Driven translocation of a polymer: Fluctuations at work

The impact of thermal fluctuations on the translocation dynamics of a polymer chain driven through a narrow pore has been investigated theoretically and by means of extensive molecular dynamics (MD) simulation. The theoretical consideration is based on the so-called velocity Langevin (V-Langevin) equation which determines the progress of the translocation in terms of the number of polymer segments, s(t), that have passed through the pore at time t due to a driving force f. The formalism is based only on the assumption that, due to thermal fluctuations, the translocation velocity v=s(t) is a Gaussian random process as suggested by our MD data. With this in mind we have derived the corresponding Fokker-Planck equation (FPE) which has a nonlinear drift term and diffusion term with a time-dependent diffusion coefficient D(t). Our MD simulation reveals that the driven translocation process follows a super diffusive law with a running diffusion coefficient D(t)?t? where ?