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Updated: Aug 12, 2026

Determination of the Gas-phase Acidities of Oligopeptides
Published on: June 24, 2013
Negative ion fragmentations of deprotonated peptides: backbone cleavages directed through both Asp and Glu
C S Brinkworth1, S Dua, A M McAnoy
1Department of Chemistry, The University of Adelaide, South Australia 5005, Australia.
Abstract:
The collision-induced spectra of [M - H](-) ions of a variety of natural and synthetic amphibian peptides containing Asp and/or Glu exhibit characteristic gamma backbone cleavage ions that identify the positions of these residues in the peptide. A theoretical study suggests that the Glu cleavage involves an S(N)i reaction of the carboxylate anion from the Glu alpha side chain to form a deprotonated cyclic lactone. The presence of either Asp or Glu or other residues that effect pronounced side-chain cleavages (e.g. Ser or Thr) results in the normal alpha and beta backbone cleavages being reduced in comparison to those cleavages which originate from side chains.
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