AN EXACT GENERAL-ANALYSIS OF LIGAND-BINDING DISPLACEMENT AND SATURATION CURVES

Quantitative analysis of a ligand-protein interaction relates binding to the free concentration of ligand molecules in solution. A theoretic al analysis is presented herein, by which intermolecular interactions can be described as a function of the added concentrations of ligand m olecules. Following this analysis, ligand binding displacement and sat uration curves can be converted directly into a linear form, even when nonradioactively labeled ligands are used to detect the ligand-protei n interaction. From the linearities obtained, relevant binding paramet ers, including the binding dissociation constant, can be calculated. O n the basis of this analysis, binding parameters have been characteriz ed for the interaction between biotin-protein A and immunoglobulins, u sing ELISA-type detection, and for the interaction of a fluorescently labeled fatty acid with a specific fatty acid binding protein.