Conformational and functional properties of hemoglobin in perturbed solvent: Kinetics of O2 release

We studied the kinetics of O2 release by oxyhemoglobin caused by sodium dithionite, in the presence and in the absence of organic cosolvents (monohydric alcohols and formamide) at 10°C. This study was performed by using standard stopped‐flow techniques coupled with microprocessor‐based data acquisition. We have fitted the experimental data to a mathematical expression obtained on the basis of a two‐state model that takes into account the kinetic heterogeneity between α‐ and β‐chains and the presence of αβ‐dimers in oxyhemoglobin solutions. Results indicate that the cosolvents mainly affect the allosteric parameter L, i.e., the T ⇄ R conformational equilibrium of hemoglobin, leaving the intrinsic deoxygenation rates of both R and T states almost unaltered. The L values obtained in the present work are in excellent agreement with analogous values previously estimated from oxygen equilibrium measurements.