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The fragmentation pathways of protonated glycine: a computational study
R A O'Hair1, P S Broughton, M L Styles
1School of Chemistry, University of Melbourne, Parkville, Victoria, Australia. r.ohair@chemistry.unimelb.edu.au
Journal of the American Society for Mass Spectrometry
|August 11, 2000
Summary
Protonated amino acids fragment into iminium ions. Computational analysis reveals that losing water and carbon monoxide is the most favored fragmentation pathway for protonated glycine.
Area of Science:
- Computational Chemistry
- Mass Spectrometry
- Organic Chemistry
Background:
- Protonated aliphatic amino acids fragment into iminium ions in the gas phase.
- Previous studies have not elucidated the neutral species lost or the fragmentation mechanism.
- Three fragmentation mechanisms have been proposed: loss of H2O and CO, dihydroxycarbene, or formic acid.
Purpose of the Study:
- To investigate the fragmentation mechanisms of protonated glycine using computational methods.
- To determine the favored pathway for neutral species loss during fragmentation.
Main Methods:
- Ab initio calculations
- Density functional theory (DFT) calculations
- Analysis of reactants, transition states, and products
Main Results:
- The fragmentation of protonated glycine was computationally modeled.
- The loss of water (H2O) and carbon monoxide (CO) was identified as the most thermodynamically and kinetically favored pathway.
- This pathway is preferred over the loss of formic acid or dihydroxycarbene.
Conclusions:
- The fragmentation of protonated glycine predominantly occurs via the loss of H2O and CO.
- Computational chemistry provides detailed insights into gas-phase fragmentation mechanisms.
- Understanding these fragmentation pathways is crucial for interpreting mass spectrometry data of amino acids.