Electrostatic energy barriers from dielectric membranes upon approach of translocating DNA molecules

TL;DR

This study models the electrostatic energy barriers encountered by DNA molecules approaching dielectric membranes, revealing how membrane properties influence attraction or repulsion, which can inform control of DNA translocation.

Contribution

The paper provides an analytical framework for understanding electrostatic interactions between DNA and dielectric membranes, highlighting the effects of membrane permittivity, charge, and polymer length.

Findings

Low permittivity membranes create repulsive barriers of 10-100 kBT.

High permittivity membranes attract DNA with similar energy magnitude.

Membrane charge density influences attraction or repulsion depending on polymer length.

Abstract

We probe the electrostatic cost associated with the approach phase of DNA translocation events. Within an analytical theory at the Debye-Huckel level, we calculate the electrostatic free energy of a rigid DNA molecule interacting with a dielectric membrane. For carbon or silicon based low permittivity neutral membranes, the DNA molecule experiences a repulsive energy barrier between 10 kBT and 100 kBT. In the case of engineered membranes with high dielectric permittivity, the membrane surface attracts the DNA with an energy of the same magnitude. Both the repulsive and attractive interactions result from image-charge effects and their magnitude survive even for the thinnest graphene-based membranes of size d~6 A. For weakly charged membranes, the electrostatic free energy is always attractive at large separation distances but switches to repulsive close to the membrane surface. We also characterise the polymer length dependence of the interaction energy. For specific values of the membrane charge density, low permittivity membranes repel short polymers but attract long polymers. Our results can be used to control the strong electrostatic free energy of DNA-membrane interactions prior to translocation events by chemical engineering of the relevant system parameters.