Nucleobases, Nucleosides and Nucleotides - Free-Radical-Induced DNA Damage and Its Repair - page 227

With Ado, only 32% of the radicals have oxidizing properties (O'Neill et al. 1985).
It has been suggested that 37% add to the C (8) position [reaction (70)] and 50%
to the C (4) position [reaction (68)] and <5% to C (5) [reaction (69)] with some H-
abstraction at the sugar moiety (Vieira and Steenken 1990; Vieira et al. 1993).
The yield of 8-oxo-Ade from Ade has been reported to be the same in the
absence of O 2 or in air-saturated solution, but is increased in the presence of
small amounts of Fe(CN) 6 3− (saturation level already at 4 10 −6 mol dm −3 ; Dias

and Vieira 1997a,b), putting a question mark behind the suggestion (Vieira and
Steenken 1991; Dias and Vieira 1997a) that in the presence of O 2 this product is
formed by the elimination of O 2 • − from the C (8)- • OH-adduct peroxyl radical.

×

10.3.3
Water Elimination and Rearrangements

In basic solution, Ura and Thy undergo a series of reactions as depicted in reac-
tions (72)−(76) for Ura as an example (Fujita and Steenken 1981). Ura dissociates
at high pH [equilibrium (72); for p K a values see Table 10.11]. Its • OH-adducts can
also be deprotonated at nitrogen leading to an oxidizing heteroatom-centered
radical [reaction (76)].