Polymer Radicals - Free-Radical-Induced DNA Damage and Its Repair - page 192

These reactions are in competition with a fast hydrolysis of the glycosidic link-
age [e.g. reaction (16)] which can be many orders of magnitude faster than that
of the parent.

These reactions are that fast that they occur at the time scale of pulse radiolysis
(Deeble et al. 1990, 1991; Ulanski and von Sonntag 2000). In DNA, such reactions
will not lead immediately to a stand break, but they may well contribute to base
release.

9.4.4
Heterolytic β -Fragmentation

Radicals can also eliminate an anion in -position thereby forming a radical

cation. This reaction becomes only fast, when the ensuing radical cation is sta-
bilized by electron donating substituents and the leaving group has a good nu-
cleofugacity. In DNA, this kind of reaction leads to strand breakage from the
C (4

β

) radical (Dizdaroglu et al. 1975). In poly(U), such reaction also occurs from
the C (2

′

) radical [reaction (14); Hildenbrand and Schulte-Frohlinde 1989a,b].
Mechanistic details are discussed in Chapters 6.9 and 11.2.

′