The Effect of DPG and IHP on the Relative Thermodynamic Affinity for CO of the Subunits of Rabbit Hemoglobin

The two chains of most hemoglobins interact differently with ligands as can be seen in two nmr resonances for bound ^(13)CO (Moon and Richards, 1972). This observation has led to interest in the possibility that the two chains have different thermodynamic affinities toward ligands (Huestis and Raftery, 1973, 1975; Moon and Richards, 1974; Huang and Redfield, 1976; Viggiano and Ho, 1979a,b). Rabbit hemoglobin possesses an unusual α-chain which causes ^(13)CO bound to it to have a different chemical shift than ^(13)CO bound to β chains (Moon and Richards, 1972, 1974) and, thereby, allows direct quantitative observation of the degree of ligation of the two subunits.