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首页> 外文期刊>Current Science: A Fortnightly Journal of Research >Dynamics of water molecules at the surface of an aqueous micelle: Atomistic molecular dynamics simulation study of a complex system
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Dynamics of water molecules at the surface of an aqueous micelle: Atomistic molecular dynamics simulation study of a complex system

机译：水性胶束表面水分子的动力学：复杂系统的原子分子动力学模拟研究

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摘要

The dynamics of water molecules and ions near an aqueous micellar interface is a subject of intense current interest, as such a system serves as a prototype of more complex biological systems, in addition to being important in its own right. We study the dynamics by using an atomistic molecular dynamics simulation of a micelle of cesium pentadecafluorooctanoate (CsPFO) in water. This micellar system is stable over a range of temperature, allowing us to perform a detailed study of the microscopic dynamics of water at the surface of the micelle, at two different temperatures. The dipolar orientational correlation function of the water molecules and the polar solvation dynamics (SD) of cesium ions and tagged water molecules are calculated. Results show that the reorientational motion of water molecules near the micelle is restricted, and as a result exhibits a slow component which is slower than its bulk value by at least two orders of magnitude, in agreement with dielectric relaxation experiments. In addition, the SD of cesium ions is found to be slowed down significantly, again by more than two orders of magnitude compared to that in the bulk water. Through an analysis of partial solvation time correlation functions, we find that the cesium ions are primarily solvated by the polar headgroups, and their SD is thus intimately coupled to micellar dynamics. Both orientational dynamics and SD show strong temperature dependence.
机译：水分子束界面附近的水分子和离子的动力学是当前引起人们极大关注的主题，因为这种系统除了本身很重要以外，还可以作为更复杂的生物系统的原型。我们通过使用原子化的五氟十六酸铯胶束（CsPFO）的原子分子动力学模拟研究动力学。这个胶束系统在一定温度范围内是稳定的，这使我们能够在两个不同的温度下对胶束表面水的微观动力学进行详细研究。计算了水分子的偶极取向相关函数以及铯离子和标记水分子的极性溶剂化动力学（SD）。结果表明，与介电弛豫实验相一致，胶束附近水分子的重新定向运动受到限制，结果显示出比其体积值慢至少两个数量级的慢组分。另外，发现铯离子的SD显着降低，与散装水中的铯相比，再次降低了两个数量级以上。通过对部分溶剂化时间相关函数的分析，我们发现铯离子主要被极性头基溶剂化，因此它们的SD与胶束动力学密切相关。取向动力学和SD都显示出强烈的温度依赖性。

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