Gelation of sickle cell haemoglobin. II. Methaemoglobin

Sickle cell methaemoglobin was assayed for gel formation by an equilibrium ultracentrifugation method previously described. A phase change from sol to gel, indicative of gelation, occurred, depending on conditions, at concentrations between 0.35 and 0.5 g/ml, considerably higher than concentrations observed previously for gelation of deoxyhaemoglobin S. Inositol hexaphosphate favours gelation, but gelation is seen also in its absence. Lowering pH toward 6 favours gelation. If gelation is assumed to require molecules in the T quaternary conformation, these results provide further evidence that methaemoglobin exists in R-T equilibrium in solution and that this equilibrium lies between the extremes exhibited by deoxyhaemoglobin (T-state) and carbon monoxide or oxyhaemoglobin (R-state).