Coarse-grained molecular dynamics simulation of binary charged lipid membranes: Phase separation and morphological dynamics

TL;DR

This study uses coarse-grained molecular dynamics simulations to explore how electrostatic interactions influence phase separation and morphological transformations in charged lipid bilayer vesicles, revealing mechanisms of pore formation and structural dynamics.

Contribution

It introduces a simulation approach to analyze the effects of electrostatic repulsion on membrane phase behavior and morphology, highlighting new insights into pore formation mechanisms.

Findings

Electrostatic repulsion delays or inhibits phase separation.

Morphological changes include pore, disk, string, and bicelle formations.

Pore formation is initiated by local molecular orientation disturbances.

Abstract

Biomembranes, which are mainly composed of neutral and charged lipids, exhibit a large variety of functional structures and dynamics. Here, we report a coarse-grained molecular dynamics (MD) simulation of the phase separation and morphological dynamics in charged lipid bilayer vesicles. The screened long-range electrostatic repulsion among charged head groups delays or inhibits the lateral phase separation in charged vesicles compared with neutral vesicles, suggesting the transition of the phase-separation mechanism from spinodal decomposition to nucleation or homogeneous dispersion. Moreover, the electrostatic repulsion causes morphological changes, such as pore formation, and further transformations into disk, string, and bicelle structures, which are spatiotemporally coupled to the lateral segregation of charged lipids. Based on our coarse-grained MD simulation, we propose a plausible mechanism of pore formation at the molecular level. The pore formation in a charged-lipid-rich domain is initiated by the prior disturbance of the local molecular orientation in the domain.