“Setting paint” analogy for the hydrophobic self‐association of tropoelastin into elastin‐like hydrogel

Alkaline tropoelastin solutions (pH 11) were optically clear at low temperatures, but a firm gel formed when the temperature was raised to 37°C. Reversion to a clear solution took place if the temperature was lowered to below 20°C within less than 2 h, but not if 37°C was maintained for several hours. The precipitated elastin‐like hydrogel thus formed did not visually redissolve at low temperatures. Tropoelastin hydrogel was stable to subsequent washings with alkaline solution at 37°C, but at 4°C some hydrogel redissolved showing that association is at least partly reversible. Washing the hydrogel with neutral 8M urea solution at 4°C dissolved less than 10% of tropoelastin in 24 h. We characterized this phenomenon by combining temperature‐controlled light microscopy analysis, ¹H NMR spectroscopy (temperature, diffusion, and relaxation time studies), and UV‐absorption‐based concentration measurements. The self‐association of tropoelastin at pH 11 is due to hydrophobic interactions in an emulsion‐like system in which the spherules coalesce in a manner like a water‐based latex paint that forms a durable hydrophobic sheet as water and the organic solvent evaporate. In the present case, the sedimentation and entanglement of the tropoelastin porous sheets means that reverse dissolution is a kinetically slow process. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 321–330, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Molecular dynamics (MD) simulations of VIP and PACAP27

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase‐activating polypeptide‐27 (PACAP27) are members of the secretin‐glucagon family containing 28 and 27 residues, respectively. NMR spectroscopy studies suggest that the N‐terminus exhibit consecutive β‐turns whereas the central and C‐terminal parts of the VIP molecule have been characterized as being two α‐helices. In contrast, similar studies carried out on PACAP suggest that the shortest active peptide segment PACAP27 in the presence of trifluoroethanol (TFE) exhibits a disordered N‐terminal domain followed by a α‐helix expanding residues 9–26 with a discontinuity between residues 20 and 21. In the present study, a series of MD trajectories of VIP and PACAP27 were carried out using two different implicit models of the solvent: the Generalized Born that use an effective Born radii described by Onufriev, Bashford, and Case (GB^OBC) and the Hawkins, Cramer, and Truhlar approximation (GB^HCT) and two different force fields: AMBER ff99 and a modified version of the latter described by Sorin and Pande (Biophys J 2005, 88, 2472‐2493), ff99SP. Comparison of the structures obtained from the MD trajectories and those derived from the NMR studies in the literature indicates that the GB^OBC method is more efficient in the exploration of the conformational space and presents a higher agreement with the experimental structure of VIP and PACAP27 in TFE. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 391–400, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Glycerol‐induced folding of unstructured disulfide‐deficient lysozyme into a native‐like conformation

2SS[6‐127,64‐80] variant of lysozyme which has two disulfide bridges, Cys6‐Cys127 and Cys64‐Cys80, and lacks the other two disulfide bridges, Cys30‐Cys115 and Cys76‐Cys94, was quite unstructured in water, but a part of the polypeptide chain was gradually frozen into a native‐like conformation with increasing glycerol concentration. It was monitored from the protection factors of amide hydrogens against H/D exchange. In solution containing various concentrations of glycerol, H/D exchange reactions were carried out at pH* 3.0 and 4°C. Then, ¹H‐¹⁵N‐HSQC spectra of partially deuterated protein were measured in a quenching buffer for H/D exchange (95% DMSO/5% D₂O mixture at pH* 5.5 adjusted with dichloroacetate). In a solution of 10% glycerol, the protection factors were nearly equal to 10 at most of residues. With increasing glycerol concentration, some selected regions were further protected, and their protection factors reached about a 1000 in 30% glycerol solution. The highly protected residues were included in A‐, B‐, and C‐helices and β3‐strand, and especially centered on Ile 55 and Leu 56. In 2SS[6‐127,64‐80], long‐range interactions were recovered due to the preferential hydration by glycerol in the hydrophobic box of the α‐domain. Glycerol‐induced recovering of the native‐like structure is discussed from the viewpoint of molten globules growing with the protein folding. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 665–675, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Puckering transitions of pseudoproline residues

The puckering transitions of pesudoprolines such as oxazolidine and thiazolidine residues (Oxa and Thz dipeptides) with trans and cis prolyl peptide bonds were explored by optimizations along the endocyclic torsion angle χ¹ using quantum‐chemical methods in the gas phase and in water. The overall shapes of the potential energy surfaces for Oxa and Thz dipeptides in the gas phase and in water are similar to those for the Pro dipeptide, although there are some differences in relative stabilities of local minima and in barriers to puckering transition. On the whole, the barriers to puckering transition for Oxa and Thz dipeptides are computed to be 0.8–3.2 kcal/mol at the B3LYP/6‐311++G(d,p) level in the gas phase and in water, which are lower by 0.5–1.9 kcal/mol than those for the Pro dipeptide. The n → σ* interactions for the delocalization of the lone pair of the prolyl amide nitrogen into the antibonding orbitals that are anti to the lone pair appear to play a role in stabilizing the nonplanar puckered transition states over the corresponding planar structures. The calculated barriers indicate that the down‐to‐up puckering transition can proceed in the orders Pro < Oxa < Thz in the gas phase and Pro ≈ Oxa < Thz in water. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 444–455, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Electrostatic interactions with histone tails may bend linker DNA in chromatin

Is linker DNA bent in the 30‐nm chromatin fiber at physiological conditions? We show here that electrostatic interactions between linker DNA and histone tails including salt condensation and release may bend linker DNA, thus affecting the higher order organization of chromatin. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 20–28, 2006 This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Thermodynamically controlled supramolecular polymerization of cytochrome b562

A hemoprotein‐based supramolecular polymer that has a covalently linked heme moiety on the protein surface has been constructed based on interprotein heme–heme pocket interactions of the chemically modified apocytochrome b₅₆₂ ( 1 ‐H63C). The thermodynamic properties of the polymer have been investigated by means of size exclusion chromatography, UV–vis spectroscopy, and circular dichroism spectroscopy. The results indicate that, as with other synthetic systems reported so far, the 1 ‐H63C hemoprotein assembly is thermodynamically controlled in aqueous solution: the degree of polymerization is dependent on the 1 ‐H63C concentration and is modulated by the addition of the end‐capping units, native heme, and/or apocytochrome b₅₆₂ mutant (apoH63C). These properties suggest a potential use for the hemoprotein self‐assembly in preparation of stimuli‐responsive functional nanobiomaterials. © 2008 Wiley Periodicals, Inc. Biopolymers 91: 194–200, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

The immunosuppressive activity and solution structures of ubiquitin fragments

Recently, ubiquitin was suggested as a promising anti‐inflammatory protein therapeutic. We found that a peptide fragment corresponding to the ubiquitin^50–59 sequence (LEDGRTLSDY) possessed the immunosuppressive activity comparable with that of ubiquitin. CD and NMR spectroscopies were used to determine the conformational preferences of LEDGRTLSDY in solution. The peptide mixture, obtained by pepsin digestion of ubiquitin, was even more potent than the intact protein. Although the peptide exhibited a well‐defined conformation in methanol, its structure was distinct from the corresponding 50–59 fragment in the native ubiquitin molecule. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 423–431, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Kinetics of the self‐aggregation and film formation of poly‐L‐proline at high temperatures explored by circular dichroism spectroscopy

Poly‐L ‐proline has been used as a model system for various purposes over a period of more than 60 years. Its relevance among the protein/peptide community stems from its use as a reference system for determining the conformational distributions of unfolded peptides and proteins, its use as a molecular ruler, and from the pivotal role of proline residues in conformational transitions and protein–protein interactions. While several studies indicate that polyproline can aggregate and precipitate in aqueous solution, a systematic study of the aggregation process is still outstanding. We found, by means of UV‐circular dichroism and IR measurements, that polyproline is predominately monomeric at room temperature at millimolar concentrations. Upon heating, the polypeptide stays in its monomeric state until the temperature reaches a threshold of ca. 60°C. At higher temperatures, the peptide aggregates as a film on the inside surface of the employed cuvette. The process proceeds on a time scale of 10³ s and can best be described by a bi‐exponential relaxation function. The respective CD and IR spectra are qualitatively different from the canonical spectra of polyproline in aqueous solution, and are indicative of a highly packed state. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 451–457, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Ultrastructure of ulvan: A polysaccharide from green seaweeds

Ultrastructural analysis of the gel forming green seaweed sulfated polysaccharide ulvan revealed a spherical‐based morphology (10–18 nm diameter) more or less aggregated in aqueous solution. At pH 13 in TBAOH (tetrabutyl ammonium hydroxyde) or NaOH, ulvan formed an open gel‐like structure or a continuous film by fusion or coalescence of bead‐like structures, while in acidic pH conditions, ulvan appeared as dispersed beads. Low concentrations of sodium chloride, copper or boric acid induced the formation of aggregates. These results highlight the hydrophobic and aggregative behavior of ulvan that are discussed in regard to the peculiar gel formation and the low intrinsic viscosity of the polysaccharide in aqueous solution. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 652–664, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Changes in the quaternary structure of amelogenin when adsorbed onto surfaces

Amelogenin is a unique protein that self‐assembles into spherical aggregates called “nanospheres” and is believed to be involved in controlling the formation of the highly anisotropic and ordered hydroxyapatite crystallites that form enamel. The adsorption behavior of amelogenin onto substrates is of great interest because protein‐surface interactions are critical to its function. We report studies of the adsorption of amelogenin onto self‐assembled monolayers containing COOH end group functionality as well as single crystal fluoroapatite, a biologically relevant surface. We found that although our solutions contained only nanospheres of narrow size distribution, smaller structures such as dimers or trimers were observed on the hydrophilic surfaces. This suggests that amelogenin can adsorb onto surfaces as small structures that “shed” or disassemble from the nanospheres that are present in solution. © 2008 Wiley Periodicals, Inc. Biopolymers 91: 103–107, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Limited proteolysis analysis of the ribosome is affected by subunit association

Our understanding of the structural organization of ribosome assembly intermediates, in particular those intermediates that result from misfolding leading to their eventual degradation within the cell, is limited because of the lack of methods available to characterize assembly intermediate structures. Because conventional structural approaches, such as NMR, X‐ray crystallography, and cryo‐EM, are not ideally suited to characterize the structural organization of these flexible and sometimes heterogeneous assembly intermediates, we have set out to develop an approach combining limited proteolysis with matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) that might be applicable to ribonucleoprotein complexes as large as the ribosome. This study focuses on the limited proteolysis behavior of appropriately assembled ribosome subunits. Isolated subunits were analyzed using limited proteolysis and MALDI‐MS and the results were compared with previous data obtained from 70S ribosomes. Generally, ribosomal proteins were found to be more stable in 70S ribosomes than in their isolated subunits, consistent with a reduction in conformational flexibility on subunit assembly. This approach demonstrates that limited proteolysis combined with MALDI‐MS can reveal structural changes to ribosomes on subunit assembly or disassembly, and provides the appropriate benchmark data from 30S, 50S, and 70S proteins to enable studies of ribosome assembly intermediates. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 410–422, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Importance of the spatial display of charged residues in heparin–peptide interactions

Many studies have examined consensus sequences required for protein‐glycosaminoglycan interactions. Through the synthesis of helical heparin binding peptides, this study probes the relationship between spatial arrangement of positive charge and heparin binding affinity. Peptides with a linear distribution of positive charge along one face of the α‐helix had the highest affinity for heparin. Moving the basic residues away from a single face resulted in drastic changes in heparin binding affinity of up to three orders of magnitude. These findings demonstrate that amino acid sequences, different from the known heparin binding consensus sequences, will form high affinity protein‐heparin binding interactions when the charged residues are aligned linearly. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 290–298, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Complex biopolymeric systems at stalk/epicuticular wax plant interfaces: A near infrared spectroscopy study of the sugarcane example

Naturally occurring macromolecules present at the epicuticular wax/stalk tissue interface of sugarcane were investigated using near infrared spectroscopy (NIRS). Investigations of water, cellulose, and wax‐cellulose interrelationships were possible using NIRS methods, where in the past many different techniques have been required. The sugarcane complex interface was used as an example of typical phenomena found at plant leaf/stalk interfaces. This detailed study showed that sugarcane cultivars exhibit spectral differences in the CH_n, water OH, and cellulose OH regions, reflecting the presence of epicuticular wax, epidermis, and ground tissue. Spectrally complex water bands (5276 cm^?1 and 7500–6000 cm^?1) were investigated via freeze‐drying experiments which revealed sequentially a complex band substructure (7500–6000 cm^?1), a developing weak H‐bonding system (～7301 cm^?1), and strong H‐bonding (～7062 cm^?1) assigned to water—cellulose interactions. Principal component analysis techniques clarified complex band trends that developed during the desorption experiment. Bands from wax‐free stalk were minimized in the 4327–4080 cm^?1 region (C? H_n vibrational modes associated with long chain fatty compounds), while bands from the stalk tissue (particularly lignin and moisture) became more pronounced. This work is a comprehensive guide to similar studies by scientists involved in a variety of plant and fiber research fields. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 642–651, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Solvent interactions with the Trp-cage peptide in 35% ethanol-water

Intermolecular NOE experiments have been used to explore interactions of water and ethanol molecules in 35% ethanol/65% water (v/v) with the peptide Trp-cage at temperatures from 5 to 25 degrees C. Magnetic dipole-dipole cross-relaxation terms sigma(HH) (NOE) and sigma(HH) (ROE) for interaction of solvent components with spins of the peptide suggest that ethanol molecules associate with backbone atoms for times of the order of nanoseconds at 5 degrees C. Formation of peptide-ethanol complexes can also account for the larger-than-expected values of cross-relaxation terms at higher temperatures. Hydrocarbon side chains of the peptide do not appear to experience such interactions with ethanol. Cross relaxation resulting from water-peptide interactions are consistent with long-lived water interactions with the backbone atoms. Water cross relaxation with nonpolar side chains of the peptide (Leu2, Ile4, Leu7, and proline residues) are only those expected for bulk solvent. However, long-lived association of both water and ethanol with the polar side chains of Tyr3 and Trp6 is indicated by the data. (c) 2008 Wiley Periodicals, Inc. Biopolymers 89: 862-872, 2008.This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com.     

The effect of deuterium oxide on the stability of the collagen model peptides H‐(Pro‐Pro‐Gly)10‐OH,H‐(Gly‐Pro‐4(R)Hyp)9‐OH,and Type I collagen

The collagen triple helix has a larger accessible surface area per molecular mass than globular proteins, and therefore potentially more water interaction sites. The effect of deuterium oxide on the stability of collagen model peptides and Type I collagen molecules was analyzed by circular dichroism and differential scanning calorimetry. The transition temperatures (T_m) of the protonated peptide (Pro‐Pro‐Gly)₁₀ were 25.4 and 28.7°C in H₂O and D₂O, respectively. The increase of the T_m of (Pro‐Pro‐Gly)₁₀ measured calorimetrically at 1.0°C min^?1 in a low pH solution from the protonated to the deuterated solvent was 5.1°C. The increases of the T_m for (Gly‐Pro‐4(R)Hyp)₉ and pepsin‐extracted Type I collagen were measured as 4.2 and 2.2°C, respectively. These results indicated that the increase in the T_m in the presence of D₂O is comparable to that of globular proteins, and much less than reported previously for collagen model peptides [Gough and Bhatnagar, J Biomol Struct Dyn 1999, 17, 481–491]. These experimental results suggest that the interaction of water molecules with collagen is similar to the interaction of water with globular proteins, when the ratio of collagen to water is very small and collagen is monomerically dispersed in the solvent. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 93–101, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Revisiting “reverse hydrophobic effect”: Applicable only to coil mutations at the surface

In a seminal paper, Pakula and Sauer (Nature, 1990, 344, 363–364) demonstrated that the increase in side‐chain hydrophobicity has a reverse relationship with protein stability. We have addressed this problem with several examples of mutants that span at different locations in protein structure based on secondary structure and solvent accessibility. We confirmed that the stability change upon single coil mutation at exposed region is reversely correlated with hydrophobicity with a single exception. In addition, we found the existence of such relationship in partially buried coil mutants. The stability of exposed helical mutants is governed by conformational properties. In buried and partially buried helical and strand mutants properties reflecting hydrophobicity have direct relationship with stability, whereas an opposite relationship was obtained with entropy and flexibility. The structural analysis of partially buried/exposed mutants showed that the surrounding residues are important for the stability change upon mutation. These results provide insights to understand the general behavior for the stability of proteins upon amino acid substitutions. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 591–599, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Physicochemical studies on the biopolymer inulin: A critical evaluation of its self‐aggregation,aggregate‐morphology,interaction with water,and thermal stability

Physicochemical properties viz., aggregation, molar mass, shape, and size of chicory inulin in solution were determined by fluorimetry, DLS, SLS, TEM, and viscometry methods. The thermal stability of the biopolymer was examined by TGA, DTA, and DSC measurements. The water vapor adsorption of desiccated inulin was also studied by the isopiestic method, and the data were analyzed in the light of the BET equation. On the basis of the obstruction to ion conductance by the inulin aggregates in solution and analysis of the data, the extent of hydration of inulin in solution was estimated. The result was coupled with the intrinsic viscosity, [η], of inulin to ascertain the shape of the biopolymer aggregates in aqueous solution. The critical aggregation concentration (cac) of inulin in aqueous as well as in salt solution was assessed by fluorimetry. The weight average molar mass, , of inulin monomer and its aggregate was found to be 4468 and 1.03 × 10⁶ g/mol, respectively, in aqueous solution. This aggregated mass was 2.4 × 10⁶ g/mol in 0.5M NH₄SCN solution. The [η] values of the soft supramolecular aggregates in solution (without and with salt) were small and comparable with globular proteins evidencing spherical geometry of the biopolymer aggregates as supported by the TEM results. In DMSO, rod‐like aggregates of inulin was found by the TEM study. The [η] of the biopolymer in the DMSO medium was therefore, higher than that in the aqueous medium. Unlike aqueous medium, the aggregation in DMSO was not associated with a cac. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 687–699, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Direct real‐time imaging of protein adsorption onto hydrophilic and hydrophobic surfaces

Atomic force microscopy has been used to follow in real time the adsorption from solution of two of the gliadin group of wheat seed storage proteins onto hydrophilic (mica) and hydrophobic (graphite) surfaces. The liquid cell of the microscope was used initially to acquire images of the substrate under a small quantity of pure solvent (1% acetic acid). Continuous imaging as an injection of gliadin solution entered the liquid cell enabled the adsorption process to be followed in situ from zero time. For ω‐gliadin, a monolayer was formed on the mica substrate during a period of ～2000 s, with the protein molecules oriented in parallel to the mica surface. In contrast, the ω‐gliadin had a relatively low affinity for the graphite substrate, as demonstrated by slow and weak adsorption to the surface. With γ‐gliadin, random deposition onto the mica surface was observed forming monodispersed structures, whereas on the graphite surface, monolayer islands of protein were formed with the protein molecules in a perpendicular orientation. Sequential adsorption experiments indicated strong interactions between the two proteins that, under certain circumstances, caused alterations to the surface morphologies of preadsorbed species. The results are relevant to our understanding of the interactions of proteins within the hydrated protein bodies of wheat grain and how these determine the processing properties of wheat gluten and dough. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 74–84, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Heating‐induced conformational change of a novel β‐(1→3)‐D‐glucan from Pleurotus geestanus

Recently, we isolated and purified a neutral polysaccharide (PGN) from edible fungus Pleurotus geestanus. Its structure was characterized by a range of physical–chemical methods, including high performance anion exchange chromatography, uronic acid, and protein analyses, size exclusion chromatography with ultraviolet, refractive index and light scattering detectors, and nuclear magnetic resonance. Our results revealed that PGN is a novel β‐(1→3)‐D ‐glucan with glucose attached to every other sugar residues at Position 6 in the backbone. It has a degree of branching of 1/2. Such structure is different from typical β‐(1→3)‐D ‐glucans schizophyllan and lentinan in which DB is 1/3 and 2/5, respectively. Rheological study showed a very interesting melting behavior of PGN in water solution: heating PGN in water leads to two transitions, in the range of 8–12.5°C and 25–60°C, respectively. The melting behavior and conformational changes were characterized by rheometry, micro‐differential scan calorimetry, atomic force microscopy, static and dynamic light scattering at different temperatures. The first heating‐induced transition corresponds to the disintegration of polymer bundles into small helical clusters, resembling the heating‐induced dissociation of SPG in water at 7°C; the second one might correspond to the dissociation of helical strands to individual chains. The ability of PGN to undergo a conformation/viscosity transition in water upon heating is very valuable to immobilize cells or enzymes or therapeutic DNA/RNA, which makes PGN a potentially useful biomaterial. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 121–131, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Interaction of α‐gliadin with polyanions: Design considerations for sequestrants used in supportive treatment of celiac disease

Copolymers of sodium 4‐styrene sulfonate (SS) and hydroxyethyl methacrylate (HEMA) were investigated as sequestrants of α‐gliadin, a gluten protein, for the treatment of gluten intolerance. The interactions of α‐gliadin with poly(SS) and poly(HEMA‐co‐SS) with 9 and 26 mol% SS content were studied at gastric (1.2) and intestinal (6.8) pH using circular dichroism and measurements of turbidity, dynamic light scattering and zeta potential. The interactions and their influence on α‐gliadin secondary and aggregated structures depended mainly on the ratio of polymer negative and protein positive charges at pH 1.2, and on polymer SS content at polymer concentrations providing in excess of negative charges at either pH. Poly(SS) could not form complex particles with α‐gliadin in a sufficient excess of negative charges. Copolymerization with HEMA enhanced the formation of complex particles. Poly(HEMA‐co‐SS) with intermediate SS content was found to be the most effective sequestrant for α‐gliadin. This study provides insight into design considerations for polymer sequestrants used in the supportive treatment of celiac disease. © 2009 Wiley Periodicals, Inc. Biopolymers 93:418–428, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com