3683-34-9Relevant academic research and scientific papers
Analysis of oxidative cytosine products in DNA exposed to ionizing radiation
Wagner, J. R.
, p. 1280 - 1286 (2007/10/02)
From ionizing radiation studies, we have previously characterized a large number of modifications of cytosine and 2'-deoxycytidine which arise by way of hydroxyl radical or base radical cation reactions.However, it remains a great challenge today to detect and quantitate these lesions in DNA.In the present work, I have developed a method for the analysis of six oxidation products of cytosine in DNA using HF acid hydrolysis and gas chromatography/mass spectrometry with isotopic dilution.The analysis of gamma-irradiated DNA indicated that uracil 5,6-glycols 5-hydroxyuracil and 5-hydroxyhydantoin are the major stable decomposition products of cytosine residues, whereas alloxane and 1-carbamoyl-2-oxo-4,5-dihydroxy-imidazolidine are formed in comparatively lower yields.These results suggest that the major pathway of OH radical induced decomposition of cytosine in DNA involves initial deamination of intermediate 5-hydroxy-6-hydroperoxides. - Keywords: Oxidative DNA damage, mass spectrometry, isotopic dilution, mutagenesis.
Reactions of some Free Radicals Derived from Uracil with Nickel(II) Compounds
Bhattacharyya, Sudhindra N.,Mandal, Parikshit C.
, p. 1205 - 1216 (2007/10/02)
Reactions of Ni(II) compounds with the transient adducts of uracil, viz.U(1-) and UOH, have been studied in the steady-state radiolysis of uracil in the presence of different Ni(II) species, e.g.NiSO4, Ni(II)EDTA, Ni(II)NTA, Ni(II)IDA and Ni(II)(IDA)2.The U(1-) radicals formed by the reaction of uracil with e(1-)aq transfer an electron to the Ni(II) species.The redox behaviour of UOH radicals has been investigated by following the ligand-degradation products of the Ni(II) complexes and the degradation of the base.The ligand-degradation products, e.g. formaldehyde and glyoxalic acid, arise from the degradation of the metal complex through its oxidation to Ni(III) by C6-UOH radical species.Unlike Cu(II) or Fe(III) ions, Ni(II) ions have very little effect on the radiosensitivity of uracil.The radiosensitising ability of the metal ions, which is dependent on electron transfer from UOH to the metal ion, is correlated with the redox potential of the metal ion couple M(n+)/M((n-1)+).
EFFECT OF COPPER(II) IONS ON THE γ-RADIOLYSIS OF URACIL
Bhattacharyya, Sudhindra N.,Mandal, Parikshit C.
, p. 2613 - 2630 (2007/10/02)
Radiation sensitization of uracil (Ura) by CuII ions has been investigated using cobalt-60 γ-rays.In N2O-saturated solution, when no additive is present, the base degradation yield, G(-Ura), is only ca. 3.3, but when CuII ions are added in either a free or complexed state to the solution before irradiation, G(-Ura) is found to increase to ca. 5.1.The enhanced degradation of the base is derived from the oxidized transient, e.g.UraOH+, although reduction of CuII to CuI has been ascribed to all the primary adducts, e.g.UraH, UraOH and Ura-.Glycol and isobarbituric acid constitute the major products of radiolysis, which are derived from the oxidized UraOH+ species.Hydroxydihydrouracil and its dimer have also been detected in significant yields when the radiolysis is carried out at comparitively high absorbed doses.The formation of these products has been ascribed to a secondary reaction between UraOH and CuI which proceeds through the intermediate formation of a Cu-C bond.
The Radiolysis of Uracil in Oxygenated Aqueous Solutions. A Study by Product Analysis and Pulse Radiolysis
Schuchmann, Man Nien,Sonntag, Clemens von
, p. 1525 - 1532 (2007/10/02)
Hydroxyl radicals are generated by the radiolysis of N2O-O2 (4:1 v/v)-saturated aqueous solutions of uracil.They add to the 5,6-double bond of the substrate .These radicals are converted by oxygen into the corresponding peroxyl radicals (I) and (II), respectively.Peroxyl radical (I) undergoes a base-induced O2(1-.) elimination (kobs 8x1E3 s-1 at pH 10.5).As an intermediate 5-hydroxy-isopyrimidine is formed which rearranges into isobarbituric acid and adds water forming 5,6-dihydro-5,6-dihydroxyuracil.Competing with this base-induced reaction of radical (I) there is a bimolecular decay of radicals (I) and (II).These processes become predominant at low pH.For this reason a strong pH dependence of G (products) is observed.The major products are (G values at pH 3 and 10 in parentheses) 5,6-dihydroxy-5,6-dihydrouracil (1.1; 2.4), isobarbituric acid (0; 1.2), N-formyl-5-hydroxyhydantoin (1.6; 0.2), 5-hydroxybarbituric acid (0.9; 0.2). 5-Hydroxybarbituric acid is formed in its keto form.Its deprotonation (k 4.4 s-1) has been followed by pulse conductometry.Details of the reaction mechanism, e.g. the involvement of oxyl radicals in the bimolecular decay of (I) and (II), are discussed.
Analysis of Radiolysis Products of Aqueous Uracil + N2O Solutions
Ali, Khondoker M. Idris,Scholes, George
, p. 449 - 456 (2007/10/02)
Various products from the irradiation of solutions of uracil+N2O with 60Co gamma rays were separated by paper chromatographic technique using 14C labelled materials.Identity of the isolated products was investigated by spectrophotometric and kinetic decomposition studies.Thus at least eight radiolytic products of uracil such as cis- and trans-uracil glycols, 5-hydroxy-6-hydro and 6-hydroxy-5-hydro compounds, isobarbituric acid and three dimeric products were identified.Yields of these products were determined at different pH values; a good material mass balance was achieved; the mechanism involved is discussed.
