Dynamics of an asymmetric bilayer lipid membrane in a viscous solvent

¹ York Centre for Complex Systems Analysis, University of York - York, YO10 5GE, UK
² Academic Division of Medical Physics, University of Leeds - Leeds, LS2 9JT, UK
³ Institute for Soft Matter Synthesis & Metrology, Department of Physics, Georgetown University Washington DC, USA

Received: 3 April 2015
Accepted: 27 June 2015

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-Delbrück length and another, , 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.