Specific fragmentation of thioxo peptides facilitates the assignment of the thioxylated amino acid

✍ Scribed by Pfeifer, Thomas; Schierhorn, Angelika; Friedemann, Rudolf; Jakob, Mario; Frank, Robert; Schutkowski, Mike; Fischer, Gunter

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 542 KB
• Volume: 32
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/(sici)1096-9888(199711)32:10<1064::aid-jms560>3.0.co;2-7

✦ Synopsis

Low-energy collision-induced dissociation (CID) product ion spectra of a series of singly protonated thioxo peptides produced by electrospray ionization (ESI) were obtained by triple-quadrupole tandem mass spectrometry. The principal feature of the spectra is a preferential cleavage of the peptide bond succeeding the thioxo peptide moiety. Thus this method provides the possibility of assigning the position of the thioxylated amino acid in oligopeptides resulting from the thioxylation procedure with LawessonÏs or a related reagent. At low collision energy, dominant B ions and/or complementary Y/ ions are observed. Higher collision energy yields internal ions that consist of two adjacent amino acids encompassing the thioxo peptide bond. The formation of these internal ions and the elimination of CO from them give evidence for the position of the thioxylated amino acid. There are strong indications of a stabilization of the B and internal ions through the formation of a thiazolone. Fragment ions resulting from the cleavage of the thioxo peptide bond are either completely absent or of very low intensity.

by John Wiley & Sons, ( Ltd.