Coarse-grained continuum model for molecular diffusion in a lipid monolayer

Abstract

Recent experimental studies of lateral diffusion of lipid molecules in bilayers using single-molecule detection techniques (Schütz et al., 1997. Biophysical J. 73:1073-1080), gave rise to speculation about confinement effects due to anomalous diffusion. Here we report a computer simulation study of the lateral diffusion of conformationally disordered lipid monolecules in a monolayer structure. No evidence for anomalous diffusion effects are found in the homogeneous monolayer studied. The classical Cohen-Turnbull theory is found to provide a good description of the simulated lateral diffusion coefficients at high densities, above a certain threshold c*. At densities c < c*, where the diffusion of the flexible lipids is governed by their >soft core> repulsion, we found an entropically activated diffusion according to D ∼ exp(-γ√c) over a large concentration regime 0.03 < c < 0.6. © 2000 Elsevier Science B.V. All rights reserved.