Construction of First-Principle Methodology for Predicting Shape and Size Distribution of Micelles

对生物系统的研究，如蛋白质三级结构的预测，在方法和溶剂效应上类似于胶束研究，也已经进行了。我们构建了一种混合型仿真方法。它结合了溶剂效应的RISM理论（分子流体的统计力学理论）、表面活性剂分子构象采样的蒙特卡罗模拟退火和传统的热力学方法。用几种简化的表面活性剂模型计算了临界胶束浓度、胶束形状和粒径分布。它正在被扩展到更现实的模型，以阐明为什么在非离子表面活性剂的情况下，平均胶束尺寸随着温度的升高而变大。我们提出一个简单的。对RISM理论进行了有效的桥接校正。将改进的RISM方法与Kirkwood-Buff理论相结合，计算了20种氨基酸和α-螺旋形谷氨酸寡肽的偏摩尔体积。桥梁修正大大提高了计算值与实验数据之间的一致性。三维版本的积分方程理论由于计算量大而不适用于混合型仿真方法。然而，它对于详细分析大型复杂溶质分子的微观溶剂化结构是非常有用的。作为一个例子，我们已经检查了熵排除体积效应在胶体和生物系统中的作用。特别是，它已经表明，在锁和键的空间相互作用中，仅通过熵的排除体积效应就产生了非常高的选择性。

Research for biological systems such as the prediction of tertiary structures of proteins, which is similar to the micelle research in the methodology and solvent effects, has also been performed.We have constructed a hybrid-type simulation method. It is a combination of the RISM theory (a statistical-mechanical theory for molecular fluids) for incorporating the solvent effects, the Monte Carlo simulated annealing for conformational sampling for a set of surfactant molecules, and a conventional thermodynamic method. It has been demonstrated for several simplified model surfactants to calculate the critical micelle concentration, micelle shape, and size distribution. It is being extended to more realistic models to elucidate why the average micelle size becomes larger as the temperature increases in cases of nonionic surfactants.We propose a simple. efficient bridge correction of the RISM theory. By combining the modified RISM method with the Kirkwood-Buff theory, the partial molar volume is calculated for the 20 amino acids and for oligopeptides of glutamic acids in extended and α-helix conformations. The bridge correction drastically improves agreement between the calculated values and the experimental data.The three-dimensional version of the integral equation theory is not applicable to the hybrid-type simulation method due to the heavy computational burden. However, it is very useful in detailed analyses of the microscopic solvation structure of a large, complicated solute molecule. As an example, we have examined the roles of the entropic excluded-volume effects in colloidal and biological systems. In particular, it has been shown that remarkably high selectivity arises in the lock and key steric interaction between macromolecules by the entropic excluded-volume effects alone.