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粒子在拥挤环境下的亚扩散:示踪粒子与拥挤粒子的尺寸影响
马义丁*,罗开富
作者单位E-mail
马义丁* 中国科学技术大学高分子科学与工程系, 中国科学院软物质化学重点实验室, 合肥 230026 yiding@mail.ustc.edu.cn 
罗开富 中国科学技术大学高分子科学与工程系, 中国科学院软物质化学重点实验室, 合肥 230026  
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DOI:10.1063/1674-0068/30/cjcp1609184
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基金项目:This work is supported by the National Natural Science Foundation of China (No.21225421 and No.21474099), the National Basic Research Program of China (No.2014CB845605)
Anomalous and Normal Diffusion of Tracers in Crowded Environments: E ect of Size Disparity between Tracer and Crowders
Yi-ding Ma*,Kai-fu Luo
Abstract:
The dynamics of tracers in crowded matrix is of interest in various areas of physics, such as the diffusion of proteins in living cells. By using two-dimensional (2D) Langevin dynamics simulations, we investigate the diffusive properties of a tracer of a diameter in crowded environments caused by randomly distributed crowders of a diameter. Results show that the emergence of subdiffusion of a tracer at intermediate time scales depends on the size ratio of the tracer to crowders δ. If δ falls between a lower critical size ratio and a upper one, the anomalous diffusion occurs purely due to the molecular crowding. Further analysis indicates that the physical origin of subdiffusion is the "cage effect". Moreover, the subdiffusion exponent α decreases with the increasing medium viscosity and the degree of crowding, and gets a minimum αmin=0.75 at δ=1. At long time scales, normal diffusion of a tracer is recovered. For δ≤1, the relative mobility of tracers is independent of the degree of crowding. Meanwhile, it is sensitive to the degree of crowding for δ>1. Our results are helpful in deepening the understanding of the diffusive properties of biomacromolecules that lie within crowded intracellular environments, such as proteins, DNA and ribosomes.
Key words:  Subdiffusion  Langevin dynamics simulations  Size disparity