OXYGEN-AFFINITY OF HEMOGLOBIN-BSH CHAINS IS CONCENTRATION DEPENDENT

Oxygen binding to isolated hemoglobin βSH chains exhibits heterotropic interactions with H+, inositol hexaphosphate and CO2 which implies different structures of the liganded and unliganded β chains. In order to find out if the dissociation behaviour of β4SH homotetramers is likewise linked to oxygenation, we have measured the oxygen affinity of the pigment as a function of the protein concentration at different pH values. We found that a decrease in protein concentration is associated with a decrease in oxygen affinity. This result accords with predictions reached from studies on the self-association of liganded and unliganded β chains. Furthermore, it was established that both at high and low protein concentrations the oxygen affinity of the β chains is pH dependent. © 1978.