Electrostatic cluster formation in lipid monolayers

TL;DR

This study investigates how divalent ions induce electrostatic-driven phase separation and clustering in lipid monolayers, revealing that electrostatic interactions primarily govern pip2 lipid clustering even at low concentrations.

Contribution

It demonstrates that electrostatic interactions, mediated by divalent ions, are the main factor driving lipid clustering and phase separation in monolayers, supported by experiments and simulations.

Findings

Divalent ions induce strong electrostatic attractions between lipids.

Clustering occurs even at low pip2 concentrations.

Simulations agree with experimental phase separation observations.

Abstract

We study phase separation in mixed monolayers of neutral and highly negatively charged lipids, induced by the addition of divalent positively charged counterions. We find good agreement between experiments on mixtures of pip2 and sopc and simulations of a simplified model in which only the essential electrostatic interactions are retained. Thus, our results support an interpretation of pip2 clustering as governed primarily by electrostatic interactions, in which divalent ions such as calcium mediate an effective attraction between like-charged lipids. Surprisingly, the mediated attractions are strong enough to give nearly complete phase separation, so that clusters can even form when the overall concentration of pip2 is low, as is the case in the cell membrane.