Reactivity differences between haemoglobins. Part XII. Spectral and reactivity studies on the α-chain of human methaemoglobin A

Abstract

Using standard methods, the polypeptide α-chain of human haemoglobin A, with the haem group attached, has been prepared and purified. The spectra of the met form and its derivatives have been characterised. The spectrum of the met form of the α-chain is distinctly different from that of methaemoglobin A and closely similar to that of methaemoglobin Norfolk and these spectra shown to be consistent with the existence of two forms of methaemoglobin. Possible structural differences between the two forms are discussed. The formation constant of the azide complex of met α-chain has been measured under different conditions of pH and temperature. The thermodynamic data for the reaction are comparable with those for other methaemoglobins.