Gas-phase fragmentation reactions of a(7) ions containing a glutamine residue


ATİK A. E. , Arslanoglu A., Yalcin T.

JOURNAL OF MASS SPECTROMETRY, vol.56, no.8, 2021 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 56 Issue: 8
  • Publication Date: 2021
  • Doi Number: 10.1002/jms.4776
  • Title of Journal : JOURNAL OF MASS SPECTROMETRY
  • Keywords: a(7) ion, CID, glutamine, imine-amide structure, peptide fragmentation, tandem mass spectrometry, COLLISION-INDUCED DISSOCIATION, DENSITY-FUNCTIONAL THEORY, AMINO-ACID, INFRARED-SPECTROSCOPY, PROTONATED PEPTIDES, SEQUENCE DATABASES, MASS-SPECTROMETRY, IR SPECTROSCOPY, LEU-ENKEPHALIN, CYCLIZATION

Abstract

The gas-phase fragmentation reactions of the a(7) ions derived from glutamine (Q) containing model heptapeptides have been studied in detail with low-energy collision-induced dissociation (CID) tandem mass spectrometry (MS/MS). Specifically, the positional effect of the Q residue has been investigated on the fragmentation reactions of a(7) ions. The study involves two sets of permuted isomers of the Q containing model heptapeptides. The first set contains the QAAAAAA sequence, and the second set involves of QYAGFLV sequence, where the position of the Q residue is changed from N- to C-terminal gradually for both peptide series. An intense loss of ammonia from the a7 ions followed by internal amino acid eliminations strongly supports forming the imine-amides structure via cyclization/rearrangement reaction for all studied a(7) ions. This is in agreement with the pioneering study reported by Bythell et al. (2010, 10.1021/ja101556g). A novel rearrangement reaction is detected upon fragmentation of imine-amide structure, which yields a protonated C-terminal amidated hexapeptide excluding the Q residue. A possible fragmentation mechanism was proposed to form the protonated C-terminal amidated hexapeptide, assisted via nucleophilic attack of the side chain amide nitrogen of the Q residue on its N-protonated imine carbon atom of the rearranged imine-amide structure. Highlights The gas-phase fragmentation reactions of a(7) ions obtained from protonated model peptides containing glutamine residue were studied by ESI-MS/MS. A rearranged imine-amide structure is the predominant even for a(7) ions. Novel rearrangement reaction is observed which forms a protonated C-terminal amidated hexapeptide excluding Q residue upon fragmentation of the imine-amide structure.