Molecular modeling of key elastic properties for inhomogeneous lipid bilayers

Fusion and fission of biological membranes play a crucial role in intracellular transport. Until recently, it was believed that membrane shape transformations involved in these processes are driven by proteins. However, recent evidence shows that lipids, by themselves, can drive membrane deformations. It has been hypothesized that the localized formation of certain lipids changes elastic properties of a membrane in such a way that the membrane deforms spontaneously. This study represents a step towards a systematic investigation of the role of various lipids in local changes of membrane elastic properties. We use coarse-grained molecular dynamics (CGMD) simulations to determine possible effects of addition of phosphatidylinositol-4-phosphate (PI4P) lipids on elastic properties of dipalmitoyl phosphatidyl choline (DPPC) lipid bilayers. We investigate the splay (bending) and the molecular tilt moduli of mixed DPPC/PI4P bilayers, as well as the line tension between domains of pure DPPC and mixed DPPC/PI4P bilayers. Although our results indicate negligible effects of PI4P on elastic properties of DPPC bilayers, the developed methodology can be applied to a wide range of lipid systems.