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Backbone and side-chain cleavages in electron detachment dissociation (EDD).
Iwona Anusiewicz1, Marek Jasionowski, Piotr Skurski
1Department of Chemistry and Henry Eyring Center for Theoretical Chemistry, University of Utah, Salt Lake City, Utah 84112, USA.
The Journal of Physical Chemistry. A
|December 8, 2005
Summary
Computational methods reveal peptide fragmentation pathways in negative-ion mode electron-detachment dissociation (EDD) mass spectrometry. C-alpha-C backbone cleavage is favored over side-chain loss, and nitrogen-centered radicals form a*/x fragments.
Area of Science:
- Computational Chemistry
- Mass Spectrometry
- Chemical Physics
Background:
- Electron-Detachment Dissociation (EDD) is a novel mass spectrometry technique for peptide analysis.
- Understanding fragmentation mechanisms is crucial for interpreting EDD spectra.
- Gas-phase radical intermediates are proposed in EDD.
Purpose of the Study:
- To computationally investigate potential energy profiles for peptide radical fragmentation.
- To determine favored fragmentation pathways in negative-ion mode EDD.
- To compare C-alpha-C backbone cleavage with side-chain loss.
Main Methods:
- Ab-initio electronic structure calculations were employed.
- Potential energy profiles were computed for various fragmentation channels.
- Barriers and energy differences for bond cleavages were determined.
Main Results:
- C-alpha-C backbone bond cleavage is energetically favored over side-chain loss.
- Loss of tyrosine side chain may compete due to electron delocalization.
- Fragmentation of nitrogen-centered radicals favors a*/x fragment formation over a/x*.
Conclusions:
- Computational analysis elucidates key fragmentation mechanisms in EDD.
- The findings support the assignment of observed fragment ions in EDD experiments.
- Energy barriers and thermoneutrality dictate preferred fragmentation pathways.