Synthesis of 13C7-labeled iodoacetanilide and application to quantitative analysis of peptides and a protein by isotope differential mass spectrometry.

(13)C(7)-Labeled iodoacetanilide has been synthesized for specific labeling of sulfhydryl groups of cysteine residues and has been successfully applied to quantitative analysis of peptides and a commercial protein in combination with (13)C-unlabeled iodoacetanilide and a MALDI mass spectrometer. Subsequent tandem mass spectrum analysis revealed that (13)C(7)-labeled iodoacetanilide remained intact during the collision-induced dissociation (CID) conditions.