Effects of partial deuteration on the properties of human hemoglobin.

The cooperativity of oxygen binding by different subunits in human hemoglobin is greatly reduced by partial deuteration. The effect depends on the time of exposure: n in Hill’s equation decreases from 2.8 to about 1.9 after the hemoglobin has been in D20 for 20 hours at 4”. Further incubation results in a gradual return to normal cooperativity: n E? 2.8 after 240 hours. These effects could be explained if the rates of deuteration of certain parts of the OL and P-chains differed. The normal alkaline Bohr effect is unchanged by deuteration. Molecules in which most of the exchangeable hydrogen has been replaced with deuterium are more resistant to denaturation by heat and to autoxidation.