The concentration dependence of the heme heme interaction of hemoglobin S

Data for oxygen equilibrium curves for Hb SS erythrocytes, both before and after separation into fractions of varying density by ultracentrifugation technique, were fitted to Hill plots and the ‘n’ values, which is a measure of the heme heme interaction of the Hb molecule, were analyzed. The heme heme interaction for the bottom fractions, which consist mainly of dense deformed cells with a very high MCHC, was found to be smaller than that for the top (undeformed cells) and middle fractions or unfractioned erythrocytes. This finding indicates that the high concentration of Hb S in the dense deformed cells is associated not only with a reduced affinity for oxygen but also a reduced heme heme interaction.