摘要
采用分子动力学模拟方法研究高分子链在不对称粒子浴中的穿孔行为,重点分析高分子链的向左(活性粒子浴)穿孔概率和平均穿孔时间与粒子活性力之间的关系.研究发现分子链进入活性粒子浴的概率随着活性粒子活性力的增大而迅速增加,并最终达到饱和(接近1);而高分子链的平均穿孔时间会随着活性力的增大呈现先减小后增大的趋势.这种穿孔时间变化的物理机制是:活性力的增大会导致分子链内应力增大,从而产生向左的拖拽力,但是当活性力增大到一定值后,活性粒子会贴边形成结晶态,抑制活性粒子的运动,增加分子链的穿孔时间.此外,我们发现在小驱动力时,穿孔时间满足对数正态分布.进一步探究了链长效应对高分子链穿孔行为的影响.模拟结果表明:在小驱动力区间下,分子链越长,活性力越大,分子链中心点受向左的拖拽力越大,越容易左穿.
Polymer translocation through a nanopore is of ubiquitous importance in many biological processes such as DNA and mRNA translocation through nuclear pores, protein transport across membrane channels. In real systems, polymer translocation process usually involves complex environments. One typical example is that there present different environments inside and outside the nanopore. It is interesting to study polymer translocation in an asymmetric environment. Here, Langevin dynamics simulation is performed to study polymer translocation through nanopore in an asymmetry bath of active particles and passive particles. The polymer is modeled by a bead-spring chain and the active particle is modeled by active Brownian particles with inherent orientation. We find that with the increase of the particle activity, the translocation probability of polymer chain toward active bath increases quickly, and finally reaches a saturation value. This may be because active particles exert a drag force on the polymer chain. Additionally, as the bath activity increases, the mean translocation time of polymer chain decreases fast and then increases slightly. The physical mechanism of the non-monotonic change is that the increase of the bath activity will induce the increase of tension in polymer chain, resulting in a drag force toward active region. However, when the bath activity is large enough, crystalline layers of active particles are formed near the boundary, which inhibits the motion of active particles and increases translocation time of the chain.Furthermore, it is found that the profile of translocation time at small active force can be fitted by log-normal distribution. Moreover, we also pay attention to the length effect of polymer chain on translocation mechanism at moderate active forces. The longer polymer chain and the higher activity of particles can lead to a larger value of drag force on the polymer chain. The results may provide an insight into the translocation behavior of polymer chain, and help understand the non-equilibrium processes in living organisms.
作者
王艳
王雯洁
夏益祺
李慧姝
Yan Wang;Wen-jie Wang;Yi-qi Xia;Hui-shu Li(School of Physics,Nanjing University,Nanjing 210093;Center for Soft Condensed Matter Physics&Interdisciplinary Research,School of Physical Science and Technology,Soochow University,Suzhou 215006)
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2019年第12期1331-1337,共7页
Acta Polymerica Sinica
基金
中国博士后科学基金(基金号2019M651935)资助项目
关键词
分子动力学方法
高分子链
活性粒子
穿孔机理
Langevin dynamics
Polymer chain
Active particle
Translocation mechanism