Structure and Reactivity of the Glutathione Radical Cation: Radical Rearrangement from the Cysteine Sulfur to the Glutamic Acid α-Carbon Atom

Authors

  • Sandra Osburn,

    1. Department of Chemistry and Biochemistry, Center for Biochemical and Biophysical Studies, Northern Illinois University, Dekalb, IL 60115 (USA)
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  • Dr. Giel Berden,

    1. University Nijmegen, Institute for Molecules and Materials, FELIX Facility, Toernooiveld 7, 6525ED Nijmegen (The Netherlands)
    2. University of Amsterdam, Science Park 904, 1098XH Amsterdam (The Netherlands)
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  • Prof. Jos Oomens,

    1. University Nijmegen, Institute for Molecules and Materials, FELIX Facility, Toernooiveld 7, 6525ED Nijmegen (The Netherlands)
    2. University of Amsterdam, Science Park 904, 1098XH Amsterdam (The Netherlands)
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  • Dr. Kerim Gulyuz,

    1. Department of Chemistry, University of Florida, Gainesville, FL 32611 (USA)
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  • Prof. Nick C. Polfer,

    1. Department of Chemistry, University of Florida, Gainesville, FL 32611 (USA)
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  • Prof. Richard A. J. O'Hair,

    1. School of Chemistry, Bio 21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Melbourne, VIC 3010 (Australia)
    2. ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, Melbourne, VIC 3010 (Australia)
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  • Prof. Victor Ryzhov

    Corresponding author
    1. Department of Chemistry and Biochemistry, Center for Biochemical and Biophysical Studies, Northern Illinois University, Dekalb, IL 60115 (USA)
    • Department of Chemistry and Biochemistry, Center for Biochemical and Biophysical Studies, Northern Illinois University, Dekalb, IL 60115 (USA)
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Abstract

A gas-phase radical rearrangement through intramolecular hydrogen-atom transfer (HAT) was studied in the glutathione radical cation, [γ-ECG]+., which was generated by a homolytic cleavage of the protonated S-nitrosoglutathione. Ion–molecule reactions suggested that the radical migrates from the original sulfur position to one of the α-carbon atoms. Experiments on the radical cations of dipeptides derived from the glutathione sequence, [γ-EC]+. and [CG]+., pointed to the glutamic acid α-carbon atom as the most likely site of the radical migration. Infrared multiple-photon dissociation (IRMPD) spectroscopy was employed to generate complementary information. IRMPD of [γ-ECG]+. in the approximately 1000–1800 cm−1 region was inconclusive owing to the relatively broad, overlapping absorption bands. However, the IRMPD spectrum of [γ-EC]+. in this region was consistent with the radical migrating from the sulfur to the α-carbon atom of glutamic acid. IRMPD in the 2800–3700 cm−1 region performed on [γ-ECG]+. is consistent with a mixture of both the original sulfur-based radical and the resulting glutamic acid α-carbon-based species. Comparisons are made with previously published condensed and gas-phase studies on intramolecular HAT in glutathione.

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