The Journal of Biologvxl Cheliistry

A detailed re-examination of the relationship between the value of the Hill constant, n, and the partial pressure necessary for oxygenation of half the hemoglobin, psO, indicates that there is a slight dependence of n on p50 for normal human hemoglobin. The value of R varies between 2.3 and 3.1 over a 50-fold variation in the value of &,o (from 0.5 to 25 mm Hg). Above values of 40 mm Hg for p50, the value of n decreases below 2. However, there is no obvious relationship between oxygen affinity and cooperativity. In fact, the Bohr effect and cooperativity are largely independent phenomena which means that the stabilizing interactions in hemoglobin are not related in any simple fashion to oxygen affinity.