Fragmentation of deprotonated N-benzoylpeptides: formation of deprotonated oxazolones.
The fragmentation reactions of deprotonated N-benzoyl peptides, specifically hippurylglycine, hippurylglyclyclycine, and hippurylphenylalanine (hippuryl = N-benzoylGly) have been studied using MS2 and MS3 experiments as well as deuterium labeling. A major fragment ion is observed at m/z 160 ([C9H6NO2]-) which, upon collisional activation, mainly eliminates CO2 indicating that the two oxygen atoms have become bonded to the same carbon. This observation is rationalized in terms of formation of deprotonated 2-phenyl-5-oxazolone. Various pathways to the deprotonated oxazolone have been elucidated through MS3 experiments. Fragmentation of deprotonated N-acetylalanylalanine gives a relatively weak signal at m/z 112 which, upon collisional activation, fragments, in part, by loss of CO2 leading to the conclusion that the m/z 112 ion is deprotonated 2,4-dimethyl-5-oxazolone.
Harrison
Alex G
AG
Department of Chemistry, University of Toronto, Toronto, Ontario, Canada. aharriso@chem.utoronto.ca
Young
Alex B
AB
D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D013058:Mass Spectrometry; D015394:Molecular Structure; D010081:Oxazolone / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D011522:Protons
D010446:Peptide Fragments; D010455:Peptides; D011522:Protons; C017369:N-hippurylglycine; D010081:Oxazolone; D005998:Glycine