Mössbauer study of cytochrome c3

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Abstract
Oxidized cytochrome c3 enriched with 57Fe heme has been investigated using the Mössbauer effect of 57Fe. The isomer shift, quadrupole splitting, and magnetic hyperfine interaction were determined at 300, 77, and 4.2 K. The electronic state is low spin ferric state and is discussed in connection with ESR data. At 4.2 K, the heme–heme interaction was observed to be more than seven times stronger than expected. A strongly reduced relaxation was also observed in the spectra obtained in applied magnetic fields of a few hundred oersteds. This shows that the neighboring ferric ions are completely unequivalent with respect to orientations of the g tensor axes.