Reactions of the Hydrated Electron with Pyrimidine Nucleosides Halogenated at the Sugar Moiety: E.S.R. and Spin-trapping with 2-methyl-2-nitrosopropane

Summary

Free radicals produced by the reactions of hydrated electrons with pyrimidine nucleosides halogenated at the sugar moiety (2′-chloro-2′-deoxyuridine and 2′-chlorothymidine) were studied by e.s.r. and spin-trapping. 2-Methyl-2-nitrosopropane was used as the spin-trap. The usual spin-trapping technique was extended to frozen and deoxygenated systems to avoid contamination of the trapped radicals with side-products by spin-trapping 2-methyl-2-nitrosopropane itself. When this method was applied to 2′-chloro-2′-deoxyuridine, a free radical at the C-2′ position of the sugar moiety was spin-trapped together with a free radical at the C-5 position of the base moiety. This indicates that hydrated electrons both add to the base moiety and eliminate halogen anions from the halogenated sugar moiety.

In the case of 2′-chlorothymidine, however, only a free radical attributed to H-addition at the C-6 position of the thymine base was observed. No radicals produced by the reaction of hydrated electrons with the halogenated sugar could be spin-trapped.

• e.s.r.
• spin-trapping
• radicals
• chlorodeoxyuridine
• chlorothymidine