Effect of phenylalanine on the fragmentation of deprotonated peptides.
The fragmentation reactions of a variety of deprotonated dipeptides and tripeptides containing phenylalanine have been studied using energy-resolved collision-induced dissociation, isotopic labeling and MS/MS/MS experiments. The benzyl a-group has a substantial effect on the fragmentation reactions observed. When the phenylalanine is in the C-terminal position of dipeptides or tripeptides a major fragmentation reaction is elimination of neutral cinnamic acid to from a deprotonated amino acid amide (c1 ion) for dipeptides and a deprotonated dipeptide amide (c2 ion) for tripeptides. Fragmentation of the [M - H]- ions of tripeptides with phenylalanine in the central position also results in substantial formation of the deprotonated amide of the N-terminal amino acid residue. When the phenylalanine residue is in the N-terminal position elimination of C7H8 from the [M - H - CO2]- ion and formation of the benzyl anion become important fragmentation pathways. Sequence ions frequently observed are the y1 ions, "b2 ions and a3-Nt ions.
Harrison
Alex G
AG
Department of Chemistry, University of Toronto, Ontario, Canada. aharriso@utoronto.ca
D010455:Peptides / Q000737:chemistry*; D010649:Phenylalanine / Q000737:chemistry*; D011522:Protons; D021241:Spectrometry, Mass, Electrospray Ionization
D010455:Peptides; D011522:Protons; D010649:Phenylalanine