Initiation and dynamics of hemifusion in lipid bilayers

TL;DR

This paper presents a theoretical model for the initiation and expansion of hemifusion in lipid bilayers, highlighting the role of intra-membrane tension and providing predictions on hemifusion dynamics and minimal tension thresholds.

Contribution

It introduces a new theoretical framework for understanding hemifusion dynamics driven by intra-membrane tension, including scaling laws and minimal tension estimates.

Findings

Hemifusion zone size scales with the square root of time.

A minimal tension threshold is necessary for hemifusion initiation.

Tension-driven fusion requires less energy than pressure-driven fusion.

Abstract

One approach to the understanding of fusion in cells and model membranes involves stalk formation and expansion of the hemifusion diaphragm. We predict theoretically the initiation of hemifusion by stalk expansion and the dynamics of mesoscopic hemifusion diaphragm expansion in the light of recent experiments and theory that suggested that hemifusion is driven by intra-membrane tension far from the fusion zone. Our predictions include a square root scaling of the hemifusion zone size on time as well as an estimate of the minimal tension for initiation of hemifusion. While a minimal amount of pressure is evidently needed for stalk formation, it is not necessarily required for stalk expansion. The energy required for tension induced fusion is much smaller than that required for pressure driven fusion.