中文摘要：

利用二维体系下的朗之万动力学模拟研宄了示踪粒子直径为σt在拥挤剂直径为口。的环境下的扩散行为．发现在中等时间尺度下示踪粒子的扩散行为与示踪粒子与拥挤粒子的直径之比6相关，6在一定范围下，单纯的拥挤效应可以使示踪粒子表现出亚扩散行为．进一步发现粒子的亚扩散行为是由于拥挤剂对其的“笼闭效应”．亚扩散指数OL随着体系粘度以及拥挤程度而下降，在6=1时取得最小值αmin=0．75．长时间尺度下，示踪粒子表现出正常扩散行为．6〈1时，粒子的扩散系数与粒子大小无关，δ〉1时，扩散系数对随拥挤剂粒子增加而增加．本研究有助于进一步了解蛋白质、DNA、核糖体等生物大分子的扩散行为的物理本质．

英文摘要：

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 a. If a falls between a lower critical size ratio and a upper one, the anomalous diffusion occurs purely due to the molecular crowding, tqlrther 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〉l. 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.