Polynucleotides and Single-Stranded DNA Fragments - Free-Radical-Induced DNA Damage and Its Repair - page 329

Table 11.3. Kinetics and yields ( G ; unit: 10 −7 mol J −1 ) of Ura release in the γ -radiolysis of
poly(U) in N 2 O-saturated aqueous solution. (Deeble et al. 1986)

Immediate Fast Slow

G (Ura) 0.57 1.5 1.0

Percentage of total G (Ura) 19 48 33

t ½ at 0 °C < 4 min

t ½ at 40 °C 2.3 h 58 h

t ½ at 50 °C 1.23 h 26 h

t ½ at 60 °C 0.83 h 10.7 h

t ½ at 70 °C 0.32 h 3.7 h

E a /kJ mol −1

68 89

S a /J mol −1 K −1

−116 −75

A/s −1 1.5 × 10 7 1.9 × 10 9

t ½ at 20 °C (extrapolated) 18 h 730 h

Table 11.4. Rate of repair of poly(U)-derived radicals by thiols at pH 7 and 4 (in parenthe-
ses). (Fahey et al. 1991)

k/dm 3 mol -1 s -1

Thiol Net charge Relative rate

Glutathione (GSH) −1 < 500 < 0.003

1.5 × 10 3

2-Mercaptoethanesulphonic acid −1 0.009

2-Mercaptoethanol 0

1.8 × 10 5
(6.1

1.0
(1.0)

10 5 )

×

2.0 × 10 5 Cysteine 0 1.1

4.1 × 10 7
(2.2 × 10 8 )

Cysteamine +1 230

(360)

(4.6 × 10 8 ) WR-1065 +2 (760)