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

We report a computer simulation study of the lateral diffusion of conformationally disordered lipid molecules in a monolayer structure. The simulations were carried out with dynamic Monte Carlo methods, employing two different representations of the internal motions 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 needed to create the free volume required for the lateral diffusion process.