Site-selective and covalent labelling of the cysteine-containing peptide glutathione with a ferrocenyl group

Site-specific labelling of the cysteine-containing peptide glutathione with a ferrocene group was achieved by reaction with ferrocenylmethanol in aqueous acidic medium. The resulting peptide was shown to be a potent competitive inhibitor of the biologically important enzyme glutathione-(S)-transferase. This approach may prove general for the labelling of proteins with ferrocene.