Electron capture at the iron-oxygen centre in single crystals of oxymyoglobin studied by electron spin resonance spectroscopy.

Exposure of single crystals of oxy-myoglobin to 60Co gamma-rays at 77 K results in electron addition to the Fe-O2 units. The resulting ESR spectrum has been analysed to give the principal values and directions for the g-tensor of this unit. The results suggest that the dioxygen ligand is strongly tilted, the direction of tilt being close to one of the bisectors of the N-Fe-N bond angles. Possible reasons for this orientation are discussed.