Chemistry Reference
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Table 10.5.
Half-lives of Iz, the Z and 8-oxo-G at various conditions of temperature and
pH (Raoul et al. 1996)
pH
Temp / °C
Iz
Z
8-oxo-G
7
20
24 h
Stable
Stable
37
147 min
Stable
Stable
5.0 (11.2)
a
min
10
65
21.8 min
Stable
20.2 (58.5)
a
min
13
20
68.6 min
n.d.
5.1 (23.8)
a
min
37
26.7 min
n.d.
65
3.1 min
3.3 min
38.6 min
n.d., Not determined.
a
Second component
Not all photooxidation pathways can be attributed to radical cations as the only
intermediate. For example, in the benzophenone-sensitized reaction, some and
β→α
-dGuo) is observed (Vialas et al.
1999). while no such isomerization occurs upon the Mn-TMPyP-mediated oxi-
dation by KHSO
5
(Vialas et al. 1999). Here, Iz is the only detected product [90%
yield; Vialas et al. 1998] which points to different intermediates in these two
systems. Ascorbate or cysteine, may intercept G
•
, and in their presence the oxa-
zolone yield is strongly reduced (Douki et al. 1999).
The redox potential of A
•
is higher by 0.27 V than that of G
•
(Table 10.2), and
thus reductants capable of reducing G
•
also reduce A
•
(Jiang et al. 1999a). In
ODNs, it also undergoes ET from a neighboring G (Bamatraf et al. 2000).
and
α→β
isomerization (in the case of
α
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