Molecular Dynamics Simulations of Anionic Lipid Bilayers in Presence of Calcium Ions

Abstract

The negatively charged phosphatidylserine (PS) lipid molecules contribute up to 17% of the lipid composition in mammalian cell membranes. Experiments have shown that PS lipids, in presence of Ca2+ ions, are involved in a number of membrane-mediated processes such as phase separation, membrane fusion, and protein topological changes.However, although experiments have been performed aimed at understanding the interactions of Ca2+ ions with PS lipids, the detailed mechanism of Ca2+ induced changes in PS-containing membranes is not well established. This is, in part, due to the lack of conformational information at the atomistic level in experimental measurements.Molecular dynamics (MD) simulation is a powerful tool in elucidating phenomena at the molecular level and has been used widely in the field of biophysics. Specifically, several atomistic MD simulation studies have been performed to study the properties of model membranes containing PS in absence and presence of Ca2+ ions. However, it remains challenging to observe changes in membrane structure due to the presence of Ca2+ ions.We are using atomistic and coarse-grained MARTINI simulations of membranes containing PS to study the role of Ca2+ ions in modifying structural and dynamic properties of the membranes.