Translational diffusion of flexible lipid chains in a Langmuir monolayer: A dynamic Monte Carlo study

Abstract

A computer simulation study of the lateral diffusion of conformationally-disordered lipid molecules in a monolayer structure is reported. The simulations were carried out with dynamic Monte Carlo methods, employing two different representations of the internal motions of the lipid chains. The results indicate that the dependence of the lateral diffusion coefficients on the density (area-per-molecule) in the monolayer is determined by the conformational behavior of the lipid chains. The classical Cohen-Turnbull theory is found to provide a good description of the simulated lateral diffusion coefficients at moderate densities. The substantial deviations found at low densities are attributed to the small density fluctuations creating the free volume needed for the lateral diffusion process.