Influence of Hofmeister Effects on Surface pH and Binding of Peptides to Membranes

Abstract

An understanding of local surface pH and binding of peptides to membranes is of interest for a number of biological processes. Ionic dispersion forces that give rise to Hofmeister effects have not previously been taken into account by theories. It is demonstrated that pH-changes near surfaces (e.g. membrane and mica) and binding of peptides to membranes depend on the specific ionic species. Near mica surfaces, the effect can be especially large: some anions, for example, Br-, experience large attractive dispersion forces that can give rise to strong co-ion adsorption and enhanced pH-gradients. The concentration of hydronium ions at a model membrane surface is obtained from a modified nonlinear Poisson−Boltzmann equation that includes ionic dispersion potentials consistently. The fraction of ionizable surface groups is treated as a self-consistent functional of the electrostatic potential. We finally demonstrate that good agreement between theoretical and experimental binding energies of peptides to membr...