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Tandem mass spectrometry of peptides: Mechanistic aspects and structural information based on neutral losses. II—Tri‐ and larger peptides
Author(s) -
Cordero Marcela M.,
Wesdemiotis Chrys
Publication year - 1994
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210290709
Subject(s) - chemistry , diketopiperazines , tripeptide , dipeptide , dissociation (chemistry) , tandem mass spectrometry , amino acid , peptide , ionization , protonation , collision induced dissociation , mass spectrometry , electrospray ionization , stereochemistry , mass spectrum , chromatography , ion , organic chemistry , biochemistry
The neutral products arising during the collisionally activated dissociation of protonated oligopeptides (MH + ) are post‐ionized by collision and detected in neutral fragment‐reionization ( + N f R + ) 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 + N f R + 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 + N f R + 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, + N f R + spectra are dominated by the heavier neutral losses; further, + N f R + and CIDI cause extensive dissociation, indicating that the collisional ionization process imparts high average internal energies.