Negative ion fragmentations of deprotonated peptides: backbone cleavages directed through both Asp and Glu.
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.
Brinkworth
C S
CS
Department of Chemistry, The University of Adelaide, South Australia 5005, Australia.
Dua
S
S
McAnoy
A M
AM
Bowie
J H
JH
D000595:Amino Acid Sequence; D000818:Animals; D001001:Anura; D001224:Aspartic Acid / Q000032:analysis*; D019471:Elementary Particle Interactions; D018698:Glutamic Acid / Q000032:analysis*; D007477:Ions; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D016339:Spectrometry, Mass, Fast Atom Bombardment
D007477:Ions; D010455:Peptides; D001224:Aspartic Acid; D018698:Glutamic Acid