Side-Chain Losses in Electron Capture Dissociation To Improve Peptide Identification
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- 作者：Mikhail M. Savitski ; Michael L. Nielsen ; Roman A. Zubarev
- 刊名：Analytical Chemistry
- 出版年：2007
- 出版时间：March 15, 2007
- 年：2007
- 卷：79
- 期：6
- 页码：2296 - 2302
- 全文大小：151K
- 年卷期：v.79,no.6(March 15, 2007)
- ISSN：1520-6882
文摘
Analysis of a database of some 20 000 conventionalelectron-capture dissociation (ECD) mass spectra ofdoubly charged ions belonging to tryptic peptides revealedwidespread appearance of w ions and related u ions thatare due to partial side chain losses from radical z
ions.Half of all z ions that begin with Leu or Ile produce wions in conventional one-scan ECD mass spectra, whichdifferentiates these isomeric residues with >97% reliability. Other residues exhibiting equally frequent sidechain losses are Gln, Glu, Asp, and Met (cysteine was notincluded in this work). Unexpectedly, Asp lost not aradical group like other amino acids but a molecule CO2,thus giving rise to a radical w ion with the possibility of aradical cascade. Losses from amino acids as distant asseven residues away from the cleavage site weredetected. The mechanism of such losses seems to berelated to radical migration from the original site at the
Cn atom in a zn ion to other C and 
C atoms. The sidechain losses confirm sequence assignment, improve thedatabase matching score, and can be useful in de novosequencing.
ions.Half of all z ions that begin with Leu or Ile produce wions in conventional one-scan ECD mass spectra, whichdifferentiates these isomeric residues with >97% reliability. Other residues exhibiting equally frequent sidechain losses are Gln, Glu, Asp, and Met (cysteine was notincluded in this work). Unexpectedly, Asp lost not aradical group like other amino acids but a molecule CO2,thus giving rise to a radical w ion with the possibility of aradical cascade. Losses from amino acids as distant asseven residues away from the cleavage site weredetected. The mechanism of such losses seems to berelated to radical migration from the original site at theCn atom in a zn ion to other C and C atoms. The sidechain losses confirm sequence assignment, improve thedatabase matching score, and can be useful in de novosequencing.