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A matrix-assisted laser desorption/ionization compatible reagent for tagging
tryptophan residues Chunyan Li, Vijay Gawandi, Adam Protos, Robert S. Phillips and I. Jonathan Amster* Department of Chemistry, University
of Georgia, Athens, Georgia 30602, USA. E-mail: jamster@uga.edu
ABSTRACT:
Chemical tagging of amino acids is an important tool in proteomics analysis, and has been used to
introduce isotope labels and mass defect labels into proteolytic peptides by derivatization of cysteine or lysine residues. Here we present a new reagent with chemical specificity
for tryptophan residues. Previously, 2-nitrobenzenesulfenyl chloride has been used as a highly specific reagent for labeling tryptophan residues. We show that this tag
undergoes UV dissociation during MALDI. The multiplicity of photofragments increases the difficulty of characterizing the derivatization products. To overcome this problem, we
have synthesized a new reagent, 2-(trifluoromethyl)benzenesulfenyl chloride, which is shown to react quantitatively with tryptophan in peptides and proteins. Most significantly, it
exhibits high photostability in MALDI-FTMS analyses.
Keywords:
tryptophan, photosensitivity, MALDI, 2-nitrobenzenesulfnenyl chloride, 2-(trifluoromethyl)benzenesulfenyl chloride
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