Relations between Aggregation of Subunits and the Oxygen Equilibrium of Human Hemoglobin

Deaggregation of human hemoglobin in solutions of high ionic strength is pH-dependent in the range 6 to 8.5. The pH optimum for aggregation of deoxy- is lower than that for oxyhemoglobin. The known favored deaggregation of oxyover deoxyhemoglobin is further characterized; the difference is more marked at lower pH values in this range. A similar difference is also seen when deaggregation is induced by acidification to pH 4.7. At high ionic strengths and also at pH 4.7 the oxygen affinity of hemoglobin is concentration-dependent. This dependence can be related to differences in deaggregation of oxy- and deoxyhemoglobin through linkage relations.