Area Expansion and Adsorption Isotherm in Protein Binding to Mixed Lipid Membranes

We present a thermodynamic analysis of protein adsorption to a mixed lipid monolayer containing a binding component and a nonbinding component at constant surface pressure. We derive the general equations for the adsorption isotherm and for the area expansion of the monolayer. In the limits of either low or high surface coverage, simplified forms of these equations are obtained. We construct simple thermodynamic models to examine the crossover from low to high surface coverage.