Nuclear magnetic resonance studies of slowly exchanging peptide protons in cytochrome c in aqueous solution

The slowly exchanging protons in oxidized and reduced horse heart cytochrome c (D20, uncorrected pH meter reading 6.5 room temperature) have been monitored by recording the 270 and 360 MHz proton nuclear magnetic resonance spectra of the reduced protein between 5 and 11 parts per million downfield from 2,2-dimethyl-2-silapentane-5-sulfonate.