Charge Regulation Effects on Peptide Adsorption on Charged Surfaces

Some studies demonstrate the relationship between charge regulation and peptide adsorption in charged lipid membranes. Based on this, a theoretical mathematical modeling was applied, in which peptides sensitive to pH interact with a charged flat surface in the presence of salt. In this context, the average electrostatic potential influences the probability of protonation of amino acids in the peptides. The model is based on an extension of the Poisson-Boltzmann equation and the Bikerman model, incorporating the effects of collective charge regulation, the dimensions of the species in solution and the packing of the species on the charged surface. The system is described by means of a variational approach, where the minimization of a Helmholtz free energy functional results in a Modified Poisson-Boltzmann equation, solved by the computational finite difference method. With this, the dependence of the peptide concentration and the average charge as a function of the distance to the charged surface was determined, which allowed the estimation of the zeta potential for direct comparisons with experimental results.