Nucleobases, Nucleosides and Nucleotides - Free-Radical-Induced DNA Damage and Its Repair - page 222

Table 10.6. Compilation of rate constants for the reactions of • OH, H • and e aq − with the
nucleobases and related compounds. (Buxton et al. 1988)

• OH

H • e aq − Substrate

Ade

6.1 × 10 9 1.0 × 10 8 9.0 × 10 9

4.6 × 10 9 8.2 × 10 9 dAdo -

5.8 × 10 9 2.0 × 10 8 1.1 × 10 10

Ado

4.1 × 10 9 1.9 × 10 8 3.8 × 10 9

AMP

6.3 × 10 9 9.2 × 10 7 1. 3 × 10 10 Cy t

6.0 × 10 9 dCyd - -

5.8 × 10 9 1. 3 × 10 10 Cyd -

1.4 × 10 10

Gua - -

9.2 × 10 9 2.0 × 10 9

Gua anion -

4.1 × 10 9a 1.7 × 10 10 dGuo -

4.7 × 10 9 6.0 × 10 9 dGMP -

7. 8 × 10 9 5.0 × 10 8 6.0 × 10 9 Guo

6.4 × 10 9 6.8 × 10 8 1.8 × 10 10

Thy

4.7 × 10 9 3.2 × 10 8

Thd -

5.7 × 10 9 4.7 × 10 8 1.5 × 10 10 Ura

5.2 × 10 9 1.4 × 10 10

Urd -

a Steenken (1989)

10.3
Reactions Induced by • OH/O •− and • H

10.3.1
Rate Constants

The nucleobases and related compounds react with • OH at close to diffusion-
controlled rates. A compilation of rate constants is given in Table 10.6. In nu-
cleosides and nucleotides, • OH attacks mainly at the base moiety, but some H-
abstraction also occurs at the sugar moiety (Chap. 3.3). It is recalled that the
high reactivity of • OH results in a very low • OH steady-state concentration, and
reactions with substrates, even when present at rather low concentrations, pre-
dominate over the their reactions with • OH-induced substrate radicals. Thus,