Nanoscale dynamics of membrane domains with different sterols.

Abstract

The plasma membrane is laterally heterogeneous, being organized into domains with different structures and compositions. An example of these domains is the so-called lipid rafts, which are enriched with cholesterol and sphingolipids and are different from the rest of the membrane structures. Despite advances in understanding these domains, the influence of sterol type on them remains unclear. This study aims to compare the effect of cholesterol or ergosterol on the dynamics of handmade domains with Sphingomyelin and POPC lipids. For this system with 20 mol% of either cholesterol or ergosterol, we ran microsecond timescale all-atom molecular dynamics simulations using GROMACS and the Slipids force field. The evaluated properties are lipid order parameters, membrane thickness, lipid local enrichment, and radial distribution functions. The ternary POPC/PSM/sterol bilayer has a markedly increased chain ordering effect on the POPC tail chains that is independent of sterol. The ternary POPC/PSM/sterol lipid bilayer's PSM tail chain order parameters are nearly identical to the original PSM values, and they appear to be sterol-independent. According to the enrichment analysis, cholesterol preferentially associates with POPC over PSM, whereas the opposite is true in the ergosterol system. Finally, we compare our thickness findings to those from AFM, which shows the distinction between ergosterol and cholesterol.