Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan 51167-87317, Iran.
Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
J Chem Phys. 2021 Mar 21;154(11):114901. doi: 10.1063/5.0040551.
Translocation of a polymer through a nano-pore is relevant in a variety of contexts such as passage of RNAs through a nuclear pore and transportation of proteins across a membrane. An essential step in polymer translocation is for the end monomers to search the pore. This process requires a characteristic time, referred to as the "attempt time" in this work. Here, we study the attempt time τ of a confined polymer inside a spherical surface by combining a scaling approach and Langevin dynamics simulations. For a moderately to strongly confined polymer, our results suggest that τ ∼ R for R > P and τ ∼ R for R < P, where R is the radius of the spherical surface and P is the persistence length of the polymer. All simulation data obtained for an intermediate range of the volume fraction of monomers ϕ(≲ 0.2) tend to collapse onto each other. This implies that τ does not explicitly depend on ϕ, in agreement with the theoretical predictions. These results will be useful for interpreting translocation as a two-step process: the initial attempt to find the pore and eventual pore crossing.
聚合物通过纳米孔的迁移在多种情况下都很重要，例如 RNA 通过核孔的传输和蛋白质穿过膜的运输。聚合物迁移的一个基本步骤是末端单体搜索孔。这个过程需要一个特征时间，在这项工作中被称为“尝试时间”。在这里，我们通过结合标度方法和 Langevin 动力学模拟来研究受限聚合物在球形表面内的尝试时间 τ。对于中等程度到强烈受限的聚合物，我们的结果表明，当 R > P 时，τ∼R，当 R < P 时，τ∼R，其中 R 是球形表面的半径，P 是聚合物的持久长度。对于单体体积分数 ϕ（≲0.2）的中间范围获得的所有模拟数据都倾向于彼此坍塌。这意味着 τ 不明显依赖于 ϕ，与理论预测一致。这些结果对于解释迁移作为一个两步过程是有用的：最初尝试寻找孔和最终的孔穿越。
