水分子作用下的手性分子变旋及氢键诱导手性转移

The structure and properties of chiral molecules, especially their environmental dependence, are prerequisites for understanding the correlation between chirality and life as well as for elucidating the pathway for chiral molecules participating in life processes. Aqueous solution is the environment for chiral molecules in vivo. The participation of water molecules has brought distinctive features to the structural transition between enantiomers of chiral molecules and hydrogen bond-induced chirality transfer. Currently, our understanding of the above-mentioned first transition is based primarily on the dilute solution, wherein hydration water and bulk-like free water coexist; and differently the understanding of the chirality transfer between chiral molecules and their solvent water is mainly based on the study of clusters consisting of chiral molecules bounded by several hydration water molecules. However, it should be stressed that a crowd or spatially confining environment, wherein many types of chiral and achiral molecules and ions coexist, is a characteristics of the living organism. In order to reveal the structures and properties of chiral molecules in this kind of complex aqueous environment, the current application will devote its efforts to understand the effects of hydration water structure, dynamic synergy of hydration water and confined water, the inhomogeneity of microstructures and dynamics relaxations, crowd and nanometer-sized spatially confining condition on the mutarotation process and hydrogen bond-induced chirality transfer between chiral molecule and hydration water. Additionally, hydrated chiral molecules surrounded by different solvents of different polarities will also be focused specially for revealing the characteristics of hydrogen bond induced chirality transfer between chiral molecules and hydration water.

手性分子结构、性质特别是其环境依赖性是理解手性与生命相关性和阐明手性分子如何参与生命过程的前提。生物体内手性分子处于水溶液环境。水分子的参与为手性分子对映异构体之间的转变、氢键诱导手性转移均带来了鲜明的特色。目前，对上述第一个转变的认识主要基于稀溶液，而对手性分子与溶剂水间手性转移的理解主要根据对结合水和手性分子所组成的团簇体系的研究。而多类手性和非手性分子、离子共存的拥挤和空间受限是生物体内环境特点。本申请重点揭示类生物体内水溶液环境中手性分子-水相互作用特点，将从结合水结构、动力学行为及水分子集体协同性、体系微观结构和动力学不均匀性等角度，来理解以结合水和受限水为主的复杂水溶液环境中手性分子结构变化过程和平衡后几何构型特点；讨论拥挤和几何受限对手性分子结构的影响；研究不同极性溶剂包围的手性分子与结合水间氢键诱导手性转移；得到结合水和受限水共存条件下手性分子-水相互作用规律。

水溶液中包含手性分子在内的溶质-水分子相互作用特点以及溶质及其近邻结合水动力学耦合是生命科学、物理、化学、环境等多学科非常基础但又非常重要的课题。我们依托该项目首次利用脉冲梯度核磁共振技术得到高价阳离子第一水合层内结合水扩散系数随温度和浓度的变化。所得结果颠覆了我们目前关于有机分子或离子在室温协同其近邻结合水扩散的传统认识。我们明确提出了水溶液新状态图的概念。该状态图更关注在非平衡降温、特别是玻璃化转变过程，水溶液中受溶质影响不同水分子各自的驰豫特征、更有效揭示水分子含量调节的溶质间相互作用。新状态图普适地将水溶液分为三个特征浓度区间，两个分界浓度点处水分子含量分别为溶质结合水数和与电解质类型无关的结合水数的固定倍数。利用该状态图可以讨论溶质-水分子、溶质-溶质相互作用；特定水溶液体系发生相分离水含量特征。我们发现了升降温均不晶化而且在降温玻璃化转变前比热异常增加的锂盐水溶液体系。该体系为利用各种手段表征和探讨液态的液液相变提供了好的平台和均合适的时间窗口。