ELECTRON SPIN RESONANCE OF CU(2) IN COPPER-HEMOGLOBIN COMPLEXES

Electron spin resonance data indicate that two cupric ions bind to a molecule of hemoglobin at pH 5.4 to 8.9. The binding sites of both ions are identical and are characterized by the presence of resolved superhyperfine structure indicating a considerably covalent bond between the metal and most probably four equivalent nitrogens. Introduction of more than two Cu(II) ions produces precipitation of the protein accompanied by changes in the ESR spectra. The ESR spectra of Cu(II) are identical in oxygenated and methemoglobin. Fe(II) of the former oxidizes partly to Fe(III). Comparison with copper-myoglobin complexes indicates that the metal sites are different in the two proteins. © 1969.