环糊精类人工通道的计算模拟研究

Artificial channels are the transmembrane pathway for water and ions. The channels are powerful tools to develop medical treatments, biotechnologies, and energy applications. A cyclodextrin-based artificial channel reported in 2015 has good biological compatibility. It can be produced in a huge quantity of monodisperse nanotubes for industrial applications. However, the working mechanism of the channel, especially the influence of configurations on the performance, is still not clear. In this work, a cyclodextrin nanotube (CyNT) will be considered. The main attention will be focused on the permeation processes of a water molecule, a potassium ion, three potassium ions, and a potassium-chloride ion pair passing through the nanotube. The potentials of mean force characterizing the permeation processes of a water molecule and ions will be drawn. Decomposition of free-energy profiles combined with structural analysis shed light on the mechanisms of permeation processes. The water permeability and ion flux can be estimated. The influence of configurations of CyNT will be checked. The relationship between the structure of CyNT with their performance will be broadly explored. The results in this work will provide theoretical basis and support for the design of novel artificial channels.

人工通道是一种水/离子跨膜被动输运的通路。在医药、生物技术、海水淡化等领域内有广泛的应用前景。2015年报道的一种基于环糊精的人工水/离子通道具有良好的生物相容性，适合于大规模量产，是一种非常有应用价值的人工通道。但该类通道工作机理，特别是通道构型对其工作效率的影响，尚不明确。本项目首次提出通过分子模拟方法直接研究该人工通道的工作机理。重点研究水分子、钾离子和氯化钾离子对穿越该人工通道的过程。计算穿越过程的自由能曲线。分解自由能曲线结合结构分析得到穿越机理。同时评估水通量和离子通量。进一步研究环糊精纳米管的构型对离子穿越的影响。以期系统探索人工通道中结构与工作效率之间的关系这一关键科学问题。为今后设计新型的人工水/离子通道提供理论基础。

在原子层面构筑分子机器用于控制微观世界的运动是当前化学领域内的一个挑战。为了优化现有分子机器的功能并设计有特定功能的结构，需要深入理解机器内部的运功模式。本项目针对四种分子机器的运动模式进行了理论研究。通过分子动力学模拟结合自由能计算方法，计算了上述四种分子机器运动的自由能曲线/曲面。并通过能量分解和结构分析，深入探讨了造成曲线/曲面中能垒的结构因素。在此基础上提出了相应的运动机理。为现有分子机器的结构优化和新分子机器的设计奠定了理论基础。