The dimerization of deoxyhemoglobin and of oxyhemoglobin. Evidence for cleavage along the same plane.

Studies on mixtures of canine and human hemoglobin incubated in the liganded form and separated in the unliganded form (and vice versa) indicate that liganded and unliganded hemoglobin cleave along the same plane in dimer formation. The separation was carried out by isoelectric focusing in polyacrylamide gels. The same result was indicated by experiments in which the canine-human hemoglobin mixture was focused in the oxy form and then refocused in the deoxy form as the oxygen in the gel reacted with dithionite. This technique clearly illustrates that, as a result of the Bohr effect, liganded and unliganded hemoglobin have dhferent isoelectric points. Electrofocusmg in gels could profitably be used to study cooperativity in allosteric enzymes.