title: Mössbauer effect in the high-potential iron-sulphur protein from Chromatium. Evidence for the state of the iron atoms.
abstract: 1. The previous Mössbauer work on Chromatium high-potential iron-sulphur protein by Moss et al. (1968) and Evans et al. (1970) was extended to high applied magnetic fields. 2. Measurements of the reduced protein confirm that it is non-magnetic. 3. Spectra of the oxidized protein in applied magnetic fields clearly indicate that some iron atoms have a positive hyperfine field, which is evidence for antiferromagnetic coupling. 4. The spectra can be interpreted in terms of two types of iron atom with positive and negative hyperfine fields of 9 and 12T respectively. 5. A consideration of the chemical shifts and other evidence suggests formal valences of two Fe(3+) and two Fe(2+) atoms in the non-magnetic reduced state, and three Fe(3+) atoms and one Fe(2+) atom in the oxidized state. 6. However, no separate Fe(3+) and Fe(2+) spectra are seen, suggesting that the d electrons are not localized on particular iron atoms.
mesh_terms: D001426:Bacterial Proteins / Q000302:isolation & purification; D001665:Binding Sites; D002844:Chromatium / Q000032:analysis*; D007501:Iron / Q000032:analysis*; D008280:Magnetics; D008667:Metalloproteins / Q000302:isolation & purification; D010084:Oxidation-Reduction; D011199:Potentiometry; D011485:Protein Binding; D011487:Protein Conformation; D013057:Spectrum Analysis; D013455:Sulfur / Q000032:analysis*
chemical_list: D001426:Bacterial Proteins; D008667:Metalloproteins; D013455:Sulfur; D007501:Iron