Physical properties of mixed bilayers containing lamellar and nonlamellar lipids: insights from coarse-grain molecular dynamics simulations.

A recently developed coarse-grain model is applied to simulate hydrated membranes containing the lamellar lipid DOPC and the nonlamellar lipid DOPE. In a first series of simulations, DOPC-water and DOPE-water systems are shown to form respectively bilayers and inverse hexagonal phases, in agreement with the well-known behaviour observed experimentally. A second set of calculations is then run to investigate several fundamental physical features of mixed DOPC-DOPE bilayers at different relative compositions. In particular, a quantitative characterisation is obtained of the internal distributions (profiles) of lateral pressure and electrical potential. These two properties, very difficult to measure experimentally, are thought to underpin many key membrane phenomena, including nonspecific lipid-mediated mechanisms of protein regulation. The molecular origin of the distributions, and their dependence on changes in the DOPC: DOPE ratio, are explained through an analysis of separate contributions from individual interaction types and molecular groups.