DNA and Double-Stranded Oligonucleotides - Free-Radical-Induced DNA Damage and Its Repair - page 431

Table 12 . 26. Product yields ( G values, unit: of 10 −7 mol J −1 ) of differently hydrated DNA
γ -irradiated under N 2 . (Swarts et al. 1996)

Product Γ = 2.5 Γ = 10.3 Γ = 13.2 Γ = 24.4 Γ = 32.8

8-oxo-G 1.0 0.81 0.84 0.72 0.69

FAPY-G 0.12 0.21 0.13 0.081 0.16

Gua 0.12 0.079 0.08 0.095 0.094

8-oxo-A 0.014 0.015 0.018 0.013 0.014

FAPY-A 0.005 0.008 0.004 0.012 0.022

2-OH-Ade 0.006 0.004 0.005 0.01 0.01

Ade 0. 21 0.13 0.14 0.16 0.17

5-OH-Ura 0.014 0.007 0.003 0.011 0.016

5-OH-Cyt 0.004 0.001 0.002 0.008 0.007

5,6-diOH-Ura 0.004 0.003 0.004 0.006 0.005

5-OH-Hyd 0.019 0.008 0.004 0.002 0.003

Cy t 0. 21 0.14 0.13 0.13 0.15

5,6-diOHThy 0.26 0.67 0.51 0.11 0.093

5-OHMe-Ura 0.05 0.027 0.022 0.035 0.03

5-OH-5,6diHThy 0.022 0.015 0.013 0.004 0.007

Tg 0.007 0.003 0.011 0.007 0.013

5-OH-5-Me-Hyd 0.017 0.006 0.001 0.003 0.004

Thy 0.019 0.12 0.13 0.17 0.20

lower the free Gua yield, as is indeed observed. The results of a detailed prod-
uct study are compiled in Table 12.26 (for H 2 and dihydropyrimidine yields as a
function of the water content see Falcone et al. 2005).
As SSBs are concerned, data are available on single crystals of dsODNs of dif-
ferent composition (Debije et al. 2001; Razskazovskiy et al. 2003a, 2003b). There
is little base sequence specificity and preference of 5 -cleavage.

Although there is a certain span for G (SSB) among the various systems studied
((

′ -cleavage vs 3 ′

10 −7 mol J −1 ), these data clearly point to the importance of SSB for-
mation by the direct effect.
In the presence of electron scavengers such as iodoacetamide, electron-gain
centers are transformed into alkyl-type radicals which preferentially abstract a

∼ 0.4 − 1.4) ×