DSpace Repository

Fragmentation of Lanthanide (III) Cationized Small Peptides: Generation of Peptide Radical Cations and Dipositive a and b ions.

Fragmentation of Lanthanide (III) Cationized Small Peptides: Generation of Peptide Radical Cations and Dipositive a and b ions.

Show full item record

Title: Fragmentation of Lanthanide (III) Cationized Small Peptides: Generation of Peptide Radical Cations and Dipositive a and b ions.
Author: Wang, Yating
Abstract: This research work examines the dissociation chemistry of tripositive complexes formed by trivalent lanthanide ions and small peptides with tandem mass spectrometry under low-energy collision-induced dissociation (CID). By fragmentation of the tripositive lanthanide(III) cationized small peptide, a new route to generate peptide radical cations has been discovered. The dipositive b ions are also observed and the mechanisms by which they fragment are investigated by MSn.
Tripositive complexes of lanthanide(III)/peptide have similar fragmentation chemistries in the gas phase when lanthanide = yttrium, lanthanum, cerium, samarium, gadolinium and terbium; [a3+H]2+ ions are formed and there are no peptide radical cations observed. When the lanthanide is europium(III), radical cations of tryptophan-, tyrosine-, phenylalanine-, methionine-containing peptides and of aliphatic peptides have been generated.
Fragmentations of tripositive Ce(III)/peptide and Eu(III)/peptide complexes show very different behaviours. Abundant CO loss is only observed for dissociation of Ce(III)/peptide complexes, whereas CO2 loss is the predominant channel for Eu(III)/peptide complexes. Similarly, CO loss and CO2 loss are the predominant channels for the dissociations of [Ce(peptide-H)]2+ and [Eu(peptide-H)]2+, respectively. Peptide radical cations are only generated by the fragmentation of Eu(III)/peptide complexes, while protonated a and b ions are only observed when Ce(III)/peptide complexes dissociate.
The dissociations of aliphatic [peptide]+ions generate [b3-H]+/ [b2-H]+ions for most peptides. In the dissociation of [a3+H]+ions, [b2-H]+ions are formed from most peptides.
[a3+H]2+ ions usually cleave at the C-terminal amide bonds, creating two singly charged ions, a [b2]+ ion and an iminium ion derived from the C-terminal residue. Some [a3+H]2+ ions also lose small neutral molecules. The composition of the peptides dictates the preferred mode of the fragmentation of [b3+H]2+ ions, either loss of CO to form [a3+H]2+, or loss of CO plus H2O.
Fragmentations of [Ce(peptide-H)]2+ ions show CO loss, and CO2 losses are observed for peptides with aromatic side chains or a methionine residue at C-terminus. For [Ce(peptide-H)(peptide)]2+ complexes, neutral losses are also observed but formation of two singly charged ions is dominant. The dissociation behaviour of [Ce(peptide-H)(CH3CN)]2+ and [Eu(peptide-H)(CH3CN)]2+ complexes are quite different. The former loses only CH3CN whereas the latter loses only CO2.
Subject: Analytical chemistry
Keywords: Tandem Mass Spectrometry
CID
MSn
Electrospray Ionization
Fragmentation
Metal/Peptide Complex
Lanthanide
Europium
Cerium
Trivalent Metal Ion
Small Peptide
Radical Cation
New Route
Dipositive b ion
Dipositive a ion
Tripositive Complex
Dipositive Complex
Aromatic Peptide
Aliphatic Peptide
Proline-containing Peptide
Type: Electronic Thesis or Dissertation
Rights: Author owns copyright, except where explicitly noted. Please contact the author directly with licensing requests.
URI: http://hdl.handle.net/10315/34980
Supervisor: Siu, K.W. Michael
Degree: PhD - Doctor of Philosophy
Program: Chemistry
Exam date: 2018-03-02
Publish on: 2018-08-27

Files in this item



This item appears in the following Collection(s)