Abstract

Lipid ordering plays a crucial role in maintaining the mechanical strength of the lipid bilayer which is influential in controlling the biological functions. This is associated with the well-known phenomena of “phase state behavior” of the bilayer. The major factors that influence the phase state behavior are the stimuli like cholesterol, the physiological conditions like temperature, pH, and the structure of the lipid molecule itself which could differ either in the head group or acyl chain.  The cholesterol concentration will influence the phase state behavior and the ordering of the lipid bilayer.  In this paper, we investigate the behavior of Phosphatidylcholine lipids with cholesterol, using Coarse-Grained Molecular Dynamics Simulation. The simulation is done with a CGMartini forcefield. The production run of all successful simulations is completed with the same biological condition with a total of 12 µs runtime. We chose four lipids, namely DLPC, POPC, DGPC, and DIPC with varied acyl chain chemical structures and investigated the influence of cholesterol. We have calculated bilayer thickness, area per lipid, order parameter, radial distribution function, and partial density which are a measure of bilayer phase state behavior. The results show that there is a perfect packing of cholesterol in the case of DLPC, which shows variations in POPC due to asymmetric chain structure (with one double bond in one acyl chain) DGPC and DIPC show fewer order parameters due to the more double bonds in the acyl chain. This study elucidates the importance of the acyl chain structure and the cholesterol composition on the phase state behavior of the lipid membrane.