title: Mössbauer spectroscopy on oxygenated sperm whale myoglobin: evidence for an Fe3+-O2- coupling at the active center.
abstract: 57Fe Mössbauer spectra of oxygenated sperm whale myoglobin (MbO2) show a well resolved quadrupole doublet with a temperature dependent splitting. The temperature dependence of the corresponding electric field gradient tensor (EFG) can be calculated from a Fe3+ term scheme for the iron at the active center. The Mössbauer spectra as well as the diamagnetc character of the MbO2-complex are then understood by an exchange coupling of the Fe3+-ion with O2- oxygen molecule ion. The resulting groundstate is a diamagnetic singlet. In order to keep the whole complex diamagnetic at room temperature, an exchange coupling with [J] greater than or equal to 300cm-1 is necessary. As the whole model is in fair agreement with many other spectroscopic data, it is believed to be a good starting point for further detailed calculations.
mesh_terms: D000818:Animals; D001665:Binding Sites; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005290:Ferric Compounds; D008024:Ligands; D009211:Myoglobin; D010100:Oxygen; D013057:Spectrum Analysis / Q000379:methods; D013696:Temperature; D014907:Whales
chemical_list: D005290:Ferric Compounds; D008024:Ligands; D009211:Myoglobin; D010100:Oxygen