Spin-density distribution in the (FeO2) - complex. Electron spin resonance of myoglobin single crystals

Leibl, W.; Nitschke, W.; Huttermann, J.

Biochimica et Biophysica Acta 8701: 20-30

1986


ISSN/ISBN: 0005-2728
DOI: 10.1016/0167-4838(86)90004-x
Accession: 021788979

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Abstract
X-irradiated oxymyoglobin (MbO2) exhibits electron spin resonance (ESR) spectra at 77 K due to two distinct FeO2 - centers formed by electron addition to the dioxygen. In single crystals with 17O and 57Fe isotope enrichment in the heme-ligand complex, the full set of spectral parameters is analyzed for one of the centers (gmax = 2.23, gint = 2.13, gmin = 1.97; HOmax = 2.66 mT, HOint = 1.61 mT, HOmin = 0.57 mT; HFe max = 1.62 mT, HFe int = 0.57 mT, HFe min = 0.49 mT) and the iron-dioxygen spin-density distribution and bonding geometry is derived. The g-tensor is evaluated for the second species at 77 K (gmax = 2.25, gint = 2.11, gmin = 1.95). Both centers transform into secondary species at 180 K for which the g-tensor elements are analyzed (gmax = 2.31, gint = 2.18, gmin = 1.93; gmax = 2.35; gint = 2.21, gmin = 1.91).