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Main-chain Structure (main-chain + structure)
Selected AbstractsAn efficient algorithm for multistate protein design based on FASTERJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2010Benjamin D. Allen Abstract Most of the methods that have been developed for computational protein design involve the selection of side-chain conformations in the context of a single, fixed main-chain structure. In contrast, multistate design (MSD) methods allow sequence selection to be driven by the energetic contributions of multiple structural or chemical states simultaneously. This methodology is expected to be useful when the design target is an ensemble of related states rather than a single structure, or when a protein sequence must assume several distinct conformations to function. MSD can also be used with explicit negative design to suggest sequences with altered structural, binding, or catalytic specificity. We report implementation details of an efficient multistate design optimization algorithm based on FASTER (MSD-FASTER). We subjected the algorithm to a battery of computational tests and found it to be generally applicable to various multistate design problems; designs with a large number of states and many designed positions are completely feasible. A direct comparison of MSD-FASTER and multistate design Monte Carlo indicated that MSD-FASTER discovers low-energy sequences much more consistently. MSD-FASTER likely performs better because amino acid substitutions are chosen on an energetic basis rather than randomly, and because multiple substitutions are applied together. Through its greater efficiency, MSD-FASTER should allow protein designers to test experimentally better-scoring sequences, and thus accelerate progress in the development of improved scoring functions and models for computational protein design. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Synthesis of novel moisture-curable polyurethanes end-capped with trialkoxysilane and their application to one-component adhesivesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2007Yukihiro Nomura Abstract Novel silane endcappers and novel polyurethanes end-capped with trimethoxysilane (silylated polyurethanes) were developed as water-curable materials in which the curing reaction occurred under humid conditions in the presence of dioctyltin diversatate as a curing catalyst. A variety of amine-terminated trimethoxysilane compounds were synthesized by the Michael addition reaction of commercially available 3-aminopropyltrimethoxysilane with acrylates, and the resulting silane endcappers were used to react with isocyanate-terminated polyurethanes, providing the silylated polyurethanes. The moisture-curable silylated polyurethanes were used for the preparation of novel one-component and solvent-free adhesives. The evaluated properties were the curing speed, the tensile shear bond strength, and the adherence to some substrates. The longer alkyl chains of the silane endcappers derived from various acrylates led to a slower curing speed, lower tensile strength at break, and longer elongation at break of the silylated polyurethanes. The tensile shear bond strength of the silylated polyurethane-based adhesive decreased with decreasing the trimethoxysilane end-capping ratio, whereas an increase in the adherence was observed. The adherence to the acrylic substrate was improved by changes in the main-chain structure of the polyurethane based on the composition of poly(propylene oxide) and poly(ethylene oxide). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2689,2704, 2007 [source] Synthesis of Substituted Polyacetylenes Grafted with Polystyrene Chains by the Macromonomer Method and Their CharacterizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 11 2006Wei Zhang Abstract Summary: A macromonomer (1) consisting of a polystyrene chain and an acetylenic chain end (,=,2,500, ,=,1.20) was prepared by atom transfer radical polymerization. Macromonomer 1 was copolymerized with phenylacetylene (2) and propargyl 2-bromopropionate (3) by using Rh catalysts at varying feed ratios from 10 to 50 wt.-% to produce graft copolymers 4 and 5, respectively. The synthesized copolymers 4 and 5 possessed a conjugated polyene main-chain and polystyrene grafts, and contained 11,34 and 16,77 wt.-% of polystyrene with of 61,400,144,000 and 19,300,22,500, respectively. Graft copolymer 4 was a yellow solid and thermally stable up to 225,°C, whereas 5 was a brown solid with weight loss beginning at 175,°C. Graft copolymers 4 and 5 exhibited UV-vis absorption edges at 525 and 425 nm, respectively, which are attributable to the conjugated main-chain structure. Copolymerization of the acetylene-terminated polystyrene-based macromonomer with monosubstituted acetylenes. [source] Shrinking Behavior of Surfactant-Grafted Thermosensitive Gels and the Mechanism of Rapid ShrinkingMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2008Kosuke Okeyoshi Abstract Surfactant-grafted hydrogels with a fast response to temperature were prepared. In order to clarify the mechanism of rapid shrinking, the effects of the grafted surfactant and the homogeneity of the main chain were investigated. Poly(NIPAAm- co -S180A) gels prepared using a chemical cross-linker (bis-PNS gels) exhibited rapid shrinking, as did PNS gels prepared by , -ray irradiation (, -PNS gels). This suggested that the rapid shrinking of the PNS gel did not depend on the homogeneity of the main-chain structure. The shrinking kinetics of the bis-PNS gels depended on the amount of the introduced surfactant, which means that shrinking is enhanced by micelle formation as a dynamic driving force. From the analysis by dynamic light scattering (DLS) and scanning microscopic light scattering (SMILS), it was suggested that the micelle structure, which induced rapid shrinking, existed in the bis-PNS gel. [source] | ||||||||||