[13] The meaning of scatchard and hill plots

Publisher Summary A number of interesting macromolecular questions are directly concerned with the binding of ligands to macromolecules. As a result, there has been a great increase in the number of publications primarily concerned with the measurement of such binding and its interpretation. A number of methods for graphical and computer-assisted analysis of the binding data have been employed. This chapter considers two commonly used graphical methods: the Scatchard plot and the Hill plot. The Hill plot, log [sites bound]/[sites free] versus log [free ligand], is also known as the “Sips plot” in the immunological literature. When redox equilibria are considered as the binding of electrons, the Hill plot and Nernst plot are fully equivalent as well. the chapter relates these common methods of data presentation to each other. It is clear that a given set of binding data contains the same information independent of the particular method used to interpret it. However, certain graphical methods show some aspects of this information more clearly than others. The chapter demonstrates the quantitative relationships that allow directly converting from one method to the others. It also demonstrates the way parameters for a number of models for apparent cooperative binding behavior may be extracted from the two plots without the need for extensive computer-dependent curve fitting.