Theoretical Study of Biopolymer Gelation

本课题以氢键的相关性和序列性为研究对象，采用热力学-力学方法，研究了多糖和蛋白质的热可逆凝胶化过程、螺旋结构和拉链状交联结构。并利用粗粒珠弹簧模型链进行了分子动力学和蒙特卡罗模拟，以补充理论研究。主要结果如下：1.螺旋缔合引起的卷曲/受阻转变和甘氨酰化我们将螺旋缔合分为两类：单螺旋的多重缔合和多螺旋缔合。当螺旋的成核和生长通过以下交联缔合比较快时，例如k-角叉菜胶溶液的凝胶化，我们推导了温度-浓度相平面上的溶胶/凝胶转变曲线，并与实验进行了比较。我们建立了一种新的方法，同时估计亩， ...更多信息 重复性和交联的长度（增强的Eldridge-Ferry方法）。结果表明，对于双螺旋连接，凝胶网络的结构从I型（由短螺旋交联的无规线圈）到II型（由短无规线圈连接的长棒状螺旋），从II型到分离的螺旋对。理论计算的CD强度随温度的变化与文献报道的实验数据吻合较好。2.侧链螺旋形成的凝胶化通过理论和MC模拟研究了带有侧链螺旋形成多糖的水溶性聚合物的热可逆凝胶化。3.序列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序列水化、序列氢键（拉链交联）凝胶化、成环等过程。结果与文献报道的相图进行了比较。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