Topological transitions in fluid lipid vesicles: activation energy and force fields

TL;DR

This paper presents a continuum model for lipid vesicle topological transitions, predicting energy barriers and force fields that align with experimental data, advancing understanding of membrane fusion and fission processes.

Contribution

The study introduces a novel continuum model that accurately predicts energy barriers and force fields for membrane topological changes, aligning with experimental observations.

Findings

Predicted the height of energetic barriers for vesicle fusion/fission.

Provided force fields capable of inducing membrane transitions.

Model results agree with experimental data on protein-mediated membrane changes.

Abstract

Lipid bilayer membranes are the fundamental biological barriers that permit life. The bilayer dynamics largely participates in orchestrating cellular workings and is characterized by substantial stability together with extreme plasticity that allows controlled morphological/topological changes. Modeling and understanding the topological change of vesicle-like membrane at the scale of a full cell has proved an elusive aim. We propose and discuss here a continuum model able to encompass the fusion/fission transition of a bilayer membrane at the scale of a Large Unilamellar Vesicle and evaluate the minimal free energy path across the transition, inspired by the idea that fusion/fission-inducing proteins have evolved in Nature towards minimal work expenditure. The results predict the correct height for the energetic barrier and provide the force field that, by acting on the membrane, can induce the transition. They are found in excellent agreement, in terms of intensity, scale, and spatial localization with experimental data on typical protein systems at play during the transition. The model may pave the way for the development of more complete models of the process where the dynamics is coupled to the fluid internal and external environment and to other applications where the topological changes do either occur or should be prevented.