Nucleobases, Nucleosides and Nucleotides - Free-Radical-Induced DNA Damage and Its Repair - page 241

Elimination of O 2 with concomitant fragmentation yields 1- N -formyl-5-hy-
droxyhydantoin [reactions (127-129]. The peroxyl radicals also give rise to oxyl
radicals upon their bimolecular decay [reaction (130)], an alternative route to 1-
N -formyl-5-hydroxyhydantoin [reactions (132), (128) and (129)]. In competition,
these oxyl radicals may also undergo a 1,2-H-shift [reaction (131)], and after
addition of oxygen eliminate HO 2 • /O 2 • − [reaction (133)]. Thus also under such
conditions, O 2 • − are likely intermediates. They are expected to react with other
peroxyl radicals present to yield the corresponding hydroperoxides. Such hydro-
peroxides are abundant intermediates in the radiolysis of air-saturated pyrimi-
dine solutions (Cadet and Teoule 1975; Wagner et al. 1987, 1990a).
A detailed kinetic study is still missing for Cyt and its derivatives, but for
dCyd product data are available (Wagner et al. 1999). They are compiled in Ta-
ble 10.16 together with the products observed upon menadione photosensitiza-
tion.