Scaling exponents of forced polymer translocation through ananopore

摘要

We investigate several properties of a translocating homopolymer through a thin pore driven byan external field present inside the pore only using Langevin Dynamics (LD) simulations in three dimensions(3D). Motivated by several recent theoretical and numerical studies that are apparently at odds with eachother, we estimate the exponents describing the scaling with chain length (N) of the average translocationtime <τ> , the average velocity of the center of mass <υ_(CM)>, and the effective radius of gyration duringthe translocation process defined as <τ>～N~α, <υ_(CM)>～N~(-δ),andR_g～N~vrespectively, and the exponentof the translocation coordinate (s-coordinate) as a function of the translocation time ～t~β.We find = 1.36±0.01, β=1.60±0.01 for ～τ~βand β=1.44±0.02 for <Δs~2(t)>～τ~β,δ=0.81±0.04, and v = 0.59 ± 0.01, where v is the equilibrium Flory exponent in 3D. Therefore, we find that <τ> is consistent with the estimate of <τ>～/<υ_(CM)>. However, as observed previously in Monte Carlo (MC)calculations by Kantor and Kardar (Y. Kantor, M. Kardar, Phys. Rev. E 69, 021806 (2004)) we also findthe exponent α = 1.36 ± 0.01 < 1 + v. Further, we find that the parallel and perpendicular components ofthe gyration radii, where one considers the “cis”and “trans”parts of the chain separately, exhibit distinctout-of-equilibrium effects. We also discuss the dependence of the effective exponents on the pore geometryfor the range of N studied here.