Interfacial Water from Molecular to Mesoscopic Scale

加州大学旧金山分校的Alenka Luzar得到了理论和计算化学计划的支持，该计划的理论研究旨在评估不同长度尺度上受限环境中水动力学的时间尺度，从氢键动力学的分子事件到介观尺度上的表面诱导蒸发动力学。在分子水平上，将发展一种新的方法来分析氢键动力学，并将其应用于选定的氨基酸和不同链长的丙氨酸基寡肽的溶液。这项工作将利用形式理论和分子动力学模拟的组合，并将涉及与中子散射实验者的直接合作。在介观尺度上，强大的伞形采样/蒙特卡罗算法的发展，与承压水系统的粗粒模型相结合，将能够计算在增加表面分离时毛细蒸发的活化势垒。这项工作的目的是提取势垒高度的标度律，以便弥合宏观测量和有限尺寸模型系统之间的差距。最后，在一个相关的项目中，将在分子动力学模拟中探索疏水口袋中自发的液-汽微相转变的发生。这项研究的结果预计将影响与界面水和疏水性的动态方面有关的学科，从胶体和材料科学到生物物理学。在有限几何条件下理解水动力学的分子方面是生物物理和细胞生物学中各种问题的核心。这项研究预计将对水的影响很重要的一些领域产生影响，从开发新的生物活性化合物和改进的光纤到研究生物结构，如蛋白质和纳米技术中研究的自组装材料。此外，研究成果将有助于设计具有最佳除湿能力的表面。这种表面在实际应用中很有希望，例如防雨涂料。

Alenka Luzar of the University of California, San Francisco, is supported by the Theoretical and Computational Chemistry Program for theoretical research directed toward assessing time scales of water dynamics in restricted environments on different length scales ranging from molecular events of hydrogen bond dynamics to kinetics of surface-induced evaporation on a mesoscopic scale. On the molecular scale, a new methodology to analyze hydrogen bond kinetics will be developed and applied to solutions of selected amino acids and alanine-based oligopeptides with varying chain length. This effort will utilize a combination of formal theory and molecular dynamics simulations, and will involve direct collaboration with neutron scattering experimentalists. On mesoscopic scales, the development of powerful umbrella sampling/Monte Carlo algorithms, in conjunction with a coarse-grained model of confined aqueous systems, will enable calculations of activation barriers for capillary evaporation at increased surface separations. This effort aims to extract a scaling law for the barrier height in order to bridge the gap between macroscopic measurements and limited-size model systems. Finally, in a related project, the occurrence of spontaneous liquid-vapor microphase transitions in a hydrophobic pocket will be explored in molecular dynamics simulations. Outcomes from this research are expected to impact disciplines concerned with dynamic aspects of interfacial water and hydrophobicity, ranging from colloids and materials science to biophysics. Understanding the molecular aspects of water dynamics in restricted geometries is central to variety of problems in biophysics and cell biology. This research is expected to impact a number of fields where the effects of water are important, from the development of new bioactive compounds and improved optical fibers to research into biological structures such as proteins and self-assembling materials studied in nanotechnology. As well, research outcomes will assist in the design of surfaces that have optimized dewetting ability. Such surfaces are promising for practical applications such as rain-repellent coatings.