Pore-blockade Times for Field-Driven Polymer Translocation

TL;DR

This paper investigates how the time a polymer blocks a pore during field-driven translocation scales with polymer length and field strength, revealing a new scaling law based on polymer dynamics near the pore.

Contribution

The study derives a new scaling law for pore-blockade times in polymer translocation, emphasizing the role of local polymer dynamics and correcting previous theoretical bounds.

Findings

Pore-blockade time scales as N^{(1+2 u)/(1+ u)}/E.

Memory effects in polymer tension influence translocation dynamics.

The correct lower bound for blockade time is ηN^{2 u}/E.

Abstract

We study pore blockade times for a translocating polymer of length $N$, driven by a field $E$ across the pore in three dimensions. The polymer performs Rouse dynamics, i.e., we consider polymer dynamics in the absence of hydrodynamical interactions. We find that the typical time the pore remains blocked during a translocation event scales as $\sim N^{(1+2\nu)/(1+\nu)}/E$, where $\nu\simeq0.588$ is the Flory exponent for the polymer. In line with our previous work, we show that this scaling behaviour stems from the polymer dynamics at the immediate vicinity of the pore -- in particular, the memory effects in the polymer chain tension imbalance across the pore. This result, along with the numerical results by several other groups, violates the lower bound $\sim N^{1+\nu}/E$ suggested earlier in the literature. We discuss why this lower bound is incorrect and show, based on conservation of energy, that the correct lower bound for the pore-blockade time for field-driven translocation is given by $\eta N^{2\nu}/E$, where $\eta$ is the viscosity of the medium surrounding the polymer.