Electron spin resonance studies of ferrihaemoglobin MOsaka

Abstract

• 1.

  1. As reported previously, the electron spin resonance spectrum of ferrihaemoglobin M_Osaka showed a doublet signal in the g = 6 region. This is considered to be due to the haem iron of the α^M-chain on the basis of measurements of electron spin resonance at each stage in the purification of ferrihaemoglobin M_Osaka.

• 2.

  2. The doublet signal is considered to occur as a result of a splitting of the degenerate g-value of 6.o. A theoretical absorption curve due to electron spin resonance for ferrihaemoglobin M_Osaka, in an amorphous state, is given and is compared with the integrated experimental curve of electron spin resonance.

• 3.

  3. When the E-term in a general spin Hamiltonian was treated as a second-order perturbation, split g-values were calculated as: g_ξ = 6 − 24E/D, g_y = 6+24E/D and g_z = 2. From the experimental g-values, the ratio of the E-term to the D-term was estimated as 0.01. A lowering of the symmetry of the ligand field on the haem iron in the α^M-chain of ferrihaemoglobin M_Osaka is discussed.