Mössbauer study of cytochrome c3

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.