College of Chemistry and Materials Science, Inner Mongolia University for Nationlities, Tongliao Inner Mongolia 028043, China.
College of Chemistry and Chemical Engineering, Bohai University, Jinzhou, Liaoning 121013, China.
J Phys Chem B. 2020 Mar 5;124(9):1806-1816. doi: 10.1021/acs.jpcb.0c00717. Epub 2020 Feb 21.
Nonmonotonic composition dependence is often observed for numerous properties in the aqueous mixtures of small amphiphilic molecules. The molecular picture underlying this structure-activity relationship, however, remains largely elusive. We herein studied water reorientation dynamics in the aqueous mixture of dimethyl sulfoxide (DMSO), which has a significant nonmonotonic composition dependence, using molecular dynamic simulation and an extended molecular jump model. The analysis indicates that this nonideal behavior is driven by the collective frame diffusion component of water reorientation, which decelerates in the water-rich regime because of the strengthened hydrogen bonds and accelerates in the water-poor regime as the hydrogen bonding network is broken into smaller aggregates. The current work therefore connects the microheterogeneity in the solvation structure of DMSO-water with its nonmonotonic hydration dynamics and sheds new light on how microsegregation leads to the multiscale hydration nonideality in general.
在小分子两亲性分子的水溶液中，经常观察到许多性质的非单调组成依赖性。然而，这种结构-活性关系的分子图像在很大程度上仍然难以捉摸。本文使用分子动力学模拟和扩展的分子跳跃模型研究了二甲基亚砜（DMSO）水溶液中水的重取向动力学，DMSO 的水溶液具有显著的非单调组成依赖性。分析表明，这种非理想行为是由水重取向的集体框架扩散分量驱动的，在富水区域由于氢键的增强而减速，在贫水区域由于氢键网络断裂成更小的聚集体而加速。因此，目前的工作将 DMSO-水的溶剂化结构中的微观不均匀性与其非单调水合动力学联系起来，为微观分相如何导致普遍的多尺度水合非理想性提供了新的认识。
