Driven polymer translocation through a nanopore: a manifestation of anomalous diffusion

Abstract

We study the translocation dynamics of a polymer chain threaded through a nanopore by an external force. By means of diverse methods (scaling arguments, fractional calculus and Monte Carlo simulation) we show that the relevant dynamic variable, the translocated number of segments $s(t)$, displays an {\em anomalous} diffusive behavior even in the {\em presence} of an external force. The anomalous dynamics of the translocation process is governed by the same universal exponent $\alpha =2/(2\nu +2-{\gamma }_1)$, where $\nu$ is the Flory exponent and ${\gamma }_1$ - the surface exponent, which was established recently for the case of non-driven polymer chain threading through a nanopore. A closed analytic expression for the probability distribution function $W(s,t)$, which follows from the relevant {\em fractional} Fokker - Planck equation, is derived in terms of the polymer chain length $N$ and the applied drag force $f$. It is found that the average translocation time scales as $\tau \propto f^{-1}{N}^{\frac{2}{\alpha }-1}$. Also the corresponding time dependent statistical moments, $<s(t)>\propto t^{\alpha }$ and $<s(t{)}^2>\propto t^{2\alpha }$ reveal unambiguously the anomalous nature of the translocation dynamics and permit direct measurement of $\alpha$ in experiments. These findings are tested and found to be in perfect agreement with extensive Monte Carlo (MC) simulations.

6 pages, 4 figures, accepted to Europhys. Lett; some references were supplemented; typos were corrected

References in corpus (1)

• Effect of Anomalous Dynamics on Unbiased Polymer Translocation

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