Pores in Bilayer Membranes of Amphiphilic Molecules: Coarse-Grained Molecular Dynamics Simulations Compared with Simple Mesoscopic Models

TL;DR

This study uses coarse-grained molecular dynamics simulations to analyze pore formation, distribution, shape, and dynamics in tensionless amphiphilic bilayer membranes, comparing results with simple mesoscopic models.

Contribution

It introduces a mesoscopic model that accurately describes pore size, shape, and distribution in fluid membranes based on molecular simulation data.

Findings

Pores are distributed similarly to repulsive hard discs.

Pore shapes are fractal, resembling two-dimensional ring polymers.

Pore size fluctuations follow a random walk in a linear potential.

Abstract

We investigate pores in fluid membranes by molecular dynamics simulations of an amphiphile-solvent mixture, using a molecular coarse-grained model. The amphiphilic membranes self-assemble into a lamellar stack of amphiphilic bilayers separated by solvent layers. We focus on the particular case of tension less membranes, in which pores spontaneously appear because of thermal fluctuations. Their spatial distribution is similar to that of a random set of repulsive hard discs. The size and shape distribution of individual pores can be described satisfactorily by a simple mesoscopic model, which accounts only for a pore independent core energy and a line tension penalty at the pore edges. In particular, the pores are not circular: their shapes are fractal and have the same characteristics as those of two dimensional ring polymers. Finally, we study the size-fluctuation dynamics of the pores, and compare the time evolution of their contour length to a random walk in a linear potential.