(757c) Spatial Distribution of Cholesterol in Symmetric and Asymmetric Lipid Bilayers Studied Using Coarse Grained MD Simulations

While the effect of cholesterol on the phase behavior of lipid bilayers is well-known, the spatial distribution of cholesterol molecules within these bilayers is not fully understood. We have performed coarse grained molecular dynamics simulations to study spatial distribution and orientation of cholesterol molecules within symmetric lipid bilayers in different phases. For the different lipid bilayers studied, we find that cholesterol molecules are mainly located at the center of the bilayer in the liquid disordered (L_d) phase. For the ordered phases, liquid ordered (L_o) and gel (L_β), cholesterol molecules are predominantly present in the bilayer leaflets. In the leaflets, the cholesterol molecules are oriented parallel to the bilayer normal, while near the center, the molecules are oriented randomly. In addition, we have studied cholesterol distribution in an asymmetric lipid bilayer. We observe that cholesterol molecules prefer to be located in the more ordered lipid leaflet. This result is in contrast with experiments done on lipid vesicles where the curvature of the vesicles is thought to play a dominant role in the distribution of cholesterol molecules.