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  • Title: Photobiological model studies on perester and pyridone tert-butoxyl radical sources (photo-Fenton-type reagents): 2'-deoxyguanosine modification by methyl radicals generated through competitive beta-cleavage in aqueous media.
    Author: Adam W, Marquardt S, Kemmer D, Saha-Möller CR, Schreier P.
    Journal: Photochem Photobiol Sci; 2002 Aug; 1(8):609-12. PubMed ID: 12659507.
    Abstract:
    In aqueous solution, UV irradiation of the photo-Fenton-type reagents perester 1 and N-tert-butoxypyridone 2 leads to the formation of tert-butoxyl radicals and methyl radicals as confirmed by product studies and by spin trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), followed by EPR spectroscopy. The methyl radicals result from the initially released tert-butoxyl radicals through beta-cleavage, a fragmentation pathway, which dominates at lower DMPO concentrations. In the presence of 2'-deoxyguanosine (dG), both photochemical radical sources afford 8-MedG [(2.3 +/- 0.3)%] and N7-MedG [(0.27 +/- 0.05)%] as modified products, whereas the direct reaction of the tert-butoxyl radicals with dG cannot compete with this beta-cleavage process.
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