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Determination of the Gas-phase Acidities of Oligopeptides
Published on: June 24, 2013
Negative ion dissociation of peptides containing hydroxyl side chains
1Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487, USA.
Rapid Communications in Mass Spectrometry : RCM
|December 7, 2007
Summary
This study investigated peptide dissociation using ESI-FTICR and MALDI-TOF, revealing side-chain losses and selective C-terminal residue cleavage in serine and threonine peptides, unlike tyrosine peptides.
Area of Science:
- Analytical Chemistry
- Mass Spectrometry
- Proteomics
Background:
- Peptide fragmentation mechanisms are crucial for protein identification and characterization.
- Understanding hydroxyl side chain reactivity in peptides informs structural analysis.
- Negative ion mode mass spectrometry offers complementary fragmentation pathways.
Purpose of the Study:
- To investigate the dissociation pathways of deprotonated peptides containing serine, threonine, or tyrosine residues.
- To compare side-chain loss and C-terminal residue cleavage mechanisms in different hydroxyl-containing amino acids.
- To elucidate the role of the C-terminal carboxylic acid group and hydroxyl side chain in peptide fragmentation.
Main Methods:
- Electrospray ionization coupled with Fourier transform ion cyclotron resonance (ESI-FTICR) using sustained off-resonance irradiation collision-induced dissociation (SORI-CID).
- Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry under post-source decay (PSD) conditions.
- Analysis of hexapeptides containing one serine, threonine, or tyrosine residue alongside five alanine residues.
Main Results:
- Negative ion SORI-CID and PSD spectra showed characteristic side-chain losses: formaldehyde (serine), acetaldehyde (threonine), and a cyclohexadienone derivative (tyrosine).
- Tyrosine-containing peptides exhibited significantly less side-chain loss compared to serine and threonine peptides, attributed to steric hindrance.
- Selective C-terminal residue elimination was observed for peptides with serine or threonine at the C-terminus, dependent on the C-terminal carboxylic acid and hydroxyl group.
Conclusions:
- The dissociation behavior of deprotonated peptides is influenced by the nature of the hydroxyl side chain.
- Steric factors play a significant role in the extent of side-chain fragmentation.
- A specific mechanism involving the C-terminal carboxylic acid and hydroxyl group is proposed for C-terminal residue loss in serine and threonine peptides.
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