Tandem mass spectrometry of peptides: Mechanistic aspects and structural information based on neutral losses. II—Tri- and larger peptides
Article first published online: 7 APR 2005
Copyright © 1994 John Wiley & Sons, Ltd.
Organic Mass Spectrometry
Volume 29, Issue 7, pages 382–390, July 1994
How to Cite
Cordero, M. M. and Wesdemiotis, C. (1994), Tandem mass spectrometry of peptides: Mechanistic aspects and structural information based on neutral losses. II—Tri- and larger peptides. Org. Mass Spectrom., 29: 382–390. doi: 10.1002/oms.1210290709
- Issue published online: 7 APR 2005
- Article first published online: 7 APR 2005
- Manuscript Accepted: 16 MAR 1994
- Manuscript Revised: 10 MAR 1994
- Manuscript Received: 15 DEC 1993
The neutral products arising during the collisionally activated dissociation of protonated oligopeptides (MH+) are post-ionized by collision and detected in neutral fragment-reionization (+NfR+) mass spectra. For the isomeric tripeptides Ala-Gly-Gly, Gly-Ala-Gly and Gly-Gly-Ala, the amino acid and dipeptide losses from the C-terminus and the diketopiperazine losses from the N-terminus allow for differentiation. These neutral fragments are identified in the corresponding +NfR+ spectra by comparison to reference collision-induced dissociative ionization (CIDI) mass spectra of individual amino acids, dipeptides and diketopiperazines. Peptides with distinct C-termini but otherwise identical sequences are found to yield +NfR+ products that are characteristic of the respective C-terminal amino acid. This is demonstrated for several peptide pairs, including leucine- and methionine-enkephalin. In general, +NfR+ spectra are dominated by the heavier neutral losses; further, +NfR+ and CIDI cause extensive dissociation, indicating that the collisional ionization process imparts high average internal energies.