TY - JOUR TI - Dopamine Detection with Fast-Scan Cyclic Voltammetry Used with Analog Background Subtraction AU - Hermans, Andre AU - Keithley, Richard B. AU - Kita, Justin M. AU - Sombers, Leslie A. AU - Wightman, R. Mark T2 - Analytical Chemistry AB - Fast-scan cyclic voltammetry has been used in a variety of applications and has been shown to be especially useful to monitor chemical fluctuations of neurotransmitters such as dopamine within the mammalian brain. A major limitation of this procedure, however, is the large amplitude of the background current relative to the currents for the solution species of interest. Furthermore, the background tends to drift, and this drift limits the use of digital background subtraction techniques to intervals less than 90 s before distortion of dopamine signals occurs. To minimize the impact of the background, a procedure termed analog background subtraction is reported here. The background is recorded, and its inverse is played back to the current transducer during data acquisition so that it cancels the background in subsequent scans. Background drift still occurs and is recorded, but its magnitude is small compared to the original background. This approach has two advantages. First it allows the use of higher gains in the current transducer, minimizing quantization noise. Second, because the background amplitude is greatly reduced, principal component regression could be used to separate the contributions from drift, dopamine, and pH when appropriate calibrations were performed. We demonstrate the use of this approach with several applications. First, transient dopamine fluctuations were monitored for 15 min in a flowing injection apparatus. Second, evoked release of dopamine was monitored for a similar period in the brain of an anesthetized rat. Third, dopamine was monitored in the brain of freely moving rats over a 30 min interval. By analyzing the fluctuations in each resolved component, we were able to show that cocaine causes significant fluctuations in dopamine concentration in the brain while those for the background and pH remain unchanged from their predrug value. DA - 2008/6// PY - 2008/6// DO - 10.1021/ac800108j VL - 80 IS - 11 SP - 4040-4048 J2 - Anal. Chem. LA - en OP - SN - 0003-2700 1520-6882 UR - http://dx.doi.org/10.1021/ac800108j DB - Crossref ER - TY - JOUR TI - Hiring and Promotion in Chemical Education AU - Oliver-Hoyo, Maria T. AU - Jones, Loretta L. AU - Kelter, Paul B. AU - Bauer, Christopher F. AU - Clevenger, John V. AU - Cole, Renée S. AU - Sawrey, Barbara A. T2 - Journal of Chemical Education AB - ADVERTISEMENT RETURN TO ISSUEPREVReportNEXTHiring and Promotion in Chemical EducationMaria T. Oliver-Hoyo , Loretta L. Jones , Paul B. Kelter , Christopher F. Bauer , John V. Clevenger , Renée S. Cole , and Barbara A. Sawrey View Author Information Department of Chemistry, North Carolina State University, Raleigh, NC 27695 Department of Chemistry and Biochemistry, University of Northern Colorado, Greely, CO Department of Teaching and Learning, Northern Illinois University, Dekalb, IL 60115 Department of Chemistry, University of New Hampshire, Durham, NH 03824 Department of Chemistry, Truckee Meadows Community College, Revo, NV Department of Chemistry and Physics, University of Central Missouri, Warrensburg, MO 64093 Associate Vice Chancellor, Undergraduate Education, University of California San Diego, LaJolla CA 92093Cite this: J. Chem. Educ. 2008, 85, 7, 898Publication Date (Web):July 1, 2008Publication History Received3 August 2009Published online1 July 2008Published inissue 1 July 2008https://doi.org/10.1021/ed085p898RIGHTS & PERMISSIONSArticle Views532Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (142 KB) Get e-AlertsSUBJECTS:Chemistry education Get e-Alerts DA - 2008/7// PY - 2008/7// DO - 10.1021/ed085p898 VL - 85 IS - 7 SP - 898 J2 - J. Chem. Educ. LA - en OP - SN - 0021-9584 1938-1328 UR - http://dx.doi.org/10.1021/ed085p898 DB - Crossref ER - TY - JOUR TI - Human Proteinpedia enables sharing of human protein data AU - Mathivanan, Suresh AU - Ahmed, Mukhtar AU - Ahn, Natalie G AU - Alexandre, Hainard AU - Amanchy, Ramars AU - Andrews, Philip C AU - Bader, Joel S AU - Balgley, Brian M AU - Bantscheff, Marcus AU - Bennett, Keiryn L AU - Björling, Erik AU - Blagoev, Blagoy AU - Bose, Ron AU - Brahmachari, Samir K AU - Burlingame, Alma S AU - Bustelo, Xosé R AU - Cagney, Gerard AU - Cantin, Greg T AU - Cardasis, Helene L AU - Celis, Julio E AU - Chaerkady, Raghothama AU - Chu, Feixia AU - Cole, Philip A AU - Costello, Catherine E AU - Cotter, Robert J AU - Crockett, David AU - DeLany, James P AU - De Marzo, Angelo M AU - DeSouza, Leroi V AU - Deutsch, Eric W AU - Dransfield, Eric AU - Drewes, Gerard AU - Droit, Arnaud AU - Dunn, Michael J AU - Elenitoba-Johnson, Kojo AU - Ewing, Rob M AU - Eyk, Jennifer Van AU - Faca, Vitor AU - Falkner, Jayson AU - Fang, Xiangming AU - Fenselau, Catherine AU - Figeys, Daniel AU - Gagné, Pierre AU - Gelfi, Cecilia AU - Gevaert, Kris AU - Gimble, Jeffrey M AU - Gnad, Florian AU - Goel, Renu AU - Gromov, Pavel AU - Hanash, Samir M AU - Hancock, William S AU - Harsha, HC AU - Hart, Gerald AU - Hays, Faith AU - He, Fuchu AU - Hebbar, Prashantha AU - Helsens, Kenny AU - Hermeking, Heiko AU - Hide, Winston AU - Hjernø, Karin AU - Hochstrasser, Denis F AU - Hofmann, Oliver AU - Horn, David M AU - Hruban, Ralph H AU - Ibarrola, Nieves AU - James, Peter AU - Jensen, Ole N AU - Jensen, Pia Hønnerup AU - Jung, Peter AU - Kandasamy, Kumaran AU - Kheterpal, Indu AU - Kikuno, Reiko F AU - Korf, Ulrike AU - Körner, Roman AU - Kuster, Bernhard AU - Kwon, Min-Seok AU - Lee, Hyoung-Joo AU - Lee, Young-Jin AU - Lefevre, Michael AU - Lehvaslaiho, Minna AU - Lescuyer, Pierre AU - Levander, Fredrik AU - Lim, Megan S AU - Löbke, Christian AU - Loo, Joseph A AU - Mann, Matthias AU - Martens, Lennart AU - Martinez-Heredia, Juan AU - McComb, Mark AU - McRedmond, James AU - Mehrle, Alexander AU - Menon, Rajasree AU - Miller, Christine A AU - Mischak, Harald AU - Mohan, S Sujatha AU - Mohmood, Riaz AU - Molina, Henrik AU - Moran, Michael F AU - Morgan, James D AU - Moritz, Robert AU - Morzel, Martine AU - Muddiman, David C AU - Nalli, Anuradha AU - Navarro, J Daniel AU - Neubert, Thomas A AU - Ohara, Osamu AU - Oliva, Rafael AU - Omenn, Gilbert S AU - Oyama, Masaaki AU - Paik, Young-Ki AU - Pennington, Kyla AU - Pepperkok, Rainer AU - Periaswamy, Balamurugan AU - Petricoin, Emanuel F AU - Poirier, Guy G AU - Prasad, T S Keshava AU - Purvine, Samuel O AU - Rahiman, B Abdul AU - Ramachandran, Prasanna AU - Ramachandra, Y L AU - Rice, Robert H AU - Rick, Jens AU - Ronnholm, Ragna H AU - Salonen, Johanna AU - Sanchez, Jean-Charles AU - Sayd, Thierry AU - Seshi, Beerelli AU - Shankari, Kripa AU - Sheng, Shi Jun AU - Shetty, Vivekananda AU - Shivakumar, K AU - Simpson, Richard J AU - Sirdeshmukh, Ravi AU - Michael Siu, K W AU - Smith, Jeffrey C AU - Smith, Richard D AU - States, David J AU - Sugano, Sumio AU - Sullivan, Matthew AU - Superti-Furga, Giulio AU - Takatalo, Maarit AU - Thongboonkerd, Visith AU - Trinidad, Jonathan C AU - Uhlen, Mathias AU - Vandekerckhove, Joël AU - Vasilescu, Julian AU - Veenstra, Timothy D AU - Vidal-Taboada, José-Manuel AU - Vihinen, Mauno AU - Wait, Robin AU - Wang, Xiaoyue AU - Wiemann, Stefan AU - Wu, Billy AU - Xu, Tao AU - Yates, John R AU - Zhong, Jun AU - Zhou, Ming AU - Zhu, Yunping AU - Zurbig, Petra AU - Pandey, Akhilesh T2 - Nature Biotechnology AB - Proteomic technologies, such as yeast two-hybrid, mass spectrometry (MS), protein/peptide arrays and fluorescence microscopy, yield multi-dimensional data sets, which are often quite large and either not published or published as supplementary information that is not easily searchable. Without a system in place for standardizing and sharing data, it is not fruitful for the biomedical community to contribute these types of data to centralized repositories. DA - 2008/2// PY - 2008/2// DO - 10.1038/nbt0208-164 VL - 26 IS - 2 SP - 164-167 J2 - Nat Biotechnol LA - en OP - SN - 1087-0156 1546-1696 UR - http://dx.doi.org/10.1038/nbt0208-164 DB - Crossref ER - TY - JOUR TI - Synthesis, Characterization, and Application of Iodoacetamide Derivatives Utilized for the ALiPHAT Strategy AU - Williams, D. Keith AU - Meadows, Corey W. AU - Bori, Ibrahim D. AU - Hawkridge, Adam M. AU - Comins, Daniel L. AU - Muddiman, David C. T2 - Journal of the American Chemical Society AB - Hydrophobic tags, derived from iodoacetamide, were synthesized, characterized, and utilized to alkylate peptide E-76, a known inhibitor of coagulation factor VIIIa, and two other cysteine containing peptides. The electrospray response of each tagged peptide was compared against the same peptide alkylated with iodoacetamide. E-76 peptide alkylated with the synthesized tags demonstrated an increase in electrospray response of up to 429 times when compared to that alkylated with iodoacetamide. DA - 2008/2// PY - 2008/2// DO - 10.1021/ja076849y VL - 130 IS - 7 SP - 2122-2123 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja076849y DB - Crossref ER - TY - CONF TI - Modeling the Effect of Varying Electrical Voltage on the Plastic Deformation of a Single Asperity in Hot-Switched RF MEMS Contacts AU - Crill, John Wesley. AU - Irving, Douglas AU - Padgett, Cliff AU - Zikry, Mohommed AU - Brenner, Don T2 - 2008 MRS Fall Meetin C2 - 2008/// C3 - Materials Research Society Symposium Proceedings DA - 2008/// DO - 10.1557/proc-1137-ee10-15 PB - Materials Research Society UR - http://dx.doi.org/10.1557/proc-1137-ee10-15 DB - Crossref ER - TY - CONF TI - Atomic scale simulations of orientation of loading axis on the growth of voids at the onset of ductile failure in single crystal Cu AU - Dongare, Avinash M. AU - Rajendran, Arunachalam AU - LaMattina, Bruce AU - Zikry, Mohammed AU - Brenner, Donald W. T2 - 2008 MRS Fall Meetin C2 - 2008/// C3 - Materials Research Society Symposium Proceedings DA - 2008/// DO - 10.1557/proc-1137-ee08-09-w10-09 PB - Materials Research Society UR - http://dx.doi.org/10.1557/proc-1137-ee08-09-w10-09 DB - Crossref ER - TY - JOUR TI - Simultaneous fragmentation of multiple ions using IMS drift time dependent collision energies AU - Baker, Erin Shammel AU - Tang, Keqi AU - Danielson, William F., III AU - Prior, David C. AU - Smith, Richard D. T2 - Journal of the American Society For Mass Spectrometry AB - Ion mobility spectrometry coupled with mass spectrometry (IMS-MS) was utilized to evaluate an ion collision energy ramping technique that simultaneously fragments a variety of species. To evaluate this technique, the fragmentation patterns of a mixture of ions ranging in mass, charge state, and drift time were analyzed to determine their optimal fragmentation conditions. The precursor ions were pulsed into the IMS-MS instrument and separated in the IMS drift cell based on mobility differences. Two differentially pumped short quadrupoles were used to focus the ions exiting the drift cell, and fragmentation was induced by collision induced dissociation (CID) between the conductance limiting orifice behind the second short quadrupole and before the first octopole in the mass spectrometer. To explore the fragmentation spectrum of each precursor ion, the bias voltages for the short quadrupoles and conductance limiting orifices were increased from 0 to 50 V above nonfragmentation voltage settings. An approximately linear correlation was observed between the optimal fragmentation voltage for each ion and its specific drift time, so a linear voltage gradient was employed to supply less collision energy to high mobility ions (e.g., small conformations or higher charge state ions) and more to low mobility ions. Fragmentation efficiencies were found to be similar for different ions when the fragmentation voltage was linearly ramped with drift time, but varied drastically when only a single voltage was used. DA - 2008/// PY - 2008/// DO - 10.1016/j.jasms.2007.11.018 VL - 19 IS - 3 SP - 411-419 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000254266400011&KeyUID=WOS:000254266400011 ER - TY - JOUR TI - High-resolution separations and improved ion production and transmission in metabolomics AU - Metz, Thomas O. AU - Page, Jason S. AU - Baker, Erin S. AU - Tang, Keqi AU - Ding, Jie AU - Shen, Yufeng AU - Smith, Richard D. T2 - Trac-Trends in Analytical Chemistry AB - The goal of metabolomics analyses is the detection and quantitation of as many sample components as reasonably possible in order to identify compounds or "features" that can be used to characterize the samples under study. When utilizing electrospray ionization to produce ions for analysis by mass spectrometry (MS), it is important that metabolome sample constituents be efficiently separated prior to ion production, in order to minimize ionization suppression and thereby extend the dynamic range of the measurement, as well as the coverage of the metabolome. Similarly, optimization of the MS inlet and interface can lead to increased measurement sensitivity. This perspective review will focus on the role of high resolution liquid chromatography (LC) separations in conjunction with improved ion production and transmission for LC-MS-based metabolomics. Additional emphasis will be placed on the compromise between metabolome coverage and sample analysis throughput. DA - 2008/// PY - 2008/// DO - 10.1016/j.trac.2007.11.003 VL - 27 IS - 3 SP - 205-214 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000255704800016&KeyUID=WOS:000255704800016 KW - electrospray ionization KW - ion mobility spectroscopy KW - liquid chromatography KW - mass spectrometry KW - metabolomics ER - TY - JOUR TI - G-quadruplex DNA assemblies: Loop length, cation identity, and multimer formation AU - Smargiasso, Nicolas AU - Rosu, Frederic AU - Hsia, Wei AU - Colson, Pierre AU - Baker, Erin Shammel AU - Bowers, Michael T. AU - De Pauw, Edwin AU - Gabelica, Valerie T2 - Journal of the American Chemical Society AB - G-rich DNA sequences are able to fold into structures called G-quadruplexes. To obtain general trends in the influence of loop length on the structure and stability of G-quadruplex structures, we studied oligodeoxynucleotides with random bases in the loops. Sequences studied are dGGGWiGGGWjGGGWkGGG, with W = thymine or adenine with equal probability, and i, j, and k comprised between 1 and 4. All were studied by circular dichroism, native gel electrophoresis, UV-monitored thermal denaturation, and electrospray mass spectrometry, in the presence of 150 mM potassium, sodium, or ammonium cations. Parallel conformations are favored by sequences with short loops, but we also found that sequences with short loops form very stable multimeric quadruplexes, even at low strand concentration. Mass spectrometry reveals the formation of dimers and trimers. When the loop length increases, preferred quadruplex conformations tend to be more intramolecular and antiparallel. The nature of the cation also has an influence on the adopted structures, with K+ inducing more parallel multimers than NH4+ and Na+. Structural possibilities are discussed for the new quadruplex higher-order assemblies. DA - 2008/// PY - 2008/// DO - 10.1021/ja801535e VL - 130 IS - 31 SP - 10208-10216 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000258080600041&KeyUID=WOS:000258080600041 ER - TY - JOUR TI - Prediction of Energies of <100> Tilt Boundaries in Al-Pb Alloy AU - Purohit, Y. AU - Irving, D. L. AU - Scattergood, R. O. AU - Brenner, D. W. T2 - Materials Research Society Symposium Proceedings DA - 2008/// PY - 2008/// VL - 1056E SP - 1056-HH01-105610 ER - TY - JOUR TI - MEMS Lubrication: An atomistic perspective of a bound+ mobile lubricant' AU - Irving, D. L. AU - Brenner, D. W. T2 - Materials Research Society Symposium Proceedings DA - 2008/// PY - 2008/// VL - 1052 SP - 29-34 ER - TY - PAT TI - Refined routes to chlorin building blocks AU - Lindsey, J. S. AU - Taniguchi, M. AU - Ra, D. AU - Mo, G. AU - Balasubramanian, T. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Procedure for preparing redox-active polymers on surfaces AU - Bocian, D. F. AU - Liu, Z AU - Lindsey, J. S. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Boron complexation strategy for use in manipulating 1-acyldipyrromethanes AU - Lindsey, J. S. AU - Muthukumaran, K. AU - Ptaszek, M. AU - Huma, H. Z. S. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Enhanced Ferromagnetism and Tunable Saturation Magnetization of Mn/C-Codoped GaN Nanostructures Synthesized by Carbothermal Nitridation AU - Wang, Zeyan AU - Huang, Baibiao AU - Yu, Lin AU - Dai, Ying AU - Wang, Peng AU - Qin, Xiaoyan AU - Zhang, Xiaoyang AU - Wei, Jiyong AU - Zhan, Jie AU - Jing, Xiangyang AU - Liu, Haixia AU - Whangbo, Myung-Hwan T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Mn/C-codoped GaN nanostructures were synthesized by carbothermal nitridation with active charcoal as the carbon source. Nanostructures such as zigzag nanowires and nanoscrews were observed by varying the reaction time and the C/Ga molar ratio of the starting material used for the synthesis. The structures and morphologies of the as-grown samples were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy measurements. The doping of both Mn and C in the GaN matrix was confirmed by X-ray photoelectron spectroscopy measurements, and the ferromagnetic properties of Mn/C-codoped GaN samples were confirmed by room-temperature magnetization measurements. The saturation magnetization of Mn/C-codoped GaN increases steadily with increasing C/Ga molar ratio of the starting material at a rate of ∼0.023 emu/g per C/Ga molar ratio, and the ferromagnetism of Mn/C-codoped GaN can be stronger than that of Mn-doped GaN by a factor of ∼40. A plausible growth mechanism was proposed, and the role of carbon codoping in tuning the morphology and ferromagnetic property was discussed. Our work suggests that carbon doping in the GaN matrix favors the N sites over the Ga sites, Mn/C-codoping in the GaN matrix is energetically favorable, and the C-codoping strongly enhances the preference of the FM coupling to the AFM coupling between the two doped Mn sites. These suggestions were probed on the basis of first-principles density functional theory electronic structure calculations for a number of model doped structures constructed with a 32-atom 2 × 2 × 2 supercell. DA - 2008/12/3/ PY - 2008/12/3/ DO - 10.1021/ja807030v VL - 130 IS - 48 SP - 16366-16373 SN - 0002-7863 ER - TY - JOUR TI - Determination of Ground-State Hole-Transfer Rates Between Equivalent Sites in Oxidized Multiporphyrin Arrays Using Time-Resolved Optical Spectroscopy AU - Song, Hee-eun AU - Kirmaier, Christine AU - Taniguchi, Masahiko AU - Diers, James R. AU - Bocian, David F. AU - Lindsey, Jonathan S. AU - Holten, Dewey T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Excited-state charge separation in molecular architectures has been widely explored, yet ground-state hole (or electron) transfer, particularly involving equivalent pigments, has been far less studied, and direct quantitation of the rate of transfer often has proved difficult. Prior studies of ground-state hole transfer between equivalent zinc porphyrins using electron paramagnetic resonance techniques give a lower limit of approximately (50 ns)(-1) on the rates. Related transient optical studies of hole transfer between inequivalent sites [zinc porphyrin (Zn) and free base porphyrin (Fb)] give an upper limit of approximately (20 ps)(-1). Thus, a substantial window remains for the unknown rates of ground-state hole transfer between equivalent sites. Herein, the ground-state hole-transfer processes are probed in a series of oxidized porphyrin triads (ZnZnFb) with the focus being on determination of the rates between the nominally equivalent sites (Zn/Zn). The strategy builds upon recent time-resolved optical studies of the photodynamics of dyads wherein a zinc porphyrin is electrochemically oxidized and the attached free base porphyrin is photoexcited. The resulting energy- and hole-transfer processes in the oxidized ZnFb dyads are typically complete within 100 ps of excitation. Such processes are also present in the triads and serve as a starting point for determining the rates of ground-state hole transfer between equivalent sites in the triads. The rate constant of the Zn/Zn hole transfer is found to be (0.8 ns)(-1) for diphenylethyne-linked zinc porphyrins and increases only slightly to (0.6 ns)(-1) when a shorter phenylene linker is utilized. The rate decreases slightly to (1.1 ns)(-1) when steric constraints are introduced in the diarylethyne linker. In general, the rate constants for ground-state Zn/Zn hole transfer in oxidized arrays are a factor of 40 slower than those for Zn/Fb transfer. Collectively, the findings should aid the design of next-generation molecular architectures for applications in solar-energy conversion. DA - 2008/11/19/ PY - 2008/11/19/ DO - 10.1021/ja805673m VL - 130 IS - 46 SP - 15636-15648 SN - 0002-7863 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-56449089593&partnerID=MN8TOARS ER - TY - JOUR TI - Photophysical characterization of imidazolium-substituted Pd(II), In(III), and Zn(II) porphyrins as photosensitizers for photodynamic therapy AU - Kee, Hooi Ling AU - Bhaumik, Jayeeta AU - Diers, James R. AU - Mroz, Pawel AU - Hamblin, Michael R. AU - Bocian, David F. AU - Lindsey, Jonathan S. AU - Holten, Dewey T2 - JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY AB - The photophysical properties of four imidazolium-substituted metalloporphyrins have been assessed to gain insights into the relative efficacy of the compounds for photodynamic therapy (PDT). A set of zinc(II), palladium(II), and chloro-indium(III) porphyrins all bear a net positive charge owing to the diethylimidazolium unit; one zinc chelate bears a negative charge owing to a bis(sulfobutyl)imidazolium unit. The photophysical properties of the cationic and anionic zinc porphyrins are very similar to one another in organic solvents, phosphate-buffered saline, and in the presence of bovine serum albumin. The properties of the zinc and palladium porphyrins bearing charged peripheral groups are generally similar to those of neutral analogs in organic solvents. The palladium porphyrin shows an essentially quantitative yield (≥0.99) of the triplet excited state compared to the zinc porphyrins (∼0.9), and all are quantitatively quenched (at the diffusion limit) by molecular oxygen in air-saturated fluid solution. If the rate constant and yield of quenching of the triplet excited state by energy or electron transfer to molecular oxygen is the same in the cellular environment as in solution, then these processes combined with the triplet yield contribute only a factor of 1.3 to the higher PDT activity of analogous palladium versus zinc porphyrins, which is much smaller than what is observed. Therefore, other factors such as transient reduction of the excited porphyrin or delivery to the target site must predominantly underlie the difference in PDT efficacy of these sensitizers. DA - 2008/12/15/ PY - 2008/12/15/ DO - 10.1016/j.jphotochem.2008.08.006 VL - 200 IS - 2-3 SP - 346-355 SN - 1873-2666 KW - Photodynamic therapy KW - Porphyrin KW - Photosensitizer KW - Imidazolium KW - Photophysics ER - TY - JOUR TI - Nanoencapsulation and Stabilization of Single-Molecule/Particle Electronic Nanoassemblies Using Low-Temperature Atomic Layer Deposition AU - Na, Jeong-Seok AU - Ayres, Jennifer A. AU - Chandra, Kusum L. AU - Gorman, Christopher B. AU - Parsons, Gregory N. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - This work addresses a significant challenge in engineered molecular systems regarding both understanding and controlling the stability of molecule/nanoparticle nanostructures under ambient exposure. Results deal specifically with molecular electronic junctions, where electronic contacts and transport are known to be sensitive to sample history and ambient exposure. We demonstrate that low-temperature atomic layer deposition can gently encapsulate and stabilize molecular electronic junctions, making it feasible to handle and transport junctions in air for many days with minimal change in electronic conduction. These findings indicate the potential for long-term stability of advanced synthetic nanoparticle/molecule nanoconstructs. For this study, conductivity through nanoparticle/molecule/nanoparticle junctions is analyzed and found to be consistent with nonresonant charge tunneling through a single or a small number of oligomeric phenylene ethynylene molecules in the electrical junction. The conductivity was stable in vacuum and inert gas, but under ambient exposure, the current initially decreased, then increased rapidly, followed by a slower rise, reaching a value exceeding 10 times larger than initially measured. After encapsulating functional devices using atomic layer deposition of aluminum oxide thin films at 30−50 °C, the junction showed conductance similar to the precoated values, and the current remained unchanged after more than 15 days under ambient exposure. The presence of the molecule junction after encapsulation was confirmed by the observed transition to Fowler−Nordheim tunneling and analysis of junction breakdown at high fields. The high conformality, precise thickness control, and low-temperature compatibility of the atomic layer deposition method make it uniquely qualified to stabilize and protect molecular junctions and systems. DA - 2008/12/25/ PY - 2008/12/25/ DO - 10.1021/jp8066298 VL - 112 IS - 51 SP - 20510-20517 SN - 1932-7447 ER - TY - JOUR TI - N-Acyldihydropyridones as Synthetic Intermediates. A Stereoselective Synthesis of Acyclic Amino Alcohols Containing Multiple Chiral Centers AU - McCall, W. Stephen AU - Grillo, Teresa Abad AU - Comins, Daniel L. T2 - JOURNAL OF ORGANIC CHEMISTRY AB - Various multisubstituted piperidines containing a phenyl group at C-2 can be opened regio- and stereoselectively with cyanogen bromide. The ring-opened products contain useful cyanamide and benzylic bromide functional groups. The benzyl bromide can be cleanly reduced, or substituted with various nucleophiles via an SN2 process to add additional heteroatoms stereoselectively. This methodology is useful for the stereoselective synthesis of uniquely substituted alkylamine derivatives containing multiple chiral centers and various functionality. Diastereomerically pure amino alcohols containing three to five contiguous stereocenters were prepared using this strategy. DA - 2008/12/19/ PY - 2008/12/19/ DO - 10.1021/jo802029y VL - 73 IS - 24 SP - 9744-9751 SN - 0022-3263 ER - TY - JOUR TI - Gene Silencing in Mammalian Cells with Light-Activated Antisense Agents AU - Young, Douglas D. AU - Lusic, Hrvoje AU - Lively, Mark O. AU - Yoder, Jeffrey A. AU - Deiters, Alexandr T2 - CHEMBIOCHEM AB - On and off the spot: The spatio-temporal light-activation of gene silencing was achieved through the complete inactivation of phosphorothioate antisense agents by installing light-removable (caged) groups at specific sites, as illustrated here. Full antisense activity was restored through a brief irradiation with UV light at 365 nm. DA - 2008/12/15/ PY - 2008/12/15/ DO - 10.1002/cbic.200800627 VL - 9 IS - 18 SP - 2937-2940 SN - 1439-7633 KW - Antisense agents KW - caged compounds KW - DNA KW - gene regulation KW - RNA ER - TY - JOUR TI - Experimental and Theoretical Characterization of the Magnetic Properties of CuF2(H2O)(2)(pyz) (pyz = pyrazine): A Two-Dimensional Quantum Magnet Arising from Supersuperexchange Interactions through Hydrogen Bonded Paths AU - Manson, Jamie L. AU - Conner, Marianne M. AU - Schlueter, John A. AU - McConnell, Amber C. AU - Southerland, Heather I. AU - Malfant, Isabelle AU - Lancaster, Tom AU - Blundell, Stephen J. AU - Brooks, Michael L. AU - Pratt, Francis L. AU - Singleton, John AU - McDonald, Ross D. AU - Lee, Changhoon AU - Whangbo, Myung-Hwan T2 - CHEMISTRY OF MATERIALS AB - The structural, electronic, and magnetic properties of the new linear chain coordination polymer CuF2(H2O)2(pyz) (pyz = pyrazine) were determined by single crystal X-ray diffraction at various temperatures, SQUID magnetometry, pulsed-field magnetization, ESR, muon-spin relaxation (μSR), and electronic structure calculations. Each Cu2+ ion of CuF2(H2O)2(pyz) is located at a distorted CuF2O2N2 octahedron with axial elongation along the Cu−N bonds. These octahedra are tethered together by strong F···H−O hydrogen bonds to yield two-dimensional (2D) square nets in the bc-plane that are linked along the a-direction by pyrazine linkages. Measurements of the g-factor by ESR along with first principles density functional theory electronic structure calculations show that the magnetic orbital of the Cu2+ ion lies in the CuF2O2 plane thus forming a 2D antiferromagnetic square lattice. A broad maximum observed in χ(T) at 10 K indicates a modest spin exchange interaction through the Cu−F···H−O−Cu supersuperexchange paths, and a theoretical fit of χ(T) to a 2D square model gives J2D/kB = −5.58(1) K (in the convention where J rather than 2J is used for spin exchange). At lower temperatures, χ(T) shows a sharp peak at ∼2.6 K, which signals a transition to a long-range magnetic ordering as confirmed by coherent precession of implanted muons. Isothermal M(B) measurements made at 0.5 K on an aligned single crystal reveal magnetic saturation, Msat, at 28.8 T (B∥a) while a higher field of 33.1 T is required to saturate the spins when B is applied perpendicular to the a-axis thus showing clear anisotropy in these orientations. The presence of strong hydrogen bonds in CuF2(H2O)2(pyz) causes the chains to adopt a tilted packing arrangement, thus leading to a novel ground-state likely characterized by spin-canting within the 2D layers and a markedly increased critical temperature relative to the well-known Cu(NO3)2(pyz) polymer chain compound. DA - 2008/12/23/ PY - 2008/12/23/ DO - 10.1021/cm8016566 VL - 20 IS - 24 SP - 7408-7416 SN - 1520-5002 ER - TY - JOUR TI - Calibration laws based on multiple linear regression applied to matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry AU - Williams, D. Keith, Jr. AU - Chadwick, M. Ashley AU - Williams, Taufika Islam AU - Muddiman, David C. T2 - JOURNAL OF MASS SPECTROMETRY AB - Abstract Operation of any mass spectrometer requires implementation of mass calibration laws to translate experimentally measured physical quantities into a m / z range. While internal calibration in Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR‐MS) offers several attractive features, including exposure of calibrant and analyte ions to identical experimental conditions (e.g. space charge), external calibration affords simpler pulse sequences and higher throughput. The automatic gain control method used in hybrid linear trap quadrupole (LTQ) FT‐ICR‐MS to consistently obtain the same ion population is not readily amenable to matrix‐assisted laser desorption/ionization (MALDI) FT‐ICR‐MS, due to the heterogeneous nature and poor spot‐to‐spot reproducibility of MALDI. This can be compensated for by taking external calibration laws into account that consider magnetic and electric fields, as well as relative and total ion abundances. Herein, an evaluation of external mass calibration laws applied to MALDI‐FT‐ICR‐MS is performed to achieve higher mass measurement accuracy (MMA). Copyright © 2008 John Wiley & Sons, Ltd. DA - 2008/12// PY - 2008/12// DO - 10.1002/jms.1451 VL - 43 IS - 12 SP - 1659-1663 SN - 1096-9888 UR - http://europepmc.org/abstract/med/18563853 KW - multiple linear regression KW - polypropylene glycol KW - calibration KW - matrix-assisted laser desorption/ionization (MALDI) KW - Fourier transform ion cyclotron mass spectrometry (FT-ICR-MS) KW - space-charge effects ER - TY - JOUR TI - Synthesis and investigation of the 5-formylcytidine modified, anticodon stem and loop of the human mitochondrial tRNA(Met) AU - Lusic, Hrvoje AU - Gustilo, Estella M. AU - Vendeix, Franck A. P. AU - Kaiser, Rob AU - Delaney, Michael O. AU - Graham, William D. AU - Moye, Virginia A. AU - Cantara, William A. AU - Agris, Paul F. AU - Deiters, Alexander T2 - NUCLEIC ACIDS RESEARCH AB - Human mitochondrial methionine transfer RNA (hmtRNAMetCAU) has a unique post-transcriptional modification, 5-formylcytidine, at the wobble position-34 (f5C34). The role of this modification in (hmtRNAMetCAU) for the decoding of AUA, as well as AUG, in both the peptidyl- and aminoacyl-sites of the ribosome in either chain initiation or chain elongation is still unknown. We report the first synthesis and analyses of the tRNA's anticodon stem and loop domain containing the 5-formylcytidine modification. The modification contributes to the tRNA's anticodon domain structure, thermodynamic properties and its ability to bind codons AUA and AUG in translational initiation and elongation. DA - 2008/11// PY - 2008/11// DO - 10.1093/nar/gkn703 VL - 36 IS - 20 SP - 6548-6557 SN - 1362-4962 ER - TY - JOUR TI - Synthesis and Antibiofilm Activity of a Second-Generation Reverse-Amide Oroidin Library: A Structure-Activity Relationship Study AU - Ballard, T. Eric AU - Richards, Justin J. AU - Wolfe, Amanda L. AU - Melander, Christian T2 - CHEMISTRY-A EUROPEAN JOURNAL AB - A second-generation library of 2-aminoimidazole-based derivatives incorporating a "reversed amide" (RA) motif in comparison to the marine natural product oroidin were synthesized and subsequently assayed for antibiofilm activity against the medically relevant Gram-negative proteobacteria P. aeruginosa and A. baumannii. Most notably, an in-depth activity profile is reported for the most active subclass of derivatives that bear linear aliphatic chains off the amide bond. Additionally, further structural modifications of the core template, such as removal of the amide bond or substitution with a triazole isostere, resulted in the discovery of analogues with antibiofilm activities that varied with respect to their inhibition and dispersal properties of P. aeruginosa and A. baumannii biofilms. DA - 2008/// PY - 2008/// DO - 10.1002/chem.200801419 VL - 14 IS - 34 SP - 10745-10761 SN - 1521-3765 KW - amino acids KW - biological activity KW - drug design KW - medicinal chemistry KW - structure-activity relationships ER - TY - JOUR TI - Composite semiconductor H2WO4 center dot H2O/AgCl as an efficient and stable photocatalyst under visible light AU - Wang, P. AU - Huang, B. B. AU - Zhang, X. Y. AU - Qin, X. Y. AU - Dai, Y. AU - Jin, H. AU - Wei, J. Y. AU - Whangbo, M. H. T2 - Chemistry (Weinheim An Der Bergstrasse, Germany) DA - 2008/// PY - 2008/// VL - 14 IS - 34 SP - 10543-10546 ER - TY - JOUR TI - Chemical bonding and graded interfacial transition regions at transition metal, Hf(Zr),/high-k gate dielectric, Hf(Zr)O(2), interfaces AU - Lucovsky, G. AU - Whitten, J. L. T2 - THIN SOLID FILMS AB - One of the most significant and challenging process integration issues for high-k dielectrics is the replacement of poly-Si gates in CMOS devices with either dual metal gates, or a single mid-band gap metal. The issue is the stability of the metal gate/high-k gate dielectric interface with respect to post-deposition thermal processing. Ab initio quantum chemistry calculations address this issue, and two questions have been resolved, providing results that are consistent with the experiment. The interface between a metal gate electrode and a high gate electrode and oxide dielectric cannot be atomically abrupt after post-deposition thermal processing. Instead there must be a chemically-graded interfacial transition region that mitigates some of the benefits of replacing dual poly-Si gates by metals, except for gate-last processing. However, electrical stress and heating during device operation will be significant driving force atomic motion, and the formation of an interfacial transition region. DA - 2008/11/3/ PY - 2008/11/3/ DO - 10.1016/j.tsf.2008.08.034 VL - 517 IS - 1 SP - 343-345 SN - 0040-6090 KW - High-k dielectrics KW - Hf(Zr)O(2) KW - Transition metal KW - Chemical bonding KW - Graded interfacial regions KW - O-atom vacancies KW - Discrete band edge ER - TY - JOUR TI - Phenylboronic acid immunoaffinity reactor coupled with flow injection chemiluminescence for determination of alpha-fetoprotein AU - Wu, Yafeng AU - Zhuang, Yafeng AU - Liu, Songqin AU - He, Lin T2 - ANALYTICA CHIMICA ACTA AB - A reusable and sensitive immunoassay based on phenylboronic acid immunoaffinity reactor in combination with flow injection chemiluminescence (CL) for determination of glycoprotein was described. The reactor was fabricated by immobilizing 3-aminophenylboronic acid (APBA) on glass microbeads with γ-glycidoxypropyltrimethoxysilane (GPMS) as linkage. The α-fetoprotein (AFP) could be easily immobilized on the APBA coated beads through sugar–boronic interaction. After an off-line incubation, the mixture of the analyte AFP with horseradish peroxidase-labeled AFP antibody (HRP-anti-AFP) was injected into the reactor. This led the trapping of free HRP-anti-AFP by the surface coated AFP on glass beads. The trapped HRP-anti-AFP was detected by chemiluminescence due to its sensitizing effect on the reaction of luminol and hydrogen peroxide. Under optimal conditions, the chemiluminescent signal was proportional to AFP concentration in the range of 10–100 ng mL−1. The whole assay process including regeneration of the reactor could be completed within 31 min. The proposed system showed acceptable detection and fabrication reproducibility, and the results obtained with the present method were in acceptable agreement with those from parallel single-analyte test of practical clinical sera. The described method enabled a low-cost, time saving and was potential to detect the serum AFP level in clinical diagnosis. DA - 2008/12/23/ PY - 2008/12/23/ DO - 10.1016/j.aca.2008.10.010 VL - 630 IS - 2 SP - 186-193 SN - 1873-4324 KW - 3-Aminophenylboronic acid KW - alpha-Fetoprotein KW - Immunoaffinity reactor KW - Regeneration KW - Flow injection chemiluminescence ER - TY - JOUR TI - Molecular Simulation of the Influence of Interface Faceting on the Shock Sensitivity of a Model Plastic Bonded Explosive AU - Shi, Yunfeng AU - Brenner, Donald W. T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - Molecular dynamics simulations are used to model the shock loading of an interface with various degrees of nanometer scale faceting between an inert binder and an energetic crystal. The facets create regions of local compression that induce exothermic reaction that leads to local hotspots and an increased shock sensitivity to detonation. Two mechanisms for compression and hotspot formation are identified that depend on the shock impedance mismatch between the binder and energetic crystal, namely shock focusing and local compression of the facets. These results provide a possible explanation for why spherical RDX crystals in cast polymer-bonded explosives appear less shock sensitive than RDX with more faceted morphologies. DA - 2008/11/27/ PY - 2008/11/27/ DO - 10.1021/jp805690w VL - 112 IS - 47 SP - 14898-14904 SN - 1520-6106 ER - TY - JOUR TI - Investigation of the Vanadyl Bond Ordering and Analysis of the Spin Exchange Interactions in Pb2V3O9 and Pb(2)AS(2)VO(9) AU - Mentre, O. AU - Koo, H. J. AU - Whangbo, M. -H. T2 - CHEMISTRY OF MATERIALS AB - The structures of Pb2V3O9 and Pb2As2VO9 were determined by X-ray diffraction to settle the issue concerning whether the arrangement of the V4+═O vanadyl bonds is ordered or disordered. The new crystal structure of Pb2V3O9 refined by using a twinned crystal differs from the previous structure, determined from a combined use of powder X-ray and neutron diffraction data, and suggests an ordered Ferro arrangement of the V4+═O vanadyl bonds as does the Antiferro crystal structure of the new Pb2As2VO9. In Pb2V3O9, a triclinic → monoclinic transition is observed at 400 °C, and the corresponding high temperature form was structurally characterized. The spin exchange interactions of Pb2V3O9 and Pb2As2VO9 were evaluated by performing qualitative spin dimer analysis based on tight binding calculations, and those of Pb2V3O9 were also examined by quantitative mapping analysis based on density functional theory calculations. To a first approximation, the spin−lattice of Pb2V3O9 is described by an alternating antiferromagnetic chain model, which is made up of the super-superexchange interactions mediated by VO4 tetrahedra between adjacent chains of corner-sharing V4+O6 octahedra. The magnetic property of Pb2As2VO9 is predicted to be paramagnetic, in agreement with experiment. DA - 2008/11/25/ PY - 2008/11/25/ DO - 10.1021/cm800924j VL - 20 IS - 22 SP - 6929-6938 SN - 0897-4756 ER - TY - JOUR TI - Do farmers value the environment? Evidence from a conservation reserve program auction AU - Vukina, Tomislav AU - Zheng, Xiaoyong AU - Marra, Michele AU - Levy, Amando T2 - INTERNATIONAL JOURNAL OF INDUSTRIAL ORGANIZATION AB - The paper uses data from one Conservation Reserve Program (CRP) auction to elicit farmers' attitudes toward the environment by analyzing their bids. The CRP pays farmers to remove chosen plots of land from agricultural production and put them to a conservation use. An interesting aspect of this auction is that winners are determined by a combination of low bids and environmental scores of individual plots. Using decision theoretic approach to model this auction we show that farmers condition their bids on the strength of their environmental scores and that they value environmental benefits, especially those that increase future soil productivity of their land. DA - 2008/11// PY - 2008/11// DO - 10.1016/j.ijindorg.2008.01.001 VL - 26 IS - 6 SP - 1323-1332 SN - 0167-7187 KW - Government auctions KW - Decision theory KW - Environmental benefits evaluation ER - TY - JOUR TI - Determinants of Substrate Internalization in the Distal Pocket of Dehaloperoxidase Hemoglobin of Amphitrite ornata AU - Nienhaus, Karin AU - Nickel, Elena AU - Davis, Michael F. AU - Franzen, Stefan AU - Nienhaus, G. Ulrich T2 - BIOCHEMISTRY AB - Dehaloperoxidase (DHP) is a small heme protein in the coelom of the terebellid polychaete Amphitrite ornata. It can act both as an oxygen storage protein (hemoglobin function) and as a dehaloperoxidase (peroxidase function). The X-ray structure of the ferric form shows that the phenolic substrate can bind inside the protein, which is not the case for a typical peroxidase. In the present study, we have used CO-ligated DHP to mimic the distal pocket of the peroxidase DHP and to probe under which conditions both a halophenol and a diatomic ligand can be accommodated in the distal pocket. To vary the structure of the distal pocket, we have compared wild-type DHP and mutants H55V and H55R at different pH values, using flash photolysis in the visible and FTIR spectroscopy in the CO stretching bands. The latter technique is extremely sensitive to even small structural changes in the CO environment and thus can report substrate binding in the distal pocket. Our results on wild-type DHP and its variants indicate that halophenols and a diatomic ligand can indeed simultaneously be present in the distal pocket if the distal histidine is in the low-pH conformation, in which its side chain is swung out of the distal pocket. The markedly different pH dependencies of enzyme activity and substrate binding are not consistent with the hypothesis that substrate dehalogenation occurs within the interior of DHP. DA - 2008/12/9/ PY - 2008/12/9/ DO - 10.1021/bi801564r VL - 47 IS - 49 SP - 12985-12994 SN - 0006-2960 ER - TY - JOUR TI - Design and synthesis of water-soluble bioconjugatable trans-AB-porphyrins AU - Muresan, Ana Z. AU - Lindsey, Jonathan S. T2 - TETRAHEDRON AB - Three free base porphyrins have been prepared that bear a polar and facially encumbering 2,4,6-tris-(carboxymethoxy)phenyl motif at one meso (5-) position. The only other substituent (15-position) comprises phenyl, formyl, or p-aminophenyl. The porphyrins exhibit solubility in water (or aqueous buffer solutions) at pH ≥7 and concentrations >1 mM at room temperature. The concise syntheses, water solubility, and bioconjugatable handle make these porphyrin constructs suitable for biological applications. DA - 2008/12/8/ PY - 2008/12/8/ DO - 10.1016/j.tet.2008.08.096 VL - 64 IS - 50 SP - 11440-11448 SN - 1464-5416 KW - Porphyrin KW - Water KW - Hydrocarbon KW - Water-soluble KW - Facial encumbrance KW - Bioconjugation ER - TY - JOUR TI - Charge Order in LuFe2O4: Antiferroelectric Ground State and Coupling to Magnetism AU - Angst, M. AU - Hermann, R. P. AU - Christianson, A. D. AU - Lumsden, M. D. AU - Lee, C. AU - Whangbo, M. -H. AU - Kim, J. -W. AU - Ryan, P. J. AU - Nagler, S. E. AU - Tian, W. AU - Jin, R. AU - Sales, B. C. AU - Mandrus, D. T2 - PHYSICAL REVIEW LETTERS AB - X-ray scattering by multiferroic ${\mathrm{LuFe}}_{2}{\mathrm{O}}_{4}$ is reported. Below 320 K, superstructure reflections indicate an incommensurate charge order with propagation close to $(\frac{1}{3}\frac{1}{3}\frac{3}{2})$. The corresponding charge configuration, also found by electronic structure calculations as most stable, contains polar $\mathrm{Fe}/\mathrm{O}$ double layers with antiferroelectric stacking. Diffuse scattering at 360 K, with $(\frac{1}{3}\frac{1}{3}0)$ propagation, indicates ferroelectric short-range correlations between neighboring double layers. The temperature dependence of the incommensuration indicates that charge order and magnetism are coupled. DA - 2008/11/28/ PY - 2008/11/28/ DO - 10.1103/physrevlett.101.227601 VL - 101 IS - 22 SP - SN - 0031-9007 ER - TY - JOUR TI - A Bipodal-Tethered Porphyrin for Attachment to Silicon Surfaces in Studies of Molecular Information Storage AU - Schmidt, Izabela AU - Jiao, Jieying AU - Bocian, David F. AU - Lindsey, Jonathan S. T2 - JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY AB - An approach for molecular information storage entails use of redox-active molecules attached to an electroactive surface. Understanding the structural features that give rise to robust molecular monolayers with high charge density is an essential objective. Toward this goal, a zinc-porphyrin bearing an all-carbon bipodal tether, 5-(1,6-heptadien-4-yl)-15-phenyl-10,20-di- p -tolylporphinatozinc(II), has been synthesized by the reaction of a dipyrromethane and a dipyrromethane-1,9-dicarbinol. The porphyrin was attached to Si(100) via a high temperature procedure. The resulting molecular monolayers exhibited surface coverages, adsorption geometries, electron-transfer rates, and stabilities under repeated electrochemical cycling that are similar to those obtained with monopodal carbon tethers. The observation that the bipodal anchor does not provide enhanced stability is surprising given that attachment is achieved via two versus one covalent linkage. DA - 2008/9// PY - 2008/9// DO - 10.1166/jnn.2008.IC85 VL - 8 IS - 9 SP - 4813-4817 SN - 1533-4899 KW - Porphyrin KW - Bipod KW - Silicon KW - Memory KW - DRAM ER - TY - JOUR TI - Synthesis of Anthracene and Azaanthracene Fluorophores via [2+2+2] Cyclotrimerization Reactions AU - Zou, Yan AU - Young, Douglas D. AU - Cruz-Montanez, Alejandra AU - Deiters, Alexander T2 - ORGANIC LETTERS AB - A highly convergent [2+2+2] cyclotrimerization approach to anthracenes and 2-azaanthracenes has been developed. It allows for the facile introduction of the anthracene moiety on alkyne and nitrile bearing molecules and the rapid construction of compound arrays. This is showcased in the assembly of a collection of fluorophores and their photochemical evaluation. DA - 2008/10/16/ PY - 2008/10/16/ DO - 10.1021/ol8019549 VL - 10 IS - 20 SP - 4661-4664 SN - 1523-7052 ER - TY - JOUR TI - Synthesis and structures of a new series of silver-vanadate hybrid solids and their optical and photocatalytic properties AU - Lin, Haisheng AU - Maggard, Paul A. T2 - INORGANIC CHEMISTRY AB - Three new silver-vanadate hybrid solids, [Ag(bpy)]4V4O12 x 2 H2O (I), [Ag(dpa)]4V4O12 x 4 H2O (II), and Ag4(pzc)2V2O6 (III) (bpy = 4,4'-bipyridine, dpa = 1,2-bis(4-pyridyl)-ethane, pzc = pyrazinecarboxylate), were synthesized by hydrothermal methods and characterized using single crystal X-ray diffraction (I, P2(1)/c, Z = 4, a = 11.375(2) A, b = 14.281(4) A, c = 13.598(3) A, beta = 91.46(1) degrees; II, P2(1)/c, Z = 8, a = 13.5748(3) A, b = 15.3372(4) A, c = 14.1854(3) A, beta = 114.1410(9) degrees; III, P1, Z = 2, a = 3.580(1) A, b = 11.839(4) A, c = 19.321(7) A, alpha = 89.110(7) degrees, beta = 87.719(9) degrees, gamma = 86.243(8) degrees), thermogravimetric analysis, and UV-vis diffuse reflectance. The structures of I and II are constructed from neutral {Ag4V4O12}n layers of clusters that are pillared via the coordination of organic ligands (bpy for I and dpa for II) to the Ag sites in each layer. Conversely, the structure of III is composed of a three-dimensional {Ag2(pzc)(+)}n coordination network with channels containing {VO3(-)}n chains. The lattice water molecules can be removed upon heating to > or = 180 degrees C for I (reversibly) and to > or = 120 degrees C for II (irreversibly). All three decompose with the removal of organic ligands at higher temperatures of > 200-300 degrees C. Their optical bandgap sizes were measured to be 2.77 eV for I, 2.95 eV for II, and 2.45 eV for III, which decrease most notably as a result of the band widening for the more extended vanadate structure in III. All three hybrid solids are photocatalytically active for the decomposition of methylene blue under UV light (lambda < 400 nm; 1.01, 0.64, and 2.65 mg L(-1) h(-1) for I, II, and III, respectively), while only III exhibits a high activity under visible-light irradiation (lambda > 400 nm; 1.20 mg L(-1) h(-1) ). These new hybrid solids are among the first reported to exhibit high photocatalytic activities under either ultraviolet or visible-light irradiation and have also been analyzed with respect to the effect of the different organic ligands on their atomic- and electronic-structures. DA - 2008/9/15/ PY - 2008/9/15/ DO - 10.1021/ic8004129 VL - 47 IS - 18 SP - 8044-8052 SN - 1520-510X ER - TY - JOUR TI - Self-assembly of CdTe nanocrystals at the water/oil interface by amphiphilic hyperbranched polymers AU - Shi, Y. F. AU - Tu, C. L. AU - Zhu, Q. AU - Qian, H. F. AU - Ren, J. C. AU - Liu, C. H. AU - Zhu, X. Y. AU - Yan, D. Y. AU - Siu-WaiKong, E. AU - He, P. T2 - Nanotechnology DA - 2008/// PY - 2008/// VL - 19 IS - 44 ER - TY - JOUR TI - New molten-salt synthesis and photocatalytic properties of La2Ti2O7 particles AU - Arney, David AU - Porter, Brittany AU - Greve, Benjamin AU - Maggard, Paul A. T2 - JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY AB - The (1 1 0)-layered perovskite La2Ti2O7 photocatalyst has been synthesized in high purities and in homogeneous microstructures within a molten Na2SO4/K2SO4 flux in short reaction times of ∼1–10 h. The La2Ti2O7 particle morphologies and sizes were investigated as a function of flux amounts (flux:La2Ti2O7 molar ratios of 1:1, 2:1, 5:1, and 10:1) and reaction times (1, 2, 5, and 10 h). Powder X-ray diffraction confirmed the structure type and high purity, and UV–vis diffuse reflectance measurements yielded optical bandgap sizes of ∼3.75–3.81 eV. Rectangular platelet morphologies are obtained with maximal dimensions of ∼500–5000 nm, but with thicknesses down to <100 nm, and which decrease in size with increasing amounts of flux used in the synthesis. Photocatalytic activities of the La2Ti2O7 products were measured under ultraviolet irradiation in aqueous methanol solutions and yielded rates for hydrogen production from 55 to 140 μmol H2 h−1 g−1, with the maximum photocatalytic rates for the smallest particles, e.g. for 1:1 and 10:1 flux:La2Ti2O7 ratios respectively. The flux-prepared La2Ti2O7 products were also photocatalytically active in pure deionized water, yielding maximal rates for hydrogen formation of 31 μmol H2 h−1 g−1. The observed photocatalytic rates were up to nearly two times greater than that obtained when La2Ti2O7 was prepared by the reported solid-state method, and indicate that the exposed crystallite edges and the (0 1 0) and (0 0 1) crystal faces play a key role in the photocatalysis mechanisms for hydrogen formation. DA - 2008/9/25/ PY - 2008/9/25/ DO - 10.1016/j.jphotochem.2008.06.005 VL - 199 IS - 2-3 SP - 230-235 SN - 1010-6030 KW - flux synthesis KW - La2Ti2O7 KW - photocatalysis ER - TY - JOUR TI - Mechanistic Investigations of the Iridium(III)-Catalyzed Aerobic Oxidation of Primary and Secondary Alcohols AU - Jiang, Bi AU - Feng, Yuee AU - Ison, Elon A. T2 - Journal of the American Chemical Society AB - The commercially available catalysts [(Cp*IrCl2)2] is employed with O2 as the terminal oxidant in the presence of catalytic amounts of Et3N for the aerobic oxidation of primary and secondary alcohols. A new mechanism for the Ir-catalyzed aerobic oxidation is also presented that suggests that the transition metal maintains its +3 oxidation state throughout the entire catalytic cycle. DA - 2008/11/5/ PY - 2008/11/5/ DO - 10.1021/ja8049595 VL - 130 IS - 44 SP - 14462-14464 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja8049595 DB - Crossref ER - TY - JOUR TI - Influence of Pb segregation on the deformation of nanocrystalline Al: Insights from molecular simulations AU - Jang, S. AU - Purohit, Y. AU - Irving, D. L. AU - Padgett, C. AU - Brenner, D. AU - Scattergood, R. O. T2 - ACTA MATERIALIA AB - Molecular dynamics straining simulations using a two-dimensional columnar model were run for pure Al with grain sizes from 5 to 30 nm, and for 10 nm grain size Al–Pb alloys containing 1, 2 and 3 at.% Pb. Monte Carlo simulations showed that all the Pb atoms segregate to the grain boundaries. Pb segregation suppresses the nucleation of partial dislocations and twins during straining. At 3 at.% Pb, no dislocations or twins are observed throughout the straining history. It also appeared that Pb tends to segregate to the same locations in grain boundaries that were favorable for partial dislocation emission. Grain boundaries with Pb segregates were very robust against dissociation during straining compared to pure Al. The yield stress determined from stress–strain curves showed a decrease with increasing Pb content, supporting a similar observation for the hardness change measured on nanocrystalline Al–Pb alloys. DA - 2008/10// PY - 2008/10// DO - 10.1016/j.actamat.2008.05.024 VL - 56 IS - 17 SP - 4750-4761 SN - 1359-6454 KW - MD simulations KW - MC simulations KW - Al-Pb alloys KW - Nanocrystalline materials KW - Plastic deformation ER - TY - JOUR TI - A general approach to triphenylenes and azatriphenylenes: total synthesis of dehydrotylophorine and tylophorine AU - McIver, Andrew AU - Young, Douglas D. AU - Deiters, Alexander T2 - CHEMICAL COMMUNICATIONS AB - A convergent and flexible synthesis of substituted triphenylenes, azatriphenylenes, and the cytotoxic alkaloids dehydrotylophorine and tylophorine has been developed. DA - 2008/// PY - 2008/// DO - 10.1039/b811068a IS - 39 SP - 4750-4752 SN - 1359-7345 ER - TY - JOUR TI - Strengthening mechanisms in nanocrystalline alloys AU - Scattergood, R. O. AU - Koch, C. C. AU - Murty, K. L. AU - Brenner, D. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - The mechanisms for strengthening nanocrystalline metals by alloy additions are reviewed and a new model for nano-particle strengthening by Orowan bypassing in nano-grains is proposed. Recent experimental results for three different nanocrystalline alloy systems, Fe–Pb, Fe–Al2O3 and Al–Pb are presented and analyzed in terms of non-equilibrium solid solution strengthening, nano-composite strengthening and Orowan particle strengthening, respectively. Conflicting alloy hardening and softening effects observed in Al–Pb appear to be the result of interplay between Orowan particle hardening and a softening mechanism due to grain-boundary segregation. Preliminary MD simulations support the latter suggestion. DA - 2008/10/15/ PY - 2008/10/15/ DO - 10.1016/j.msea.2007.04.132 VL - 493 IS - 1-2 SP - 3-11 SN - 0921-5093 KW - nanocrystalline alloys KW - strengthening mechanisms KW - Orowan model ER - TY - JOUR TI - Regiospecifically alpha-C-13-labeled porphyrins for studies of ground-state hole transfer in multiporphyrin arrays AU - Muresan, Ana Z. AU - Thamyongkit, Patchanita AU - Diers, James R. AU - Holten, Dewey AU - Lindsey, Jonathan S. AU - Bocian, David F. T2 - JOURNAL OF ORGANIC CHEMISTRY AB - Insight into the electronic communication between the individual constituents of multicomponent molecular architectures is essential for the rational design of molecular electronic and/or photonic devices. To clock the ground-state hole/electron-transfer process in oxidized multiporphyrin architectures, a p-diphenylethyne-linked zinc porphyrin dyad was prepared wherein one porphyrin bears two 13C atoms and the other porphyrin is unlabeled. The 13C atoms are located at the 1- and 9-positions (α-carbons symmetrically disposed to the position of linker attachment), which are sites of electron/spin density in the a1u HOMO of the porphyrin. The 13C labels were introduced by reaction of KS13CN with allyl bromide to give the allyl isothiocyanate, which upon Trofimov pyrrole synthesis followed by methylation gave 2-(methylthio)pyrrole-2-13C. Reaction of the latter with paraformaldehyde followed by hydrodesulfurization gave dipyrromethane-1,9-13C, which upon condensation with a dipyrromethane-1,9-dicarbinol bearing three pentafluorophenyl groups gave the tris(pentafluorophenyl)porphyrin bearing 13C labels at the 1,9-positions and an unsubstituted meso (5-) position. Zinc insertion, bromination at the 5-position, and Suzuki coupling with an unlabeled porphyrin bearing a suitably functionalized diphenylethyne linker gave the regiospecifically labeled zinc porphyrin dyad. Examination of the monocation of the isotopically labeled dyad via electron paramagnetic resonance (EPR) spectroscopy (and comparison with the monocations of benchmark monomers, where hole transfer cannot occur) showed that the hole transfer between porphyrin constituents of the dyad is slow (<106 s−1) on the EPR time scale at room temperature. The slow rate stems from the a1u HOMO of the electron-deficient porphyrins, which has a node at the site of linker connection. In contrast, analogous dyads of electron-rich porphyrins (wherein the HOMO is a2u and has a lobe at the site of linker connection) studied previously exhibit rates of hole transfer that are fast (>5 × 107 s−1) on the EPR time scale at room temperature. DA - 2008/9/19/ PY - 2008/9/19/ DO - 10.1021/jo8012836 VL - 73 IS - 18 SP - 6947-6959 SN - 0022-3263 ER - TY - JOUR TI - Polarization-dependent fluorescence of proteins bound to nanopore-confined lipid bilayers AU - Li, R.-Q. AU - Marek, A. AU - Smirnov, Alex I. AU - Grebel, H. T2 - The Journal of Chemical Physics AB - Lipid bilayers are essential structural component of biological membranes of all the living species: from viruses and bacteria to plants and humans. Biophysical and biochemical properties of such membranes are important for understanding physical mechanisms responsible for drug targeting. Binding events between proteins and the membrane may be ascertained by introducing fluorescence markers (chromophores) to the proteins. Here we describe a novel biosensing platform designed to enhance signals of these fluorescence markers. Nanoporous aluminum oxide membranes with and without gold (Au) surface coating have been employed for optical detection of bound conjugated streptavidin to biotinylated lipid bilayers—a model system that mimics protein docking to the membrane surface. Unexpectedly, it was found that fluorescence signals from such structures vary when pumped with E-polarized and H-polarized incident optical beams. The origin of the observed polarization-dependent effects and the implications for enhanced fluorescence detection in a biochip format are being discussed. DA - 2008/// PY - 2008/// DO - 10.1063/1.2972143 VL - 129 IS - 9 SP - 095102 J2 - J. Chem. Phys. LA - en OP - SN - 0021-9606 UR - http://dx.doi.org/10.1063/1.2972143 DB - Crossref ER - TY - JOUR TI - On the possibility of ferromagnetism in carbon-doped anatase TiO2 AU - Yang, K. S. AU - Dai, Y. AU - Huang, B. B. AU - Whangbo, M. H. T2 - Applied Physics Letters DA - 2008/// PY - 2008/// VL - 93 IS - 13 ER - TY - JOUR TI - Molecular dynamics simulations of deformation in nanocrystalline Al-Pb alloys AU - Jang, S. AU - Purohit, Y. AU - Irving, D. AU - Padgett, C. AU - Brenner, D. AU - Scattergood, R. O. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Abstract A modified embedded-atom method (MEAM) potential was developed and used for molecular dynamics (MD) straining simulations of Al–Pb alloys with a grain size of 10 nm and Pb content up to 3 at.%. Monte Carlo (MC) simulations done at 300 K indicated that all the Pb is segregated to the grain boundaries in these alloys. As the Pb content increases, partial dislocation nucleation at grain boundaries is suppressed, and the plastic strain is accommodated by mechanisms other than dislocation slip. The increasing Pb content was accompanied by a reduction in the yield and peak stress values. DA - 2008/10/15/ PY - 2008/10/15/ DO - 10.1016/j.msea.2007.05.130 VL - 493 IS - 1-2 SP - 53-57 SN - 0921-5093 KW - MD straining simulation KW - Al-Pb alloys KW - grain boundary segregation ER - TY - JOUR TI - Investigation of the scope of a new route to ABCD-bilanes and ABCD-porphyrins AU - Dogutan, Dilek Kiper AU - Lindsey, Jonathan S. T2 - JOURNAL OF ORGANIC CHEMISTRY AB - A new route to bilanes and porphyrins bearing four distinct meso substituents has been studied to elucidate the scope and gain entry to previously inaccessible compounds. The route entails (i) synthesis of a 1-bromo-19-acylbilane by acid-catalyzed condensation of a 1-acyldipyrromethane and a 9-bromodipyrromethane-1-carbinol and (ii) intramolecular cyclization of the 1-bromo-19-acylbilane in the presence of a metal salt (MgBr2, 3 mol equiv) and a non-nucleophilic base (DBU, 10 mol equiv) in a noncoordinating solvent (toluene) at 115 degrees C exposed to air to afford the corresponding magnesium(II) porphyrin. In this study, two sets of bilanes were initially prepared to explore substituent effects. In the first set, all bilanes vary only in the nature of the substituent at the 10-position. In the second set, all bilanes vary only in the nature of the substituent attached to the acyl unit (the 20-position). The substituents examined at the 10- and 20-positions include alkyl, aryl (electron-rich, electron-deficient, hindered), heteroaryl, ester, or no substituent (-H). The bilanes were obtained in 35-87% yield, and the target porphyrins in up to 60% yield. Further study of the scope focused on bilanes and porphyrins bearing three heterocyclic substituents (o-, m-, p-pyridyl) or four alkyl groups (ethyl, propyl, butyl, pentyl), in which case microwave irradiation was used for the porphyrin-forming step. Altogether, 17 bilanes and 19 porphyrins were prepared and characterized. In summary, the new route provides access to meso-substituted bilanes and porphyrins for which access is limited via other methods. DA - 2008/9/5/ PY - 2008/9/5/ DO - 10.1021/jo8010396 VL - 73 IS - 17 SP - 6728-6742 SN - 1520-6904 ER - TY - JOUR TI - Defect dependent ferromagnetism in MgO doped with Ni and Co AU - Narayan, J. AU - Nori, Sudhakar AU - Pandya, D. K. AU - Avasthi, D. K. AU - Smirnov, A. I. T2 - Applied Physics Letters AB - We have investigated magnetic properties of MgO single crystals doped with Ni and Co impurities, and studied changes in magnetic properties after heavy ion irradiation. These results are compared with doped single-crystal thin films that contain a higher concentration of trapped defects. The as-grown bulk single crystals, which contain a small equilibrium concentration of vacancies, exhibit a perfect paramagnetic behavior throughout the temperature range and magnetic field. By introducing defects either by ion irradiation or by thin film deposition, which have trapped defects, we are able to achieve defect-mediated ferromagnetic ordering. DA - 2008/8/25/ PY - 2008/8/25/ DO - 10.1063/1.2977614 VL - 93 IS - 8 SP - 082507 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.2977614 DB - Crossref ER - TY - JOUR TI - Atomistic modeling of the segregation of lead impurities to a grain boundary in an aluminum bicrystalline solid AU - Purohit, Y. AU - Jang, S. AU - Irving, D. L. AU - Padgett, C. W. AU - Scattergood, R. O. AU - Brenner, D. W. T2 - MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING AB - Using Monte Carlo simulations, new insights into the atomic segregation of lead (Pb) impurities to a Σ5 〈1 0 0〉 {2 1 0} tilt aluminum (Al) grain boundary have been obtained. Interatomic interactions in the Al–Pb alloy system were described using a modified embedded atom method potential with parameters that fit to the results of density functional calculations. The simulations predict segregation of Pb impurities along the Al grain boundary prior to the formation of Pb clusters. Analyses of grain boundary energies for varying concentrations of Pb suggests that grain boundaries in Al can be thermodynamically stabilized by Pb impurities with respect to a dilute solid solution of Pb in Al. DA - 2008/10/15/ PY - 2008/10/15/ DO - 10.1016/j.msea.2007.05.128 VL - 493 IS - 1-2 SP - 97-100 SN - 1873-4936 KW - bicrystal KW - Monte Carlo KW - segregation KW - grain boundary energy KW - grain growth ER - TY - JOUR TI - Microwave, Photo- and Thermally Responsive PNIPAm-Gold Nanoparticle Microgels AU - Budhlall, Bridgette M. AU - Marquez, Manuel AU - Velev, Orlin D. T2 - LANGMUIR AB - Microwave-, photo- and thermo-responsive polymer microgels that range in size from 500 to 800 μm and are swollen with water were prepared by a novel microarray technique. We used a liquid−liquid dispersion technique in a system of three immiscible liquids to prepare hybrid PNIPAm-co-AM core−shell capsules loaded with AuNPs. The spontaneous encapsulation is a result of the formation of double oil-in-water-in-oil (o/w/o) emulsion. It is facilitated by adjusting the balance of the interfacial tensions between the aqueous phase (in which a water-soluble drug may be dissolved), the monomer phase and the continuous phase. The water-in-oil (w/o) droplets containing 26 wt% NIPAm and Am monomers, 0.1 wt% Tween-80 surfactant, FITC fluorescent dye and colloidal gold nanoparticles spontaneously developed a core−shell morphology that was fixed by in situ photopolymerization. The results demonstrate new reversibly swelling and deswelling AuNP/PNIPAm hybrid core−shell microcapsules and microgels that can be actuated by visible light and/or microwave radiation (≤1250 nm) and/or temperature. This is the first study to demonstrate that incorporating AuNPs speeds up the response kinetics of PNIPAm, and hence enhances the sensitivity to external stimuli of PNIPAm. These microgels can have potential applications for microfluidic switches or microactuators, photosensors, and various nanomedicine applications in controlled delivery and release. DA - 2008/10/21/ PY - 2008/10/21/ DO - 10.1021/la8019556 VL - 24 IS - 20 SP - 11959-11966 SN - 0743-7463 ER - TY - JOUR TI - Investigations with O-linked protein glycosylations by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry AU - Williams, Taufika Islam AU - Saggese, Diana A. AU - Toups, Kristina L. AU - Frahm, Jennifer L. AU - An, Hyun Joo AU - Li, Bensheng AU - Lebrilla, Carlito B. AU - Muddiman, David C. T2 - JOURNAL OF MASS SPECTROMETRY AB - Abstract Posttranslational modifications such as glycosylation can play a fundamental role in signaling pathways that transform an ordinary cell into a malignant one. The development of a protocol to detect these changes in the preliminary stages of disease can lead to a sensitive and specific diagnostic for the early detection of malignancies such as ovarian cancer in which differential glycan patterns are linked to etiology and progression. Small variations in instrument parameters and sample preparation techniques are known to have significant influence on the outcome of an experiment. For an experiment to be effective and reproducible, these parameters must be optimized for the analyte(s) under study. We present a detailed examination of sample preparation and matrix‐assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI‐FT‐ICR‐MS) analysis of O ‐linked glycans globally cleaved from mucin glycoproteins. Experiments with stable isotope‐labeled biomolecules allowed for the establishment of appropriate acquisition times and excitation voltages for MALDI‐FT‐ICR‐MS of oligosaccharides. Quadrupole ion guide optimization studies with mucin glycans identified conditions for the comprehensive analysis of the entire mass range of O ‐linked carbohydrates in this glycoprotein. Separately optimized experimental parameters were integrated in a method that allowed for the effective study of O ‐linked glycans. Copyright © 2008 John Wiley & Sons, Ltd. DA - 2008/9// PY - 2008/9// DO - 10.1002/jms.1398 VL - 43 IS - 9 SP - 1215-1223 SN - 1076-5174 UR - http://europepmc.org/abstract/med/18324610 KW - Fourier transform ion cyclotron mass spectrometry (FT-ICR-MS) KW - matrix-assisted laser desorption/ionization (MALDI) KW - mucin KW - O-linked glycans KW - protein glycosylations ER - TY - JOUR TI - Construction of a versatile high precision ambient Ionization source for direct analysis and imaging AU - Sampson, J. S. AU - Hawkridge, A. M. AU - Muddiman, David T2 - Journal of the American Society for Mass Spectrometry AB - The design and construction of a high precision ambient ionization source matrix-assisted laser desorption electrospray ionization (MALDESI) are described in full detail, including a complete parts list. The computer controlled high precision motion control system and high repetition rate Explorer laser are demonstrated during MALDESI-FT-ICR analysis of peptides and proteins ranging from 1 to 17 kDa. The high stability ionization source platform described herein demonstrates both the advantages of the new MALDESI source and versatility for application to numerous desorption and ionization techniques. DA - 2008/// PY - 2008/// DO - 10.1016/j.jasms.2008.06.013 VL - 19 IS - 10 SP - 1527–1534 ER - TY - JOUR TI - Comparison of Electron-Transfer Rates for Metal- versus Ring-Centered Redox Processes of Porphyrins in Monolayers on Au(111) AU - Jiao, Jieying AU - Schmidt, Izabela AU - Taniguchi, Masahiko AU - Lindsey, Jonathan S. AU - Bocian, David F. T2 - LANGMUIR AB - The standard electron-transfer rate constants ( k ( 0 )) are measured for redox processes of Fe versus Zn porphyrins in monolayers on Au(111); the former undergoes a metal-centered redox process (conversion between Fe (III) and Fe (II) oxidation states) whereas the latter undergoes a ring-centered redox process (conversion between the neutral porphyrin and the pi-cation radical). Each porphyrin contains three meso-mesityl groups and a benzyl thiol for surface attachment. Under identical solvent (propylene carbonate)/electrolyte (1.0 M Bu 4NCl) conditions, the Zn (II) center has a coordinated Cl (-) ion when the porphyrin is in either the neutral or oxidized state. In the case of the Fe porphyrin, two species are observed a low-potential form ( E l (0) approximately -0.6 V) wherein the metal center has a coordinated Cl (-) ion when it is in either the Fe (II) or Fe (III) state and a high-potential form ( E h (0) approximately +0.2 V) wherein the metal center undergoes ligand exchange upon conversion from the Fe (III) to Fe (II) states. The k ( 0 ) values observed for all of the porphyrins depend on surface concentration, with higher concentrations resulting in slower rates, consistent with previous studies on porphyrin monolayers. The k ( 0 ) values for the ring-centered redox process (Zn chelate) are 10-40 times larger than those for the metal-centered process (Fe chelate); the k ( 0 ) values for the two forms of the Fe porphyrin differ by a factor of 2-4 (depending on surface concentration), the Cl (-) exchanging form generally exhibiting a faster rate. The faster rates for the ring- versus metal-centered redox process are attributed to the participating molecular orbitals and their proximity to the surface (given that the porphyrins are relatively upright on the surface): a pi molecular orbital that has significant electron density at the meso-carbon atoms (one of which is the site of attachment of the linker to the surface anchoring thiol) versus a d-orbital that is relatively well localized on the metal center. DA - 2008/10/21/ PY - 2008/10/21/ DO - 10.1021/la8019843 VL - 24 IS - 20 SP - 12047-12053 SN - 0743-7463 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-55549087896&partnerID=MN8TOARS ER - TY - JOUR TI - Chemistry surrounding Group 7 complexes that possess Poly(pyrazolyl)borate ligands AU - Lail, M. AU - Pittard, K. A. AU - Gunnoe, T. B. T2 - Organotransition metal chemistry of poly(pyrazolyl)borates, pt 1 DA - 2008/// PY - 2008/// VL - 56 SP - 95-153 ER - TY - JOUR TI - Density Functional Characterization of the Band Edges, the Band Gap States, and the Preferred Doping Sites of Halogen-Doped TiO2 AU - Yang, Kesong AU - Dai, Ying AU - Huang, Baibiao AU - Whangbo, Myung-Hwan T2 - CHEMISTRY OF MATERIALS AB - First-principles density functional theory (DFT) electronic structure calculations were carried out for model halogen-doped anatase TiO2 structures to evaluate the effect of halogen doping on the band edges and the photocatalytic activity of TiO2. The model structures of X-doped TiO2 were constructed by using the 48-atom 2 × 2 × 1 supercell of anatase TiO2 with one O or one Ti atom replaced with X (=F, Cl, Br, I). The unit cell parameters and the atom positions of the resulting X-doped TiO2 with X at an O site (X@O) and that with X at a Ti site (X@Ti) were optimized by performing first-principles DFT calculations. On the basis of the optimized structures of X-doped TiO2 with X@O and X@Ti, the defect formation energies and the plots of the density of states were calculated to analyze the band edges, the band gap states, and the preferred doping sites. Our work shows that the doping becomes more difficult in the order F < Cl < Br < I for X-doped TiO2 with X@O, while the doping becomes less difficult in the order F < Cl < Br < I for X-doped TiO2 with X@Ti. Under O-rich growth condition, it is energetically more favorable to substitute Br and I for a Ti site than for an O site, while it is energetically more favorable to substitute F and Cl for an O site than for a Ti site. Under Ti-rich condition, it is energetically more favorable to substitute all X (=F, Cl, Br, I) for an O site than for a Ti site. The I atoms in I-doped TiO2 with I@Ti are present as I5+ (s2) ions, while in X-doped TiO2 with X@Ti (X = F, Cl, Br) the F, Cl, and Br are present as F3+ (s2p2), Cl4+ (s2p1), and Br4+ (s2p1) ions, respectively. I-doped TiO2 either with I@Ti or with I@O has a doubly filled band gap state, which significantly reduces the optical band gap with respect to that of undoped TiO2. DA - 2008/10/28/ PY - 2008/10/28/ DO - 10.1021/cm801741m VL - 20 IS - 20 SP - 6528-6534 SN - 1520-5002 ER - TY - JOUR TI - Conformational Dynamics Associated with Photodissociation of CO from Dehaloperoxidase Studied Using Photoacoustic Calorimetry AU - Miksovska, Jaroslava AU - Horsa, Simona AU - Davis, Michael F. AU - Franzen, Stefan T2 - BIOCHEMISTRY AB - Herein, we present photoacoustic calorimetry and transient absorption studies of the dynamics and energetics associated with dissociation of a ligand from Fe2+ dehaloperoxidase (DHP) from Amphitrite ornata. Our data show that CO photodissociation is associated with an endothermic (ΔH = 8 ± 3 kcal mol−1) volume expansion (ΔV = 9.4 ± 0.6 mL mol−1) that occurs within 50 ns upon photodissociation. No additional thermodynamics were detected on slower time scales (up to 10 μs), suggesting that the dissociated ligand rapidly escapes from the heme-binding pocket into the surrounding solvent. Similar volume and enthalpy changes were observed for CO photodissociation in the presence of the substrate, 2,4-dichlorophenol or 4-bromophenol, indicating that either the substrate does not bind in the protein distal cavity at ambient temperature or its presence does not impact the thermodynamic profile associated with ligand dissociation. We attribute a fast ligand exchange between the protein active site and the surrounding solvent to the high flexibility of the distal histidine residue, His55, that provides a direct pathway between the heme-binding pocket and the protein exterior. The dynamics and energetics of conformational changes observed for dissociation of a ligand from DHP differ significantly from those measured previously for photodissociation of CO from the structural homologue myoglobin, suggesting that structural dynamics in DHP are fine-tuned to enhance the peroxidase function of this protein. DA - 2008/11/4/ PY - 2008/11/4/ DO - 10.1021/bi8012033 VL - 47 IS - 44 SP - 11510-11517 SN - 0006-2960 ER - TY - JOUR TI - Small-molecule inhibitors of microRNA miR-21 function AU - Gumireddy, Kiranmai AU - Young, Douglas D. AU - Xiong, Xin AU - Hogenesch, John B. AU - Huang, Qihong AU - Deiters, Alexander T2 - ANGEWANDTE CHEMIE-INTERNATIONAL EDITION AB - Short, but significant, microRNAs (miRNAs) are an important class of gene regulators. Small-molecule modifiers of miRNA function, such as 1 (see schematic representation), were identified in a cellular screen for miRNA-pathway inhibitors. Such compounds are expected to be useful tools for the elucidation of detailed mechanisms of miRNA action and may serve as lead structures for the development of new therapeutic agents. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2008/// PY - 2008/// DO - 10.1002/anie.200801555 VL - 47 IS - 39 SP - 7482-7484 SN - 1521-3773 KW - antitumor agents KW - cell-based assays KW - inhibitors KW - medicinal chemistry KW - microRNA ER - TY - JOUR TI - Poly(ethylene glycol) monolayer formation and stability on gold and silicon nitride substrates AU - Cerruti, Marta AU - Fissolo, Stefano AU - Carraro, Carlo AU - Ricciardi, Carlo AU - Majumdar, Arun AU - Maboudian, Roya T2 - LANGMUIR AB - Poly(ethylene glycol) (PEG) self-assembled monolayers (SAMs) are extensively used to modify substrates to prevent nonspecific protein adsorption and to increase hydrophilicity. X-ray photoelectron spectroscopy analysis, complemented by water contact angle measurements, is employed to investigate the formation and stability upon aging and heating of PEG monolayers formed on gold and silicon nitride substrates. In particular, thiolated PEG monolayers on gold, with and without the addition of an undecylic spacer chain, and PEG monolayers formed with oxysilane precursors on silicon nitride have been probed. It is found that PEG-thiol SAMs are degraded after less than two weeks of exposure to air and when heated at temperatures as low as 120 degrees C. On the contrary, PEG-silane SAMs are stable for more than two weeks, and fewer molecules are desorbed even after two months of aging, compared to those desorbed in two weeks from the PEG-thiol SAMs. A strongly bound hydration layer is found on PEG-silane SAMs aged for two months. Heating PEG-silane SAMs to temperatures as high as 160 degrees C improves the quality of the monolayer, desorbing weakly bound contaminants. The differences in stability between PEG-thiol SAMs and PEG-silane SAMs are ascribed to the different types of bonding to the surface and to the fact that the thiol-Au bond can be easily oxidized, thus causing desorption of PEG molecules from the surface. DA - 2008/10/7/ PY - 2008/10/7/ DO - 10.1021/la801357v VL - 24 IS - 19 SP - 10646-10653 SN - 0743-7463 ER - TY - JOUR TI - Photoluminescence-enhanced biocompatible quantum dots by phospholipid functionalization AU - Shi, Yunfeng AU - He, Peng AU - Zhu, Xinyuan T2 - MATERIALS RESEARCH BULLETIN AB - A simple two-step strategy using phospholipid (PPL) to functionalize core/shell CdSe/ZnS quantum dots (QDs) has been described. The experimental data show that the use of S–H terminated PPL results not only in the high colloidal stability of core/shell CdSe/ZnS QDs in the aqueous phase, but also in the significant enhancement of photoluminescence. The degree of the enhancement is a function of the PPL–CdSe/ZnS QDs sample concentration. These results might be promising for future biological platform in new devices ranging from photovoltaic cells to biosensors and other devices. DA - 2008/10/2/ PY - 2008/10/2/ DO - 10.1016/j.materresbull.2007.10.034 VL - 43 IS - 10 SP - 2626-2635 SN - 1873-4227 KW - nanostructures KW - surfaces KW - chemical synthesis ER - TY - JOUR TI - Microwave-assisted synthesis of unnatural amino acids AU - Young, Douglas D. AU - Torres-Kolbus, Jessica AU - Deiters, Alexander T2 - BIOORGANIC & MEDICINAL CHEMISTRY LETTERS AB - Microwave irradiation has been proven to be a useful tool in the rapid assembly of racemic unnatural amino acids in only two steps. Additional benefits of this methodology are the commercial availability of the inexpensive starting materials and the high yields and high purities of the final amino acid products. DA - 2008/10/15/ PY - 2008/10/15/ DO - 10.1016/j.bmcl.2008.09.025 VL - 18 IS - 20 SP - 5478-5480 SN - 0960-894X KW - microwave KW - microwave synthesis KW - amino acid KW - unnatural amino acid KW - peptide synthesis KW - protein synthesis KW - unnatural amino acid KW - mutagenesis ER - TY - JOUR TI - Hydroarylation of unactivated olefins catalyzed by platinum(II) complexes AU - McKeown, Bradley A. AU - Foley, Nicholas A. AU - Lee, John P. AU - Gunnoe, T. Brent T2 - ORGANOMETALLICS AB - The Pt(II) complex [(tbpy)Pt(Ph)(THF)][BAr′4] catalyzes the hydroarylation of olefins utilizing unactivated substrates. Preliminary studies indicate that the reactions proceed via Pt-mediated C−H activation rather than a traditional Friedel−Crafts pathway. DA - 2008/8/25/ PY - 2008/8/25/ DO - 10.1021/om8006008 VL - 27 IS - 16 SP - 4031-4033 SN - 0276-7333 ER - TY - JOUR TI - Ag@AgCl: A highly efficient and stable photocatalyst active under visible light AU - Wang, Peng AU - Huang, Baibiao AU - Qin, Xiaoyan AU - Zhang, Xiaoyang AU - Dai, Ying AU - Wei, Jiyong AU - Whangbo, Myung-Hwan T2 - ANGEWANDTE CHEMIE-INTERNATIONAL EDITION AB - Plasmonic photocatalyst [email protected], in which Ag nanoparticles are deposited on the surfaces of AgCl particles (SEM image depicted), was prepared by treating Ag2MoO4 with HCl to form AgCl powder and then reducing some Ag+ ions in the surface region of the AgCl particles to Ag0. This photocatalyst is highly efficient, for example in the degradation of organic dyes, and stable under visible light. DA - 2008/// PY - 2008/// DO - 10.1002/anie.200802483 VL - 47 IS - 41 SP - 7931-7933 SN - 1521-3773 KW - heterogeneous catalysis KW - nanostructures KW - photocatalysts KW - photochemistry KW - silver ER - TY - JOUR TI - The effect of particle design on cellular internalization pathways AU - Gratton, Stephanie E. A. AU - Ropp, Patricia A. AU - Pohlhaus, Patrick D. AU - Luft, J. Christopher AU - Madden, Victoria J. AU - Napier, Mary E. AU - DeSimone, Joseph M. T2 - PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA AB - The interaction of particles with cells is known to be strongly influenced by particle size, but little is known about the interdependent role that size, shape, and surface chemistry have on cellular internalization and intracellular trafficking. We report on the internalization of specially designed, monodisperse hydrogel particles into HeLa cells as a function of size, shape, and surface charge. We employ a top-down particle fabrication technique called PRINT that is able to generate uniform populations of organic micro- and nanoparticles with complete control of size, shape, and surface chemistry. Evidence of particle internalization was obtained by using conventional biological techniques and transmission electron microscopy. These findings suggest that HeLa cells readily internalize nonspherical particles with dimensions as large as 3 mum by using several different mechanisms of endocytosis. Moreover, it was found that rod-like particles enjoy an appreciable advantage when it comes to internalization rates, reminiscent of the advantage that many rod-like bacteria have for internalization in nonphagocytic cells. DA - 2008/8/19/ PY - 2008/8/19/ DO - 10.1073/pnas.0801763105 VL - 105 IS - 33 SP - 11613-11618 SN - 0027-8424 KW - PRINT KW - shape KW - size KW - surface charge ER - TY - JOUR TI - Mismatched Hartmann-Hahn conditions cause proton-mediated intermolecular magnetization transfer between dilute low-spin nuclei in NMR of static solids AU - Nevzorov, Alexander A. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Mismatched Hartmann−Hahn conditions between the protons and dilute spins (such as 15N) are found to cause intermolecular magnetization transfer between the low-gamma nuclei over long distances. This transfer is purely proton mediated and occurs even in the absence of direct 15N−15N couplings. This has been demonstrated experimentally using a static single crystal of n-acetyl Leucine with intermolecular distances between the 15N nuclei exceeding 6.5 Å. A quantum-mechanical explanation of this phenomenon is given based on the average-Hamiltonian theory which was confirmed by detailed numerical many-spin simulations. The theory and experiment presented in the present paper may help in the development of solid-state NMR methods for studying interhelical contacts in membrane proteins, as well as for their spectral assignment. DA - 2008/8/27/ PY - 2008/8/27/ DO - 10.1021/ja804326b VL - 130 IS - 34 SP - 11282-+ SN - 0002-7863 ER - TY - JOUR TI - Prostate-specific antigen detection by using a reusable amperometric immunosensor based on reversible binding and leasing of HRP-anti-PSA from phenylboronic acid modified electrode AU - Liu, Songqin AU - Zhang, Xiaoting AU - Wu, Yafeng AU - Tu, Yifeng AU - He, Lin T2 - CLINICA CHIMICA ACTA AB - In recent years, many automated immunoassay analyzers have been developed for accurate diagnosis of various disease states and to improve effective drug administration. Amperometric immunoassay has been increasingly applied to laboratory medicine due to its ease in automation, rapid speed and low detection limits. It is important to develop reusable immunologically-sensitive elements for prostate-specific antigen (PSA) detection. The strategy for the immunosensor construction is based on the enzyme-conjugated prostate-specific antibody (HRP-anti-PSA) reversible binding with a self-assembled phenylboronic acid monolayer on gold. After incubating an HRP-anti-PSA modified electrode in a PSA solution, a decrease in the electrocatalytic response of the HRP-anti-PSA modified electrode to the reduction of H2O2 is observed. The photometric activity assays show that this decrease of the electrocatalytic response arises from the formation of immunocomplexes of HRP-conjugated anti-PSA and its antigen, not from the loss of bound HRP-anti-PSA from the electrode surface. Analytical performances and optimal conditions of the described immunosensor are also investigated. Under the optimal conditions, the amperometric immunosensor shows a linear increase of the relative intensity in 2 PSA concentration range from 2 to 15 ng/ml and 15 to 120 ng/ml, respectively. This method could be used for rapid analysis of PSA and potentially other antigens. DA - 2008/9// PY - 2008/9// DO - 10.1016/j.cca.2008.04.031 VL - 395 IS - 1-2 SP - 51-56 SN - 1873-3492 KW - electrocatalytic KW - amperometric immunosensor KW - phenylboronic acid assembled monolayer KW - reusable KW - prostate-specific antigen KW - immunocomplex ER - TY - JOUR TI - Examination of chlorin-bacteriochlorin energy-transfer dyads as prototypes for near-infrared molecular imaging probes AU - Kee, Hooi Ling AU - Nothdurft, Ralph AU - Muthiah, Chinnasamy AU - Diers, James R. AU - Fan, Dazhong AU - Ptaszek, Marcin AU - Bocian, David F. AU - Lindsey, Jonathan S. AU - Culver, Joseph P. AU - Holten, Dewey T2 - PHOTOCHEMISTRY AND PHOTOBIOLOGY AB - Abstract New classes of synthetic chlorin and bacteriochlorin macrocycles are characterized by narrow spectral widths, tunable absorption and fluorescence features across the red and near‐infrared (NIR) regions, tunable excited‐state lifetimes (<1 to >10 ns) and chemical stability. Such properties make dyad constructs based on synthetic chlorin and bacteriochlorin units intriguing candidates for the development of NIR molecular imaging probes. In this study, two such dyads ( FbC‐FbB and ZnC‐FbB ) were investigated. The dyads contain either a free base (Fb) or zinc (Zn) chlorin (C) as the energy donor and a free base bacteriochlorin (B) as the energy acceptor. In both constructs, energy transfer from the chlorin to bacteriochlorin occurs with a rate constant of ∼(5 ps) −1 and a yield of >99%. Thus, each dyad effectively behaves as a single chromophore with an exceptionally large Stokes shift (85 nm for FbC‐FbB and 110 nm for ZnC‐FbB ) between the red‐region absorption of the chlorin and the NIR fluorescence of the bacteriochlorin (λ f = 760 nm, Φ f = 0.19, τ ∼ 5.5 ns in toluene). The long‐wavelength transitions (absorption, emission) of each constituent of each dyad exhibit narrow (≤20 nm) spectral widths. The narrow spectral widths enabled excellent selectivity in excitation and detection of one chlorin–bacteriochlorin energy‐transfer dyad in the presence of the other upon diffuse optical tomography of solution‐phase phantoms. DA - 2008/// PY - 2008/// DO - 10.1111/j.1751-1097.2008.00409.x VL - 84 IS - 5 SP - 1061-1072 SN - 1751-1097 ER - TY - JOUR TI - Effects of spin-orbit coupling on magnetic properties of discrete and extended magnetic systems AU - Dai, Dadi AU - Xiang, Hongjun AU - Whangbo, Myung-Hwan T2 - JOURNAL OF COMPUTATIONAL CHEMISTRY AB - In accounting for the magnetic properties of discrete and extended compounds with unpaired spins, it is crucial to know the nature of their ground and low-lying excited states. In this review we surveyed quantum mechanical descriptions on how these states are affected by spin-orbit coupling and attempted to provide a conceptual framework with which to think about spin-orbit coupling and its applications. DA - 2008/10// PY - 2008/10// DO - 10.1002/jcc.21011 VL - 29 IS - 13 SP - 2187-2209 SN - 0192-8651 KW - spin-orbit coupling KW - magnetic properties KW - spin angular momentum KW - orbital angular momentum ER - TY - JOUR TI - Development and characterization of an ionization technique for analysis of biological macromolecules: Liquid matrix-assisted laser desorption electrospray ionization AU - Sampson, Jason S. AU - Hawkridge, Adam M. AU - Muddiman, David C. T2 - ANALYTICAL CHEMISTRY AB - We have developed an atmospheric pressure ionization technique called liquid matrix-assisted laser desorption electrospray ionization (liq-MALDESI) for the generation of multiply charged ions by laser desorption from liquid samples deposited onto a stainless steel sample target biased at a high potential. This variant of our previously reported MALDESI source does not utilize an ESI emitter to postionize neutrals. Conversely, we report desorption and ionization from a macroscopic charged droplet. We demonstrate high mass resolving power single-acquisition FT-ICR-MS analysis of peptides and proteins ranging from 1 to 8.6 kDa at atmospheric pressure. The liquid sample acts as a macroscopic charged droplet similar to those generated by electrospray ionization, whereby laser irradiation desorbs analyte from organic matrix containing charged droplets generating multiply charged ions. We have observed a singly charged radical cation of an electrochemically active species indicating oxidation occurs for analytes and therefore water; the latter would play a key role in the mechanism of ionization. Moreover, we demonstrate an increase in ion abundance and a concurrent decrease in surface tension with an increase in the applied potential. DA - 2008/9/1/ PY - 2008/9/1/ DO - 10.1021/ac8001935 VL - 80 IS - 17 SP - 6773-6778 SN - 0003-2700 ER - TY - JOUR TI - Analysis of electronic structures and chemical bonding of metal-rich compounds. I. Density functional study of Pt metal, LiPt2, LiPt, and Li2Pt AU - Lee, Changhoon AU - Whangbo, Myung-Hwan AU - Koehler, Juergen T2 - JOURNAL OF COMPUTATIONAL CHEMISTRY AB - First principles density functional theory calculations were carried out for the series of metal-rich compounds, LiPt2, LiPt, and Li2Pt, and elemental Pt for comparison, to probe the bonding picture that captures the essence of their electronic structures. Our analysis shows that the 5d-electron configuration of Pt in these compounds is close to (5d)10, and the electrons released from the Li atoms in the Li/Pt binary compounds are delocalized among the Pt0 atoms and Li+ ions through the interactions of the Pt 5d orbitals of each Pt with the Pt 6s/6p of neighboring Pt atoms and the Li 2s/2p orbitals of neighboring Li atoms. The electron counting schemes best representing the electronic structures of Pt metal, LiPt2, LiPt and Li2Pt are Pt0 (d10), Li+[Pt0 (d10)]2(e−), Li+[Pt0 (d10)](e−), and (Li+)2[Pt0 (d10)](2e−), respectively, and hence the Pt atoms of the Li/Pt binary compounds are predicted to exist as partially negative anions. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008 DA - 2008/10// PY - 2008/10// DO - 10.1002/jcc.21020 VL - 29 IS - 13 SP - 2154-2160 SN - 1096-987X KW - Pt-Li binary compounds KW - metal-rich compounds KW - electron counting KW - chemical bonding KW - electronic structure ER - TY - JOUR TI - Effects of N-pyrrole substitution on the anti-biofilm activities of oroidin derivatives against Acinetobacter baumannii AU - Richards, Justin J. AU - Reed, Catherine S. AU - Melander, Christian T2 - BIOORGANIC & MEDICINAL CHEMISTRY LETTERS AB - Bacteria of the genus Acinetobacter spp. are rapidly emerging as problematic pathogens in healthcare settings. This is exacerbated by the bacteria’s ability to form robust biofilms. Marine natural products incorporating a 2-aminoimidazole (2-AI) motif, namely from the oroidin class of marine alkaloids, have served as a unique scaffold for developing molecules that have the ability to inhibit and disperse bacterial biofilms. Herein we present the anti-biofilm activity of a small library of second generation oroidin analogues against the bacterium Acinetobacter baumannii. DA - 2008/8/1/ PY - 2008/8/1/ DO - 10.1016/j.bmcl.2008.06.089 VL - 18 IS - 15 SP - 4325-4327 SN - 0960-894X KW - biofilm KW - inhibition KW - dispersion KW - marine natural products KW - oroidin ER - TY - JOUR TI - Characterization of the magnetic and structural properties of copper carbodiimide, CuNCN, by neutron diffraction and first-principles evaluations of its spin exchange interactions AU - Liu, Xiaohui AU - Dronskowski, Richard AU - Kremer, Reinhard K. AU - Ahrens, Martin AU - Lee, Changhoon AU - Whangbo, Myung-Hwan T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - The crystal structure of copper carbodiimide, CuNCN, was determined from neutron diffraction data at room temperature and at 4 K, and the electrical resistivity, specific heat, and magnetic susceptibility measurements were carried out. The spin exchange interactions of CuNCN were evaluated by performing first-principles density functional theory electronic structure calculations. CuNCN is a semiconductor containing Jahn−Teller distorted CuN6 octahedra around the divalent copper ions, and the material shows a very small and almost temperature-independent magnetic susceptibility. Our electronic structure calculations evidence that the spin exchange interactions of CuNCN are dominated by two antiferromagnetic spin exchange paths leading to a triangular lattice antiferromagnet within the ab plane. Because the coupling between the layers (along the c axis) is small, CuNCN may be regarded a two-dimensional S = 1/2 frustrated triangular Heisenberg quantum antiferromagnet. DA - 2008/7/24/ PY - 2008/7/24/ DO - 10.1021/jp8007199 VL - 112 IS - 29 SP - 11013-11017 SN - 1932-7447 ER - TY - JOUR TI - Using laboratory chemicals to imitate illicit drugs in a forensic chemistry activity AU - Hasan, Shawn AU - Bromfield-Lee, Deborah AU - Oliver-Hoyo, Maria T. AU - Cintron-Maldonado, Jose A. T2 - JOURNAL OF CHEMICAL EDUCATION AB - This forensic chemistry activity utilizes presumptive forensic testing procedures and laboratory chemicals that produce screening results similar to controlled substances. For obvious reasons, obtaining heavily regulated controlled substances to create an undergraduate student activity is not practical for most educational institutions. We were able to identify over-the-counter and laboratory chemicals that mimic actual street drugs in terms of physical properties and color response. Using these selected chemicals, the screening aspect of drug testing provides students with the opportunity to understand what obstacles a forensic chemist faces when analyzing a sample of unknown identity. Chemical spot tests (CSTs) and thin-layer chromatography (TLC) were chosen owing to their simplicity, versatility, common use by forensic chemists, availability, and cost of the reagents and equipment needed. Students are expected to explain how simple color reactions can screen for illicit drugs, to describe how TLC can be used to separate and tentatively identify drugs, to predict how polarity changes affect TLC results, and to explain why CSTs and TLC serve for screening purposes only. DA - 2008/6// PY - 2008/6// DO - 10.1021/ed085p813 VL - 85 IS - 6 SP - 813-816 SN - 1938-1328 ER - TY - JOUR TI - Top-down identification and quantification of stable isotope labeled proteins from Aspergillus flavus using online nano-flow reversed-phase liquid chromatography coupled to a LTQ-FTICR mass spectrometer AU - Collier, Timothy S. AU - Hawkridge, Adam M. AU - Georgianna, D. Ryan AU - Payne, Gary A. AU - Muddiman, David C. T2 - ANALYTICAL CHEMISTRY AB - Online liquid chromatography-mass spectrometric (LC-MS) analysis of intact proteins (i.e., top-down proteomics) is a growing area of research in the mass spectrometry community. A major advantage of top-down MS characterization of proteins is that the information of the intact protein is retained over the vastly more common bottom-up approach that uses protease-generated peptides to search genomic databases for protein identification. Concurrent to the emergence of top-down MS characterization of proteins has been the development and implementation of the stable isotope labeling of amino acids in cell culture (SILAC) method for relative quantification of proteins by LC-MS. Herein we describe the qualitative and quantitative top-down characterization of proteins derived from SILAC-labeled Aspergillus flavus using nanoflow reversed-phase liquid chromatography directly coupled to a linear ion trap Fourier transform ion cyclotron resonance mass spectrometer (nLC-LTQ-FTICR-MS). A. flavus is a toxic filamentous fungus that significantly impacts the agricultural economy and human health. SILAC labeling improved the confidence of protein identification, and we observed 1318 unique protein masses corresponding to 659 SILAC pairs, of which 22 were confidently identified. However, we have observed some limiting issues with regard to protein quantification using top-down MS/MS analyses of SILAC-labeled proteins. The role of SILAC labeling in the presence of competing endogenously produced amino acid residues and its impact on quantification of intact species are discussed in detail. DA - 2008/7/1/ PY - 2008/7/1/ DO - 10.1021/ac800254z VL - 80 IS - 13 SP - 4994-5001 SN - 1520-6882 ER - TY - JOUR TI - Thermal conductivity of semi-insulating, p-type, and n-type GaN films on sapphire AU - Jagannadham, K. AU - Berkman, E. A. AU - Elmasry, N. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - The thermal conductivity of undoped, n-type, and p-type GaN films deposited on (0001) substrates of sapphire was measured by the 3-ω method in the temperature range between 215 and 300K. The thickness, thermal conductivity, and heat capacity of the individual layers were used to simulate the experimental value of the increment in temperature of the heater using a multilayer model. The thermal conductivity of undoped GaN film was found to be much higher than that of p-type film. Also, the thermal conductivity of n-type GaN film was slightly smaller than that of p-type film. Modeling of the temperature dependence of the thermal conductivity in the films showed that phonon-dopant and three-phonon umklapp scattering are important. Smaller thickness and hence smaller volume fraction of the film with lower dislocation density was also found to be responsible for lower thermal conductivity in n- and p-type GaN films. DA - 2008/5// PY - 2008/5// DO - 10.1116/1.2899379 VL - 26 IS - 3 SP - 375-379 SN - 1520-8559 ER - TY - JOUR TI - Temperature-dependent regulation of proteins in Aspergillus flavus: Whole organism stable isotope labeling by amino acids AU - Georgianna, D. Ryan AU - Hawkridge, Adam M. AU - Muddiman, David C. AU - Payne, Gary A. T2 - JOURNAL OF PROTEOME RESEARCH AB - Stable isotope labeling by amino acids in cell culture (SILAC) has been used in many different organisms including yeast, mammalian cells, and Arabidopsis cell culture. We present an adaptation of this method to quickly quantify protein changes in response to environmental stimuli regulating biosynthesis of the carcinogen aflatoxin in the fungus Aspergillus flavus. Changes in relative protein concentrations in response to temperature were quantified and compared to changes in aflatoxin biosynthesis and the transcription of the aflatoxin biosynthetic genes. In a comparison between conducive (28 °C) and nonconducive (37 °C) temperatures for aflatoxin biosynthesis, 31 proteins were found to be more abundant at 37 °C and 18 more abundant at 28 °C. The change in expression of the aflatoxin pathway enzymes closely followed the strong repression of both aflatoxin biosynthesis and transcription of the aflatoxin pathway genes observed at 37 °C. Transcripts corresponding to the 379 proteins quantified by SILAC were analyzed using microarrays, but their expression did not always correlate well with transcript levels of encoding genes. This is the first reported labeling of a multicellular free-living prototroph using the SILAC procedure to compare 13C6-arginine-labeled samples to 12C6-arginine-labeled samples for quantitative proteomics. The data presented shows the utility of this procedure in quantifying changes in protein expression in response to environmental stimuli. DA - 2008/7// PY - 2008/7// DO - 10.1021/pr8001047 VL - 7 IS - 7 SP - 2973-2979 SN - 1535-3907 KW - SILAC KW - mass spectrometry KW - proteomics KW - Aspergillus flavus KW - aflatoxin ER - TY - JOUR TI - Synthesis of a 2-aminoimidazole library for antibiofilm screening utilizing the Sonogashira reaction AU - Richards, Justin J. AU - Melander, Christian T2 - JOURNAL OF ORGANIC CHEMISTRY AB - The divergent synthesis of a 21-member library composed of 2-aminoimidazole compounds for evaluation as novel antibiofilm molecules is presented. The Sonogashira reaction was employed with three regioisomeric aryl iodides and 11 different alkynes to generate variously substituted diverse ring systems. Good to excellent yields (80-97%) for the reaction were obtained, and the products provide adequate handles for further manipulation into more advanced analogues. DA - 2008/7/4/ PY - 2008/7/4/ DO - 10.1021/jo800618q VL - 73 IS - 13 SP - 5191-5193 SN - 0022-3263 ER - TY - JOUR TI - Synthesis and screening of an oroidin library against Pseudomonas aeruginosa biofilms AU - Richards, Justin J. AU - Ballard, T. Eric AU - Huigens, Robert W., III AU - Melander, Christian T2 - CHEMBIOCHEM AB - A 50-compound library based on the marine natural product oroidin was synthesized and assayed for anti-biofilm activity against PAO1 and PA14, two strains of the medically relevant gamma-proteobacterium Pseudomonas aeruginosa. Through structure-activity relationship (SAR) analysis of analogues based on the oroidin template, several conclusions can be drawn as to what structural properties of the synthetic derivatives are necessary to elicit a biological response. Notably, the most active analogues identified were those that contained a 2-aminoimidazole (2-AI) motif and a dibrominated pyrrolecarboxamide subunit. Here we disclose the synthesis and subsequently determined biological activity of this unique class of compounds as inhibitors of biofilm formation that have no direct antibiotic effect. DA - 2008/5/23/ PY - 2008/5/23/ DO - 10.1002/cbic.200700774 VL - 9 IS - 8 SP - 1267-1279 SN - 1439-4227 KW - biological activity KW - drug design KW - medicinal chemistry KW - natural products KW - structure-activity relationships ER - TY - JOUR TI - Structure and magnetic properties of oxychalcogenides A(2)F(2)Fe(2)OQ(2) (A = sr, ba; Q = s, se) with Fe2O square planar layers representing an antiferromagnetic checkerboard spin lattice AU - Kabbour, Houria AU - Janod, Etienne AU - Corraze, Benoit AU - Danot, Michel AU - Lee, Changhoon AU - Whangbo, Myung-Hwan AU - Cario, Laurent T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - The oxychalcogenides A2F2Fe2OQ2 (A = Sr, Ba; Q = S, Se), which contain Fe2O square planar layers of the anti-CuO2 type, were predicted using a modular assembly of layered secondary building units and subsequently synthesized. The physical properties of these compounds were characterized using magnetic susceptibility, electrical resistivity, specific heat, (57)Fe Mossbauer, and powder neutron diffraction measurements and also by estimating their exchange interactions on the basis of first-principles density functional theory electronic structure calculations. These compounds are magnetic semiconductors that undergo a long-range antiferromagnetic ordering below 83.6-106.2 K, and their magnetic properties are well-described by a two-dimensional Ising model. The dominant antiferromagnetic spin exchange interaction between S = 2 Fe(2+) ions occurs through corner-sharing Fe-O-Fe bridges. Moreover, the calculated spin exchange interactions show that the A2F2Fe2OQ2 (A = Sr, Ba; Q = S, Se) compounds represent a rare example of a frustrated antiferromagnetic checkerboard lattice. DA - 2008/7/2/ PY - 2008/7/2/ DO - 10.1021/ja711139g VL - 130 IS - 26 SP - 8261-8270 SN - 1520-5126 ER - TY - JOUR TI - Ruthenium(II) complexes possessing the eta(6)-p-cymene ligand AU - Sumiyoshi, Taisuke AU - Gunnoe, T. Brent AU - Petersen, Jeffrey L. AU - Boyle, Paul D. T2 - INORGANICA CHIMICA ACTA AB - Complexes possessing a soft donor η6-arene and hard donor acetylacetonate ligand, [(η6-p-cymene)Ru(κ2-O,O-acac-μ-CH)]2[OTf]2 (1) (OTf = trifluoromethanesulfonate; acac = acetylacetonate) and [(η6-p-cymene)Ru(κ2-O,O-acac)(THF)][BAr4′](2) {Ar′ = 3,5-(CF3)–C6H3}, were prepared and fully characterized. The lability of the μ-CH linkage for complex 1 and the THF ligand of 2 allow access to the unsaturated cation [(η6-p-cymene)Ru(κ2-O,O-acac)]+. The reaction of [(η6-p-cymene)Ru(κ2-O,O-acac)(THF)][BAr4′](2) with KTp {Tp = hydridotris(pyrazolyl)borate} produces [TpRu(η6-p-cymene)][BAr4′](5). The azide complex [(η6-p-cymene)Ru(κ2-O,O-acac)(N3Ar)][BAr4′](6) forms upon reaction of [(η6-p-cymene)Ru(κ2-O,O-acac)(THF)][BAr4′](2)with N3Ar (Ar = p-tolyl), and reaction of [(η6-p-cymene)Ru(κ2-O,O-acac)(THF)][BAr4′](2) with CHCl3 at 100 °C yields the chloride-bridged binuclear complex [{(η6-p-cymene)Ru}2(μ-Cl)3][BAr4′](7). The details of solid-state structures of [(η6-p-cymene)Ru(κ2-O,O-acac-μ-CH)]2[OTf]2 (1), [TpRu(η6-p-cymene)][BAr4′](5) and [{(η6-p-cymene)Ru}2(μ-Cl)3][BAr4′](7) are disclosed. DA - 2008/7/27/ PY - 2008/7/27/ DO - 10.1016/j.ica.2007.10.012 VL - 361 IS - 11 SP - 3254-3262 SN - 1873-3255 KW - p-cymene KW - ruthenium KW - acetylacetonate KW - half-sandwich complex ER - TY - JOUR TI - Microscopic, chemical and molecular methods for examining fossil preservation AU - Schweitzer, Mary Higby AU - Avci, Recep AU - Collier, Timothy AU - Goodwin, Mark B. T2 - COMPTES RENDUS PALEVOL AB - Advances in technology over the past two decades have resulted in unprecedented access to data from biological specimens. These data have expanded our understanding of physical characteristics, physiological, cellular and subcellular processes, and evolutionary relationships at the molecular level and beyond. Paleontological and archaeological sciences have recently begun to apply these technologies to fossil and subfossil representatives of extinct organisms. Data derived from multidisciplinary, non-traditional techniques can be difficult to decipher, and without a basic understanding of the type of information provided by these methods, their usefulness for fossil studies may be overlooked. This review describes some of these powerful new analytical tools, the data that may be accessible through their use, advantages and limitations, and how they can be applied to fossil material to elucidate characteristics of extinct organisms and their paleoecological environments. Des avancées technologiques intervenues au cours des deux dernières décades ont permis d’accéder à des données sans précédent sur des échantillons biologiques. Ces données ont élargi notre compréhension des caractéristiques physiques, des processus physiologiques cellulaires et subcellulaires, ainsi que des relations évolutives au niveau de la molécule et au-delà. Les sciences paléontologiques et archéologiques se sont récemment orientées vers l’application de ces technologies à des représentants fossiles ou subfossiles d’organismes disparus. Les bénéfices de ces techniques, qui sont du domaine de multiples disciplines, sont difficiles à déchiffrer et, sans une connaissance de base du type d’information fourni par ces méthodes, leur utilité pour l’étude des fossiles peut ne pas être bien mesurée. Cet article décrit certains de ces nouveaux outils analytiques puissants, les données qu’ils permettent d’obtenir, leurs avantages et leurs limites, et comment ils peuvent être appliqués au matériel fossile pour élucider les caractéristiques d’organismes disparus et leurs environnements paléoécologiques. DA - 2008/4// PY - 2008/4// DO - 10.1016/j.crpv.2008.02.005 VL - 7 IS - 2-3 SP - 159-184 SN - 1777-571X KW - molecular preservation KW - diagenesis KW - fossil KW - ancient DNA KW - ancient protein KW - dinosaur KW - mass spectrometry ER - TY - JOUR TI - Metal-molecule interactions upon deposition of copper overlayers on reactively functionalized porphyrin monolayers on Si(100) AU - Anariba, Franklin AU - Schmidt, Lzabela AU - Muresan, Ana Z. AU - Lindsey, Jonathan S. AU - Bocian, David F. T2 - LANGMUIR AB - The interaction of evaporated Cu deposited on a series of porphyrins in monolayers covalently attached to Si(100) substrates was investigated using cyclic voltammetry and FTIR spectroscopy. Each porphyrin contains a triallyl tripod attached to the porphyrin via a p-phenylene unit. The tripod anchors the porphyrin to the Si(100) substrate via hydrosilylation of the allyl groups. Two of the porphyrins are Zn chelates that possess meso p-cyanophenyl substituentsone, ZnP-CND, contains a single group opposite (distal) to the tripodal surface anchor, whereas the other, ZnP-CNL, contains two groups orthogonal (lateral) to the surface anchor. A third Zn porphyrin, ZnP, containing nonreactive p-tolyl groups at all three nonanchoring meso positions, was examined for comparison. The fourth porphyrin, FbP-HD, is a metal-free species (free base) that contains nonreactive phenyl (distal) and p-tolyl groups (lateral) at the three nonanchoring meso positions. The fifth porphyrin, CuP-HD, is the Cu chelate of FbP-HD, and serves as a reference complex for evaluating the effects of Cu metal deposition onto FbP-HD. The studies indicate that all of the porphyrin monolayers are robust under the conditions of Cu deposition, experiencing no noticeable degradation. In addition, the Cu metal does not penetrate through the monolayer to form electrically conductive filaments. For the ZnP-CND monolayers, the deposited Cu quantitatively reacts/complexes with the distal cyano group. In contrast, for the ZnP-CNL monolayers no reaction/complexation of the lateral cyano groups is observed. For the FbP-HD monolayers, Cu deposition results in quantitative insertion of Cu into the free base porphyrin. Collectively, the studies demonstrate that porphyrin monolayers are amenable to direct deposition of Cu overlayers and that functionalization of the porphyrins can be used to mediate the attributes of the metal-molecule junction. DA - 2008/7/1/ PY - 2008/7/1/ DO - 10.1021/la800472c VL - 24 IS - 13 SP - 6698-6704 SN - 0743-7463 ER - TY - JOUR TI - Mass measurement accuracy comparisons between a double-focusing magnetic sector and a time-of-flight mass analyzer AU - Bereman, Michael S. AU - Lyndon, Matthew M. AU - Dixon, R. Brent AU - Muddiman, David C. T2 - RAPID COMMUNICATIONS IN MASS SPECTROMETRY AB - Abstract We report a direct comparison of the mass measurement accuracies (MMAs) obtained on different mass spectrometry instrument types; a magnetic sector as the ‘gold standard’ and an electrospray ionization time‐of‐flight (ESI‐TOF) instrument. Sixty samples, obtained from the Department of Chemistry at North Carolina State University, were analyzed on each instrument. Data are presented and compared between the different instruments. The average absolute MMAs achieved for the magnetic sector and Agilent ESI‐TOF mass spectrometers were 3.0 and 1.1 ppm, respectively. Copyright © 2008 John Wiley & Sons, Ltd. DA - 2008/5// PY - 2008/5// DO - 10.1002/rcm.3544 VL - 22 IS - 10 SP - 1563-1566 SN - 0951-4198 ER - TY - JOUR TI - Light-regulated RNA-small molecule interactions AU - Young, Douglas D. AU - Deiters, Alexander T2 - CHEMBIOCHEM AB - Regulating RNA with light. An RNA aptamer capable of specifically binding one isomer of a photoisomerizable spiropyran small molecule was engineered. The reversibility of the light-switchable aptamer recognition was then characterized by SPR imaging. This RNA–small molecule pair has significant implications in the light-regulation of biological functions and the reversible control of gene expression. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2268/2008/z800051_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2008/5/23/ PY - 2008/5/23/ DO - 10.1002/cbic.200800051 VL - 9 IS - 8 SP - 1225-1228 SN - 1439-4227 KW - aptamer KW - light KW - riboswitch KW - RNA KW - spiropyran ER - TY - JOUR TI - Light-activated deoxyguanosine: photochemical regulation of peroxidase activity AU - Lusic, Hrvoje AU - Lively, Mark O. AU - Deiters, Alexander T2 - MOLECULAR BIOSYSTEMS AB - Photochemical activation of a deoxyribozyme with peroxidase activity was achieved by the synthesis and incorporation of a caged deoxyguanosine. DA - 2008/// PY - 2008/// DO - 10.1039/b800166a VL - 4 IS - 6 SP - 508-511 SN - 1742-206X ER - TY - JOUR TI - Late transition metal anions acting as p-metal elements AU - Koehler, Juergen AU - Whangbo, Myung-Hwan T2 - SOLID STATE SCIENCES AB - A brief review is given for those extended solids of transition metal compounds in which their transition metal atoms are best described as existing as anions. Analyses of the electronic structures of metal-rich fluorides and oxides containing octahedral metallo-complexes [MIn6−xSnx] (M = Fe, Ni, Ru, Os, Ir and Pt) indicate that their transition metal atoms M are present as anions with the valence electron configuration (n + 1)s2nd10. In compounds RE2M2In (RE = rare earth element, M = Pt, Cu and Au), Ca5Au4, Ca3Hg2 and Ca5M3 (M = Cu, Au, Zn, Cd and Hg), the transition metal atoms exist as dimeric Zintl anions with the valence electron configuration (n + 1)s2nd10(n + 1)p1. Consequently, the frontier orbitals of these compounds are not described by the transition metal nd orbitals, but by the transition metal (n + 1)p orbitals. A similar situation is found for most 18-electron half-Heusler compounds (e.g., ScAuSn), for which the valence electron configuration of the transition metal is given by (n + 1)s2nd10(n + 1)p2. DA - 2008/4// PY - 2008/4// DO - 10.1016/j.solidstatesciences.2007.12.001 VL - 10 IS - 4 SP - 444-449 SN - 1293-2558 KW - zintl anion KW - transition metal anion KW - electronic structure KW - density functional characterization KW - intermetallic compound KW - p metals ER - TY - JOUR TI - Inhibition of HIV fusion with multivalent gold nanoparticles AU - Bowman, Mary-Catherine AU - Ballard, T. Eric AU - Ackerson, Christopher J. AU - Feldheim, Daniel L. AU - Margolis, David M. AU - Melander, Christian T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - The design and synthesis of a multivalent gold nanoparticle therapeutic is presented. SDC-1721, a fragment of the potent HIV inhibitor TAK-779, was synthesized and conjugated to 2.0 nm diameter gold nanoparticles. Free SDC-1721 had no inhibitory effect on HIV infection; however, the (SDC-1721)-gold nanoparticle conjugates displayed activity comparable to that of TAK-779. This result suggests that multivalent presentation of small molecules on gold nanoparticle surfaces can convert inactive drugs into potent therapeutics. DA - 2008/6/4/ PY - 2008/6/4/ DO - 10.1021/ja710321g VL - 130 IS - 22 SP - 6896-+ SN - 0002-7863 ER - TY - JOUR TI - Factors determining the efficacy of nuclear delivery of antisense oligonucleotides by gold nanoparticles AU - Liu, Yanli AU - Franzen, Stefan T2 - BIOCONJUGATE CHEMISTRY AB - The present study investigates the applicability of nanoparticle delivery vectors for two-stage targeting that involves both cell entry by endocytosis and nuclear targeting using viral peptide signals. A nanoparticle vector consists of four components: a carrier nanoparticle, a stabilizer, targeting peptides, and a therapeutic cargo. Extensive study of bovine serum albumin (BSA)-peptide stabilized nanoparticle conjugates demonstrated limitations of these systems due to colloidal instability when oligonucleotides and multiple peptides were attached to the BSA protein. We found that the widely used protein streptavidin (SA) was an appropriate alternative to BSA for cell-targeting experiments. Targeting peptides and gene splicing oligonucleotides were attached to SA-nanoparticles using biotin labels. The present study uses a gene-splicing assay as a test for oligonucleotide delivery to the cell nucleus. Successful modification of gene splicing by an antisense oligonucleotide indicates that the latter must have crossed the plasma membrane, entered the nucleus, found the target sequence in the newly transcribed pre-mRNA, and hybridized to it in the spliceosome strongly enough to displace the splicing factors designed to interact with the target sequence. Targeting nanoparticles that carry gene-splicing oligonucleotides were compared with a control experiment that used lipofectamine (LF). While enhanced activity was observed in the control experiment, in the presence of LF, no gene splicing was observed for the nanoparticle targeting vectors without LF. We conclude that sequestration of cargo from the harsh conditions of the endosome is a desirable strategy for cell-targeting nanoparticles. DA - 2008/5// PY - 2008/5// DO - 10.1021/bc700421u VL - 19 IS - 5 SP - 1009-1016 SN - 1520-4812 ER - TY - JOUR TI - Effects of a direct-fed microbial (Primalac) on turkey poult performance and susceptibility to oral Salmonella challenge AU - Grimes, J. L. AU - Rahimi, S. AU - Oviedo, E. AU - Sheldon, B. W. AU - Santos, F. B. O. T2 - POULTRY SCIENCE AB - A study was conducted to determine 1) the effect of a dietary direct-fed microbial (DFM) on turkey poult performance, 2) the effect of a DFM on a Salmonella challenge, and 3) the effect of feed processing on the efficacy of the dietary DFM. Day-of-hatch Large White female poults were placed in 2 rooms in 2 Petersime batteries per room. Twelve pens of 7 birds each were used in each battery (24 pens per room, 336 birds total). One of 4 dietary feed treatments was assigned to each pen (6 pens per room for each diet). One room housed non-Salmonella-challenged poults, and the other room housed poults challenged with a 1-mL oral gavage of Salmonella (10(10) cfu/mL). A single batch of starter ration was split into 4 parts and used to provide 4 dietary treatments: 1) mash feed with no DFM (M), 2) mash feed with DFM (Primalac; 0.9 kg/tonne of feed, MD), 3) pelleted (20-s steam conditioning at 80 degrees C) and crumbled feed with no DFM (C), and 4) pelleted and crumbled feed with DFM (CD). Feed and deionized, distilled water were provided ad libitum. Data were collected and analyzed separately for each room. Mortality was recorded for each pen on a daily basis and totaled by week and for the 3-wk period. Individual BW and feed consumption, by pen, were measured weekly. Weekly and cumulative BW gains and feed to gain ratios (F:G) were calculated. Liver, spleen, total and lower intestinal tract weights, intestinal length, and most-probable-number Salmonella populations were determined for one randomly selected bird per pen. Feeding processed feed resulted in improved BW and F:G. Feeding the DFM improved 3-wk cumulative F:G in birds not gavaged and reduced relative intestinal weight in birds gavaged. Salmonella populations were reduced 1 log by feeding DFM. Dietary DFM improved bird performance, reduced Salmonella populations, and was not affected by feed processing. DA - 2008/7// PY - 2008/7// DO - 10.3382/ps.2008-00498 VL - 87 IS - 7 SP - 1464-1470 SN - 1525-3171 KW - direct-fed microbial KW - probiotic KW - feed pelleting KW - Salmonella KW - turkey ER - TY - JOUR TI - Effect of substrate geometry on polymer molecular weight and polydispersity during surface-initiated polymerization AU - Gorman, Christopher B. AU - Petrie, Randall J. AU - Genzer, Jan T2 - MACROMOLECULES AB - Poly(methyl methacrylate) (PMMA) anchored chains were grown on porous silicon (p-Si) and anodically etched aluminum oxide (AAO) substrates via surface-initiated atom transfer radical polymerization (ATRP). Using hydrogen fluoride, the chains could be cleaved from the substrates, as evidenced by infrared spectroscopy. The molecular weights and molecular weight distributions of PMMA could be analyzed directly on these substrates (after cleaving the chains from the support) using direct ionization mass spectrometry (DIOS-MS) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). Two principal conclusions were drawn from the study. First, matrix-free DIOS-MS was effective at direct analysis of the polymers up to a molecular weight of ≈6 kDa; the signal-to-noise ratio for heavier polymer chains diminished rapidly. Second, under the same polymerization conditions, PMMA grown on both p-Si and AAO substrates had a much lower molecular weight and a broader molecular weight distribution than that grown in solution. Confinement effects imposed by the pores during the polymerization are proposed as the likely mechanism for the reduced growth rates and more polydisperse chains. DA - 2008/7/8/ PY - 2008/7/8/ DO - 10.1021/ma8004857 VL - 41 IS - 13 SP - 4856-4865 SN - 1520-5835 ER - TY - JOUR TI - Determination of the spin-lattice relevant for the quaternary magnetic oxide Bi4Cu3V2O14 on the basis of tight-binding and density functional calculations AU - Koo, Hyun-Joo AU - Whangbo, Myung-Hwan T2 - INORGANIC CHEMISTRY AB - The quaternary magnetic oxide Bi4Cu3V2O14 consists of Cu4O8 triple chains made up of corner-sharing CuO4 square planes. To determine its spin-lattice, the spin exchange interactions of Bi4Cu3V2O14 were evaluated by performing a spin dimer analysis based on tight-binding calculations and a mapping analysis based on first principles density functional theory calculations. Both calculations show that the spin-lattice of Bi4Cu3V2O14 is not an antiferromagnetically coupled diamond chain, which results from an idealized view of the structure of the Cu4O8 triple chain and a neglect of super-superexchange interactions. The correct spin-lattice is an antiferromagnetic chain made up of antiferromagnetic linear trimers coupled through their midpoints via super-superexchange interaction, which predicts that Bi4Cu3V2O14 has an antiferromagnetic spin ground state and has no spin frustration, both in agreement with experiment. DA - 2008/6/2/ PY - 2008/6/2/ DO - 10.1021/ic800216j VL - 47 IS - 11 SP - 4779-4784 SN - 1520-510X ER - TY - JOUR TI - Dependence of plasmon polaritons on the thickness of indium tin oxide thin films AU - Rhodes, C. AU - Cerruti, M. AU - Efremenko, A. AU - Losego, M. AU - Aspnes, D. E. AU - Maria, J.-P. AU - Franzen, S. T2 - Journal of Applied Physics AB - The evolution of polariton features with increasing thickness in p-polarized (TM) reflectance spectra of indium tin oxide (ITO) thin films deposited on BK7 glass reveals the nature of plasmons in conducting thin films without interference from band-to-band transitions or the tendency of very thin films to form islands, both of which are complicating factors with the noble metals Au and Ag. Although the dependence on energy, film thickness, and angle of incidence is complex, these features are accurately described by the three-phase (substrate/overlayer/ambient) Fresnel model using only the Drude free-electron representation for the dielectric function of the ITO film. For film thicknesses less than 80nm the relevant excitation is a one-dimensional screened-bulk plasmon (SBP) that corresponds to charge transfer across the entire film. The associated SBP polariton (SBPP) occurs at the energy of the SBP and is relatively independent of the angle of incidence. For film thicknesses greater than 120nm, the relevant excitation is the surface plasmons (SP). The associated surface plasmon polariton (SPP) exhibits the usual strong dependence of energy on the angle of incidence. For larger thicknesses this structure gradually weakens, in agreement with theory. No other collective excitations are observed. The optimum thicknesses for the SPP in ITO is 160nm, whereas the SBPP is observed only when the film thickness is less than 70nm. The SBPP exhibits many of the features that make the SPP attractive for both science and technology, but has not been observed previously. Our results show that ITO films, in particular, and conducting-metal-oxide films in general provide new opportunities for investigating plasmons in conductors and obtaining new insights into plasmons, plasmon polaritons, and related optical phenomena. DA - 2008/5// PY - 2008/5// DO - 10.1063/1.2908862 VL - 103 IS - 9 SP - 093108 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.2908862 DB - Crossref ER - TY - JOUR TI - Control of bacterial biofilms with marine alkaloid derivatives AU - Huigens, Robert W., III AU - Ma, Luyan AU - Gambino, Christopher AU - Moeller, Peter D. R. AU - Basso, Anne AU - Cavanagh, John AU - Wozniak, Daniel J. AU - Melander, Christian T2 - MOLECULAR BIOSYSTEMS AB - Bacterial biofilms are defined as a community of surface-attached bacteria that are protected by an extracellular matrix of biomolecules. We have recently reported the synthesis of a small molecule, denoted TAGE, based on the natural product bromoageliferin and demonstrated that TAGE has anti-biofilm activity against Pseudomonas aeruginosa. Herein we demonstrate that TAGE: (1) does not have selective toxicity against cells within the biofilm state, (2) will inhibit biofilm development under flow conditions, indicating that the CV staining protocol correlates with the ability to be active under biomimetic conditions, and (3) will disperse preformed P. aeruginosa biofilms. We also present preliminary toxicity work that indicates that TAGE is devoid of cytotoxicity in rat and mice cell lines. Advanced derivatives of TAGE have generated compounds shown to be exceedingly effective as biofilm inhibitors against the γ-proteobacteria in this study (P. aeruginosa strains PAO1, PA14, PDO300, and Acinetobacter baumannii). TAGE derivatives also possessed anti-biofilm activity against the β-proteobacterium Bordetella bronchiseptica (Rb50) and the Gram-positive bacterium Staphylococcus aureus;TAGE derivatives inhibited the formation of biofilms, however, some of this activity is attributed to microbicidal activity. The TAGE derivatives presented in this study, however, do not disperse pre-formed biofilms with the same efficiency as TAGE. DA - 2008/// PY - 2008/// DO - 10.1039/b719989a VL - 4 IS - 6 SP - 614-621 SN - 1742-2051 ER - TY - JOUR TI - Aromatic C-H activation and catalytic hydrophenylation of ethylene by TpRu{P(OCH2)(3)CEt}(NCMe)Ph AU - Foley, Nicholas A. AU - Ke, Zhuofeng AU - Gunnoe, T. Brent AU - Cundari, Thomas R. AU - Petersen, Jeffrey L. T2 - ORGANOMETALLICS AB - The complexes TpRu{P(OCH2)3CEt}(L)R {L = PPh3 or NCMe; R = Cl, OTf (OTf = trifluoromethanesulfonate), or Ph; Tp = hydridotris(pyrazolyl)borate} and TpRu{P(OCH2)3CEt}(η3-C3H4Me) were synthesized and isolated. TpRu{P(OCH2)3CEt}(NCMe)Ph was found to initiate C−H activation of benzene and to catalyze the hydrophenylation of ethylene to produce ethylbenzene. Ethylene C−H activation to ultimately produce TpRu{P(OCH2)3CEt}(η3-C3H4Me) kinetically competes with the catalytic hydrophenylation of ethylene. Computational studies were undertaken on reactions in the proposed catalytic ethylene hydrophenylation cycle as well as key side reactions. DA - 2008/7/14/ PY - 2008/7/14/ DO - 10.1021/om800275b VL - 27 IS - 13 SP - 3007-3017 SN - 1520-6041 ER - TY - JOUR TI - Ambient aerodynamic ionization source for remote analyte sampling and mass spectrometric analysis AU - Dixon, R. Brent AU - Sampson, Jason S. AU - Hawkridge, Adam M. AU - Muddiman, David C. T2 - ANALYTICAL CHEMISTRY AB - The use of aerodynamic devices in ambient ionization source development has become increasingly prevalent in the field of mass spectrometry. In this study, an air ejector has been constructed from inexpensive, commercially available components to incorporate an electrospray ionization emitter within the exhaust jet of the device. This novel aerodynamic device, herein termed remote analyte sampling, transport, and ionization relay (RASTIR) was used to remotely sample neutral species in the ambient and entrain them into an electrospray plume where they were subsequently ionized and detected using a linear ion trap Fourier transform mass spectrometer. Two sets of experiments were performed in the ambient environment to demonstrate the device's utility. The first involved the remote (approximately 1 ft) vacuum collection of pure sample particulates (i.e., dry powder) from a glass slide, entrainment and ionization at the ESI emitter, and mass spectrometric detection. The second experiment involved the capture (vacuum collection) of matrix-assisted laser desorbed proteins followed by entrainment in the ESI emitter plume, multiple charging, and mass spectrometric detection. This approach is in principle a RASTIR-assisted matrix-assisted laser desorption electrospray ionization source (Sampson, J. S.; Hawkridge, A. M.; Muddiman, D. C. J. Am. Soc. Mass Spectrom. 2006, 17, 1712-1716; Rapid Commun. Mass Spectrom. 2007, 21, 1150-1154.). A detailed description of the device construction, operational parameters, and preliminary small molecule and protein data are presented. DA - 2008/7/1/ PY - 2008/7/1/ DO - 10.1021/ac800289f VL - 80 IS - 13 SP - 5266-5271 SN - 1520-6882 ER - TY - JOUR TI - A cyclotrimerization route to cannabinoids AU - Teske, Jesse A. AU - Deiters, Alexander T2 - ORGANIC LETTERS AB - Three members of the cannabinoid class, cannabinol, cannabinol methyl ether, and cannabinodiol, were synthesized using a microwave-mediated [2 + 2 + 2] cyclotrimerization reaction as the key step. This approach provides a high level of synthetic flexibility allowing for the facile synthesis of cannabinoid analogues. DA - 2008/6/5/ PY - 2008/6/5/ DO - 10.1021/ol800589e VL - 10 IS - 11 SP - 2195-2198 SN - 1523-7052 ER - TY - JOUR TI - Swallowtail bacteriochlorins. Lipophilic absorbers for the near-infrared AU - Borbas, K. Eszter AU - Ruzie, Christian AU - Lindsey, Jonathan S. T2 - ORGANIC LETTERS AB - Bacteriochlorins absorb strongly in the near-infrared spectral region and hence are ideally suited for diverse photomedical applications, yet naturally occurring bacteriochlorins have limited stability and synthetic malleability. A de novo route has been exploited to prepare synthetic bacteriochlorins that bear a geminal dimethyl group in each pyrroline ring for stability and a symmetrically branched 1,5-dimethoxypentyl group attached to each pyrrole ring for solubility in lipophilic media. DA - 2008/5/15/ PY - 2008/5/15/ DO - 10.1021/ol800436u VL - 10 IS - 10 SP - 1931-1934 SN - 1523-7060 ER - TY - JOUR TI - Studying O-linked protein glycosylations in human plasma AU - Williams, Taufika Islam AU - Saggese, Diana A. AU - Muddiman, David C. T2 - JOURNAL OF PROTEOME RESEARCH AB - Recent investigations have implicated aberrant glycosylations in various malignancies, including epithelial ovarian cancer (EOC). The protocol here identifies O-linked carbohydrate patterns in EOC plasma glycoproteins through chemical cleavage and purification of these glycans. Dialyzed plasma is subjected to reductive β-elimination with alkaline borohydride to release O-linked oligosaccharides from glycoproteins. Enrichment of released glycans, as well as removal of peptide and other contaminants, is followed by carbohydrate pattern analysis with MALDI-FT-ICR-MS. DA - 2008/6// PY - 2008/6// DO - 10.1021/pr800066e VL - 7 IS - 6 SP - 2562-2568 SN - 1535-3893 UR - http://europepmc.org/abstract/med/18422354 KW - protein O-glycosylations KW - plasma KW - epithelial ovarian cancer (EOC) KW - matrix-assisted laser desorption/iozation (MALDI) KW - Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR-MS) ER - TY - JOUR TI - Selective etching via soft lithography of conductive multilayered gold films with analysis of electrolyte solutions AU - Gerber, Ralph W. AU - Oliver-Hoyo, Maria T. T2 - JOURNAL OF CHEMICAL EDUCATION AB - This experiment is designed to expose undergraduate students to the process of selective etching by using soft lithography and the resulting electrical properties of multilayered films fabricated via self-assembly of gold nanoparticles. Students fabricate a conductive film of gold on glass, apply a patterned resist using a polydimethylsiloxane stamp, and etch the unprotected gold. The resulting pattern is evaluated for changes in current, voltage flow, and resistance relative to the initial properties of the nonetched films. Students determine how changes in resistance applied to a conductive pattern affect the flow of current and voltage. Comparisons are made among different electrolyte solutions to demonstrate the electrical difference between strong, weak, and nonelectrolyte solutions, and how stronger electrolytes provide for better current flow. DA - 2008/8// PY - 2008/8// DO - 10.1021/ed085p1108 VL - 85 IS - 8 SP - 1108-1111 SN - 1938-1328 ER - TY - JOUR TI - Reversible addition-fragmentation chain transfer polymerization in DNA biosensing AU - He, Peng AU - Zheng, Weiming AU - Tucker, Eric Z. AU - Gorman, Christopher B. AU - He, Lin T2 - ANALYTICAL CHEMISTRY AB - Reversible addition-fragmentation chain transfer polymerization is employed here to allow detector-free visualization of specific DNA sequences for which dynamic polymer growth is used in signal amplification. In particular, surface-initiated polymer growth was regulated by the immobilization of chain transfer agents on the Au surface where DNA hybridization occurred. A linear polymer growth was observed as a function of the reaction time, characteristic of "living" polymer reactions. Significant improvement in assay sensitivity was realized in comparison to the previously reported polymerization-based sensing method by enhancing polymer growth rate and reducing background noises caused by nonspecific adsorption. Direct visualization of fewer than 2,000 copies of a short oligonucleotide sequence was demonstrated in a detector-free fashion. DA - 2008/5/15/ PY - 2008/5/15/ DO - 10.1021/ac702608k VL - 80 IS - 10 SP - 3633-3639 SN - 0003-2700 ER - TY - JOUR TI - Pyrazole formation: Examination of kinetics, substituent effects, and mechanistic pathways AU - Sloop, Joseph C. AU - Lechner, Brent AU - Washington, Gary AU - Bumgardner, Carl L. AU - Loehle, W. David AU - Creasy, William T2 - INTERNATIONAL JOURNAL OF CHEMICAL KINETICS AB - Abstract Reaction kinetics for the condensation of 1,3‐diketones 1a–o with selected arylhydrazines (aryl = Ph, 4‐NO 2 Ph, 4‐CH 3 OPh, and 2,4‐diNO 2 Ph) was studied using 19 F NMR spectroscopy. Product regioselectivity is modulated by reactant ratios, substituents, and acidity. Reaction rates were found to be influenced by substituents on the diketones and on phenylhydrazines as well as by acidity of the reaction medium with rates varying as much as 1000‐fold. Hammett ρ values for these cyclizations were determined. The reaction was found to be first order in both the diketone and arylhydrazine. The rate‐determining step for pyrazole formation shifts as a function of pH. Mechanistic details and reaction pathways supporting these findings are proposed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 370–383, 2008 DA - 2008/7// PY - 2008/7// DO - 10.1002/kin.20316 VL - 40 IS - 7 SP - 370-383 SN - 0538-8066 ER - TY - JOUR TI - Preparation and reactivity of a monomeric octahedral platinum(IV) amido complex AU - Munro-Leighton, C. AU - Feng, Y. AU - Zhang, J. AU - Alsop, N. M. AU - Gunnoe, T. B. AU - Boyle, P. D. AU - Petersen, J. L. T2 - Inorganic Chemistry DA - 2008/// PY - 2008/// DO - 10.1021/icS00843b VL - 47 IS - 14 SP - 6124-6126 ER - TY - JOUR TI - Photoinduced dissociation of water and transport of hydrogen between silver clusters AU - Zhang, Yu AU - Whitten, Jerry L. T2 - JOURNAL OF PHYSICAL CHEMISTRY A AB - Theoretical electronic structure calculations are reported for the dissociation of water adsorbed on a 31-atom silver cluster, Ag31, and subsequent transfer of a H to a second Ag31 cluster leaving OH on the first cluster. Both ground and excited electronic state processes are considered for two choices of Ag cluster separation, 6.35 and 7.94 A, on the basis of preliminary calculations for a range of separation distances. The excited electronic state of interest is formed by photoemission of an electron from one Ag cluster and transient attachment of the photoemitted electron to the adsorbed water molecule. A very large energy barrier is found for the ground-state process (3.53 eV at a cluster separation of 6.35 A), while the barrier in the excited state is small (0.38 eV at a cluster separation of 6.35 A). In the excited state, partial occupancy of an OH antibonding orbital facilitates OH stretch and concomitant movement of the negatively charged OH toward the electron-hole in the metal cluster. The excited-state pathway for dissociation of water and transfer of H begins with the formation of an excited electronic state at 3.59-3.82 eV. Stretch of the OH bond occurs with little change in energy (0.38-0.54 eV up to a stretch of 1.96 A). In this region of OH stretch the molecule must return to the ground-state potential energy surface to fully dissociate and to transfer H to the other Ag cluster. Geometry optimizations are carried out using a simplex algorithm and a semigrid method. These methods allow the total energy to be calculated directly using configuration interaction theory. DA - 2008/7/17/ PY - 2008/7/17/ DO - 10.1021/jp800528j VL - 112 IS - 28 SP - 6358-6363 SN - 1089-5639 ER - TY - JOUR TI - Mapping Local Protein Electrostatics by EPR of pH-Sensitive Thiol-Specific Nitroxide AU - Voinov, Maxim A. AU - Ruuge, Andres AU - Reznikov, Vladimir A. AU - Grigor’ev, Igor A. AU - Smirnov, Alex I. T2 - Biochemistry AB - A first thiol-specific pH-sensitive nitroxide spin-label of the imidazolidine series, methanethiosulfonic acid S-(1-oxyl-2,2,3,5,5-pentamethylimidazolidin-4-ylmethyl) ester (IMTSL), has been synthesized and characterized. X-Band (9 GHz) and W-band (94 GHz) EPR spectral parameters of the new spin-label in its free form and covalently attached to an amino acid cysteine and a tripeptide glutathione were studied as a function of pH and solvent polarity. The pKa value of the protonatable tertiary amino group of the spin-label was found to be unaffected by other ionizable groups present in side chains of unstructured small peptides. The W-band EPR spectra were shown to allow for pKa determination from precise g-factor measurements. Is has been demonstrated that the high accuracy of pKa determination for pH-sensitive nitroxides could be achieved regardless of the frequency of measurements or the regime of spin exchange: fast at X-band and slow at W-band. IMTSL was found to react specifically with a model protein, iso-1-cytochrome c from the yeast Saccharomyces cerevisiae, giving EPR spectra very similar to those of the most commonly employed cysteine-specific label MTSL. CD data indicated no perturbations to the overall protein structure upon IMTSL labeling. It was found that for IMTSL, giso correlates linearly with Aiso, but the slopes are different for the neutral and charged forms of the nitroxide. This finding was attributed to the solvent effects on the spin density at the oxygen atom of the NO group and on the excitation energy of the oxygen lone-pair orbital. DA - 2008/5// PY - 2008/5// DO - 10.1021/bi800272f VL - 47 IS - 20 SP - 5626–5637 SN - 0006-2960 1520-4995 UR - http://dx.doi.org/10.1021/bi800272f ER - TY - JOUR TI - Kinamycin-mediated DNA cleavage under biomimetic conditions AU - Ballard, T. Eric AU - Melander, Christian T2 - TETRAHEDRON LETTERS AB - The kinamycins are biologically active secondary metabolites characterized by an uncommon diazobenzo[b]fluorene skeleton. Kinamycin D has been shown to potently cleave DNA under mild biomimetic conditions. Use of the endogenously abundant reductant glutathione at 570 μM, kinamycin D effectively cleaved DNA in a concentration, temperature, and time-dependent fashion. Dithiothreitol also proved effective at low concentration while other reductants failed to induce DNA cleavage. Mechanistic consequences of the DNA cleavage results are described. DA - 2008/5/5/ PY - 2008/5/5/ DO - 10.1016/j.tetlet.2008.03.019 VL - 49 IS - 19 SP - 3157-3161 SN - 0040-4039 ER - TY - JOUR TI - Coordination-driven face-directed self-assembly of trigonal prisms. Face-based conformational chirality AU - Caskey, Douglas C. AU - Yamamoto, Takuya AU - Addicott, Chris AU - Shoemaker, Richard K. AU - Vacek, Jaroslav AU - Hawkridge, Adam M. AU - Muddiman, David C. AU - Kottas, Gregg S. AU - Michl, Josef AU - Stang, Peter J. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - The coordination-driven self-assembly of four different trigonal prisms from 3 equiv of one of four different tetrapyridyl star connectors and 6 equiv of a platinum linker dication in nitromethane is presented. This face-directed approach affords high yields without template assistance. The prisms have been characterized by multinuclear and DOSY NMR and dual ESI-FT-ICR mass spectrometry. The use of a conformationally chiral star connector leads to a conformationally chiral prism when connector arm ends attached to a vertex have a strongly correlated twist sense and chirality is communicated across polyhedral faces, edges, and vertices. Molecular mechanics results suggest that in the smallest prism 3d collective effects dominate and the all-P and all-M conformers are strongly favored. NMR data prove that the two edges of the pyridine rings in the triflate salts of 3a−3d are distinct. An Eyring plot of rates obtained from line-shape analysis and 1-D EXCHSY NMR yields an activation enthalpy ΔH‡ of ∼12 kcal/mol and activation entropy ΔS‡ of ∼−15 cal/mol·K for the edge interconversion process, compatible with pyridine rotation around the Pt−N bond. For 3c, this behavior is observed only up to ∼318 K. At higher temperatures, the Eyring plot is again linear but follows a very different straight line, with a ΔH‡ of ∼35 kcal/mol and ΔS‡ of ∼60 cal/mol·K. This highly unusual result is further investigated and discussed in the following companion paper. DA - 2008/6/18/ PY - 2008/6/18/ DO - 10.1021/ja710715e VL - 130 IS - 24 SP - 7620-7628 SN - 1520-5126 ER - TY - JOUR TI - Construction and screening of a 2-aminoimidazole library identifies a small molecule capable of inhibiting and dispersing bacterial biofilms across order, class, and phylum AU - Rogers, Steven A. AU - Melander, Christian T2 - ANGEWANDTE CHEMIE-INTERNATIONAL EDITION AB - A team of three: 2-Aminoimidazole, triazole, and tether units together resulted in conjugates (see picture, n=4–6 for the most active compounds) that are capable of inhibiting and dispersing bacteria biofilms without inducing bacterial death. Such biofilms have been implicated in a plethora of medical problems, including infection of implanted medical devices and the mortality of cystic fibrosis patients. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z800862_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2008/// PY - 2008/// DO - 10.1002/anie.200800862 VL - 47 IS - 28 SP - 5229-5231 SN - 1521-3773 KW - biofilms KW - combinatorial chemistry KW - dispersion KW - inhibition KW - marine natural products ER - TY - JOUR TI - Comprehensive characterization of hybrid junctions comprised of a porphyrin monolayer sandwiched between a coinage metal overlayer and a Si(100) substrate AU - Anariba, Franklin AU - Tiznado, Hugo AU - Diers, James R. AU - Schmidt, Izabela AU - Muresan, Ana Z. AU - Lindsey, Jonathan S. AU - Zaera, Francisco AU - Bocian, David F. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - The promise of molecular electronics has stimulated a variety of approaches for making hybrid junctions wherein molecules are sandwiched between two metal contacts or a metal and a semiconductor contact. However, the fate of molecules subsequent to deposition of a top metal contact has generally not been well characterized. Toward this goal, the interaction of evaporated Cu, Ag, and Au films deposited in varying thicknesses (3, 5, and 8 nm) on a series of monolayer-coverage porphyrins covalently attached to Si(100) substrates was investigated. Each porphyrin contains a triallyl tripod attached to the porphyrin via a p-phenylene unit, which anchors the porphyrin to the Si(100) substrate via hydrosilylation of the allyl groups. All of the porphyrins are Zn chelates bearing meso p-tolyl substituents orthogonal (lateral) to the tripodal surface anchor, but contain different substituents in the meso position opposite (distal) to the surface anchor, p-tolyl, α,α,α-trifluoro-p-tolyl, pentafluorophenyl, or p-cyanophenyl, to test the potential for the distal meso substituents to impart different characteristics to the metal/molecule/Si junction. The methods of interrogation used include ellipsometry, atomic force microscopy, FTIR spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, and current−voltage measurements. The studies indicate that all of the porphyrin monolayers are robust under the conditions of metal deposition, experiencing no noticeable degradation, and that none of the distal functional groups reacts with the deposited metal, except for the nitrile group of the p-cyanophenyl-substituted porphyrin, which reacts/complexes with Cu. Neither Cu nor Ag penetrates through the monolayer to an appreciable extent to form electrically conductive filaments, whereas Au does penetrate through the porphyrin monolayer and contacts the Si substrate. Collectively, the studies provide a comprehensive assessment of the characteristics of the metal (Cu, Ag, Au)/porphyrin monolayer/Si junctions. DA - 2008/6/26/ PY - 2008/6/26/ DO - 10.1021/jp802428y VL - 112 IS - 25 SP - 9474-9485 SN - 1932-7447 ER - TY - JOUR TI - Accessing the near-infrared spectral region with stable, synthetic, wavelength-tunable bacteriochlorins AU - Taniguchi, Masahiko AU - Cramer, David L. AU - Bhise, Anil D. AU - Kee, Hooi Ling AU - Bocian, David F. AU - Holten, Dewey AU - Lindsey, Jonathan S. T2 - NEW JOURNAL OF CHEMISTRY AB - The near-infrared (NIR) spectral region has been comparatively under-utilized for diverse materials and medical applications owing to the lack of chromophores that afford stability, solubility, synthetic malleability, and tunable photophysical features. Bacteriochlorins are attractive candidates in this regard; however, preparation via modification of naturally occurring bacteriochlorophylls or reduction of porphyrins or chlorins has proved cumbersome. To overcome such limitations, a dibromobacteriochlorin (BC-Br3Br13) was prepared de novo by the acid-catalyzed condensation of an 8-bromodihydrodipyrrin-acetal. BC-Br3Br13 bears (1) a geminal dimethyl group in each reduced ring to block adventitious dehydrogenation, and (2) bromo groups at the 3- and 13-positions for further chemical modifications. BC-Br3Br13 was subjected to four types of Pd-mediated coupling reaction (Suzuki, Stille, Sonogashira, dehalogenation) to give bacteriochlorins bearing substituents at the 3- and 13-positions (phenyl, vinyl, acetyl, phenylethynyl), and a benchmark bacteriochlorin lacking such substituents. The 3,13-divinylbacteriochlorin was transformed to the 3,13-diformylbacteriochlorin. Depending on the substituents at the 3- and 13-positions, the position of the long-wavelength absorption maximum (Qy(0,0) band) lies between 713 and 771 nm, the fluorescence emission maximum lies between 717 and 777 nm, and the fluorescence quantum yield ranges from 0.15 to 0.070. The ability to introduce a wide variety of functional groups via Pd-mediated coupling reactions and the tunable absorption and emission spectral properties suggest that synthetic bacteriochlorins are viable candidates for a wide variety of photochemical applications. DA - 2008/// PY - 2008/// DO - 10.1039/b717803d VL - 32 IS - 6 SP - 947-958 SN - 1369-9261 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-45149130353&partnerID=MN8TOARS ER - TY - JOUR TI - The role of creep in the time-dependent resistance of Ohmic gold contacts in radio frequency microelectromechanical system devices AU - Rezvanian, O. AU - Brown, C. AU - Zikry, M. A. AU - Kingon, A. I. AU - Krim, J. AU - Irving, D. L. AU - Brenner, D. W. T2 - Journal of Applied Physics AB - It is shown that measured and calculated time-dependent electrical resistances of closed gold Ohmic switches in radio frequency microelectromechanical system (rf-MEMS) devices are well described by a power law that can be derived from a single asperity creep model. The analysis reveals that the exponent and prefactor in the power law arise, respectively, from the coefficient relating creep rate to applied stress and the initial surface roughness. The analysis also shows that resistance plateaus are not, in fact, limiting resistances but rather result from the small coefficient in the power law. The model predicts that it will take a longer time for the contact resistance to attain a power law relation with each successive closing of the switch due to asperity blunting. Analysis of the first few seconds of the measured resistance for three successive openings and closings of one of the MEMS devices supports this prediction. This work thus provides guidance toward the rational design of Ohmic contacts with enhanced reliabilities by better defining variables that can be controlled through material selection, interface processing, and switch operation. DA - 2008/7/15/ PY - 2008/7/15/ DO - 10.1063/1.2953072 VL - 104 IS - 2 SP - 024513 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.2953072 DB - Crossref ER - TY - JOUR TI - Tailoring a bacteriochlorin building block with cationic, amphipathic, or lipophilic substituents AU - Ruzie, Christian AU - Krayer, Michael AU - Balasubramanian, Thiagarajan AU - Lindsey, Jonathan S. T2 - JOURNAL OF ORGANIC CHEMISTRY AB - Bacteriochlorins are attractive candidates for photodynamic therapy (PDT) of diverse medical indications owing to their strong absorption in the near-infrared (NIR) region, but their use has been stymied by lack of access to stable, synthetically malleable molecules. To overcome these limitations, a synthetic free base 3,13-dibromobacteriochlorin (BC-Br3Br13) has been exploited as a building block in the synthesis of diverse bacteriochlorins via Pd-mediated coupling reactions (Sonogashira, Suzuki, and reductive carbonylation). Each bacteriochlorin is stable to adventitious dehydrogenation by virtue of the presence of a geminal dimethyl group in each pyrroline ring. The target bacteriochlorins bear cationic, lipophilic, or amphipathic substituents at the 3- and 13- (β-pyrrolic) positions. A dicarboxybacteriochlorin was converted to amide derivatives via the intermediate diacid chloride. A diformylbacteriochlorin was subjected to reductive amination to give aminomethyl derivatives. A set of 3,5-disubstituted aryl groups bearing lipophilic or amphipathic groups was introduced via Suzuki coupling. Altogether 22 free base bacteriochlorins have been prepared. Eight aminoalkylbacteriochlorins were quaternized with methyl iodide at two or four amine sites per molecule, which resulted in water solubility. Each bacteriochlorin exhibits a Qy absorption band in the range of 720−772 nm. The ability to introduce a wide variety of peripheral functional groups makes these bacteriochlorins attractive candidates for diverse applications in photomedicine including PDT in the NIR region. DA - 2008/8/1/ PY - 2008/8/1/ DO - 10.1021/jo800736c VL - 73 IS - 15 SP - 5806-5820 SN - 1520-6904 ER - TY - PAT TI - Synthesis of porphyrins designed for attachment to electroactive surfaces via one or more carbon tethers AU - Lindsey, J. S. AU - Loewe, R. S. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Stereoselective synthesis of acyclic amino alcohols via von Braun ring opening of chiral piperidines AU - McCall, W. Stephen AU - Grillo, Teresa Abad AU - Comins, Daniel L. T2 - ORGANIC LETTERS AB - Multisubstituted piperidines containing a phenyl group at C-2 can be opened regio- and stereoselectively with cyanogen bromide. The ring-opened products contain useful cyanamide and benzylic bromide functional groups. This methodology is useful for the stereoselective synthesis of uniquely substituted alkylamine derivatives containing multiple chiral centers and various functionality. DA - 2008/8/7/ PY - 2008/8/7/ DO - 10.1021/ol801123x VL - 10 IS - 15 SP - 3255-3257 SN - 1523-7052 ER - TY - JOUR TI - Spin-orbit coupling and ion displacements in multiferroic TbMnO(3) AU - Xiang, H. J. AU - Wei, Su-Huai AU - Whangbo, M. -H. AU - Da Silva, Juarez L. F. T2 - PHYSICAL REVIEW LETTERS AB - The magnetic and ferroelectric (FE) properties of TbMnO3 are investigated on the basis of relativistic density functional theory calculations. We show that, due to spin-orbit coupling, the spin-spiral plane of TbMnO3 can be either the bc or ab plane, but not the ac plane. As for the mechanism of FE polarization, our work reveals that the "pure electronic" model by Katsura, Nagaosa, and Balatsky is inadequate in predicting the absolute direction of FE polarization. Our work indicates that to determine the magnitude and the absolute direction of FE polarization in spin-spiral states, it is crucial to consider the displacements of the ions from their centrosymmetric positions. DA - 2008/7/18/ PY - 2008/7/18/ DO - 10.1103/physrevlett.101.037209 VL - 101 IS - 3 SP - SN - 0031-9007 ER - TY - JOUR TI - Rational or statistical routes from 1-acyldipyrromethanes to meso-substituted porphyrins. Distinct patterns, multiple pyridyl substituents, and amphipathic architectures AU - Dogutan, Dilek Kiper AU - Ptaszek, Marcin AU - Lindsey, Jonathan S. T2 - JOURNAL OF ORGANIC CHEMISTRY AB - New methodology is described for the synthesis of porphyrins bearing four (A4, cis-A2B2, cis-ABC2, trans-A2B2) or fewer (A, cis-AB, cis-A2, trans-A2) meso substituents. The method entails condensation of two 1-acyldipyrromethanes in the presence of a metal salt (MgBr2, 3 mol equiv) and a noncoordinating base (DBU, 10 mol equiv) in a noncoordinating solvent (toluene) with heating (conventional or microwave irradiation) and exposure to air. The rational synthesis of trans-A2B2- or trans-A2-porphyrins was achieved via condensation of two identical 1-acyldipyrromethanes. The statistical synthesis of various meso-substituted porphyrins was achieved via condensation of two nonidentical 1-acyldipyrromethanes. Both routes possess attractive features including (1) no scrambling, (2) good yield (up to 60%) at high concentration (100 mM) for the macrocycle-forming step, (3) reasonable scope (aryl, heteroaryl, alkyl, or no substituent), (4) short reaction time (∼2 h) via microwave irradiation, (5) magnesium porphyrins as the products, which easily undergo demetalation, and (6) facile chromatographic purification. A key advantage of the statistical route is to obtain a cis-substituted porphyrin without the corresponding trans isomer. For example, reaction of an A/B-substituted 1-acyldipyrromethane and the fully unsubstituted 1-formyldipyrromethane gave the magnesium chelates of three porphyrins: the trans-A2B2-porphyrin, the “hybrid” cis-AB-porphyrin, and porphine (no trans-AB-porphyrin can form), which were readily demetalated and separated as the free base species. Altogether 26 1-acyldipyrromethanes and 26 target porphyrins have been prepared, including many with two different pyridyl substituents. One set of amphipathic porphyrins includes cis-A2B2- or cis-A2BC-porphyrins wherein A = pentyl and B/C = pyridyl (o-, m-, p-). Taken together, the rational and statistical routes enable facile conversion of readily available 1-acyldipyrromethanes to diverse porphyrins bearing 1−4 meso substituents for which access is limited via other methods. DA - 2008/8/15/ PY - 2008/8/15/ DO - 10.1021/jo800588n VL - 73 IS - 16 SP - 6187-6201 SN - 0022-3263 ER - TY - JOUR TI - Microwave activation of enzymatic catalysis AU - Young, Douglas D. AU - Nichols, Jason AU - Kelly, Robert M. AU - Deiters, Alexander T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Microwave irradiation can be used to regulate biocatalysis. Herein, the utilization of hyperthermophilic enzymes in a microwave reactor is reported. While these enzymes are inactive at low temperatures, they can be activated with microwave irradiation. To the best of our knowledge, this is the first illustration of a specific microwave effect in enzymatic catalysis. DA - 2008/8/6/ PY - 2008/8/6/ DO - 10.1021/ja802404g VL - 130 IS - 31 SP - 10048-+ SN - 0002-7863 ER - TY - JOUR TI - Interfacial and solvent effects govern the formation of tris(dibenzylidenacetone)dipalladium(0) microstructures AU - Leonard, Donovan N. AU - Cerruti, Marta AU - Duscher, Gerd AU - Franzen, Stefan T2 - LANGMUIR AB - Organometallic palladium adducts have application as catalysts and as precursors for nanoparticle synthesis. Herein, we study the spontaneous formation of molecular crystals of the organometallic reagent tris(dibenzylidenacetone)dipalladium(0) (Pd2(DBA)3) in THF/H2O binary solvent systems. We report structural and chemical characterization of the resulting diverse structures with shapes including hexagonal platelets, rods, cubes, and stars. Optical microscopy, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectroscopy were used to determine representative structures and corresponding compositions when formed either in a binary solution or upon evaporation on a surface. The difference in Pd2(DBA)3 particle morphology was attributed to differences in the surface tension of growing crystalline faces. The formation of a majority of rods or hexagonal platelets in solution was shown to be determined by the ratio of THF to H2O in the solvent, whereas supersaturation effects and interfacial surface tension played a major role in creating the shape of particles formed upon evaporation of Pd2(DBA)3 droplets on a surface. DA - 2008/8/5/ PY - 2008/8/5/ DO - 10.1021/la801039j VL - 24 IS - 15 SP - 7803-7809 SN - 0743-7463 ER - TY - PAT TI - Transient optical state change materials useful in copy-protected compact discs AU - Selingfreund, R. H. AU - Gerger, S. AU - Vig, R. AU - Li, J. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Theoretical treatment of excited electronic states of adsorbates on metals: Electron attachment to CO2 adsorbed on K-modified Pt(111) AU - Sremaniak, Laura S. AU - Whitten, Jerry L. T2 - SURFACE SCIENCE AB - Abstract Theoretical studies of photoinduced processes involving electron attachment to CO 2 adsorbed on Pt(1 1 1) in the presence of a coadsorbed K atom are reported. First principles theoretical methods suitable for describing electronic states embedded in a near continuum of metal to metal excitations are described. Wave functions are constructed by ab initio configuration interaction methods which allow a rigorous resolution of states and differentiation between competing pathways of molecular desorption and dissociation. An embedding theory is used to achieve high accuracy in the adsorbate-surface region. Compared to CO 2 adsorbed on Pt(1 1 1), the K promoter lowers the work function of the system from 5.6 to 5.2 eV and decreases the energy required to form the electron attached excited electronic state from 6.8 to 5.6 eV. However, stabilization of CO 2 depends strongly on orientation and proximity to the K adatom. The most favorable pathway leading to dissociation requires that CO 2 be adsorbed at a site that does not share Pt atoms with the K adsorption site, i.e., at next-nearest neighbor sites. As was found for Pt(1 1 1) without a K adatom, the dissociation pathway involves bending of CO 2 in the excited state followed by possible dissociation on the excited state surface where the barrier height is reduced from its value of 1.0 eV on the Pt surface to 0.34 eV. As is the case for the unmodified surface, dissociation could also occur after return to the ground state potential energy surface via vibrational processes. DA - 2008/2/15/ PY - 2008/2/15/ DO - 10.1016/j.susc.2007.11.029 VL - 602 IS - 4 SP - 834-842 SN - 1879-2758 KW - theory KW - chemisorption KW - photochemistry KW - platinum KW - carbon dioxide ER - TY - JOUR TI - Suppression of Ge-O and Ge-N bonding at Ge-HfO2 and Ge-TiO2 interfaces by deposition onto plasma-nitrided passivated Ge substrates: Integration issues Ge gate stacks into advanced devices AU - Lee, S. AU - Long, J. P. AU - Lucovsky, G. AU - Whitten, J. L. AU - Seo, H. AU - Luning, J. T2 - MICROELECTRONICS RELIABILITY AB - A study of changes in nano-scale morphology of thin films of nano-crystalline transition metal (TM) elemental oxides, HfO2 and TiO2, on plasma-nitrided Ge(1 0 0) substrates, and Si(1 0 0) substrates with ultra-thin (∼0.8 nm) plasma-nitrided Si suboxide, SiOx, x < 2, or SiON interfacial layers is presented. Near edge X-ray absorption spectroscopy (NEXAS) has been used to determine nano-scale morphology of these films by Jahn-Teller distortion removal of band edge d-state degeneracies. These results identify a new and novel application for NEXAS based on the resonant character of the respective O K1 and N K1 edge absorptions. This paper also includes a brief discussion of the integration issues for the introduction of this Ge breakthrough into advanced semiconductor circuits and systems. This includes a comparison of nano-crystalline and non-crystalline dielectrics, as well as issues relative to metal gates. DA - 2008/3// PY - 2008/3// DO - 10.1016/j.microrel.2007.07.068 VL - 48 IS - 3 SP - 364-369 SN - 0026-2714 ER - TY - JOUR TI - Soluble precipitable porphyrins for use in targeted molecular brachytherapy AU - Yao, Zhen AU - Borbas, K. Eszter AU - Lindsey, Jonathan S. T2 - NEW JOURNAL OF CHEMISTRY AB - In a new therapy that aims to concentrate and immobilize therapeutic radionuclides in nanoscale assemblies within solid tumors, a soluble precipitable reagent (SPR) is administered as the radionuclide carrier and is converted to non-diffusible precipitate by an enzyme located in tumor tissues. To meet the objective of such an SPR, we have prepared and examined a class of porphyrin–alkyldiphosphates that are soluble in aqueous solution and that are rendered insoluble upon removal of the two phosphate groups. The porphyrins examined herein are of the trans-AB architecture wherein the substituents are a bis(dihydroxyphosphoryloxy)alkyl group and a phenyl (or p-bromophenyl) group. Provisions for later incorporation of radionuclides have been established by preparation of the analogous copper chelate or the meso-iodo free-base porphyrin. Altogether, four porphyrins bearing a bis(dihydroxyphosphoryloxy)alkyl group were examined and found to exhibit satisfactory solubility in water (>1 mM). Dephosphorylation reactions have been carried out in vitro using the enzyme shrimp alkaline phosphatase. In each case, enzyme-induced precipitation was observed. The soluble-to-insoluble conversion has been examined by visual inspection, absorption spectroscopy, electrospray ionization mass spectrometry, and nephelometry using non-radiolabeled porphyrins. DA - 2008/// PY - 2008/// DO - 10.1039/b714127k VL - 32 IS - 3 SP - 436-451 SN - 1369-9261 ER - TY - JOUR TI - On the cyclability of the thermochromism in CuMoO4 and its tungsten derivatives CuMo1-xWxO4 (x < 0.12) AU - Thiry, Anne-Emmanuelle AU - Gaudon, Manuel AU - Payen, Christophe AU - Daro, Nathalie AU - Letard, Jean-Francois AU - Gorsse, Stephane AU - Deniard, Philippe AU - Rocquefelte, Xavier AU - Demourgues, Alain AU - Whangbo, Myung-Hwan AU - Jobic, Stephane T2 - CHEMISTRY OF MATERIALS AB - The cyclability of thermochromism in CuMoO4 and its solid solution CuMo1–xWxO4 (x < 0.12) was investigated by optical absorbance, differential scanning calorimetry, and magnetic susceptibility measurements. The high temperature form is found to progressively lose its ability to become the low temperature form with increasing the number of cooling/warming cycles. DA - 2008/3/25/ PY - 2008/3/25/ DO - 10.1021/cm703600g VL - 20 IS - 6 SP - 2075-2077 SN - 1520-5002 ER - TY - PAT TI - Methods and intermediates for the synthesis of dipyrrin-substituted porphyrinic macrocycles AU - Yu, L. AU - Muthukumaran, K. AU - Sreedharan, P. AU - Lindsey, J. S. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Metal complexation of 1-acyldipyrromethanes and porphyrins formed therefrom AU - Lindsey, J. S. AU - Muthukumaran, K. AU - Sharada, D. S. AU - Muresan, A. Z. AU - Youngblood, W. J. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Investigation of hexadecanethiol self-assembled monolayers on cadmium tin oxide thin films AU - Rhodes, Cnissy L. AU - Brewer, Scott H. AU - Folmer, Jaap AU - Franzen, Stefan T2 - THIN SOLID FILMS AB - This study reports the use of variable angle reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy to investigate the formation of a 1-hexadecanethiol adlayer on cadmium tin oxide (CTO) thin film surfaces. These adlayers appear to be robust, ordered monolayers. The optical and electronic properties of CTO thin films chemically vapor deposited onto glass substrates were also investigated. The reflectance of the CTO films was dependent upon the incident angle of the impinging radiation and revealed a reflectance decrease indicative of a plasma frequency in the mid-IR using p-polarized radiation. DA - 2008/2/29/ PY - 2008/2/29/ DO - 10.1016/j.tsf.2007.08.098 VL - 516 IS - 8 SP - 1838-1842 SN - 0040-6090 KW - plasma frequency KW - surface plasmon KW - conducting thin film KW - Fourier-transform infrared spectroscopy ER - TY - JOUR TI - Inhibition and dispersion of Pseudomonas aeruginosa biofilms with reverse amide 2-aminoimidazole oroidin analogues AU - Richards, Justin J. AU - Ballard, T. Eric AU - Melander, Christian T2 - ORGANIC & BIOMOLECULAR CHEMISTRY AB - The marine alkaloid oroidin along with a small library of reverse amide (RA) 2-aminoimidazoles were synthesized and assayed for anti-biofilm activity against PAO1 and PA14, two strains of the medically relevant gamma-proteobacterium Pseudomonas aeruginosa. Analogues that contained a long, linear alkyl chain were more potent inhibitors than the natural product at preventing the formation of PAO1 and PA14 biofilms. The most active compound in the series was also shown to disperse established PAO1 and PA14 biofilms at low micromolar concentrations. DA - 2008/// PY - 2008/// DO - 10.1039/b719082d VL - 6 IS - 8 SP - 1356-1363 SN - 1477-0539 ER - TY - PAT TI - Formation of self-assembled monolayers of redox SAMs on silicon for molecular memory applications AU - Bocian, D. F. AU - Kuhr, W. G. AU - Lindsey, J. S. AU - Dabke, R. B. AU - Liu, Z. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Enhanced nanocomposite combustion accelerant and methods for making the same AU - Brousseau, L. C. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Characterization of magnetic and electronic properties of trimetallic nitride endohedral fullerenes by SQUID magnetometry and electron paramagnetic resonance AU - Smirnova, Tatyana I. AU - Smirnov, Alex I. AU - Chadwick, Thomas G. AU - Walker, Kenneth L. T2 - CHEMICAL PHYSICS LETTERS AB - Magnetic and electronic properties of high-purity trimetallic nitride endohedral fullerenes Er3N@C80, Lu3N@C80, Sc3N@C80 diluted in a diamagnetic host were characterized by SQUID DC magnetometry and electron paramagnetic resonance (EPR) at multiple frequencies. The Er3N@C80 sample followed the Curie–Weiss law with negligible Weiss temperature of 0.16 K. Based on temperature dependence and isothermal saturation magnetization the effective magnetic moment of Er3N@C80 was estimated as 10.2 μB. The magnetic behavior of these fullerenes is ascribed to quenching of the orbital moment of the metal ions due to interactions between the metal centers with the nitrogen and the fullerene cage. DA - 2008/3/3/ PY - 2008/3/3/ DO - 10.1016/j.cplett.2008.01.036 VL - 453 IS - 4-6 SP - 233-237 SN - 1873-4448 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-44549085132&partnerID=MN8TOARS ER - TY - PAT TI - Boron complexation strategy for use in manipulating 1-acyldipyrromethanes AU - Lindsey, J. S. AU - Muthukumaran, K. AU - Ptaszek, M. AU - Huma, H. Z. AU - S. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Synthesis of phosphono-substituted porphyrin compounds for attachment to metal oxide surfaces AU - Lindsey, J. S. AU - Loewe, R. S. AU - Muthukumaran, K. AU - Ambroise, A. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - PAT TI - Synthesis of 2-aralkyloxyadenosines, 2-alkoxyadenosines, and their analogs AU - Moorman, A. R. AU - Scannell, M. AU - Balasubramanian, T. AU - Outcalt, R. AU - Leung, E. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Synthesis and excited-state photodynamics of a chlorin-bacteriochlorin dyad-through-space versus through-bond energy transfer in tetrapyrrole arrays AU - Muthiah, Chinnasamy AU - Kee, Hooi Ling AU - Diers, James R. AU - Fan, Dazhong AU - Ptaszek, Marcin AU - Bocian, David F. AU - Holten, Dewey AU - Lindsey, Jonathan S. T2 - PHOTOCHEMISTRY AND PHOTOBIOLOGY AB - Abstract Understanding energy transfer among hydroporphyrins is of fundamental interest and essential for a wide variety of photochemical applications. Toward this goal, a synthetic free base ethynylphenylchlorin has been coupled with a synthetic free base bromobacteriochlorin to give a phenylethyne‐linked chlorin–bacteriochlorin dyad ( FbC‐pe‐FbB ). The chlorin and bacteriochlorin are each stable toward adventitious oxidation because of the presence of a geminal dimethyl group in each reduced pyrrole ring. A combination of static and transient optical spectroscopic studies indicate that excitation into the Q y band of the chlorin constituent (675 nm) of FbC‐pe‐FbB in toluene results in rapid energy transfer to the bacteriochlorin constituent with a rate of ∼(5 ps) −1 and efficiency of >99%. The excited bacteriochlorin resulting from the energy‐transfer process in FbC‐pe‐FbB has essentially the same fluorescence characteristics as an isolated monomeric reference compound, namely a narrow (12 nm fwhm) fluorescence emission band at 760 nm and a long‐lived (5.4 ns) Q y excited state that exhibits a significant fluorescence quantum yield (Φ f = 0.19). Förster calculations are consistent with energy transfer in FbC‐pe‐FbB occurring predominantly by a through‐space mechanism. The energy‐transfer characteristics of FbC‐pe‐FbB are compared with those previously obtained for analogous phenylethyne‐linked dyads consisting of two porphyrins or two oxochlorins. The comparisons among the sets of dyads are facilitated by density functional theory calculations that elucidate the molecular‐orbital characteristics of the energy donor and acceptor constituents. The electron‐density distributions in the frontier molecular orbitals provide insights into the through‐bond electronic interactions that can also contribute to the energy‐transfer process in the different types of dyads. DA - 2008/// PY - 2008/// DO - 10.1111/j.1751-1097.2007.00258.x VL - 84 IS - 3 SP - 786-801 SN - 1751-1097 ER - TY - PAT TI - Nanoparticle delivery vehicle AU - Franzen, S. AU - Feldheim, D. L. AU - Tkachenko, A. G. AU - Godek, M. L. AU - Ryan, J. A. AU - Anderson, M. F. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Investigation of the scanning tunneling microscopy image, the stacking pattern and the bias-voltage dependent structural imstability of 2,2'-bipyridine molecules adsorbed on Au(111) in terms of electronic structure calculations AU - Suh, Y. AU - Park, S. S. AU - Kang, J. AU - Hwang, Y. G. AU - Jung, D. AU - Kim, D. H. AU - Lee, K. H. AU - Whangbo, M. H. T2 - Bulletin of the Korean Chemical Society DA - 2008/// PY - 2008/// VL - 29 IS - 2 SP - 438-444 ER - TY - PCOMM TI - Effect of plasma protein depletion on BNP-32 recovery AU - Hawkridge, Adam M. AU - Muddiman, David C. AU - Helmlein, Denise M. AU - Cataliotti, Alessandro AU - Burnett, John C., Jr. AB - Depletion of abundant proteins from plasma and serum is an important initial step in many biomarker discovery platforms(1). Decreasing the concentrations of highly abundant proteins (e.g., albumin, IgG, and antitrypsin) facilitates the use of contemporary proteomics technologies, such as gel electrophoresis and mass spectrometry, for detection and identification of low-abundant proteins. Furthermore, decreasing abundant protein concentrations may also improve immunoprecipitation recovery efficiencies for targeted low-abundant species by decreasing nonspecific binding (i.e., shielding the antigen-binding domain) to the antibody and/or solid supports. A notable pitfall to depletion strategies is the potential for unintentionally removing low-abundant plasma or serum proteins. These low-abundant species may be bound specifically or nonspecifically to the depletion ligand, depletion target protein (e.g., carrier proteins), or the solid support(s). Thus, it is important to critically evaluate the effectiveness of abundant plasma protein depletion for enhancing the study of low-abundant protein biomarker(s). We have been actively developing a targeted biomarker discovery platform for characterizing the circulating forms of B-type natriuretic peptide (BNP) that includes protein depletion strategies, immunoprecipitation, gel electrophoresis, isotope dilution (absolute quantification), and nanoflow liquid chromatography coupled to high-performance hybrid Fourier transform mass … DA - 2008/5// PY - 2008/5// DO - 10.1373/clinchem.2007.098038 SP - 933-934 ER - TY - JOUR TI - Coupled orientational and displacive degrees of freedom in the high-temperature plastic phase of the carbon tetrabromide alpha-CBr(4) AU - Folmer, Jacob C. W. AU - Withers, Ray L. AU - Welberry, T. R. AU - Martin, James D. T2 - PHYSICAL REVIEW B AB - Two-dimensional single-crystal synchrotron x-ray diffraction of the high-temperature plastic phase of $\mathrm{C}{\mathrm{Br}}_{4}$ reveals relatively sharp $\mathbf{G}\ifmmode\pm\else\textpm\fi{}\frac{1}{2}$ ${{110}}^{*}$ sheets of diffuse intensity (where $\mathbf{G}$ represents the set of average structure $Fm\text{\ensuremath{-}}3m$ allowed Bragg reflections). This intense and highly structured diffuse scattering arises from the large amplitude excitation of transverse polarized displacive modes of distortion and shows that a set of six possible orientations of the individual $\mathrm{C}{\mathrm{Br}}_{4}$ molecules in the plastic phase are strongly coupled with displacive relaxational degrees of freedom. Using Monte Carlo simulations to model the diffuse intensity, the displacive relaxations are shown to be along the molecular nearest-neighbor $\frac{1}{2}⟨110⟩$ real space directions associated with the relative orientations of individual and nearest-neighbor $\mathrm{C}{\mathrm{Br}}_{4}$ tetrahedra. DA - 2008/4// PY - 2008/4// DO - 10.1103/physrevb.77.144205 VL - 77 IS - 14 SP - SN - 1098-0121 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-42049094259&partnerID=MN8TOARS ER - TY - PAT TI - Synthesis of nicotine derivatives from nicotine AU - Comins, D. L. AU - D., Smith E. C2 - 2008/// DA - 2008/// PY - 2008/// ER - TY - JOUR TI - Surface plasmon polaritons and screened plasma absorption in indium tin oxide compared to silver and gold AU - Franzen, Stefan T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - This study addresses the ability of a conducting metal oxide to act as a material capable of supporting surface plasmon polaritons (SPPs). By use of a two-phase Fresnel model that provides insight into the difference between polariton-induced and absorptive decreases in reflectivity, indium tin oxide (ITO) is compared to the noble metals gold and silver, which are widely used as materials for surface plasmon resonance (SPR) detection of analytes. The study builds on application of the Drude free electron model that provides an explanation for the observed optical extinctions as a function of ITO film thickness, including the dependence of wavenumber on angle, by use of only two adjustable parameters, the plasma frequency ωp and the damping Γ. Herein, models of the dispersion and absorption include both the real and imaginary parts of the dielectric function to obtain the plasma absorption spectra and dispersion curves for ITO, Ag, and Au. ITO is found to have surface plasmon dispersion curves and plasma absorption free from interband transitions as observed in Ag but not Au. Au has significant contribution from bound electrons that damps the plasma absorption and broadens the dispersion curve of the SPP. Ag is more like a free-electron conductor than Au but still has some absorption in the frequency range above the observed surface plasmon. ITO is a nearly ideal free-electron conductor. DA - 2008/4/17/ PY - 2008/4/17/ DO - 10.1021/jp7097813 VL - 112 IS - 15 SP - 6027-6032 SN - 1932-7455 ER - TY - JOUR TI - Origin of the structural and magnetic anomalies of the layered compound SrFeO2: A density functional investigation AU - Xiang, H. J. AU - Wei, Su-Huai AU - Whangbo, M. -H. T2 - PHYSICAL REVIEW LETTERS AB - The structural and magnetic anomaly of the layered compound SrFeO2 are examined by first-principles density functional calculations and Monte Carlo simulations. The down-spin Fe 3d electron occupies the d(z(2)) level rather than the degenerate (d(xz), d(yz)) levels, which explains the absence of a Jahn-Teller instability, the easy ab-plane magnetic anisotropy, and the observed three-dimensional (0.5, 0.5, 0.5) antiferromagnetic order. Monte Carlo simulations show that the strong interlayer spin exchange is essential for the high Néel temperature. DA - 2008/4/25/ PY - 2008/4/25/ DO - 10.1103/physrevlett.100.167207 VL - 100 IS - 16 SP - SN - 0031-9007 ER - TY - JOUR TI - Jetting and detonation initiation in shock induced collapse of nanometer-scale voids AU - Shi, Yunfeng AU - Brenner, Donald W. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - Molecular dynamics simulations have been used to characterize the dynamics of the shock-induced asymmetric collapse of nanometer-scale voids in cubane nitrogen and to characterize how this dynamics couples with local chemistry to increase the shock sensitivity relative to homogeneous initiation. Mesoscopic-scale features of the void collapse correspond well to experimentally observed features of micrometer-scale bubble collapse, including a transition from single to double jetting with an increasing transverse void length. An analytic model is developed for the enhanced shock sensitivity as a function of void size and shape that reproduces the simulation results. At the atomic level, the simulations show vibrational up-pumping of molecules in the jet front because of collisions with the downstream wall followed by bi-molecular reactive dynamics from continued jet impact that triggers the onset of initiation. These results provide important new insights into the coupling of hydrodynamic void collapse and the enhanced shock sensitivity of energetic materials. DA - 2008/4/24/ PY - 2008/4/24/ DO - 10.1021/jp7119735 VL - 112 IS - 16 SP - 6263-6270 SN - 1932-7455 ER - TY - JOUR TI - Identification of cuticular lipids eliciting interspecific courtship in the German cockroach, Blattella germanica AU - Eliyahu, Dorit AU - Nojima, Satoshi AU - Capracotta, Sonja S. AU - Comins, Daniel L. AU - Schal, Coby T2 - NATURWISSENSCHAFTEN DA - 2008/5// PY - 2008/5// DO - 10.1007/s00114-007-0339-7 VL - 95 IS - 5 SP - 403-412 SN - 1432-1904 KW - Blatta orientalis KW - contact pheromone KW - methyl ketone KW - 11-methylheptacosan-2-one KW - 27-oxo-11-methylheptacosan-2-one ER - TY - JOUR TI - Electronic structure study of the [Ag-Ag](4-), [Au-Au](4-), and [Hg-Hg](2-) zintl anions in the intermetallic compounds Yb3Ag2, Ca5Au4, and Ca3Hg2: Transition metal anions as p-metal elements AU - Koehler, Juergen AU - Whangbo, Myung-Hwan T2 - CHEMISTRY OF MATERIALS AB - The chemical bonding of the M2 dimers (M = Ag, Au, Hg) present in Yb3Ag2, Ca5Au4 and Ca3Hg2 was examined on the basis of first principles electronic band structure calculations. In these compounds, the 6s- and 5d-block bands of M are completely filled while the frontier levels of M are given by partially filled 6p-block bands such that the transition metal atoms M are best described as anions with electron configuration (5d)10(6s)2(6p)1. Thus, the M2 dimers (M = Ag, Au, Hg) of Yb3Ag2, Ca5Au4 and Ca3Hg2 are present as [Ag−Ag]4−, [Au−Au]4−, and [Hg−Hg]2− Zintl-anions, respectively, in these compounds in which the M2 dimers have a single bond formed by the pσ−pσ interaction between the 5p and 6p orbitals of M atoms. The anions of late transition metal elements are different from those of late main group elements in their tendency for covalent bond formation. DA - 2008/4/22/ PY - 2008/4/22/ DO - 10.1021/cm703590d VL - 20 IS - 8 SP - 2751-2756 SN - 1520-5002 ER - TY - JOUR TI - Effects of counterion mobility, surface morphology, and charge screening on the electron-transfer rates of porphyrin monolayers AU - Jiao, Jieying AU - Nordfund, Eric AU - Lindsey, Jonathan S. AU - Bocian, David F. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - The standard electron-transfer rate constants (k0) for the oxidation of porphyrin monolayers are reported for a number of solvent/electrolyte systems and electroactive surfaces. The goal is to explain the inverse correlation between the electron-transfer rates and the porphyrin surface concentration (Roth et al., J. Phys. Chem. B 2002, 106, 8639−8648). Each porphyrin is a zinc chelate and contains three meso-mesityl groups and a benzyl alcohol or benzyl thiol for surface attachment. The solvent/electrolyte systems include (i) the organic solvent propylene carbonate containing electrolytes with a common cation and anions of different size/mobility (PF6-, ClO4-, and Cl-) and (ii) neat ionic liquids with a common cation and anions of different size/mobility [(CF3SO2)2N- and (NC)2N-]. The substrates include Si(100), Au(111), and TiN. The k0 values observed using electrolytes with PF6-, ClO4-, and (CF3SO2)2N- counterions are similar to one another, whereas those observed using electrolytes Cl- and (NC)2N- counterions are 2−5 times faster. The faster rates for the latter anions are attributed to their smaller size/higher mobility. The k0 values observed for monolayers on Si(100) and Au(111) are similar to one another; the k0 values for monolayers on TiN are ∼5-fold faster. The faster rates for the TiN substrate are attributed to a rougher surface morphology (as determined via atomic force microscopy measurements) which results in an actual surface concentration that is lower than the concentration based on the geometrical area of a planar substrate. The k0 values determined for mixed monolayers where the electroactive porphyrin is co-deposited with an electroinactive porphyrin are dependent only on the concentration of the redox-active species, not on the total porphyrin concentration. This behavior is consistent with space-charge effects being the principal determinant of the inverse correlation between the electron-transfer rates and the porphyrin surface concentration. The space charge effects can be mitigated, but not eliminated, by using smaller, more mobile counterions and rougher surfaces. DA - 2008/4/17/ PY - 2008/4/17/ DO - 10.1021/jp800123u VL - 112 IS - 15 SP - 6173-6180 SN - 1932-7447 ER - TY - BOOK TI - Nitroxides : applications in chemistry, biomedicine, and materials science DA - 2008/// PY - 2008/// PB - Weinheim: Wiley-VCH SN - 9783527318896 ER - TY - JOUR TI - Design, synthesis, and photophysical characterization of water-soluble chlorins AU - Borbas, K. Eszter AU - Chandrashaker, Vanampally AU - Muthiah, Chinnasamy AU - Kee, Hooi Ling AU - Holten, Dewey AU - Lindsey, Jonathan S. T2 - JOURNAL OF ORGANIC CHEMISTRY AB - The use of chlorins as photosensitizers or fluorophores in a range of biological applications requires facile provisions for imparting high water solubility. Two free base chlorins have been prepared wherein each chlorin bears a geminal dimethyl group in the reduced ring and a water-solubilizing unit at the chlorin 10-position. In one design (FbC1-PO3H2), the water-solubilizing unit is a 1,5-diphosphonopent-3-yl (“swallowtail”) unit, which has previously been used to good effect with porphyrins. In the other design (FbC2-PO3H2), the water-solubilizing unit is a 2,6-bis(phosphonomethoxy)phenyl unit. Two complementary routes were developed for preparing FbC2-PO3H2 that entail introduction of the protected phosphonate moieties either in the Eastern-half precursor to the chlorin or by derivatization of an intact chlorin. Water-solubilization is achieved in the last step of each synthesis upon removal of the phosphonate protecting groups. The chlorins FbC1-PO3H2 and FbC2-PO3H2 are highly water-soluble (>10 mM) as shown by 1H NMR spectroscopy (D2O) and UV−vis absorption spectroscopy. The photophysical properties of the water-soluble chlorins in phosphate-buffered saline solution (pH 7.4) at room temperature were investigated using static and time-resolved absorption and fluorescence spectroscopic techniques. Each chlorin exhibits dominant absorption bands in the blue and the red region (λ = 398, 626 nm), a modest fluorescence yield (Φf ≈ 0.11), a long singlet excited-state lifetime (τ = 7.5 ns), and a high yield of intersystem crossing to give the triplet state (Φisc = 0.9). The properties of the water-soluble chlorins in aqueous media are comparable to those of hydrophobic chlorins in toluene. The high aqueous solubility combined with the attractive photophysical properties make these compounds suitable for a wide range of biomedical applications. DA - 2008/4/18/ PY - 2008/4/18/ DO - 10.1021/jo7026728 VL - 73 IS - 8 SP - 3145-3158 SN - 1520-6904 ER - TY - JOUR TI - Coordination-driven self-assembly of cavity-cored multiple crown ether derivatives and poly[2]pseudorotaxanes AU - Ghosh, Koushik AU - Yang, Hai-Bo AU - Northrop, Brian H. AU - Lyndon, Matthew M. AU - Zheng, Yao-Rong AU - Muddiman, David C. AU - Stang, Peter J. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - The synthesis of a new 120° diplatinum(II) acceptor unit and the self-assembly of a series of two-dimensional metallacyclic polypseudorotaxanes that utilize both metal–ligand and crown ether−dialkylammonium noncovalent interactions are described. Judiciously combining complementary diplatinum(II) acceptors with bispyridyl donor building blocks, with an acceptor and/or donor possessing a pendant dibenzo[24]crown-8 (DB24C8) moiety, allows for the formation of three new rhomboidal bis-DB24C8, one new hexagonal tris-DB24C8, and four new hexakis-DB24C8 metallacyclic polygons in quantitative yields. The size and shape of each assembly, as well as the location and stoichiometry of the DB24C8 macrocycle, can be precisely controlled. Each polygon is able to complex two, three, or six dibenzylammonium ions without disrupting the underlying metallacyclic polygons, thus producing eight different poly[2]pseudorotaxanes and demonstrating the utility and scope of this orthogonal self-assembly technique. The assemblies are characterized with one-dimensional multinuclear (1H and 31P) and two-dimensional (1H−1H COSY and NOESY) NMR spectroscopy as well as mass spectrometry (ESI-MS). Further analysis of the size and shape of each assembly is obtained through molecular force-field simulations. 1H NMR titration experiments are used to establish thermodynamic binding constants and poly[2]pseudorotaxane/dibenzylammonium stoichiometries. Factors influencing the efficiency of poly[2]pseudorotaxane formation are discussed. DA - 2008/4/16/ PY - 2008/4/16/ DO - 10.1021/ja711502t VL - 130 IS - 15 SP - 5320-5334 SN - 1520-5126 ER - TY - JOUR TI - Inhibition and dispersion of proteobacterial biofilms AU - Richards, J. J. AU - Huigens, R. W. AU - Ballard, T. E. AU - Basso, A. AU - Cavanagh, J. AU - Melander, C. T2 - Chemical Communications (Cambridge, England) DA - 2008/// PY - 2008/// IS - 14 SP - 1698-1700 ER - TY - JOUR TI - Electrochemistry of cytochrome P450 enzyme on nanoparticle-containing membrane-coated electrode and its applications for drug sensing AU - Liu, Songqin AU - Peng, Lei AU - Yang, Xiaodi AU - Wu, Yafeng AU - He, Lin T2 - ANALYTICAL BIOCHEMISTRY AB - In the current study, we describe an improved system to study the two-electron delivery reaction pathway of cytochrome P450, family 2, subfamily B, polypeptide 6 (CYP2B6) in vitro. In particular, a biocompatible film containing colloidal gold nanoparticles and chitosan was used to encapsulate CYP2B6 on an electrode. The electrocatalytic behaviors of CYP2B6 toward common drugs in the absence of NADHP–cytochrome P450 reductase as electron donor were studied. In an anaerobic solution, direct and reversible electron transfer between the electroactive heme center of CYP2B6 and the electrode was observed with a formal potential of –0.454 ± 0.006 V at pH 7.4. In an air-saturated solution, an increase in the bioelectrocatalytic reduction current was observed after drug addition. The bioelectrocatalytic products were analyzed using high-performance liquid chromatography (HPLC) and electrospray ionization–mass spectrometry (ESI–MS). Both results confirmed that C-hydroxylation and heteroatom release were the main pathways for CYP2B6-mediated drug oxidation, similar to what occurred in vivo. The use of immobilized proteins in nanoparticle-containing films in drug biosensing was also demonstrated. DA - 2008/4/15/ PY - 2008/4/15/ DO - 10.1016/j.ab.2007.12.001 VL - 375 IS - 2 SP - 209-216 SN - 1096-0309 KW - cytochrome p450 2136 KW - colloidal gold nanoparticles KW - Bupropion KW - bioelectrocatalysis KW - drug metabolism ER - TY - JOUR TI - Electrochemical dopamine detection: Comparing gold and carbon fiber microelectrodes using background subtracted fast scan cyclic voltammetry AU - Zachek, Matthew K. AU - Hermans, Andre AU - Wightman, R. Mark AU - McCarty, Gregory S. T2 - JOURNAL OF ELECTROANALYTICAL CHEMISTRY AB - Electrochemical detection is becoming increasingly important for the detection of biological species. Most current biological research with electrochemical detection is done with carbon fiber electrodes due to their many beneficial properties. The ability to build electrochemical sensor from noble metals instead of carbon fibers may be beneficial in developing inexpensive multiplexed electrochemical detection schemes. To advance understanding and to test the feasibility of using noble metal electrochemical sensors the detection of dopamine, a biologically important small molecule was studied here. Specifically, dopamine detection on gold microelectrodes was characterized and compared to P-55 carbon fiber microelectrodes of the same geometry, using background subtracted fast scan cyclic voltammetry. While not as sensitive to dopamine as carbon fibers, it was observed that gold microelectrodes have six times the saturation coverage per area and 40 times the linear working range. Selectivity to dopamine, in comparison to several other neurotransmitters and their derivatives, is also quantitatively described. DA - 2008/3/15/ PY - 2008/3/15/ DO - 10.1016/j.jelechem.2007.11.007 VL - 614 IS - 1-2 SP - 113-120 SN - 1572-6657 KW - dopamine KW - carbon fiber microelectrode KW - Au microelectrode ER - TY - JOUR TI - Synthesis and regioselective substitution of C-6 alkoxy derivatives of (S)-nicotine AU - Ondachi, Pauline W. AU - Comins, Daniel L. T2 - TETRAHEDRON LETTERS AB - Enantiopure (S)-6-alkoxynicotine derivatives have been synthesized in two steps from (S)-nicotine via (S)-6-iodonicotine. Deprotonation and substitution at the C-5 position of the pyridine ring of (S)-6-methoxynicotine were achieved using mesityllithium as the base at 0 °C. Conditions for the C-4 lithiation/substitution of (S)-6-isopropoxynicotine and (S)-5-chloro-6-methoxynicotine were also developed. DA - 2008/1/14/ PY - 2008/1/14/ DO - 10.1016/j.tetlet.2007.11.041 VL - 49 IS - 3 SP - 569-572 SN - 0040-4039 KW - (S)-nicotine KW - alkoxynicotine KW - lithiation KW - regioselective deprotonation ER - TY - JOUR TI - Microwave-mediated Nickel-catalyzed cyclotrimerization reactions: Total synthesis of illudinine AU - Teske, Jesse A. AU - Deiters, Alexander T2 - JOURNAL OF ORGANIC CHEMISTRY AB - Rapid and efficient [2 + 2 + 2] cyclotrimerization reactions were discovered through the application of microwave irradiation in conjunction with a Ni(CO)(2)(PPh(3))(2) catalyst. This enables the facile construction of highly substituted indane, isoindoline, and tetraline core structures. The developed microwave-mediated Ni-catalyzed cyclotrimerization reaction was employed as the key step in a concise synthesis of the isoquinoline natural product illudinine. This represents the first example of a Ni-catalyzed cyclotrimerization reaction in total synthesis. DA - 2008/1/4/ PY - 2008/1/4/ DO - 10.1021/jo7020955 VL - 73 IS - 1 SP - 342-345 SN - 1520-6904 ER - TY - JOUR TI - Light-triggered polymerase chain reaction AU - Young, Douglas D. AU - Edwards, Wesleigh F. AU - Lusic, Hrvoje AU - Lively, Mark O. AU - Deiters, Alexander T2 - CHEMICAL COMMUNICATIONS AB - Photochemical control of the polymerase chain reaction has been achieved through the incorporation of light-triggered nucleotides into DNA. DA - 2008/// PY - 2008/// DO - 10.1039/b715152g IS - 4 SP - 462-464 SN - 1364-548X ER - TY - JOUR TI - Interfacial Surface Properties of Thiol-Protected Gold Nanoparticles:  A Molecular Probe EPR Approach AU - Khlestkin, Vadim K. AU - Polienko, Julya F. AU - Voinov, Maxim A. AU - Smirnov, Alex I. AU - Chechik, Victor T2 - Langmuir AB - We present a molecular probe technique for accessing interfacial surface electrostatics of ligand-protected gold nanoparticles. A series of ligands with variable length of the hydrocarbon bridge between the anchoring sulfur and the reporting pH-sensitive nitroxide is described. The protonation state of this probe is directly observed by EPR spectroscopy. For tiopronin-protected Au nanoparticles, we observed an increase in pKa of up to ca. 1.1 pH units that was affected by the position of the reporter moiety with respect to the monolayer interface. DA - 2008/2// PY - 2008/2// DO - 10.1021/la702823n VL - 24 IS - 3 SP - 609-612 J2 - Langmuir LA - en OP - SN - 0743-7463 1520-5827 UR - http://dx.doi.org/10.1021/la702823n DB - Crossref ER - TY - JOUR TI - Analysis of the spin lattice model for the spin-gapped layered compounds Na3Cu2SbO6 and Na2Cu2TeO6 on the basis of electronic structure calculations AU - Koo, Hyun-Joo AU - Whangbo, Myung-Hwan T2 - INORGANIC CHEMISTRY AB - The spin lattice model for the spin-gapped layered magnetic solids Na3Cu2SbO6 and Na2Cu2TeO6 was examined by evaluating the three spin exchange interactions of their Cu2MO6 (M = Sb, Te) layers in terms of spin dimer analysis based on extended Hückel tight binding calculations and mapping analysis based on first principles density functional theory electronic band structure calculations. For both compounds, our calculations show that the two strongest spin exchange interactions, that is, the Cu−O···O−Cu super-superexchange (J2) and the Cu−O−Cu superexchange (J1) interactions, form alternating chains that interact weakly through the Cu−O−Cu superexchange (J3) interactions. The dominant one of the three spin exchange interactions is J2, and it is antiferromagnetic in agreement with the fact that both of the compounds are spin gapped. For Na3Cu2SbO6 and Na2Cu2TeO6, the superexchange J1 is calculated to be ferromagnetic, hence, leading to the alternating chain model in which antiferromagnetic and ferromagnetic spin exchange interactions alternate. This picture does not agree with the recent experimental analysis, which showed that the temperature-dependent magnetic susceptibilities of both compounds should be described by the alternating chain model in which two antiferromagnetic spin exchange interactions of different strengths alternate. DA - 2008/1/7/ PY - 2008/1/7/ DO - 10.1021/ic701153z VL - 47 IS - 1 SP - 128-133 SN - 1520-510X ER - TY - JOUR TI - Using the Relationship between Vehicle Fuel Consumption and CO2 Emissions To Illustrate Chemical Principles AU - Pinto, Gabriel AU - Oliver-Hoyo, Maria T. T2 - Journal of Chemical Education AB - This instructional resource utilizes consumer product information by which students compare theoretical stoichiometric calculations to CO2 car emissions and fuel consumption data. Representing graphically the emission of CO2 versus consumption of fuel provides a tangible way of connecting concepts studied in chemistry classes to everyday life. Considerable simplification of an otherwise complex chemistry problem provides comparable theoretical and actual data. Practice with unit conversion and graphing enhance this activity promoting skills used by professionals to perform emission measurements. This activity may be used to bring awareness of car emissions issues such as the environmental impact of CO2 emissions and the differences of hybrid engines or gasoline versus diesel engines. Scientific literacy can be approached by incorporating exercises such as this one into chemistry classroom activities. Students have expressed keen interest in this type of "tangible" chemistry where a concrete example of everyday life puts textbook chemistry in context. DA - 2008/2// PY - 2008/2// DO - 10.1021/ed085p218 VL - 85 IS - 2 SP - 218 J2 - J. Chem. Educ. LA - en OP - SN - 0021-9584 1938-1328 UR - http://dx.doi.org/10.1021/ed085p218 DB - Crossref ER - TY - JOUR TI - Quantitative study of solvent and surface effects on analyte ionization in desorption ionization on silicon (DIOS) mass spectrometry AU - Liu, Qiang AU - He, Lin T2 - JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY AB - Deuterated solvents and DIOS surfaces derivatized with different functional groups are used to investigate impacts of local chemical environment on analyte ionization. Both solvent molecules and surface functional groups are found to directly participate in analyte protonation in the condensed phase. The corresponding protonation effectiveness is quantitatively estimated based on the relative MS peak intensities of [M+2]+/[M+1]+. A direct correlation between ionization of triethylamine and the relative acidities of the surface and the solvent is evident. In addition, the proton donating effectiveness of a solvent is found to be related to its vapor pressure. Improved MS detection of small molecules via proper surface treatment and solvent selection is demonstrated. DA - 2008/1// PY - 2008/1// DO - 10.1016/j.jasms.2007.10.002 VL - 19 IS - 1 SP - 8-13 SN - 1044-0305 ER - TY - JOUR TI - Post-processing of IEPR spectra by convolution filtering: Calculation of a harmonics' series and automatic separation of fast-motion components from spin-label EPR spectra AU - Smirnov, Alex I. T2 - JOURNAL OF MAGNETIC RESONANCE AB - This communication reports on post-processing of continuous wave EPR spectra by a digital convolution with filter functions that are subjected to differentiation or the Kramers-Krönig transform analytically. In case of differentiation, such a procedure improves spectral resolution in the higher harmonics enhancing the relative amplitude of sharp spectral features over the broad lines. At the same time high-frequency noise is suppressed through filtering. These features are illustrated on an example of a Lorentzian filter function that has a principal advantage of adding a known magnitude of homogeneous broadening to the spectral shapes. Such spectral distortion could be easily and accurately accounted for in the consequent least-squares data modeling. Application examples include calculation of higher harmonics from pure absorption echo-detected EPR spectra and resolving small hyperfine coupling that are unnoticeable in conventional first derivative EPR spectra. Another example involves speedy and automatic separation of fast and broad slow-motion components from spin-label EPR spectra without explicit simulation of the slow motion spectrum. The method is illustrated on examples of X-band EPR spectra of partially aggregated membrane peptides. DA - 2008/1// PY - 2008/1// DO - 10.1016/j.jmr.2007.10.006 VL - 190 IS - 1 SP - 154-159 SN - 1090-7807 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-36849012041&partnerID=MN8TOARS KW - EPR KW - data processing KW - filtering KW - spin-labeling EPR KW - data modeling KW - membrane peptides ER - TY - JOUR TI - Activation of sp(3) carbon-hydrogen bonds complex and subsequent metal-mediated formation AU - Foley, N. A. AU - Gunnoe, T. B. AU - Cundari, T. R. AU - Boyle, P. D. AU - Petersen, J. L. T2 - Angewandte Chemie [International Edition in English] DA - 2008/// PY - 2008/// VL - 47 IS - 4 SP - 726-730 ER - TY - JOUR TI - A compact water-soluble porphyrin bearing an iodoacetamido bioconjugatable site AU - Borbas, K. Eszter AU - Kee, Hooi Ling AU - Holten, Dewey AU - Lindsey, Jonathan S. T2 - ORGANIC & BIOMOLECULAR CHEMISTRY AB - A broad range of applications requires access to porphyrins that are compact, water-soluble, and bioconjugatable. A symmetrically branched hydrocarbon chain (‘swallowtail’) bearing polar end groups imparts high (>10 mM) aqueous solubility upon incorporation at one of the meso positions of a trans-AB-porphyrin. Two such swallowtail-porphyrins (1a, 1b) equipped with a conjugatable group (carboxylic acid, bromophenyl) have been prepared previously. The synthesis of three new water-soluble trans-AB-porphyrins is reported, where each porphyrin bears a diphosphonate-terminated swallowtail group and an amino (2a), acetamido (2b), or iodoacetamido (2c) group. The amine affords considerable versatility for functionalization. The iodoacetamide provides a sulfhydryl-reactive site for bioconjugation. Porphyrins 2a–2c were fully characterized in aqueous solution by 1H NMR spectroscopy (in D2O), ESI-MS, static absorption spectroscopy, and static and time-resolved fluorescence spectroscopy. Porphyrins 2a–2c exhibit characteristic porphyrin absorption and emission bands in aqueous solution, with a strong, sharp absorption band in the blue region (∼401 nm) and emission in the red region (∼624, 686 nm). Porphyrin 2b in aqueous phosphate buffer or phosphate-buffered saline solution exhibits a fluorescence quantum yield of ∼0.04 and an excited singlet-state lifetime of ∼11 ns. Collectively, the facile synthesis, amenability to bioconjugation, large spacing between the main absorption and fluorescence features, and long singlet excited-state lifetime make this molecular design quite attractive for a range of biomedical applications. DA - 2008/// PY - 2008/// DO - 10.1039/b715072e VL - 6 IS - 1 SP - 187-194 SN - 1477-0539 ER - TY - JOUR TI - Targeting RNA with cysteine-constrained peptides AU - Burns, Virginia A. AU - Bobay, Benjamin G. AU - Basso, Anne AU - Cavanagh, John AU - Melander, Christian T2 - BIOORGANIC & MEDICINAL CHEMISTRY LETTERS AB - A combined approach for targeting RNA with novel, biologically active ligands has been developed using a cyclic peptide library and in silico modeling. This approach has successfully identified novel cyclic peptide constructs that can target bTAR RNA. Subsequently, RNA/peptide interactions were effectively modeled using the HADDOCK docking program. DA - 2008/1/15/ PY - 2008/1/15/ DO - 10.1016/j.bmcl.2007.11.096 VL - 18 IS - 2 SP - 565-567 SN - 0960-894X KW - RNA KW - cyclic peptides KW - HADDOCK ER - TY - JOUR TI - Synthesis and characterization of phospholipid-functionalized silver nanoparticles AU - He, Peng AU - Zhu, Xinyuan T2 - MATERIALS RESEARCH BULLETIN AB - Functionalizations of silver nanoparticles (AgNPs) by phospholipids (PLs) have been manifested well by means of covalent connection between AgNPs with PLs. After functionalization, the attached PLs can self-assemble into bilayer structures on the surfaces of AgNPs. TEM displays the images of pure AgNPs and functionalized AgNPs with certain thickness of the phospholipid bilayers, as a result of chemical connection existing in AgNPs-PL conjugates. UV–vis and IR spectra confirm the strong Ag–S interaction between silver and sulfur produced during the reactions. This new modification method for AgNPs offers a good opportunity to functionalize nanoparticles with biological activity. DA - 2008/3/4/ PY - 2008/3/4/ DO - 10.1016/j.materresbull.2007.04.014 VL - 43 IS - 3 SP - 625-630 SN - 1873-4227 KW - nanostructures KW - surfaces KW - chemical synthesis ER - TY - JOUR TI - On the anisotropy of the magnetic properties of CsYbZnSe3 AU - Chan, George H. AU - Lee, Changhoon AU - Dai, Dad AU - Whangbo, Myung-Hwan AU - Ibers, James A. T2 - INORGANIC CHEMISTRY AB - DC magnetic susceptibility measurements on CsYbZnSe3 show a broad magnetic transition at ≈10 K and pronounced differences between zero-field-cooled and field-cooled data that lead to experimental effective magnetic moments of 4.26(5) BM and 4.39(4) BM, respectively. Specific heat measurements confirm that there is neither long-range ordering nor a phase transition between 1.8 and 380 K. First-principles electronic structure calculations with and without inclusion of spin–orbit coupling effects show that the spins of CsYbZnSe3 prefer to orient along [010] rather than along either [100] or [001] of this orthorhombic material and that the spin exchange between adjacent Yb3+ ions along [100] is substantially antiferromagnetic. The magnetic properties of CsYbZnSe3 are best described by an Ising uniform antiferromagnetic chain model. DA - 2008/3/3/ PY - 2008/3/3/ DO - 10.1021/ic701961f VL - 47 IS - 5 SP - 1687-1692 SN - 1520-510X ER - TY - PCOMM TI - Human Proteinpedia enables sharing of human protein data AU - Mathivanan, S. AU - Ahmed, M. AU - Ahn, N. G. AU - Alexandre, H. AU - Amanchy, R. AU - Andrews, P. C. AU - Bader, J. S. AU - Balgley, B. M. AU - Bantscheff, M. AU - Bennett, K. L. AU - Bjorling, E. AU - Blagoev, B. AU - Bose, R. AU - Brahmachari, S. K. AU - Burlingame, A. S. AU - Bustelo, X. R. AU - Cagney, G. AU - al, DA - 2008/// PY - 2008/// SP - 164-167 ER - TY - JOUR TI - Evaluation of Alzheimer's disease by analysis of MR images using multilayer perceptrons and committee machines AU - Santos, W. P. AU - Souza, R. E. AU - Silva, A. F. D. AU - Filho, P. B. Santos T2 - COMPUTERIZED MEDICAL IMAGING AND GRAPHICS AB - Alzheimer's disease is the most common cause of dementia, yet hard to diagnose precisely without invasive techniques, particularly at the onset of the disease. This work approaches image analysis and classification of synthetic multispectral images composed by diffusion-weighted magnetic resonance (MR) cerebral images for the evaluation of cerebrospinal fluid area and its correlation with the advance of Alzheimer's disease. The MR images were acquired from a unique volunteer with Alzheimer's, using an image system based on a clinical 1.5T tomographer. The classification methods are based on multilayer perceptrons and committee machines and the classification results are used to correlate clinical and imaging findings. The classification results are used to improve the usual analysis of the ADC map. DA - 2008/1// PY - 2008/1// DO - 10.1016/j.compmedimag.2007.08.004 VL - 32 IS - 1 SP - 17-21 SN - 1879-0771 KW - Alzheimer's disease KW - magnetic resonance imaging KW - multispectral image analysis KW - multilayer perceptrons KW - committee machines ER - TY - JOUR TI - Asymmetric synthesis of C-2-symmetric vicinal diamines via reductive dimerization of N-acylpyridinium and related salts AU - Bharathi, Pandi AU - Comins, Daniel L. T2 - ORGANIC LETTERS AB - A new route to C2-symmetric diamines via an asymmetric reductive dimerization of 1-acylpyridinium salts and their benzo derivatives is described. This method is practical as the starting heterocycles and chiral auxiliaries are readily available. The titanium reducing agent is inexpensive and easy to prepare. Several novel enantiopure C2-symmetric diamine derivatives were synthesized using this method. DA - 2008/1/17/ PY - 2008/1/17/ DO - 10.1021/ol702595d VL - 10 IS - 2 SP - 221-223 SN - 1523-7052 ER - TY - JOUR TI - A new family of multiferrocene complexes with enhanced control of structure and stoichiometry via coordination-driven self-assembly and their electrochemistry AU - Yang, Hai-Bo AU - Ghosh, Koushik AU - Zhao, Yue AU - Northrop, Brian H. AU - Lyndon, Matthew M. AU - Muddiman, David C. AU - White, Henry S. AU - Stang, Peter J. T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - The design and synthesis of a new family of multiferrocene complexes with enhanced control of structure and stoichimetry via coordination-driven self-assembly is described. Insight into the structure and electronic properties of all supramolecules was obtained by electrochemical studies. The collective results provide an enhanced understanding of the influence of structural factors on the electrochemistry of multifunctional electroactive supramolecular architectures. DA - 2008/1/23/ PY - 2008/1/23/ DO - 10.1021/ja710349j VL - 130 IS - 3 SP - 839-+ SN - 1520-5126 ER - TY - JOUR TI - Synthesis, characterization, and application of lodoacetamide derivatives utilized for the ALiPHAT strategy AU - Williams, D. K. AU - Meadows, C. W. AU - Bori, I. D. AU - Hawkridge, A. M. AU - Comins, D. L. AU - Muddiman, David T2 - Journal of the American Chemical Society DA - 2008/// PY - 2008/// DO - 10.1021/jao076849y VL - 130 IS - 7 SP - 2122- ER - TY - JOUR TI - Synthesis of polylactide using a zinc complex containing (S)-N-ethyl-N-phenyl-2-pyrrolidinemethanamine AU - Jeong, Jong Hwa AU - An, Young Hun AU - Kang, Youn K. AU - Nguyen, Quang Trung AU - Lee, Hyosun AU - Novak, Bruce M. T2 - POLYHEDRON AB - The reaction between ZnCl2 and (S)-N-ethyl-N-phenyl-2-pyrrolidinemethanamine (S-EPP) as a chiral ligand affords [ZnCl2(S-EPP)], whose structure has been determined by X-ray crystallography. [ZnEt2(S-EPP)] has demonstrated high activity toward the polymerization of rac-lactide with a maximum turnover frequency (TOF) of 121. Despite the intended stereocontrol by employing a chiral ligand, however, the observed heterotacticity was limited to under 0.6. The MWDs of the PLAs were found to be modulated by changing the solvent or controlling the concentration of the monomer in the solution. The glass transition temperature (Tg) was critically dependent on the MW within the narrow MWD regime, but the dependence became significantly shallow when the MWD was broadened. DA - 2008/1/20/ PY - 2008/1/20/ DO - 10.1016/j.poly.2007.09.021 VL - 27 IS - 1 SP - 319-324 SN - 0277-5387 KW - (S)-N-ethyl-N-phenyl-2-pyrrolidinemethanamine KW - chiral zinc complex KW - polylactide KW - stereocontrol of polylactide KW - X-ray structure ER - TY - JOUR TI - Synthesis and characterization of phospholipid-modified multiwalled carbon nanotubes AU - He, Peng AU - Zhu, Xinyuan T2 - MATERIALS RESEARCH BULLETIN AB - A simple three-step strategy to functionalize multiwalled carbon nanotubes using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine phospholipids has been described. The resulting phospholipid-modified multiwalled carbon nanotubes were analyzed by TEM, AFM, NMR, IR, UV–vis and TGA techniques. The experimental results show that the use of amine-terminated phospholipids not only improves the dispersity of multiwalled carbon nanotubes in both aqueous and organic solvents greatly, but also results in the significant enhancement of biocompatibility. These findings will serve as a future biological platform for new devices ranging from biosensors to nano-detectors. DA - 2008/1/8/ PY - 2008/1/8/ DO - 10.1016/j.materresbull.2007.02.024 VL - 43 IS - 1 SP - 141-148 SN - 1873-4227 KW - nanostructures KW - surface KW - chemical synthesis ER - TY - JOUR TI - Surface passivation using oligo(ethylene glycol) in ATRP-assisted DNA detection AU - Lou, Xinhui AU - He, Lin T2 - SENSORS AND ACTUATORS B-CHEMICAL AB - We recently reported a DNA sensing method using polymerization to amplify signal outputs [X. Lou, M.S. Lewis, C.B. Gorman, L. He, Anal. Chem. 77 (2005) 4698–4705]. In the current report an optimization of sensor surface chemistry is conducted in which (S–CH2CH2–OEG6–OMe)2 is used as the preferred surface passivation agent to reduce nonspecific adsorption experienced during ATRP-assisted DNA detection. The presence of oligo(ethylene glycol) (OEG) moieties on the sensor surface significantly reduces background adsorption of proteins, polymers, and reaction monomers used during DNA detection. The level of reduction in background nonspecific adsorption closely depends on the incubation solvent and the incubation time used, as evidenced by the ellipsometric and surface plasmon resonance (SPR) results. Reflectance FTIR results suggest that the surfaces with moderately ordered SAMs exhibit better protein resistance, consistent to the previous observations. Subsequent DNA binding experiments show no apparent decrease in DNA hybridization and ligation efficiencies when OEGylated self-assembled monolayers are used as the passivation layer. Improved DNA detection sensitivity is achieved from reduced background noises. DA - 2008/1/29/ PY - 2008/1/29/ DO - 10.1016/j.snb.2007.07.130 VL - 129 IS - 1 SP - 225-230 SN - 0925-4005 KW - surface passivation KW - oligo(ethylene glycol) KW - self-assembled monolayer KW - DNA sensing ER - TY - JOUR TI - Substrate binding triggers a switch in the iron coordination in dehaloperoxidase from Amphitrite ornata: HYSCORE experiments AU - Smirnova, Tatyana I. AU - Weber, Ralph T. AU - Davis, Mike F. AU - Franzen, Stefan T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB - Dehaloperoxidase (DHP) from the terebellid polychaete Amphitrite ornata is the first known hemoglobin to exhibit efficient peroxidase activity in the oxidation of phenolic substrates. Hyperfine sublevel correlation spectroscopic (HYSCORE) analysis of the ferric form of DHP was carried out to characterize effects of the substrate 2,4,6-trifluorophenol (TFP) binding on the iron coordination in order to elucidate the molecular mechanism of the change in protein function from a globin to a peroxidase. Continuous wave EPR spectra show that heme iron of DHP at pH 6.0 exists in the high spin state. HYSCORE spectra recorded at magnetic field corresponding to g = 2 revealed the presence of exchangeable protons with hyperfine coupling of ca. 6 MHz, consistent with a water molecule being the sixth ligand in the iron coordination. These protons' spectral features disappeared upon substrate binding. This observation highlights the proposed role of the substrate as a trigger for the switch from hemoglobin to peroxidase function. DA - 2008/2/20/ PY - 2008/2/20/ DO - 10.1021/ja0772952 VL - 130 IS - 7 SP - 2128-+ SN - 0002-7863 ER - TY - JOUR TI - Studies toward the Synthesis of 4-(2-R-ethyl)amino-2,2,5,5-tetramethyl-3-imidazoline 1-Oxyls. Nucleophilic Substitution of Bromide in the N-Alkyl Chain of the 1,2,4-Oxadiazol-2-one Precursor AU - Polienko, Julya F. AU - Schanding, Thomas AU - Gatilov, Yury V. AU - Grigor'ev, Igor A. AU - Voinov, Maxim A. T2 - The Journal of Organic Chemistry AB - A synthetic approach to access the new nitroxides of the amidine type exhibiting pH-dependent EPR spectra through substitution of a halide in the exo-N-halogenoalkyl chain of 1-(2-bromoethyl)-6-oxyl-5,5,7,7-tetramethyltetrahydroimidazo[1,5-b][1,2,4]oxadiazol-2-one is reported. In this approach, an oxycarbonyl moiety of the oxadiazolone heterocycle plays the role of a “protecting group” for the amidine functionality. A nucleophilic cleavage of the oxadiazolone heterocycle under mild nonbasic conditions, applicable to substrates bearing substituents vulnerable to attack by strong basic nucleophiles, is elaborated. The approach allows for the new amidine nitroxides bearing various functional groups (e.g., such as CN, N3, NH2, COOEt) to be synthesized. A series of nitroxides obtained through the Staudinger/intermolecular aza-Wittig reaction of the azido derivative is also described. The nitroxides synthesized here were found to have pH-dependent two-component EPR spectra indicative of a slow, on the EPR time scale, R• ⇆ R•H+ chemical exchange, and pKa values ranging from 2.8 to 12.5 units. The guanidine derivatives synthesized in this work show the highest pKa values (pKa = 10.2 and 12.5, respectively) ever reported for the nitroxide pH-probes of a “basic type”. DA - 2008/1// PY - 2008/1// DO - 10.1021/jo701803a VL - 73 IS - 2 SP - 502–510 SN - 0022-3263 1520-6904 UR - http://dx.doi.org/10.1021/jo701803a ER - TY - JOUR TI - Phenanthridine synthesis via [2+2+2] cyclotrimerization reactions AU - Sripada, Lakshminath AU - Teske, Jesse A. AU - Deiters, Alexander T2 - ORGANIC & BIOMOLECULAR CHEMISTRY AB - A concise synthesis of phenanthridines via a microwave-assisted [2+2+2] cyclotrimerization reaction has been developed. DA - 2008/// PY - 2008/// DO - 10.1039/b716519f VL - 6 IS - 2 SP - 263-265 SN - 1477-0520 ER - TY - JOUR TI - On the correct spin lattice for the spin-gapped magnetic solid NH4CuPO4 center dot H2O AU - Koo, Hyun-Joo AU - Whangbo, Myung-Hwan T2 - JOURNAL OF SOLID STATE CHEMISTRY AB - NH4CuPO4·H2O is a spin-gapped compound that has been described in terms of an isolated antiferromagnetic spin dimer model. To explore the origin of this spin gap, we examined the spin exchange interactions of NH4CuPO4·H2O by performing qualitative spin dimer analysis based on extended Hückel tight binding calculations and also by carrying out quantitative mapping analysis based on first principles density functional theory electronic band structure calculations. Our study indicates that, to a first approximation, the magnetic properties of NH4CuPO4·H2O should be described by an antiferromagnetic and ferromagnetic alternating chain. DA - 2008/2// PY - 2008/2// DO - 10.1016/j.jssc.2007.11.033 VL - 181 IS - 2 SP - 276-281 SN - 1095-726X KW - spin dimer analysis KW - electronic band structure calculations KW - spin exchange interactions KW - NH4CuPO4 center dot H2O ER - TY - JOUR TI - Infusion of dye molecules into Red clover necrotic mosaic virus AU - Loo, LiNa AU - Guenther, Richard H. AU - Lommel, Steven A. AU - Franzen, Stefan T2 - CHEMICAL COMMUNICATIONS AB - The Red clover necrotic mosaic viruscapsid is utilized to package and release molecules through reversible depletion and re-addition of divalent cations. DA - 2008/// PY - 2008/// DO - 10.1039/b714748a IS - 1 SP - 88-90 SN - 1359-7345 ER - TY - JOUR TI - Characterization of monolayer formation on aluminum-doped zinc oxide thin films AU - Rhodes, Crissy L. AU - Lappi, Simon AU - Fischer, Daniel AU - Sambasivan, Sharadha AU - Genzer, Jan AU - Franzen, Stefan T2 - LANGMUIR AB - The optical and electronic properties of aluminum-doped zinc oxide (AZO) thin films on a glass substrate are investigated experimentally and theoretically. Optical studies with coupling in the Kretschmann configuration reveal an angle-dependent plasma frequency in the mid-IR for p-polarized radiation, suggestive of the detection of a Drude plasma frequency. These studies are complemented by oxygen depletion density functional theory studies for the calculation of the charge carrier concentration and plasma frequency for bulk AZO. In addition, we report on the optical and physical properties of thin film adlayers of n-hexadecanethiol (HDT) and n-octadecanethiol (ODT) self-assembled monolayers (SAMs) on AZO surfaces using reflectance FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Our characterization of the SAM deposition onto the AZO thin film reveals a range of possible applications for this conducting metal oxide. DA - 2008/1/15/ PY - 2008/1/15/ DO - 10.1021/la701741m VL - 24 IS - 2 SP - 433-440 SN - 0743-7463 ER - TY - JOUR TI - Anti-Markovnikov hydroamination and hydrothiolation of electron-deficient vinylarenes catalyzed by well-defined monomeric copper(I) amido and thiolate complexes AU - Munro-Leighton, Colleen AU - Delp, Samuel A. AU - Alsop, Nikki M. AU - Blue, Elizabeth D. AU - Gunnoe, T. Brent T2 - CHEMICAL COMMUNICATIONS AB - Monomeric Cu(I) amido and thiolate complexes that are supported by the N-heterocyclic carbene ligand 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) catalyze the hydroamination and hydrothiolation of electron-deficient vinylarenes with reactivity patterns that are consistent with an intermolecular nucleophilic addition of the amido/thiolate ligand of (IPr)Cu(XR) (X = NH or S; R = Ph, CH2Ph) to free vinylarene. DA - 2008/// PY - 2008/// DO - 10.1039/b715507g IS - 1 SP - 111-113 SN - 1359-7345 ER -