Hydration of polar interfaces. A generalised mean-field model

Abstract

A generalized non-local electrostatic model has been proposed for the description of the hydration of arbitrary polar surfaces, including interfaces with a finite thickness. This model is suitable for the description of complex biological surfaces, such as the surfaces of lipid bilayer membranes. It is designed so as to resemble as closely as possible the Gouy–chapman diffuse double-layer theory, for the sake of the simplicity of model use. The molecular meaning of the model parameters is discussed and the chief determinants of the surface hydration are identified. The concept of simple solvent polarization is shown to be less suitable for the description of the interfacial hydration than the local excess-charge density approach, which corresponds to a generalized, submolecular polarization. A general scheme for the calculation of the hydration between two thick, structured interfaces has been developed. The effects of surface structure on the hydration-dependent interfacial repulsion have been investigated. The magnitude and the range of the hydration pressure are shown to increase dramatically as a consequence of the water penetration and binding into the interfacial region. Interfacial swelling and dynamics, consequently, may affect the properties of, and the interactions between, structured surfaces.