EPR study of the hemoglobin rotational correlation time and microviscosity during the polymerization of hemoglobin S

Abstract

The microviscosity and the protein rotational correlation time are analyzed in samples of hemoglobin A and hemoglobin S with the intracellular concentration at 36ºC and during spontaneous deoxygenation. With this purpose, we use glutathione and carbonmonoxy hemoglobin labeled with 4 maleimido 2,2,6,6-tetramethyl-piperidine-l-oxyl (TEMPO) as probes and 4 maleimido TEMPO bound to the hemoglobin (A and S) as a spin label. The saturation transfer electron paramagnetic resonance experiment showed the sigmoidal behavior, and the increase (about twice) of the hemoglobin rotational correlation time and microviscosity during the polymerization process of hemoglobin S. The delay time determined by this method coincides with that obtained in proton magnetic resonance experiments. These results help to explain the temporal behavior of the proton relaxation times obtained in samples of hemoglobin A and S under the same experimental conditions.