Oxygen equilibrium studies of purified Hb Camperdown [βl04(G6)Arg→Ser] have revealed an increased oxygen affinity at acid pH, while it is decreased for pH values above 7.4. This accounts for an almost 40% reduction in the alkaline Bohr effect. The effects of chloride and organophosphate effectors on the oxygen affinity of Hb Camperdown are inhibited by 40-50%. in chloridefree Hepes buffer, Hb Camperdown exhibits a lower oxygen affinity than normal Hb A. The present results confirm the important role of the positively charged residues lining theβ1β2interface in regulating the functional properties of hemoglobin.