One-electron reduction of selenomethionine oxide |
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| Authors: | Annika Assmann Marija Bonifačić Karlis Briviba Helmut Sies Klaus-Dieter Asmus |
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| Affiliation: | 1. Institut für Physiologische Chemie I, Heinrich-Heine-Universit?t Düsseldorf, Postfach 101007, D-40001, Düsseldorf, Germany;2. Department of Physical Chemistry, Ruder Bo?kovi? Institute, Bijenicka c. 54, HR-10000, Zagreb, Croatia;3. Radiation Laboratory and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, USA |
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| Abstract: | Experimental evidence is provided that selenomethionine oxide (MetSeO) is more readily reducible than its sulfur analogue, methionine sulfoxide (MetSO). Pulse radiolysis experiments reveal an efficient reaction of MetSeO with one-electron reductants, such as e-aq (k = 1.2 × 1010M-1s-1), CO·-2 (k = 5.9 × 108 M-1s-1) and (CH3)2) C·OH (k = 3.5 × 107M-1s-1), forming an intermediate selenium-nitrogen coupled zwitterionic radical with the positive charge at an intramolecularly formed Se∴ N 2σ/1σ* three-electron bond, which is characterized by an optical absorption with λmax at 375 nm, and a half-life of about 70 μs. The same transient is generated upon HO· radical-induced one-electron oxidation of selenomethionine (MetSe). This radical thus constitutes the redox intermediate between the two oxidation states, MetSeO and MetSe. Time-resolved optical data further indicate sulfur-selenium interactions between the Se∴ N transient and GSH. The Se∴ N transient appears to play a key role in the reduction of selenomethionine oxide by glutathione. |
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| Keywords: | Selenomethionine oxide glutathione pulse radiolysis odd-electron bonds |
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