Eur. Phys. J. E (2014) 37: 69
https://doi.org/10.1140/epje/i2014-14069-2

Regular Article

Elasticity and mechanical instability of charged lipid bilayers in ionic solutions

¹ Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, 84105, Be’er Sheva, Israel
² Department of Biomedical Engineering, Ben Gurion University of the Negev, 84105, Be’er Sheva, Israel
³ Department of Mechanical and Aerospace Engineering, University of California, 95616, Davis, CA, USA
⁴ Department of Mathematics, University of California, 95616, Davis, CA, USA

^* e-mail: ofarago@bgu.ac.il

Received: 4 May 2014
Revised: 29 June 2014
Accepted: 16 July 2014
Published online: 15 August 2014

Abstract

We use coarse-grained Monte Carlo simulations to study the elastic properties of charged membranes in solutions of monovalent and pentavalent counterions. The simulation results of the two cases reveal trends opposite to each other. The bending rigidity and projected area increase with the membrane charge density for monovalent counterions, while they decrease for the pentavalent ions. These observations can be related to the counterion screening of the lipid charges. While the monovalent counterions only weakly screen the Coulomb interactions, which implies a repulsive Coulomb system, the multivalent counterions condense on the membrane and, through spatial charge correlations, make the effective interactions due to the charged lipids attractive. The differences in the elastic properties of the charged membranes in monovalent and multivalent counterion solutions are reflected in the mechanisms leading to their mechanical instability at high charge densities. In the former case, the membranes develop pores to relieve the electrostatic tensile stresses, while in the latter case, the membrane exhibits large wavelength bending instability.