Dynamics of an asymmetric bilayer lipid membrane in a viscous solvent

Abstract

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