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.
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.
Adam
Waldemar
W
Institut für Organische Chemie, Am Hubland, D-97074 Würzburg, Germany. adam@chemie.uni-wuerzburg.de
Marquardt
Stefan
S
Kemmer
Diana
D
Saha-Möller
Chantu R
CR
Schreier
Peter
P
D002851:Chromatography, High Pressure Liquid; D003849:Deoxyguanosine / Q000737:chemistry*; D004952:Esters / Q000737:chemistry*; D006868:Hydrolysis; D007202:Indicators and Reagents; D018462:Photobiology; D011728:Pyridones / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D004952:Esters; D007202:Indicators and Reagents; D011728:Pyridones; D014867:Water; D003849:Deoxyguanosine