Memory effects during the unbiased translocation of a polymer through a nanopore

Through a detailed Langevin dynamics simulation study, the role of memory effects during unbiased translocation is explored. Tests are devised to uncover the presence of memory effects by directly measuring forward/backward-correlated motion as well as the associated change in the dynamics. Conducting these tests at low and high viscosities, a range of behaviours across different time scales is revealed: short-time forward correlations at all viscosities, quasi-static behaviour at low viscosity, and long-time backward correlations at high viscosity. By applying these tests at different portions of the translocation process, these memory effects are also shown to vary as translocation proceeds. Combining this information with standard measurements, a physical picture of unbiased translocation as the diffusion of a local minimum is proposed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3699979]