@article{islam_gurgel_rojas_carbonell_2019, title={Use of a Branched Linker for Enhanced Biosensing Properties in IgG Detection from Mixed Chinese Hamster Ovary Cell Cultures}, volume={30}, ISSN={["1043-1802"]}, DOI={10.1021/acs.bioconjchem.8b00918}, abstractNote={Tris(2-aminoethyl)-amine (TREN), a branched amine, was coupled to planar surfaces of alkanethiol self-assembled monolayers (SAMs) to increase the grafting density of IgG-binding peptide (HWRGWV or HWRGWVG) on gold surfaces. One of the three primary amine pendant groups of TREN anchors onto the SAM, while the other two are available for grafting with the C-termini of the peptide. The ellipsometric peptide density on the SAM-branched amine was 1.24 molecules nm–2. The surfaces carrying the peptides were investigated via surface plasmon resonance (SPR) to quantify the adsorption of IgG and showed maximum binding capacity, Qm of 4.45 mg m–2, and dissociation constant, Kd of 8.7 × 10–7 M. Real-time dynamic adsorption data was used to determine adsorption rate constants, ka values, and the values were dependent on IgG concentration. IgG binding from complex mixtures of Chinese hamster ovary supernatant (CHO) was investigated and regeneration studies were carried out. Compared to the unbranched amine-based surfaces, the branched amines increased the overall sensitivity and selectivity for IgG adsorption from complex mixtures. Regeneration of the branched amine-based surfaces was achieved with 0.1 M NaOH, with less than 10% decline in peptide activity after 12 cycles of regeneration-binding.}, number={3}, journal={BIOCONJUGATE CHEMISTRY}, author={Islam, Nafisa and Gurgel, Patrick V. and Rojas, Orlando J. and Carbonell, Ruben G.}, year={2019}, month={Mar}, pages={815–825} }
 @article{shen_rojas_genzer_gurgel_carbonell_2016, title={Affinity interactions of human immunoglobulin G with short peptides: role of ligand spacer on binding, kinetics, and mass transfer}, volume={408}, ISSN={["1618-2650"]}, DOI={10.1007/s00216-015-9135-y}, number={7}, journal={ANALYTICAL AND BIOANALYTICAL CHEMISTRY}, author={Shen, Fei and Rojas, Orlando J. and Genzer, Jan and Gurgel, Patrick V. and Carbonell, Ruben G.}, year={2016}, month={Mar}, pages={1829–1841} }
 @article{heller_wimbish_gurgel_pourdeyhimi_carbonell_2016, title={Reducing diffusion limitations in Ion exchange grafted membranes using high surface area nonwovens}, volume={514}, ISSN={["1873-3123"]}, DOI={10.1016/j.memsci.2016.02.046}, abstractNote={Polybutylene terephthalate (PBT) nonwovens can be readily grafted with glycidyl methacrylate (GMA) via UV induced radical polymerization to create uniform and conformal polymer brush networks around each fiber that can be chemically modified to function as anion or cation exchangers. Protein binding capacities achieved by these grafted materials are many times larger than monolayer coverage around the fibers, but require very long residence times to reach equilibrium due to diffusional limitations within the grafted layers. The rates of adsorption of proteins by ion exchange were measured in an islands-in-the-sea (I/S) PBT nonwoven with average fiber diameter of approximately 1 µm and in a commercially available PBT nonwoven with average fiber diameter of approximately 3 µm. Both nonwovens were grafted successfully with poly(glycidyl methacrylate) (PGMA) and they showed almost identical ion exchange equilibrium protein binding capacities at similar weight % grafting. However, the grafted I/S nonwoven membrane exhibited a substantially higher amount of protein binding at short times and it was able to reach equilibrium in a fraction of the time required by the grafted commercial nonwoven with larger fiber diameters. The faster rate of protein adsorption observed with the I/S PBT nonwoven is the result of the thinner PGMA graft layer thicknesses around the fibers compared to those in the commercial PBT with the same weight % grafting. The data for the rate of adsorption of protein through the functionalized PGMA grafted layers was analyzed using a shrinking core model.}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Heller, Michael and Wimbish, Robert and Gurgel, Patrick V. and Pourdeyhimi, Behnam and Carbonell, Ruben G.}, year={2016}, month={Sep}, pages={53–64} }
 @article{liu_gurgel_carbonell_2015, title={Preparation and characterization of anion exchange adsorptive nonwoven membranes with high protein binding capacity}, volume={493}, ISSN={["1873-3123"]}, DOI={10.1016/j.memsci.2015.06.002}, abstractNote={An anion exchange poly(butylene therephthalate) (PBT) nonwoven membrane with high protein binding capacity was developed by covalent coupling of diethylamine (DEA) to photo-induced poly(glycidyl methacrylate) (polyGMA) brushes grafted to the PBT fibers. The grafted layers were characterized using FTIR and SEM. The rates of adsorption of bovine serum albumin (BSA) to membranes with different grafted layer thicknesses (different average DEA concentrations) were determined. The static BSA binding capacities were found to be 820, 400 and 183 mg BSA/g-membrane at average DEA concentrations of 0.84, 0.35 and 0.20 mmol DEA/g-membrane respectively. These high capacities are indicative of multilayer binding of protein within the grafted layers. The larger binding capacities required longer adsorption times to reach equilibrium, indicating a diffusional resistance to mass transfer within the grafted layers. The average diffusion coefficient was determined. A column packed with anion exchange nonwoven membranes was used to separate human immunoglobulin G (hIgG) from human serum albumin (HSA). The obtained purity and yield of hIgG flowing through the column were 93.4±2% and 94.5±1.5% respectively. The purity and yield of HSA bound and eluted from the membrane were 98±1% and 94±4% respectively. The nonwoven packed column exhibited a high flow permeability (1.1×10−8 cm2) due to high bed porosity (78%).}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Liu, Haiyan and Gurgel, Patrick V. and Carbonell, Ruben G.}, year={2015}, month={Nov}, pages={349–359} }
 @article{islam_shen_gurgel_rojas_carbonell_2014, title={Dynamic and equilibrium performance of sensors based on short peptide ligands for affinity adsorption of human IgG using surface plasmon resonance}, volume={58}, ISSN={["1873-4235"]}, DOI={10.1016/j.bios.2014.02.069}, abstractNote={This paper characterizes the potential of novel hexameric peptide ligands for on-line IgG detection in bioprocesses. Surface Plasmon Resonance (SPR) was used to study the binding of human IgG to the hexameric peptide ligand HWRGWV, which was covalently grafted to alkanethiol self-assembled monolayers (SAM) on gold surfaces. Peptide coupling on SAMs was verified, followed by covalent grafting of peptides with a removable Fmoc or acetylated N-termini via their C-termini to produce active peptide SPR sensors that were tested for IgG binding. The dynamics and extent of peptide–IgG binding were compared with results from a conventional system using protein A attached on a gold surface via disulfide monolayers. IgG binding to protein A on disulfide monolayers yielded equilibrium dissociation constants of 1.4×10–7 M. The corresponding dissociation constant value for the acetylated version of the peptide (Ac-HWRGWV) supported on alkanethiol SAM was 5.8×10–7 M and that for HWRGWV on the alkanethiol SAM (after de-protection of Fmoc-HWRGWVA) was 1.2×10–6 M. Maximum IgG binding capacities, Qm of 6.7, 3.8, and 4.1 mg m−2 were determined for the protein A and the two forms of HWRGWV-based biosensors, respectively. Real-time data for the kinetics of adsorption were used to determine the apparent rate constants for adsorption and desorption. The results were analyzed to understand the mechanism of IgG binding to the protein and peptide ligands. It was found that the peptide–IgG binding was reaction controlled, however the protein A–IgG binding mechanism was partially mass transfer (diffusion) controlled. The adsorption rate constants, ka, for the protein A ligand increased with decreasing concentration of analyte and the peptide ligand ka values was constant at different IgG concentrations and flow rates.}, journal={BIOSENSORS & BIOELECTRONICS}, author={Islam, Nafisa and Shen, Fei and Gurgel, Patrick V. and Rojas, Orlando J. and Carbonell, Ruben G.}, year={2014}, month={Aug}, pages={380–387} }
 @article{islam_gurgel_rojas_carbonell_2014, title={Effects of Composition of Oligo(ethylene glycol)-Based Mixed Monolayers on Peptide Grafting and Human Immunoglobulin Detection}, volume={118}, ISSN={["1932-7455"]}, DOI={10.1021/jp411469u}, abstractNote={Alkanethiols carrying ethylene glycol units (EGn, n = 3 or 6) with amine termini (EG3NH2 or EG6NH2) were coadsorbed with a “diluent”, hydroxyl-terminated alkanethiol (EG3OH), to form mixed self-assembled monolayers (SAMs). The mixed SAMs were characterized, and hexameric peptide ligand His-Trp-Arg-Gly-Trp-Val (HWRGWV), which shows affinity binding toward the Fc (constant fragment) of human immunoglobulin (IgG), was grafted onto different dilutions of EG6NH2–EG3OH mixed SAMs for preparation of IgG detection surfaces. The specificity toward IgG was optimal for peptides grafted on SAMs prepared from 10% EG6NH2 precursor solution, even though this surface did not have the highest number of peptides per unit area. Surface plasmon resonance (SPR) experiments showed that IgG bound to the peptides on the mixed SAM with a dissociation constant Kd of 9.33 × 10–7, maximum binding capacity Qm of 3.177 mg m–2, and adsorption rate constant ka of 1.99 m3 mol–1 s–1. IgG binding from complex mixtures of Chinese Hamster Ov...}, number={10}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Islam, Nafisa and Gurgel, Patrick V. and Rojas, Orlando J. and Carbonell, Ruben G.}, year={2014}, month={Mar}, pages={5361–5373} }
 @article{liu_gurgel_carbonell_2013, title={Affinity chromatographic purification of human immunoglobulin M from human B lymphocyte cell culture supernatant}, volume={70}, ISSN={["1873-295X"]}, DOI={10.1016/j.bej.2012.10.003}, abstractNote={Abstract Compared to immunoglobulin G purification with extensively studied affinity ligands such as protein A and protein G, little work has been done on affinity chromatographic purification of immunoglobulin M. Hexamer peptide ligand HWRGWV, previously shown to bind specifically to the Fc fragment of IgG, also demonstrated potential for IgM purification. This study presents further characterization and investigation of this ligand for its potential for purification of IgM. Different running conditions were employed in order to improve the recovery and purity of IgM. The final recovery and purity of the antibody is feedstock dependent, but can reach levels of both recovery and purity as high as 95%. The dependence of the recovery and purity on total loading amount and initial IgM concentration were investigated and discussed. Although relatively low dynamic binding capacities (DBC) in the range of 4.6–13.1 mg IgM/mL resin at linear flow rates from 173 to 35 cm/h were obtained for IgM compared to IgG because of the large molecular weight of IgM, the DBC value of HWRGWV for IgM is much greater than protein-based IgM affinity ligands found in the literature and is competitive with current commercially available affinity ligands, such as KAPTIVE-M, CaptureSelect IgM and Ultralink Immobilized Mannan Binding Protein.}, journal={BIOCHEMICAL ENGINEERING JOURNAL}, author={Liu, Zhuo and Gurgel, Patrick V. and Carbonell, Ruben G.}, year={2013}, month={Jan}, pages={63–70} }
 @article{liu_gurgel_carbonell_2013, title={Affinity chromatographic purification of human immunoglobulin a from chinese hamster ovary cell culture supernatant}, volume={29}, ISSN={["1520-6033"]}, DOI={10.1002/btpr.1652}, abstractNote={Hexamer peptide ligand HWRGWV, initially screened from a solid phase combinatorial peptide library for immunoglobulins G (IgG) purification, is shown to also have potential for immunoglobulin A (IgA) purification. The determined dissociation constants for hIgA on HWRGWV resins at three different peptide densities from 0.11 to 0.55 meq/g fall in the range of 10−6–10−7 M, which are somewhat lower than those for hIgG. Although relatively low dynamic binding capacity (DBC) in the range of 9.2–16.8 mg IgA/mL resin at linear flow rates from 173 to 35 cm/h were obtained for IgA compared to IgG, the DBC value of HWRGWV for IgA is much greater than current commercially available affinity ligands. Although relatively lower binding affinity to secretory IgA compared to monomeric IgA was observed, the peptide ligand resins exhibit great potential for large-scale purification of both human IgA and secretory IgA. Recoveries of 96.0% and 94.3%, and purities of 90.3% and 91.7% were achieved for human IgA and secretory IgA purification, respectively, from spiked Chinese hamster ovary cell culture supernatants without an extra afterwash step. Over 95% in purities were achieved for IgA and secretory IgA with an extra afterwash step; however, the recoveries would decrease at least 15% and 40% for IgA and secretory IgA, respectively. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013}, number={1}, journal={BIOTECHNOLOGY PROGRESS}, author={Liu, Zhuo and Gurgel, Patrick V. and Carbonell, Ruben G.}, year={2013}, pages={91–98} }
 @article{menegatti_naik_gurgel_carbonell_2012, title={Alkaline-stable peptide ligand affinity adsorbents for the purification of biomolecules}, volume={1245}, DOI={10.1016/j.chroma.2012.04.072}, abstractNote={A strategy of modification of resin surface chemistry is presented to produce hydrophilic peptide-based alkaline-stable affinity adsorbents for the purification of biopharmaceuticals from complex media. In this work, the peptide-based affinity adsorbent HWRGWV-Toyopearl resin for the purification of IgG is presented as an example. When prepared by direct peptide synthesis on the chromatographic matrix, the peptide-based resin showed lability under alkaline conditions. In fact, the regeneration with aqueous 0.1 M NaOH caused the leaching of 40% of the peptide ligand, resulting in a decrease of IgG yield from 85% to 23%. It was found that the ligand leaching was caused by the coupling of a significant amount of peptide by alkaline-labile ester bonds. A method was designed to prevent the formation of ester bonds and allow the synthesis of the ligand exclusively on alkaline-stable bonds. The method consists in activating the hydrophilic base resin, blocking the hydroxyl groups responsible for alkaline lability and performing the peptide synthesis exclusively via alkaline-stable amide bonds. Repeated cycles of IgG purification from a cell culture medium were performed, each followed by cleaning with aqueous NaOH (0.1 M, 0.5 M and 1 M). The IgG yield decreased from 91% to 85% after 200 purification cycles with 0.1 M NaOH. However, the IgG purity remained almost constant at around 95% based on SDS-PAGE analysis. The procedure presented is rapid, efficient and inexpensive and does not require any equipment other than the conventional instrumentation for peptide synthesis. The method also has a broad application since it is valid for any peptide ligand identified for the purification of a biopharmaceutical target.}, journal={Journal of Chromatography A}, author={Menegatti, S. and Naik, A. D. and Gurgel, P. V. and Carbonell, R. G.}, year={2012}, month={Jul}, pages={55–64} }
 @article{heldt_gurgel_jaykus_carbonell_2012, title={Porcine parvovirus removal using trimer and biased hexamer peptides}, volume={7}, ISSN={1860-6768}, url={http://dx.doi.org/10.1002/biot.201000397}, DOI={10.1002/biot.201000397}, abstractNote={Assuring the microbiological safety of biological therapeutics remains an important concern. Our group has recently reported small trimeric peptides that have the ability to bind and remove a model nonenveloped virus, porcine parvovirus (PPV), from complex solutions containing human blood plasma. In an effort to improve the removal efficiency of these small peptides, we created a biased library of hexamer peptides that contains two previously reported trimeric peptides designated WRW and KYY. This library was screened and several hexamer peptides were discovered that also removed PPV from solution, but there was no marked improvement in removal efficiency when compared to the trimeric peptides. Based on simulated docking experiments, it appeared that hexamer peptide binding is dictated more by secondary structure, whereas the binding of trimeric peptides is dominated by charge and hydrophobicity. This study demonstrates that trimeric and hexameric peptides may have different, matrix-specific roles to play in virus removal applications. In general, the hexamer ligand may perform better for binding of specific viruses, whereas the trimer ligand may have more broadly reactive virus-binding properties.}, number={4}, journal={Biotechnology Journal}, publisher={Wiley}, author={Heldt, Caryn L. and Gurgel, Patrick V. and Jaykus, Lee-Ann and Carbonell, Ruben G.}, year={2012}, month={Apr}, pages={558–565} }
 @article{naik_menegatti_reese_gurgel_carbonell_2012, title={Process for purification of monoclonal antibody expressed in transgenic Lemna plant extract using dextran-coated charcoal and hexamer peptide affinity resin}, volume={1260}, DOI={10.1016/j.chroma.2012.08.043}, abstractNote={The production of therapeutic proteins using transgenic plants offers several advantages, including low production cost, absence of human pathogens, presence of glycosylation mechanisms, and the ability to fold complex therapeutic proteins into their proper conformation. However, impurities such as phenolic compounds and pigments encountered during purification are quite different from those faced during purification from mammalian cell culture supernatants. This paper deals with the development of a pretreatment and affinity separation process for the purification of a monoclonal antibody from transgenic Lemna plant extract. A pretreatment step is described using dextran-coated charcoal for the removal of pigments and phenolic compounds without reducing the antibody concentration. Then, the peptide affinity ligand HWRGWV coupled to a commercial polymethacrylate resin is used for the capture and purification of MAb from the pretreated plant extract. The final yield and purity of the MAb obtained were 90% and 96% respectively. The performance of the hexamer peptide resin after the pretreatment step was found to be similar to that obtained with a commercial Protein A resin.}, journal={Journal of Chromatography A}, author={Naik, A. D. and Menegatti, S. and Reese, H. R. and Gurgel, P. V. and Carbonell, R. G.}, year={2012}, pages={61–66} }
 @article{liu_gurgel_carbonell_2012, title={Purification of human immunoglobulins A, G and M from Cohn fraction II/III by small peptide affinity chromatography}, volume={1262}, ISSN={["1873-3778"]}, DOI={10.1016/j.chroma.2012.09.026}, abstractNote={This work describes attempts to purify human IgG, IgA and IgM from Cohn fraction II/III using HWRGWV affinity peptide resin. The effects of peptide density and different elution additives on recovery of the three antibodies were investigated. At low peptide density, salting-in salts such as magnesium chloride and calcium chloride facilitated antibody elution. Ethylene glycol, urea and arginine also facilitated elution because of their ability to decrease hydrophobic interactions, hydrogen bonding and electrostatic interactions. However, at high peptide density, no recovery improvements were observed because of increased non-specific hydrophobic interactions. The final elution conditions for each antibody were chosen based on the resulting yields and purities when a 10:2:1mg/mL mixture of human IgG, IgA and IgM was used as starting material. Different pretreatment methods were employed in order to improve the purity of antibodies from Cohn fraction II/III. After pretreatment with caprylic acid precipitation or combination of caprylic acid and polyethylene glycol precipitation, purities over 95% and yields of about 60% were obtained for hIgG, which are comparable to current chromatographic purification methods involving two chromatography steps when hIgG is isolated from plasma fractions. A hIgA-enriched fraction with 42% hIgA and 56% hIgG, as well as a hIgM enriched fraction with 46% hIgM, 28% hIgA and 24% hIgG, were obtained as the by-products.}, journal={JOURNAL OF CHROMATOGRAPHY A}, author={Liu, Zhuo and Gurgel, Patrick V. and Carbonell, Ruben G.}, year={2012}, month={Nov}, pages={169–179} }
 @article{zheng_gurgel_carbonell_2011, title={Effects of UV Exposure and Initiator Concentration on the Spatial Variation of Poly(glycidyl methacrylate) Grafts on Nonwoven Fabrics}, volume={50}, ISSN={["0888-5885"]}, DOI={10.1021/ie1021333}, abstractNote={This paper describes the spatial uniformity of grafted layers of poly(glycydyl methacrylate) on the fibers of polypropylene nonwoven fabrics, and how they depend on the UV pretreatment step, the ad...}, number={10}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Zheng, Yong and Gurgel, Patrick V. and Carbonell, Ruben G.}, year={2011}, month={May}, pages={6115–6123} }
 @article{liu_gurgel_carbonell_2011, title={Effects of peptide density and elution pH on affinity chromatographic purification of human immunoglobulins A and M}, volume={1218}, ISSN={["1873-3778"]}, DOI={10.1016/j.chroma.2011.09.038}, abstractNote={A family of linear hexamer peptide ligands HWRGWV, HYFKFD and HFRRHL, initially identified for their affinity to the Fc portion of human immunoglobulin G (hIgG), also have potential for use in the purification of human immunoglobulins A (hIgA) and M (hIgM). HWRGWV demonstrated the strongest binding affinity to hIgM, followed by hIgA and hIgG respectively. The effects of N-terminal acetylation of the peptide, as well as elution buffer pH, on the chromatographic elution of human IgG, IgA and IgM from HWRGWV resins at various peptide densities (0.04–0.55 meq/g) were investigated. Over 80% recovery and 90% purity were achieved for human IgG and IgA isolation from complete minimum essential medium (cMEM) using HWRGWV resin at optimum peptide densities. For human IgM, 75.7% recovery and 86.0% purity were achieved by using HWRGWV at a low peptide density of 0.04 meq/g. Although HYFKFD and HFRRHL exhibited their ability for isolation of human IgG, IgA and IgM from cMEM as well, HWRGWV is the best option among them for large-scale purification of human IgG, IgA and IgM based on conditions tested.}, number={46}, journal={JOURNAL OF CHROMATOGRAPHY A}, author={Liu, Zhuo and Gurgel, Patrick V. and Carbonell, Ruben G.}, year={2011}, month={Nov}, pages={8344–8352} }
 @article{naik_menegatti_gurgel_carbonell_2011, title={Performance of hexamer peptide ligands for affinity purification of immunoglobulin G from commercial cell culture media}, volume={1218}, DOI={10.1016/j.chroma.2010.11.071}, abstractNote={Previous work has reported on the identification and characterization of the hexapeptide ligands HWRGWV, HYFKFD, and HFRRHL for the affinity capture of IgG through specific binding to its Fc fragment. This paper addresses issues related to the successful application of these ligands, on a commercial methacrylate chromatographic resin, for the purification of IgG from mammalian cell culture fluids. The concentrations of sodium chloride and sodium caprylate in the binding buffer were optimized to maximize the purity and yield of IgG upon elution. Screening of several regeneration conditions found that either 2M guanidine-HCl or a combination of 0.85% phosphoric acid followed by 2M urea resulted in complete recovery of the IgG adsorption capacity and that the column could be reused over many cycles. The hexapeptide ligands were used for the purification of humanized and chimeric monoclonal antibodies from two commercial CHO cell culture fluids. The chimeric MAb of IgG1 subclass was purified using the HWRGWV resin whereas the humanized MAb of IgG4 subclass was purified using the HWRGWV, HYFKFD and HFRRHL resins. The purities and yields obtained for both the MAbs were found to be higher than 94% and 85% respectively. These results compare well with the yields and purities obtained using Protein G columns. The residual DNA and host cell protein reduction obtained by the HWRGWV resin was in the range of 4 log reduction value (LRV) and 2 LRV respectively, comparable to those reported for Protein A resins. The dynamic binding capacity of all three peptide resins for the humanized monoclonal antibody was in the range of 20mg/mL.}, number={13}, journal={Journal of Chromatography A}, author={Naik, A. D. and Menegatti, S. and Gurgel, P. V. and Carbonell, R. G.}, year={2011}, month={Apr}, pages={1691–1700} }
 @article{yang_gurgel_williams_bobay_cavanagh_muddiman_carbonell_2010, title={Binding site on human immunoglobulin G for the affinity ligand HWRGWV}, volume={23}, number={3}, journal={Journal of Molecular Recognition}, author={Yang, H. O. and Gurgel, P. V. and Williams, D. K. and Bobay, B. G. and Cavanagh, J. and Muddiman, D. C. and Carbonell, R. G.}, year={2010}, pages={271–282} }
 @article{yang_gurgel_carbonell_2009, title={Purification of human immunoglobulin G via Fc-specific small peptide ligand affinity chromatography}, volume={1216}, ISSN={["1873-3778"]}, DOI={10.1016/j.chroma.2008.12.004}, abstractNote={Chromatographic resins of a family of linear Fc-binding hexamer peptides (HWRGWV, HYFKFD, and HFRRHL) exhibited the ability to selectively adsorb and isolate human IgG (hIgG) from complete mammalian cell culture medium (cMEM). Among them, the HWRGWV resin with a peptide density of 0.08 mequiv./g of resin was able to purify hIgG from cMEM with both purity and yield as high as 95%, comparable to Protein A and A2P agarose gels. The influences of N-terminal acetylation of the HWRGWV resin, ligand density on the resin, initial hIgG concentration, and temperature on IgG isolation were also investigated. The results indicate that these small peptide ligands, especially HWRGWV, offer a potential alternative to the use of Protein A or Protein G for large scale affinity chromatography.}, number={6}, journal={JOURNAL OF CHROMATOGRAPHY A}, author={Yang, Haiou and Gurgel, Patrick V. and Carbonell, Ruben G.}, year={2009}, month={Feb}, pages={910–918} }
 @article{heldt_gurgel_jaykus_carbonell_2008, title={Identification of trimeric peptides that bind porcine parvovirus from mixtures containing human blood plasma}, volume={24}, ISSN={["1520-6033"]}, DOI={10.1021/bp070412c}, abstractNote={Virus contamination in human therapeutics is of growing concern as more therapeutic products from animal or human sources come into the market. All biopharmaceutical processes are required to have at least two distinct viral clearance steps to remove viruses. Most of these steps work well for enveloped viruses and large viruses, whether enveloped or not. That leaves a class of small non-enveloped viruses, like parvoviruses and hepatitis A, which are not easily removed by these typical steps. In this study, we report the identification of trimeric peptides that bind specifically to porcine parvovirus (PPV) and their potential use to remove this virus from process solutions. All of the trimeric peptides isolated completely removed all detectable PPV from buffer in the first nine column volumes, corresponding to a clearance of 4.5–5.5 log of infectious virus. When the virus was spiked into a more complex matrix consisting of 7.5% human blood plasma, one of the trimers, WRW, was able to remove all detectable PPV in the first three column volumes, after which human blood plasma began to interfere with the binding of the virus to the peptide resin. These trimer resins removed considerably more virus than weak ion exchange resins. The results of this work indicate that small peptide ligand resins have the potential to be used in virus removal processes where removal of contaminating virus is necessary to ensure product safety.}, number={3}, journal={BIOTECHNOLOGY PROGRESS}, author={Heldt, Caryn L. and Gurgel, Patrick V. and Jaykus, Lee-Ann and Carbonell, Ruben G.}, year={2008}, pages={554–560} }
 @misc{carbonell_shen_gurgel_wiltshire-lyerly_hammond_burton_2008, title={Prion protein binding materials and methods of use}, volume={7,393,658}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Carbonell, R. G. and Shen, H. and Gurgel, P. V. and Wiltshire-Lyerly, V. and Hammond, D. J. and Burton, S. J.}, year={2008}, month={Jan} }
 @article{heldt_hernandez_mudiganti_gurgel_brown_carbonell_2006, title={A  colorimetric assay for viral agents that produce cytopathic effects}, volume={135}, DOI={10.1016/j.j.viromet.2006.01.022}, number={1}, journal={Journal of Virological Methods}, author={Heldt, C. L. and Hernandez, R. and Mudiganti, U. and Gurgel, P. V. and Brown, D. T. and Carbonell, R. G.}, year={2006}, pages={56–65} }
 @article{gregori_gurgel_lathrop_edwardson_lambert_carbonell_burton_hammond_rohwer_2006, title={Reduction in infectivity of endogenous transmissible spongiform encephalopathies present in blood by adsorption to selective affinity resins}, volume={368}, ISSN={["0140-6736"]}, DOI={10.1016/S0140-6736(06)69897-8}, abstractNote={Background Transmissible spongiform encephalopathies (TSE) can be contracted through blood transfusion. Selective adsorption of the causative agent from donated blood might be one of the best ways of managing this risk. In our study, affinity resin L13, which reduces brain-derived infectivity spiked into human red blood cell concentrate by around 4 log10ID50, and its equivalent, L13A, produced on a manufacturing scale, were assessed for their ability to remove TSE infectivity endogenously present in blood. Methods 500 mL of scrapie-infected hamster whole blood was leucoreduced at full scale before passage through the affinity resins. Infectivity of whole blood, leucoreduced whole blood (challenge), and the recovered blood from each flow-through was measured by limiting dilution titration. Findings Leucoreduction removed 72% of input infectivity. 15 of 99 animals were infected by the challenge, whereas none of the 96 or 100 animals inoculated with the final flow-throughs from either resin developed the disease after 540 days. The limit of detection of the bioassay was 0·2 infectious doses per mL. The overall reduction of the challenge infectivity was more than 1·22 log10ID. The results showed removal of endogenous TSE infectivity from leucoreduced whole blood by affinity ligands. The same resins adsorb normal and abnormal prion protein from human infections with variant, sporadic, and familial Creutzfeldt-Jakob disease, in the presence of blood components. Interpretation TSE affinity ligands, when incorporated into appropriate devices, can be used to mitigate the risks from TSE-infected blood, blood products, and other materials exposed to TSE infectivity.}, number={9554}, journal={LANCET}, author={Gregori, Luisa and Gurgel, Patrick V. and Lathrop, Julia T. and Edwardson, Peter and Lambert, Brian C. and Carbonell, Ruben G. and Burton, Steven J. and Hammond, David J. and Rohwer, Robert G.}, year={2006}, month={Dec}, pages={2226–2230} }
 @article{gregori_lambert_gurgel_gheorghiu_edwardson_lathrop_macauley_carbonell_burton_hammond_et al._2006, title={Reduction of transmissible spongiform encephalopathy infectivity from human red blood cells with prion protein affinity ligands}, volume={46}, ISSN={["1537-2995"]}, DOI={10.1111/j.1537-2995.2006.00865.x}, abstractNote={BACKGROUND: There is a demonstrated risk of infection by transmissible spongiform encephalopathies (TSEs) through transfusion from asymptomatic donors. Currently, blood-borne TSE infectivity cannot be detected with a diagnostic test, nor is it likely to be amenable to inactivation; however, its depletion with specific adsorp-tive ligand resins is possible. STUDY DESIGN AND METHODS: Six ligands that bind the prion protein, PrP, were selected by screening large solid-phase combinatorial chemical libraries. The selected resins were placed in columns and challenged with a unit of leukoreduced human red blood cells (RBCs) spiked with hamster brain–derived scrapie infectivity. The performance of each ligand was assessed by comparing the TSE infectivity titer in the RBCs before and after passage through each of five resin columns in series. RESULTS: Four resins were able to reduce infectivity titer by 3 to more than 4 log ID50 per mL. The reduction was not due to nonspecific matrix interactions since a chemical modification of the most effective ligand completely abolished its ability to bind infectivity (negative control). A small subfraction of the infectivity, 0.01 percent, could not be removed, even upon repeated passage through successive columns. CONCLUSION: If endogenous TSE infectivity in RBCs binds to the ligands in the same proportion as brain-derived infectivity spiked into RBCs, the four most effective ligands would remove 3 to 4 log ID50 per mL. A follow-up experiment is in progress to test whether endogenous blood-borne infectivity is also reduced.}, number={7}, journal={TRANSFUSION}, author={Gregori, Luisa and Lambert, Brian C. and Gurgel, Patrick V. and Gheorghiu, Liliana and Edwardson, Peter and Lathrop, Julia T. and MacAuley, Claudia and Carbonell, Ruben G. and Burton, Steven J. and Hammond, David and et al.}, year={2006}, month={Jul}, pages={1152–1161} }
 @article{yang_gurgel_carbonell_2005, title={Hexamer peptide affinity resins that bind the Fc region of human immunoglobulin G}, volume={66}, ISSN={["1397-002X"]}, DOI={10.1111/j.1747-0285.2006.00342.x}, abstractNote={Abstract: A family of linear hexapeptides composed of histidine on the N-terminus followed by aromatic amino acid(s) and positively charged amino acid(s) has been identified through a three-step screening of a synthetic solid phase library. These peptides were able to recognize human immunoglobulin G (HIgG) through its Fc region, and their selectivity to Fc is comparable to Protein A. This is the first known report of short peptides that are able to bind HIgG by recognizing its Fc portion. One of the ligands from the identified family, HWRGWV, was examined for its ability to isolate HIgG from complex mixtures. It was found that HWRGWV possessed the potential to purify HIgG from complete mammalian cell culture medium containing 10% fetal calf serum with purity comparable to commercially available resins, but using milder elution conditions. HWRGWV bound all HIgG subclasses and IgGs from bovine, mouse, goat, and rabbit. The broad affinity spectrum as well as its Fc recognition ability may be useful in capturing and detecting both polyclonal and monoclonal antibodies.}, journal={JOURNAL OF PEPTIDE RESEARCH}, author={Yang, H and Gurgel, PV and Carbonell, RG}, year={2005}, month={Dec}, pages={120–137} }
 @article{wang_salm_gurgel_carbonell_2005, title={Small Peptide Ligands for Affinity Separations of Biological Molecules}, DOI={10.1002/0470025018.ch3}, journal={CHEMICAL ENGINEERING TRENDS AND DEVELOPMENTS}, author={Wang, Guangquan and Salm, Jeffrey R. and Gurgel, Patrick V. and Carbonell, Ruben G.}, year={2005}, pages={63–83} }
 @article{gurgel_carbonell_swaisgood_2001, title={Identification of peptide ligands generated by combinatorial chemistry that bind alpha-lactalbumin}, volume={36}, ISSN={["0149-6395"]}, DOI={10.1081/SS-100106100}, abstractNote={α-Lactalbumin is a whey protein with high digestibility and low potential for causing allergic problems in infants, making it a strong candidate for use in infant formulas. The development of an efficient and scalable process for isolation of α-lactalbumin is necessary to allow its use on a large scale. Affinity chromatography using short peptides as ligands is a promising technique because it allows the recovery of specific proteins without the use of harsh chemicals or problems due to ligand release. In the present paper we describe the identification of the hexapeptide WHWRKR, obtained from a combinatorial library, that shows affinity for α-lactalbumin.}, number={11}, journal={SEPARATION SCIENCE AND TECHNOLOGY}, author={Gurgel, PV and Carbonell, RG and Swaisgood, HE}, year={2001}, pages={2411–2431} }
 @article{gurgel_carbonell_swaisgood_2001, title={Studies of the binding of alpha-lactalbumin to immobilized peptide ligands}, volume={49}, ISSN={["1520-5118"]}, DOI={10.1021/jf010462b}, abstractNote={The present work investigates the mechanism of binding of alpha-lactalbumin to the peptide ligand WHWRKR and its variants HWRKR and acetylated WHWRKR immobilized on a polymethacrylate chromatographic resin. The presence of two temperature-dependent binding mechanisms and one temperature-independent mechanism was demonstrated. Injections of different forms of alpha-lactalbumin (apo-alpha-lactalbumin, D87A mutant alpha-lactalbumin) displayed similar behaviors when compared to native alpha-lactalbumin, while lysozyme showed little or no binding to the WHWRKR and AcWHWRKR resins. An alternative process for isolation of alpha-lactalbumin from WPI was shown, using consecutive injections of WPI with limited elution.}, number={12}, journal={JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY}, author={Gurgel, PV and Carbonell, RG and Swaisgood, HE}, year={2001}, month={Dec}, pages={5765–5770} }
 @article{gurgel_carbonell_swaisgood_2000, title={Fractionation of whey proteins with a hexapeptide ligand affinity resin}, volume={9}, ISSN={["0923-179X"]}, DOI={10.1023/A:1011191818927}, number={6}, journal={BIOSEPARATION}, author={Gurgel, PV and Carbonell, RG and Swaisgood, HE}, year={2000}, pages={385–392} }
 @misc{hammond_carbonell_shen_gurgel_wiltshire-lyerly_burton, title={Prion protein binding materials and methods of use}, volume={7,510,848}, number={2009 Mar. 31}, author={Hammond, D. J. and Carbonell, R. G. and Shen, H. and Gurgel, P. V. and Wiltshire-Lyerly, V. and Burton, S. J.} }
 @misc{carbonell_yang_gurgel, title={Purification of immunoglobulins using affinity chromatography and peptide ligands}, volume={7,408,030}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Carbonell, R. G. and Yang, H. and Gurgel, P. V.} }