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Electrospray ionization ion trap multiple‐stage mass spectrometric fragmentation pathways of leucine and isoleucine: an ab initio computational study
Author(s) -
Armirotti Andrea,
Scapolla Carlo,
Benatti Umberto,
Damonte Gianluca
Publication year - 2007
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3198
Subject(s) - chemistry , fragmentation (computing) , tandem mass spectrometry , isoleucine , ion trap , ab initio , electrospray ionization , mass spectrometry , selected reaction monitoring , computational chemistry , ion , tandem , electrospray , analytical chemistry (journal) , leucine , amino acid , chromatography , organic chemistry , biochemistry , materials science , computer science , composite material , operating system
We recently demonstrated the possibility to distinguish between leucine and isoleucine in several tryptic peptides by means of consecutive tandem mass steps (Armirotti et al. J . Am . Soc . Mass Spectrom . 2007; 18: 57), exploiting a gas‐phase rearrangement of the immonium ion of Ile. In the present paper we explore the tandem mass spectrometric behaviour of the two amino acids. We propose a plausible structure for the diagnostic m/z 69 ion of Ile, that was reported for the first time in 1996 (Hulst and Kientz J . Mass . Spectrom . 1996; 31: 1188), and we explain why its formation is favoured with respect to Leu. Our conclusions are supported by ab initio quantum chemistry calcultations and isotope‐labelled standards experiments. Copyright © 2007 John Wiley & Sons, Ltd.