Effective Attraction Interactions between Like-charge Macroions Bound to Binary Fluid Lipid Membranes

TL;DR

This study uses integral equation theory to analyze how macroions interact on binary lipid membranes, revealing how lipid composition and macroion concentration influence attraction and repulsion mechanisms.

Contribution

It introduces a detailed theoretical framework for understanding membrane-mediated macroion interactions considering lipid redistribution and concentration effects.

Findings

Line tension dominates attraction at low macroion concentration.

Increasing charged lipids causes a transition from repulsive to attractive and back to repulsive interactions.

Finite macroion concentration alters the lipid redistribution and shifts the attraction maximum.

Abstract

Using integral equation theory of liquids to a binary mixed fluid lipid membrane, we study the membrane-mediated interactions between the macroions and the redistribution of neutral and charged lipids due to binding macroions. We find that when the concentration of binding macroions is infinitely dilute, the main contribution to the attractive potential between macroions is the line tension between neutral and charged lipids of the membrane, and the bridging effect also contributes to the attraction. As the relative concentration of charged lipids is increased, we observe a repulsive - attractive - repulsive potential transition due to the competition between the line tension of lipids and screened electrostatic macroion-macroion interactions. For the finite concentration of macroions, the main feature of the attraction is similar to the infinite dilution case. However, due to the interplay of formation of charged lipid - macroion complexes, the line tension of redistributed binary lipids induced by single macroion is lowered in this case, and the maximum of attractive potential will shift toward the higher values of the charged lipid concentration.