Skip to main content
. Author manuscript; available in PMC: 2011 Jun 10.
Published in final edited form as: J Phys Chem B. 2010 Jun 10;114(22):7672–7680. doi: 10.1021/jp101717u

Scheme 1.

Scheme 1

Primary reaction pathways leading to free base release by DNA exposed to the direct effect of ionizing radiation. The radical pathway, 1–2–3, is initiated by electron ejection from the DNA backbone, 1, followed by deprotonation at a dRib carbon, 2, to give the neutral radical dRib(Cn'-H)• that, when the DNA film is dissolved in water, leads to fbr, 3.28 The molecular pathway, 4, contains no trappable radical intermediate; spur reactions produce a deoxyribose carbocation, dRib(Cn'-H)+, that in the presence of water, 5, yields fbr.29 Alternatively, dRib(Cn'-H)+ can be formed via 1–2–6, in which dRib(Cn'-H)• is oxidized by Base•+, a base centered hole that must be in close proximity to dRib(Cn'-H)•. Migration of a hole through the base stack increases the likelihood of 6. Competing with base-to-base hole transfer, Reaction 12, are three reactions: 9 - an alternative route to dRib(Cn'-H)•, 10 - trapping of the hole by deprotonation at the base, which can be reversible, and 11 - a back reaction to parent base. Another back Reaction is 7, which reconstitutes the parent dRib.