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Abstract
The tetramer-dimer equilibrium for human carbon monoxide-hemoglobin (HbCO) has been studied in the ultracentrifuge from pH 7.0 to 10.75 by Edelstein et al. (1970) and Andersen et al. (1971). Alkaline denaturation at high pH values during the long times required for the equilibrium studies (12 hrs.) did not allow the collection of sufficiently extensive data for fitting to proton equilibrium models since a plot of the equilibrium constant as a function of pH did not approach a plateau at high pH values. The rate of the absorbance change at 245 nm following a rapid pH jump in the stopped-flow apparatus was assigned to the tetramer dimer process. These rate studies were at pH 10.6. A flow-flash study by Gibson and Antonini (1967) at pH 7.0 and 0.25 uM initial concentration of tetramer gave a relaxation rate constant of 1.24 sec Observations of slowly varying absorbance changes at 429 nm of deoxygenated hemoglobin at pH 7.0 following rapid deoxygenation were interpreted by Kellet and Gutfreund (1970) so as to give a dissociation constant for the tetramer of 1.35 sec”'*'.
