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

对生物体系的研究，如预测蛋白质的三级结构，在方法学和溶剂效应上类似于胶束研究，我们构建了一种杂交型模拟方法。它结合了RISM理论(分子流体的统计力学理论)，用于考虑溶剂效应的RISM理论，用于表面活性剂分子构象采样的蒙特卡罗模拟退火法，以及传统的热力学方法。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。它正被扩展到更现实的模型，以解释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。RISM理论的有效桥式修正。将改进的RISM方法与Kirkwood-Buff理论相结合，计算了扩展构象和α-螺旋构象中的20个氨基酸和谷氨酸寡肽的偏摩尔体积。电桥修正大大提高了计算值与实验值之间的一致性。由于计算负担较大，三维版本的积分方程组理论不适用于混合型模拟方法。然而，它对于详细分析大而复杂的溶质分子的微观溶剂化结构是非常有用的。作为一个例子，我们研究了熵排除体积效应在胶体和生物体系中的作用。特别是，研究表明，仅通过熵排除体积效应，大分子之间的锁键空间相互作用就会产生非常高的选择性。

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.