COMPUTATION OF THE ELECTROSTATIC INTERACTION ENERGY BETWEEN A PROTEIN AND A CHARGED SURFACE

Protein-surface interactions play a central part in many situations both in vivo and ex vivo, but it is not yet possible to predict the extent of interaction quantitatively as a function of protein structure and surface and solution properties. A method for doing so is presented for systems dominated by electrostatic interactions, based on a continuum model of the electrostatic potential in and around a protein molecule near a charged surface in an electrolyte solution. The governing equations are solved by a boundary element approach which uses the method of images to treat the presence of an infinite planar charged surface exactly without any truncation. The potential distribution is used to obtain the protein-surface interaction energy; the boundary element approach allows this to be done rigorously, without approximating the self-energy contribution. The method is applied to determining the electrostatic interaction between a positively charged ribonuclease A molecule and a negatively charged surface at various orientations and separations. The strongest electrostatic attraction is found for ribonuclease A with its active site facing the surface, while in certain orientations the interaction can be repulsive.