In this study we investigate, using all-atom molecular-dynamics computer simulations, the in-plane diffusion of a doxorubicin drug molecule in a thin film of water confined between two silica surfaces. We find that the molecule diffuses along the channel in the manner of a Gaussian diffusion process, but with parameters that vary according to its varying transversal position. Our analysis identifies that four Gaussians, each describing particle motion in a given transversal region, are needed to adequately describe the data. Each of these processes by itself evolves with time at a rate slower than that associated with classical Brownian motion due to a predominance of anticorrelated displacements. Long adsorption events lead to ageing, a property observed when the diffusion is intermittently hindered for periods of time with an average duration which is theoretically infinite. This study presents a simple system in which many interesting features of anomalous diffusion can be explored. It exposes the complexity of diffusion in nanoconfinement and highlights the need to develop new understanding.

中文翻译：

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阿霉素药物分子在二氧化硅纳米缝中的扩散是非高斯的，间歇的并且是反相关的

在这项研究中，我们使用全原子分子动力学计算机模拟研究了阿霉素药物分子在两个二氧化硅表面之间的水薄膜中的面内扩散。我们发现分子以高斯扩散过程的方式沿通道扩散，但参数根据其变化的横向位置而变化。我们的分析表明，需要四个高斯函数来描述数据，每个高斯函数分别描述给定横向区域中的粒子运动。由于反相关位移的优势，每个过程本身随时间的发展都比与经典布朗运动有关的过程慢。长时间的吸附会导致老化，当扩散被间歇性地阻止一段时间（平均时间在理论上是无限的）时观察到的特性。这项研究提出了一个简单的系统，其中可以探索异常扩散的许多有趣特征。它揭示了纳米约束扩散的复杂性，并强调了发展新认识的必要性。