Synthesis of 13C-Labeled iodoacetanilide and application to quantitative peptide analysis by isotope differential mass spectrometry

13C-Labeled and unlabeled iodoacetanilides have been synthesized for covalent modification of the sulfhydryl groups of cysteine residues in proteins or peptides. A combination of these reagents, coupled with mass spectrometry, is a powerful tool for quantitative analysis of peptides and hence proteins.