Solvent-free simulations of fluid membrane bilayers

A molecular level model for lipid bilayers is presented. Lipids are represented by rigid, asymmetric, soft spherocylinders in implicit solvent. A simple three parameter potential between pairs of lipids gives rise to a rich assortment of phases including (but not limited to) micelles, fluid bilayers, and gel-like bilayers. Monte Carlo simulations have been carried out to verify self-assembly, characterize the phases corresponding to different potential parametrizations, and to quantify the physical properties associated with those parameter sets corresponding to fluid bilayer behavior. The studied fluid bilayers have compressibility moduli in agreement with experimental systems, but display bending moduli at least three times larger than typical biological membranes without cholesterol.