Dynamics of an asymmetric bilayer lipid membrane in a viscous solvent

TL;DR

This paper develops a detailed model of asymmetric bilayer lipid membrane dynamics in viscous solvents, revealing new modes of motion and the influence of membrane asymmetry on these dynamics.

Contribution

It introduces a comprehensive model including membrane thickness fluctuations and intermonolayer friction, highlighting new dynamic modes and the effects of asymmetry.

Findings

Identification of three bilayer motion modes

Discovery of a new intermonolayer surface motion mode

Asymmetry couples different dynamic modes

Abstract

Bilayer lipid membranes (BLMs) are an essential component of many biological systems, forming a functional barrier between the cell and the surrounding environment. When the membrane relaxes from a structural perturbation, the dynamics of the relaxation depends on the bilayer structure. We present a model of a BLM in a viscous solvent, including an explicit description of a 'thick' membrane, where the fluctuations in the thickness of a monolayer leaflet are coupled to changes in the lipid density within that monolayer. We find dispersion relations describing three intuitive forms of bilayer motion, including a mode describing motion of the intermonolayer surface not noted previously in the literature. Two intrinsic length scales emerge that help characterise the dynamics; the well known Saffman-Delbruck length and another, $\ell_r$, resulting from the intermonolayer friction. The framework also allows for asymmetry in the BLM parameters between the monolayer leaflets, which is found to couple dynamic modes of bilayer motion.