Curvature effects in charge-regulated lipid bilayers

TL;DR

This paper develops a theoretical framework for electrostatic interactions in charge-regulated lipid bilayers, revealing how charge regulation influences membrane curvature, symmetry, and free energy, with implications beyond simple electrostatic effects.

Contribution

It introduces a combined Debye-Hückel and Poisson-Boltzmann theory to analyze curvature effects in charge-regulated lipid membranes, highlighting novel phenomena like symmetry breaking and non-linear flexoelectricity.

Findings

Charge regulation can induce symmetry breaking in bilayers.

Non-linear curvature dependence of membrane free energy.

pH effects extend beyond electrostatic renormalization.

Abstract

We formulate a theory of electrostatic interactions in lipid bilayer membranes where both monolayer leaflets contain dissociable moieties that are subject to charge regulation. We specifically investigate the coupling between membrane curvature and charge regulation of a lipid bilayer vesicle using both the linear Debye-H\"uckel (DH) and the non-linear Poisson-Boltzmann (PB) theory. We find that charge regulation of an otherwise symmetric bilayer membrane can induce charge symmetry breaking, non-linear flexoelectricity and anomalous curvature dependence of free energy. The pH effects investigated go beyond the paradigm of electrostatic renormalization of the mechano-elastic properties of membranes.