HYDRATION OF POLAR INTERFACES - A GENERALIZED MEAN-FIELD MODEL

A generalized non-local electrostatic model has been proposed for the description of the hydration of arbitrary polar surfaces, including in terfaces with a finite thickness. This model is suitable for the descr iption of complex biological surfaces, such as the surfaces of lipid b ilayer membranes. It is designed so as to resemble as closely as possi ble 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 th e local excess-charge density approach, which corresponds to a general ized, sub-molecular polarization. A general scheme for the calculation of the hydration between two thick, structured interfaces has been de veloped. The effects of surface structure on the hydration-dependent i nterfacial repulsion have been investigated. The magnitude and the ran ge of the hydration pressure are shown to increase dramatically as a c onsequence of the water penetration and binding into the interfacial r egion. Interfacial swelling and dynamics, consequently, may affect the properties of, and the interactions between, structured surfaces.