Natural abundance 13C-NMR study of paramagnetic horse heart ferricytochrome c cyanide complex: assignment of hyperfine shifted heme methyl carbon resonances.

Hyperfine shifted heme methyl carbon resonances of paramagnetic horse heart ferricytochrome c cyanide complex (Cyt-c(CN)) have been observed for the first time in the natural abundance 13C-NMR spectrum and assigned using 1H-13C heteronuclear chemical shift correlated spectroscopy (1H-13C COSY). Individual heme methyl carbon NMR signal assignment permits a direct comparison between the hyperfine shifts of heme methyl carbon and attached methyl proton resonances which provides a useful information on the delocalization mechanism of the unpaired spin from the pi-conjugated system of porphyrin ring into the peripheral methyl side chains.