ELECTRON PARAMAGNETIC RESONANCE OF NITRIC OXIDE CYTOCHROME C

A virtually identical electron paramagnetic resonance (epr) spectrum of NO-terrocytochrome c was obtained in solution at pH 12, pH 7 and in powdered form. The spectrum is entirely different from the one reported by previous authors. There are two sets of N14 hyperfine structure, one from N14O and the other due to the imidazole nitrogen of the axial histidine residue. Cytochrome c powder (ferri or ferro) which does not yield NO-ferrocytochrome c when dissolved in pH 7 buffer, was found to react with NO to give an identical epr pattern, indicating some structural change around the heme group in the dry state. © 1969.