Colombo MF, Sanches R. Hydration-dependent conformational states of hemoglobin. Equilibrium and kinetic behavior.
Biophys Chem 1990;
36:33-9. [PMID:
2207271 DOI:
10.1016/0301-4622(90)85004-p]
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Abstract
The equilibrium and kinetics of methemoglobin conversion to hemichrome induced by dehydration were investigated by visible absorption spectroscopy. Below about 0.20 g water per g hemoglobin only hemichrome was present in the sample; above this value, an increasing proportion of methemoglobin appeared with the increase in hydration. The transition between the two derivatives showed a time-dependent biphasic behavior and was observed to be reversible. The rates obtained for the transition of methemoglobin to hemichrome were 0.31 and 1.93 min-1 and for hemichrome to methemoglobin 0.05 and 0.47 min-1. We suggest that hemichrome is a reversible conformational state of hemoglobin and that the two rates observed for the transition between the two derivatives reflect the alpha- and beta-chains of hemoglobin.
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