Hydrogen Atom Abstraction at C5 Formation of Purine 5,8-Cyclonucleosides

Hydrogen Atom Abstraction at C5 Formation of Purine 5, 8-Cyclonucleosides 

Evidence for the OH induced formation of purine 5, 8-cyclonucleosides has been provided in early model studies involving nucleosides [118], nucleotides [119, 120], and isolated DNA [121]. This may be explained in terms of OH-mediated hydrogen atom abstraction from the C5 -hydroxymethyl group followed by intramolecular cyclization that occurs with a rate constant k = 1.6 x 10s s 1 in the case of 

MS-MS measurements performed recently in our laboratory have shown that the yield of radiation-induced formation of (5 R)-cydodAdo (44a) in cellular DNA is at best around 0.2 lesions/109 normal nucleotides/Gy. This is in agreement with the fact that the shielding effect exerted by cellular constituents on the extent of radiation-induced damage to DNA bases and sugar is about three orders of magnitude with respect to naked DNA [12]. 

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