Computer simulation of the temperature- and hydration-dependent lateral diffusion of phosphatidylcholine in lipid bilayers.

A lattice model of a lipid bilayer near the so-called main phase transition between the liquid crystalline (L alpha) and the gel (L beta) phase is presented. It is based on a two-state model. Jump dynamics are defined for the lattice molecules to simulate lateral diffusion. The temperature and hydration dependence of the lateral diffusion coefficients of the model are calculated for the L alpha phase using Monte Carlo simulation techniques. The results obtained allow the estimation of the hydration dependent part of the lateral diffusion activation energy by thermodynamical quantities. We compare these results with measured activation energies of dipalmitoylphosphatidylcholine (DPPC) and propose a model to describe the total lateral diffusion activation energy of such systems.