Electron paramagnetic resonance study of nitrosyl haemoglobin M Iwate

The nitrosyl derivative of haemoglobin M Iwate, a haemoglobin variant which has functional beta chains and non-functional alpha chains, is known to exist only in a low affinity form. It shows a nine-line superhyperfine (SHF) pattern in the low temperature electron paramegnetic resonance (e.p.r.) spectrum, even in the presence of inositol hexaphosphate. This provides further support for the suggestion (Chevion, M., Stern, A., Peisach, J., Blumberg, W. E. and Simon, S. Biochemistry 1978 bd17, 1745) that the beta chains of tetrameric, fully ligated, nitrosyl derivatives of all haemoglobins invariably exhibit an e.p.r. spectrum with a nine-line SHF pattern regardless of the affinity state of the molecule. On the other hand, nitrosyl ferrous alpha chains within the haemoglobin tetramer can exhibit an e.p.r. spectrum with either a nine-line or a three-line SHF pattern which is dependent upon the affinity state of the molecule.