The shapes of Scatchard plots for systems with two sets of binding sites

Abstract

Introduction One of the most familiar and important processes in biochemistry is the reversible combination of small ions or molecules with specific sites on the surface of a protein or other biopolymer. The interaction of ligand with macromolecule of biological systems is one of the most extensively studied phenomena in biochemical research. Such studies are an essential part of the physico-chemical characterization of many biological phenomena ranging from enzyme catalysis and its control, hormone action, membrane transport, and nerve conduction to muscle contraction and other forms of mobility) -3 Protein-surfactant interactions have been extensively studied as the ligand-protein binding affinities. It is important for understanding the stabilization of membrane and food emulsions and foams that the interactions between the protein and surfactant which lead to the formation of such complexes are characterized? -5 Moreover, denaturation of protein with surfactant by determining the strength and number of binding sites and the magnitude of the interaction between multiple sites provide the essential data for the evaluation of the structure of the protein and its relationship with the function of protein. 6-~° Experimentally the measurement of binding is straightforward. However, interpretation of the data requires different models of analysis that depend on various features of the binding process. A number of methods for graphical and computer-assisted analysis of the binding data have been employed. The purpose of this paper is to consider the most common presentation of ligand-acceptor binding data in the biological sciences; the Scatchard Plot. Although, there are many reports on Scatchard plots for systems with one set of binding sites, there are relatively few reports on the shapes of Scatchard plots for systems with two sets of binding sites. ~2-~3 The similarities that can exist between the shapes of Scatchard plots in systems with one set and two sets of binding sites, have caused some misinterpretations of the binding process. 14-~6 This lead us to evaluate the shapes of Scatchard plots for hypothetical systems with two sets of binding sites and different kinds of co-operativity on each set.