Nucleobases, Nucleosides and Nucleotides - Free-Radical-Induced DNA Damage and Its Repair - page 284

Table 10. 28 . G values (unit: 10 −7 mol J −1 ) of inorganic phosphate release in the γ -radiolysis
of aqueous solutions of some 3 ′ - and 5 ′ -monoucleotides (Raleigh et al. 1974). Data from
Greenstock and Shierman (1975) are given in brackets

Nucleotide N 2 O O 2

3 ′ 5 ′ 3 ′ 5 ′

AMP 1.02 (1.0) 0.36 (0.29) 0.22 0.29

GMP 0.45 0.24 (0.22) 0.14 0.22

CMP 0.70 (0.67) 0.37 (0.38) 0.72 0.43

UMP 0.75 (0.76) 0.44 (0.45) 0.80 0.48

TMP 0.86 0.37 (0.35) - -

dAMP 0.81 0.34 (0.34) 0.13 0.31

dGMP (0.42) (0.23)

dUMP (0.37)

dCMP (0.37)

(per • OH) when O 2 is present. Lacking an obvious trend, it is premature to come
up with a convincing mechanistic proposal. In the ribo -series, the C (2 ′ ) radicals

certainly contribute to phosphate release as discussed above.

10.8.5
Oxidation at C (4 ′ )

Some of the sugars that are formed in the radiolysis of Thd also have the C (4 )

radical as precursor (Dizdaroglu et al. 1976) (for a quantum-chemical study of
conformation of the C (4

′

) radical and hyperfine coupling constents see Parr and
Wetmore 2004). The water elimination reactions as depicted in reactions (285)
and (288) are generally proton-catalyzed. Yet, the ensuing products are also ob-
served in neutral solution. Their yields are given in Table 10.27.

′