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Side-chain losses in electron capture dissociation to improve peptide identification
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, MMS, Medical Mass Spectrometry.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, MMS, Medical Mass Spectrometry.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, MMS, Medical Mass Spectrometry.
2007 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 79, no 6, 2296-2302 p.Article in journal (Refereed) Published
Abstract [en]

Analysis of a database of some 20 000 conventional electron-capture dissociation (ECD) mass spectra of doubly charged ions belonging to tryptic peptides revealed widespread appearance of w ions and related u ions that are due to partial side chain losses from radical z. ions. Half of all z. ions that begin with Leu or Ile produce w ions in conventional one-scan ECD mass spectra, which differentiates these isomeric residues with >97% reliability. Other residues exhibiting equally frequent side chain losses are Gln, Glu, Asp, and Met (cysteine was not included in this work). Unexpectedly, Asp lost not a radical group like other amino acids but a molecule CO2, thus giving rise to a radical w. ion with the possibility of a radical cascade. Losses from amino acids as distant as seven residues away from the cleavage site were detected. The mechanism of such losses seems to be related to radical migration from the original site at the αCn atom in a Zn. ion to other αC and βC atoms. The side chain losses confirm sequence assignment, improve the database matching score, and can be useful in de novo sequencing.

Place, publisher, year, edition, pages
2007. Vol. 79, no 6, 2296-2302 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-95358DOI: 10.1021/ac0619332ISI: 000244867100013PubMedID: 17274597OAI: oai:DiVA.org:uu-95358DiVA: diva2:169535
Available from: 2007-01-17 Created: 2007-01-17 Last updated: 2017-12-14Bibliographically approved
In thesis
1. New Proteomics Methods and Fundamental Aspects of Peptide Fragmentation
Open this publication in new window or tab >>New Proteomics Methods and Fundamental Aspects of Peptide Fragmentation
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Nya Proteomik Metoder och Fundamentala Aspekter av Peptid Fragmentering
Abstract [en]

The combination of collision-activated dissociation, (CAD) and electron capture dissociation, (ECD) yielded a 125% increase in protein identification. The S-score was developed for measuring the information content in MS/MS spectra. This measure made it possible to single out good quality spectra that were not identified by a search engine. Poor quality MS/MS data was filtered out, streamlining the identification process.

A proteomics grade de novo sequencing approach was developed enabling to almost completely sequence 19% of all MS/MS data with 95% reliability in a typical proteomics experiment.

A new tool, Modificomb, for identifying all types of modifications in a fast, reliable way was developed. New types of modifications have been discovered and the extent of modifications in gel based proteomics turned out to be greater than expected.

PhosTShunter was developed for sensitive identification of all phosphorylated peptides in an MS/MS dataset.

Application of these programs to human milk samples led to identification of a previously unreported and potentially biologically important phosphorylation site.

Peptide fragmentation has been studied. It was shown emphatically on a dataset of 15.000 MS/MS spectra that CAD and ECD have different cleavage preferences with respect to the amino acid context.

Hydrogen rearrangement involving z• species has been investigated. Clear trends have been unveiled. This information elucidated the mechanism of hydrogen transfer.

Partial side-chain losses in ECD have been studied. The potential of these ions for reliably distinguishing Leu/Iso residues was shown. Partial sidechain losses occurring far away from the cleavage site have been detected.

A strong correlation was found between the propensities of amino acids towards peptide bond cleavage employing CAD and the propensity of amino acids to accept in solution backbone-backbone H-bonds and form stable motifs. This indicated that the same parameter governs formation of secondary structures in solution and directs fragmentation in peptide ions by CAD.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 56 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 264
Keyword
Bioinformatics, Proteomics, Peptide fragmentation, Bioinformatik
Identifiers
urn:nbn:se:uu:diva-7438 (URN)978-91-554-6775-X (ISBN)
Public defence
2007-02-08, B21, BMC, Husargatan 3, Uppsala, 14:15
Opponent
Supervisors
Available from: 2007-01-17 Created: 2007-01-17 Last updated: 2013-09-04Bibliographically approved

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