A simple method to identify cysteine residues by isotopic labeling and ion trap mass spectrometry

Abstract

A simple method was developed to facilitate the identification of cysteine-containing peptides based on S-carboxymethylation of cysteine residues with isotopically enriched bromoacetic acid. An ion trap mass spectrometer with high-resolution scan functionality allows identification of the unique isotopic distribution patterns specific to the modified peptides.

Identification of phosphopeptides by chemical modification with an isotopic tag and ion trap mass spectrometry

“…The derivatization reagent was a mixture of 1:1 CH 3 NH 2 /CD 3 NH 2 ; thus, derivatized peptides would yield peaks in the mass spectrum with specific isotope distributions corresponding to the presence of a phosphate group. The isotope distributions can be recognized by high-resolution zoomscan, 22 allowing easy identification of the presence and determination of the number of phosphate residues in the peptides.…”

“…The method described here is based on the combined strengths of isotopic labeling to provide a specific fingerprint of phosphopeptides, and zoom scan capabilities of modern ion trap instruments to provide the unique monoisotopic distribution patterns. 22 The procedure was demonstrated on $10 pmol of sample and should not require significantly more sample handling than is usual for typical peptide identification experiments. The MS/MS spectra of underivatized phosphopeptides are usually dominated by fragment ions resulting from the neutral loss of phosphate, from which it is not always possible to obtain detailed information on phosphorylation.…”

Sequencing of anti-thyroxine monoclonal antibody Fab fragment by ion trap mass spectrometry

“…An aliquot of fresh aqueous DTT solution (10 µL, 200 mM) was added and the mixture was incubated at 50 °C for 3 h and then allowed to cool to ambient temperature. The modification of thiol groups was carried out by the addition of an aliquot of an equimolar mixture (1:1) of BrCH 2 COOH and Br 13 CH 2 13 COOH (25 µL, 200 mM, pre‐adjusted to pH 8.0 with 2 M NaOH) 15. The resulting mixture was incubated in the dark for 10 min at ambient temperature.…”

Current chemical tagging strategies for proteome analysis by mass spectrometry

“…Cysteine tags that contain elements with a characteristic isotope pattern, like chlorine or bromine, can be used to identify Cys-peptides in mass spectra, as demonstrated by Adamczyk et al [92][93] and Aebersold and co-workers [94]. Alternatively, MS spectra can be acquired before and after alkylation and Cys residues can be identified from the mass shifts that are observed [95][96].…”