Abstract
A general model of cooperativity has been developed that combines the concepts of preferential binding, tertiary subunit interaction, and quaternary constraint. The models of Monod, Wyman and Changeux, and of Koshland etal., are limiting cases of this general theory. Another special case of the general model, approximating the Perutz description of hemoglobin, fits mono- and bi-phasic hemoglobin oxygenation data, over a wide range of 2–3 Diphosphoglycerate (DPG) concentrations, with a total of five adjustable parameters, and predicts that the change from deoxy to oxy quaternary structure occurs just before or just after the third heme is oxygenated, depending on the DPG level.