Journal
INTERNATIONAL JOURNAL OF MASS SPECTROMETRY
Volume 316, Issue -, Pages 133-139Publisher
ELSEVIER
DOI: 10.1016/j.ijms.2011.12.001
Keywords
Ion-molecule reactions; Cysteine radical cations; Cysteine radical anions; Radical rearrangement
Funding
- Northern Illinois University
- Center for Biochemical and Biophysical Studies
- ARC Center of Excellence in Free Radical Chemistry and Biotechnology
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The gas-phase reactivity of sulfur-based radical ions of cysteine derivatives and Cys-containing small peptides was studied via the use of ion-molecule reactions inside a quadrupole ion trap mass spectrometer. Both the radical cations M center dot+ and the anions (M-2H)(center dot-) were generated via the gas-phase homolysis of the S-NO bond of the S-nitrosylated precursors of the following: Cys, N-Ac-Cys, CysOMe, Gly-Cys, Cys-Gly, gamma-Glu-Cys, gamma-Glu-Cys-Gly, and Gly-Cys-Arg. The radical ions were allowed to react with the following volatile neutral reagents: allyl iodide, allyl bromide, nitric oxide, 1-propane thiol, 3-mercaptopropionic acid, dimethyl disulfide and dimethyl sulfide. The charge has little effect on the types of products formed, with typical S-based radical reactivity being observed. In several systems (N-Ac-Cys, Cys-Gly, Gly-Cys, gamma-Glu-Cys-Gly, and Gly-Cys-Arg) the radical was found to lose its reactivity very rapidly, which is consistent with S-to-alpha-carbon radical rearrangement via hydrogen atom transfer. The observed radical reactivity serves as a model for studying the chemistry of cysteine-based thiyl radicals in protein systems. (c) 2011 Elsevier B.V. All rights reserved.
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