Interactions Between Charged Rods Near Salty Surfaces

TL;DR

This study combines theoretical modeling and simulations to explore how charged membranes influence DNA-like rods, revealing that surface confinement alters screening behavior, leading to long-range interactions unlike typical salt solutions.

Contribution

It introduces a model analyzing membrane polarization effects on DNA interactions, highlighting the impact of surface confinement on screening and interaction range.

Findings

Screening fields decay algebraically due to surface confinement.

Surface polarization enhances effective multipole moments of rods.

Interactions become long-ranged compared to bulk salt systems.

Abstract

Using both theoretical modeling and computer simulations we study a model system for DNA interactions in the vicinity of charged membranes. We focus on the polarization of the mobile charges in the membranes due to the nearby charged rods (DNA) and the resulting screening of their fields and inter-rod interactions. We find, both within a Debye-Huckel model and in Brownian dynamics simulations, that the confinement of the mobile charges to the surface leads to a qualitative reduction in their ability to screen the charged rods to the degree that the fields and resulting interactions are not finite-ranged as in systems including a bulk salt concentration, but rather decay algebraically and the screening effect is more like an effective increase in the multipole moment of the charged rod.