Theoretical Study of Biopolymer Gelation

本课题着眼于氢键的相关性和顺序性，采用统计力学方法研究了多糖和蛋白质的热可逆凝胶化、其螺旋的形成以及拉链状交联点的结构。利用粗晶钢珠弹簧模型链进行了分子动力学和蒙特卡罗模拟，补充了理论研究的不足。主要研究结果如下：1.螺旋的螺旋/螺旋转变和螺旋缔合凝胶化我们将螺旋的缔合分为两种不同的类型：单螺旋的多重缔合和多螺旋的缔合。当螺旋的成核和生长较快时，例如k-卡拉胶溶液的凝胶化，我们在温度-浓度相平面上推导了溶胶/凝胶转变曲线，并与实验进行了比较。我们建立了一种同时估计Mu…的新方法更多的多重性和交叉链接的长度(增广的Eldridge-Ferry方法)。结果表明，对于双螺旋连接，凝胶网络结构由I型(由短螺旋交联的无规螺旋)向II型(由短无规螺旋连接的长棒状螺旋)转变，并由II型转变为分离的螺旋对。2.侧链螺旋的凝胶作用研究了侧链螺旋形成多糖的水溶性聚合物的热可逆凝胶行为。顺序氢键利用缔合聚合物溶液理论和MC模拟方法研究了水溶性聚合物的顺序水合作用(PNIPAM)、顺序氢键凝胶化(拉链交联)、成环作用等。结果与文献报道的相图进行了比较。较少

Focusing on the correlation and sequential property of hydrogen bonds, this project studied thermoreversible gelation of polysaccharides and proteins, their helix formation, and structure of zipper-like crosslink junctions by statistical-mechanical method. It also carried out Molecular Dynamics- and Monte Carlo simulation by using coarse-grained bead-spring model chains to compliment theoretical study. The main results obtained are summarized as follow :1.Coil/Helix Transition and Gelation by Association of HelicesWe classified association of helices into two different categories : multiple association of single helices and association by multiple helices. When nucleation and growth of helices are fast compared by the following cross-linking association, for instance gelation of k-carrageenan solution, we derived the sol/gel transition curve on the temperature-concentration phase plane and compared with the experiments. We have established a new method to simultaneously estimate the mu … More ltiplicity and the length of cross-links (Augmented Eldridge-Ferry method). It was shown that, for double helical junctions, the structure of the gel networks changes from TypeI (random coils cross-linked by short helices) to TypeII (long rod-like helices connected by short random coils), and from TypeII to separated helical pairs. The theoretically calculated CD intensity as a function of the temperature agreed well with the reported experimental data.2.Gelation by Side-Chain HelicesThermoreversible gelation of water-soluble polymers carrying side-chain helix-forming polysaccharides was studied by theory and MC simulation. The splicing force of coiled-coil (supercoil) was calculated to estimate elasticity of the gels.3.Sequential Hydrogen BondsSequential hydration of water-soluble polymers (PNIPAM), gelation by sequential hydrogen bonds (zipper cross-links), loop formation, etc were studied by theory of associating polymer solutions and by MC simulations. The results were compared by the phase diagrams reported in the literature. Less