Radical Formation in the Gas‐Phase Ozonolysis of Deprotonated Cysteine |
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Authors: | Dr George N Khairallah Dr Alan T Maccarone Dr Huong T Pham Timothy M Benton Dr Tony Ly Dr Gabriel da?Silva Prof Stephen J Blanksby Prof Richard A J O'Hair |
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Institution: | 1. School of Chemistry and Bio21 Institute, University of Melbourne, Melbourne, Victoria 3010 (Australia);2. ARC Centre of Excellence for Free Radical Chemistry and Biotechnology (Australia);3. School of Chemistry, University of Wollongong, New South Wales 2522 (Australia);4. Department of Chemical and Biomolecular Engineering, The University of Melbourne, Melbourne, Victoria 3010 (Australia);5. Central Analytical Research Facility, Queensland University of Technology, Queensland 4001 (Australia) |
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Abstract: | Although the deleterious effects of ozone on the human respiratory system are well‐known, many of the precise chemical mechanisms that both cause damage and afford protection in the pulmonary epithelial lining fluid are poorly understood. As a key first step to elucidating the intrinsic reactivity of ozone with proteins, its reactions with deprotonated cysteine Cys?H]? are examined in the gas phase. Reaction proceeds at near the collision limit to give a rich set of products including 1) sequential oxygen atom abstraction reactions to yield cysteine sulfenate, sulfinate and sulfonate anions, and significantly 2) sulfenate radical anions formed by ejection of a hydroperoxy radical. The free‐radical pathway occurs only when both thiol and carboxylate moieties are available, implicating electron‐transfer as a key step in this reaction. This novel and facile reaction is also observed in small cys‐containing peptides indicating a possible role for this chemistry in protein ozonolysis. |
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Keywords: | cysteine gas‐phase reactions mass spectrometry ozone radicals |
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