论文标题

通过时间序列建模来捕获纳米级孔中的宽度溶质动力学并预测纳米级毛孔的选择性

Capturing Subdiffusive Solute Dynamics and Predicting Selectivity in Nanoscale Pores with Time Series Modeling

论文作者

Coscia, Benjamin J., Shirts, Michael R.

论文摘要

在数学上对分子水平上的复杂运输现象进行建模可能是识别传输机制和预测宏观特性的强大工具。我们使用两个不同的随机时间序列模型,这些模型是从长分子动力学(MD)模拟轨迹进行参数化的,该轨迹的交联HII相溶解液晶体(LLC)膜,以预测溶质平均平方位移(MSDS)和溶质磁通量和溶质磁通量,从而在溶质的选择性中,从而在溶质的选择性中,并在溶质的选择性中,在大型旋转长度长度孔中。首先,使用异常扩散理论,我们展示了如何将溶质动力学作为分数扩散过程进行建模至连续的时间随机步行。从MD模拟中,我们将住所时间的分布,居住时间之间的跳跃长度和啤酒花之间的相关性进行参数化。我们探讨了异常扩散建模方法的两种变体。第一个将一组参数应用于溶质位移,第二个参数基于溶质的径向距离距离最接近的孔中心的径向距离进行了两组参数。接下来,我们概括了马尔可夫状态模型,将系统的配置状态视为马尔可夫的过程,每个状态都有不同的传输属性。对于状态和状态之间的过渡,我们将位置波动的分布和时间相关结构参数化,以作为表征的手段,并允许我们预测溶质MSD。 MD和Markov State依赖模型生成的轨迹之间的定性差异可能会限制其有用性。最后,我们演示了如何使用这些模型来估计质量跨度毛孔的溶质的通量,并根据这些数量,是膜对每种溶质的选择性。这项工作有助于连接微观化学依赖性溶质运动,这些溶质运动不会遵循宏观膜性能的简单扩散行为。

Mathematically modeling complex transport phenomena at the molecular level can be a powerful tool for identifying transport mechanisms and predicting macroscopic properties. We use two different stochastic time series models, parameterized from long molecular dynamics (MD) simulation trajectories of a cross-linked HII phase lyotropic liquid crystal (LLC) membrane, in order to predict solute mean squared displacements (MSDs) and solute flux, and thus solute selectivity, in macroscopic length pores. First, using anomalous diffusion theory, we show how solute dynamics can be modeled as a fractional diffusion process subordinate to a continuous time random walk. From the MD simulations, we parameterize the distribution of dwell times, hop lengths between dwells and correlation between hops. We explore two variations of the anomalous diffusion modeling approach. The first applies a single set of parameters to the solute displacements and the second applies two sets of parameters based on the solute's radial distance from the closest pore center. Next, we generalize Markov state models, treating the configurational states of the system as a Markov process where each state has distinct transport properties. For each state and transition between states, we parameterize the distribution and temporal correlation structure of positional fluctuations as a means of characterization and to allow us to predict solute MSDs. Qualitative differences between MD and Markov state dependent model-generated trajectories may limit its usefulness. Finally, we demonstrate how one can use these models to estimate flux of a solute across a macroscopic-length pore and, based on those quantities, the membrane's selectivity towards each solute. This work helps to connect microscopic chemically-dependent solute motions that do not follow simple diffusive behavior with macroscopic membrane performance.

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