Attractive Interaction between Fully Charged Lipid Bilayers in a Strongly-Confined Geometry

TL;DR

This study demonstrates electrostatic attraction between highly charged lipid bilayers in confined spaces, explained by counterion correlations beyond classical theories, with experimental validation showing reduced water layer thickness and dielectric constant effects.

Contribution

It provides experimental evidence for counterion-mediated attraction between charged bilayers and tests the limits of the Strong Coupling theory in confined geometries.

Findings

Thinner water layers between like-charged bilayers in experiments.

Electrostatic attraction explained by counterion correlations.

Decrease in water dielectric constant due to surface charge effects.

Abstract

We investigate the interaction between highly charged lipid bilayers in the presence of monovalent counterions. Neutron and X-ray reflectivity experiments show that the water layer between like-charged bilayers is thinner than for zwitterionic lipids, demonstrating the existence of counterintuitive electrostatic attractive interaction between bilayers. Such attraction can be explained by taking into account the correlations between counterions within the Strong Coupling limit, which falls beyond the classical Poisson-Boltzmann theory of electrostatics. Our results show the limit of the Strong Coupling continuous theory in a highly confined geometry and are in agreement with a decrease in the water dielectric constant due to a surface charge-induced orientation of water molecules.