"Water-free" computer model for fluid bilayer membranes

TL;DR

This paper introduces a simplified, solvent-free computer model for bilayer membranes, capturing phase transitions, mechanical properties, and pore formation, providing insights into membrane behavior without explicit solvent simulation.

Contribution

The study presents a novel, efficient model that simulates membrane properties and phase transitions without embedding solvent, advancing computational membrane research.

Findings

Membrane undergoes solid-fluid phase transition with decreasing density.

Surface tension and bending modulus are quantified from thermal undulations.

Pore formation occurs at low densities, facilitating molecule diffusion.

Abstract

We use a simple and efficient computer model to investigate the physical properties of bilayer membranes. The amphiphilic molecules are modeled as short rigid trimers with finite range pair interactions between them. The pair potentials have been designed to mimic the hydrophobic interactions, and to allow the simulation of the membranes without the embedding solvent as if the membrane is in vacuum. We find that upon decreasing the area density of the molecules the membrane undergoes a solid-fluid phase transition, where in the fluid phase the molecules can diffuse within the membrane plane. The surface tension and the bending modulus of the fluid membranes are extracted from the analysis of the spectrum of thermal undulations. At low area densities we observe the formation of pores in the membrane through which molecules can diffuse from one layer to the other. The appearance of the pores is explained using a simple model relating it to the area dependence of the free energy.