Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Powai 400076, India.
Soft Matter. 2020 Aug 14;16(30):7103-7115. doi: 10.1039/d0sm00711k. Epub 2020 Jul 13.
Spontaneous persistent motions driven by active processes play a central role in maintaining living cells far from equilibrium. In the majority of research studies, the steady state dynamics of an active system has been described in terms of an effective temperature. By contrast, we have examined a prototype model for diffusion in an activity-induced rugged energy landscape to describe the slow dynamics of a tagged particle in a dense active environment. The expression for the mean escape time from the activity-induced rugged energy landscape holds only in the limit of low activity and the mean escape time from the rugged energy landscape increases with activity. The precise form of the active correlation will determine whether the mean escape time will depend on the persistence time or not. The activity-induced rugged energy landscape approach also allows an estimate of the non-equilibrium effective diffusivity characterizing the slow diffusive motion of the tagged particle due to activity. On the other hand, in a dilute environment, high activity augments the diffusion of the tagged particle. The enhanced diffusion can be attributed to an effective temperature higher than the ambient temperature and this is used to calculate the Kramers' mean escape time, which decreases with activity. Our results have direct relevance to recent experiments on tagged particle diffusion in condensed phases.
自发持续运动由活跃的过程驱动，在维持远离平衡的活细胞方面起着核心作用。在大多数研究中，活性系统的稳态动力学是用有效温度来描述的。相比之下，我们研究了扩散在活性诱导的崎岖能量景观中的原型模型，以描述在密集的活性环境中标记粒子的缓慢动力学。从活性诱导的崎岖能量景观中逃脱的平均逃逸时间的表达式仅在低活性的极限下成立，并且从崎岖能量景观中逃脱的平均逃逸时间随活性的增加而增加。活性相关的精确形式将决定平均逃逸时间是否取决于持久性时间。活性诱导的崎岖能量景观方法还允许估计由于活性而导致标记粒子的缓慢扩散运动的非平衡有效扩散系数。另一方面，在稀溶液环境中，高活性会增强标记粒子的扩散。增强的扩散可归因于高于环境温度的有效温度，这用于计算 Kramers 的平均逃逸时间，该时间随活性降低。我们的结果与最近在凝聚相中标记粒子扩散的实验直接相关。
