Pyrolysis Radicals Formed by Ultrasound in Aqueous Solutions of Nucleotides: A Spin Trapping Study

Evidence for the formation of pyrolysis radicals from nucleotides induced by ultrasound in argon-saturated solutions is presented. The method of spin trapping with 3,5-dibromo-2,6-dideuterio-4-nitrosobenzene sulfonate was applied to examine the possibility of detecting new radicals specifically generated in the high-temperature zones surrounding the collapsing cavitation bubbles of highly concentrated solutions of nucleotides. At low nucleotide concentrations (0.05 mol dm-3) the spin-trapped radicals produced by sonolysis are due to H atom and OH radical reactions, typically addition to the 5,6 double bond of the base moiety. At high concentration (1.0 mol dm-3) the pyrolysis radicals (typically methyl radicals) were found for thymidine 5'-monophosphate, 2'-deoxy-uridine 5'-monophosphate, cytidine 5'-monophosphate, uridine 5'-monophosphate, and also for 2-deoxy-D-ribose and D-ribose. These results indicate that pyrolysis radicals can be detected when the nucleotides are accumulated at high concentrations in the interfacial regions of the cavitation bubbles.