The Dynamics of a Highly Curved Membrane Revealed by All-atom Molecular Dynamics Simulation of a Full-scale Vesicle

TL;DR

This study uses advanced all-atom molecular dynamics simulations to explore the biophysical properties and phase behavior of a highly curved, full-scale vesicle, revealing curvature-induced phase coexistence and membrane organization.

Contribution

First all-atom simulation of a full-scale, asymmetric vesicle over 10 microseconds, uncovering curvature effects on membrane dynamics and phase behavior.

Findings

Curvature induces phase coexistence not seen in flat membranes.

Lipid composition and properties vary with membrane curvature.

Membrane packing defects are influenced by high curvature.

Abstract

In spite of the great success that all-atom molecular dynamics simulations have seen in revealing the nature of the lipid bilayer, the interplay between a membrane's curvature and dynamics remains elusive. This is largely due to the computational challenges involved in simulating a highly curved membrane, as the one found in a small vesicle. In the present work, thanks to the computing power of Anton2, we present the first all-atom molecular dynamics simulation of a full-scale, realistically composed (both heterogeneous and asymmetric) vesicle of a meaningful time scale (over 10 microseconds), which reveals unique biophysical properties of various lipid molecules (diffusion coefficients, surface areas per lipid, order parameters) and packing defects in a highly curved environment. Most interestingly, a bilayer of the same lipid composition demonstrating no phase coexistence when flat shows very strong indictors of phase coexistence when highly curved. Lipid molecules found in the curvature-induced different phases are carefully verified by their distinct composition, area per lipid, parking defects, as well as diffusion coefficient. The result of the all-atom molecular dynamics simulations is consistent with previous experimental and theoretical models and enhance the understanding of nanoscale dynamics and membrane organization of small, highly curved organelles.