title: Reduction of 1,4-quinone and ubiquinones by hydrogen atom transfer under UVA irradiation.
abstract: 1,4-Benzoquinone, coenzyme Q0 and Q10 were reacted with a series of hydrogen donors in the ESR cavity in the presence or absence of UVA irradiation. The signals of the radicals generated from the hydrogen donors or of those of the semiquinones were detected. The reaction mechanism was interpreted by a hydrogen atom transfer instead of the usual electron transfer mechanism on the basis of the redox potentials of the reactants and the Marcus theory. The hydrogen atom transfer is explained by the excited triplet state of quinones, which, on the basis of quantum mechanic calculations, may be reached even under visible light. In some cases, hydrogen atom transfer was also observed without irradiation, although to a lesser extent.
authors.affiliation: Istituto di Biochimica, Universita, Ancona, Italy.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Biondi
authors.forename: Roberta
authors.initials: R
authors.lastname: Galeazzi
authors.forename: Gianpaolo
authors.initials: G
authors.lastname: Littarru
authors.forename: Lucedio
authors.initials: L
authors.lastname: Greci
mesh_terms: D016227:Benzoquinones / Q000378:metabolism* / Q000528:radiation effects; D003067:Coenzymes; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism* / Q000528:radiation effects; D006860:Hydrogen Bonding; D006861:Hydrogen Peroxide; D010084:Oxidation-Reduction; D011522:Protons; D013816:Thermodynamics; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D016227:Benzoquinones; D003067:Coenzymes; D005609:Free Radicals; D011522:Protons; D014451:Ubiquinone; C004532:quinone; D006859:Hydrogen; D006861:Hydrogen Peroxide; C024989:coenzyme Q10