Characterization of phospholipid-cholesterol bilayers as self-assembled amphiphile block polymers that contain headgroups

TL;DR

This study uses self-consistent field theory to model phospholipid-cholesterol bilayers, revealing how cholesterol influences membrane structure, thickness, and lipid tilt, with results aligning with experimental observations.

Contribution

It introduces a theoretical SCFT-based model of phospholipid-cholesterol bilayers that captures key structural effects and thermodynamic properties, advancing understanding of membrane regulation.

Findings

Cholesterol causes membrane thickening and lipid tilt reduction.

The chemical potential of cholesterol varies linearly with concentration.

Interactions between headgroups and solvent significantly influence membrane structure.

Abstract

Cholesterol is known to modulate the structure and function of biological membranes. In this study, we use self-consistent field theory (SCFT) to investigate phospholipid/cholesterol bilayer membranes modeled with two types of diblock copolymers. These copolymer-based bilayers serve as biomimetic platforms with applications in areas such as drug delivery. Our simulations identify a minimum free energy configuration characterized by phospholipid tails tilted relative to the membrane normal. The model quantitatively captures the well-known area condensation effect as cholesterol concentration increases, along with membrane thickening and reduced tilt angle. Thermodynamically, we observe a linear dependence between cholesterol's chemical potential and its concentration within the 37-50% range, consistent with experimental results. Additionally, we analyze the effects of block copolymer length and headgroup interactions on bilayer structure. Interactions between phospholipid headgroups and the solvent emerge as the most influential. This work provides a theoretical framework for understanding cholesterol's regulatory role in membrane structure and mechanics.