An Application of a Self-consistent Mean-Field Theoretical Model to POPC-PSM-Cholesterol Bilayers

TL;DR

This study applies a self-consistent mean-field theoretical model to analyze the lateral organization and inhomogeneity of POPC-PSM-Cholesterol bilayers, revealing phase separation and the influence of chain asymmetry, validated against experimental data.

Contribution

The paper introduces a novel application of a self-consistent mean-field model to ternary lipid mixtures, incorporating molecular dynamics data to predict membrane lateral organization.

Findings

Bilayers exhibit phase separation into ordered and disordered regions.

Asymmetric chain structure of POPC affects bilayer inhomogeneity.

Model results align with experimental observations.

Abstract

The connection between membrane inhomogeneity and the structural basis of lipid rafts has sparked interest in the lateral organization of model lipid bilayers of two and three components. In an effort to investigate anisotropic lipid distribution in mixed bilayers, a self-consistent mean-field theoretical model is applied to palmitoyloleoylphosphatidylcholine (POPC) - palmitoyl sphingomyelin (PSM) - Cholesterol mixtures. The compositional dependence of lateral organization in these mixtures is mapped onto a ternary plot. The model utilizes molecular dynamics simulations to estimate interaction parameters and to construct chain conformation libraries. We find that at some concentration ratios the bilayers separate spatially into regions of higher and lower chain order coinciding with areas enriched with PSM and POPC respectively. To examine the effect of the asymmetric chain structure of POPC on bilayer lateral inhomogeneity, we consider POPC-POPC interactions with and without angular dependence. Results are compared with experimental data and with results from a similar model for mixtures of dioleoylphosphatidylcholine (DOPC), steroyl sphingomyelin, and Cholesterol.