The effect of 2,3‐diphosphoglycerate on the oxygen dissociation curve of human haemoglobin.

Abstract

O2 dissociation curves for concentrated human Hb solutions (1.6 mmol dm-3 in heme) were measured by mixing known quantities of oxy- and deoxyhemoglobin solutions and measuring the resulting partial pressure of O2 with an oxygen electrode. Observations in the presence of 2,3-diphosphoglycerate support previous conclusions derived from experiements at low Hb concentrations, the validity of which was questioned. The 2 affinity state model of Monod, Wyman and Changeux does not fully describe the actions of 2,3-diphosphoglycerate, and a model in which this allosteric effector not only binds preferentially to the T state but also lowers the O2 affinity of this state gives an improved fit to the data.