The Effect of Cholesterol in SOPC Lipid Bilayers at Low Temperatures

We study the behavior of lipid bilayers composed of SOPC (1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine) with different concentrations of cholesterol, ranging from 10 mol% to 50 mol% at 273 K. To this end, we carry out extensive atomistic molecular dynamic simulations with the aid of the Slipid force field aiming at computing basic bilayer parameters, as well as thermodynamic properties and structural characteristics. The obtained results are compared to available relevant experimental data and the outcome of atomistic simulations performed on bilayers composed of analogous phospholipids. Our results show a good quantitative, as well as qualitative, agreement with the main trends associated with the concentration increase in cholesterol. Moreover, it comes out that a change in the behavior of the bilayer is brought about at a concentration of about 30 mol% cholesterol. At this very concentration, some of the bilayer properties are found to exhibit a saturation and a significant long-range ordering of the lipid molecules in the membrane shows up.