Enhancement of Radiation-induced Base Release from Nucleosides in Alkaline Solution: Essential Role of the O· −Radical
- 1 January 1992
- journal article
- Published by Taylor & Francis in International Journal of Radiation Biology
- Vol. 61 (4) , 443-449
- https://doi.org/10.1080/09553009214551191
Abstract
The effect of pH on base release in the gamma-radiolysis of N2O-saturated solutions of a number of nucleosides (including uridine, 3-methyluridine, 2',3'-O-isopropylidene-uridine, and adenosine) has been investigated. For all these nucleotides, independent of the base or sugar moiety, base release is very low at pH below 10 (G approximately (0.3-0.7) x 10(-7) mol J-1), but increases drastically to G approximately (3-4) x 10(-7) mol J-1 at pH greater than or equal to 13. This phenomenon had already been previously reported and attributed to an OH(-)-induced transfer of a base radical into a sugar radical. However, it is now shown that at pH 12, where base release starts to increase, a lowering of the dose-rate does not affect the yield of free base. The increase in base release is accompanied by an overall reduction of chromophore loss of similar magnitude (with 2',3'-O-isopropylidene-uridine and 3-methyluridine), as well as by an increase in the yield of oxidizing radicals by a factor of 2 (with uridine). The measured rate constant of the reaction of .OH/O.- with the nucleosides is also pH-dependent, as .OH reacts faster than O.- with the nucleosides by a factor of 6-7. It is concluded that the increase in base release at high pH is caused by the increasing participation of O.-, which, unlike .OH, attacks the nucleosides preferentially at their sugar moieties, and is not due to an OH(-)-induced radical transfer from the base to the sugar moiety.Keywords
This publication has 10 references indexed in Scilit:
- The SO4 ·̄induced Oxidation of 2′-Deoxyuridine-5′-phosphate, Uridine-5′-phosphate and Thymidine-5′-phosphate. An ESR Study in Aqueous SolutionZeitschrift für Naturforschung C, 1990
- Critical Review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (⋅OH/⋅O− in Aqueous SolutionJournal of Physical and Chemical Reference Data, 1988
- Radiation-chemical production and lifetimes of trialkoxymethyl carbocations in aqueous solutionJournal of the American Chemical Society, 1986
- Pattern of hydroxyl radical addition to uracil and methyl- and carboxyl-substituted uracils. Electron transfer of hydroxyl adducts with N,N,N',N'-tetramethyl-p-phenylenediamine and tetranitromethaneJournal of the American Chemical Society, 1981
- Free-Radical Reactions of Carbohydrates as Studied by Radiation TechniquesPublished by Elsevier ,1980
- Oxidation of phenolates and phenylenediamines by 2-alkononyl radicals produced from 1,2-dihydroxy- and 1-hydroxy-2-alkoxyalkyl radicalsThe Journal of Physical Chemistry, 1979
- Radiation Chemistry of DNA Model Compounds, IX. Carbohydrate Products in the γ-Radiolysis of Thymidine in Aqueous Solution. The Radical-Induced Scission of the N-Glycosidic BondZeitschrift für Naturforschung B, 1976
- Electron spin resonance and pulse radiolysis studies of the reactions of OH and O- radicals with aromatic and olefinic compoundsThe Journal of Physical Chemistry, 1972
- Nucleotides. IV.1 Conversion of Ribonucleosides to New 2',3'-Ketal Derivatives2Journal of the American Chemical Society, 1965
- Spectrophotometric studies on nucleic acid derivatives and related compounds as a function of pH: II. Natural and synthetic pyrimidine nucleosidesBiochimica et Biophysica Acta, 1952