- Simple Syntheses of Isouramil and Isobarbituric Acid
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Peroxodisulfate oxidations of uracil and 6-aminouracil followed by hydrolysis led to efficient syntheses of isobarbituric acid and isouramil.
- Behrman
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- PROCESS FOR STRAIGHTENING KERATIN FIBRES WITH A HEATING MEANS AND DENATURING AGENTS
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The invention relates to a process for straightening keratin fibres, comprising: (i) a step in which a straightening composition containing at least two denaturing agents is applied to the keratin fibres, (ii) a step in which the temperature of the keratin fibres is raised, using a heating means, to a temperature of between 110 and 250° C.
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- Simultaneous determination of five oxidative DNA lesions in human urine
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A method, involving a HPLC prepurification followed by a GC/MS analysis, has been set up for the measurement of nucleic acid oxidation products in human urine. For this purpose, isotopically labeled internal standards have been prepared and used for isotope dilution mass spectrometric detection. Using this approach, four oxidized DNA bases, i.e., 5-hydroxyuracil, 5- (hydroxymethyl)uracil, 8-oxo-7,8-dihydroadenine, and 8-oxo-7,8- dihydroguanine, together with 8-oxo-7,8-dihydro-2'-deoxyguanosine have been simultaneously quantified in human urine samples. The levels of the oxidized nucleic acid constituents, as expressed in picomoles per milliliter, were determined to be, in decreasing order: 8-oxo-7,8-dihydroguanine (583 ± 376) > 5-(hydroxymethyl)uracil (121 ± 56) > 5-hydroxyuracil (58 ± 23) > 8-oxo- 7,8-dihydro-2'-deoxyguanosine (30 ± 15) > 8-oxo-7,8-dihydroadenine (7 ± 4). Attempts to determine the amount of 5,6-dihydroxy-5,6-dihydrothymine, 5- hydroxycytosine, and 2,6-diamino-4-hydroxy-5-formamidopyrimidine using the above HPLC-GC/MS method were unsuccessful.
- Ravanat, Jean-Luc,Guicherd, Pascale,Tuce, Zorana,Cadet, Jean
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p. 802 - 808
(2007/10/03)
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- Measurement of oxidative damage at pyrimidine bases in γ-irradiated DNA
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Oxidized nucleobases represent one of the main classes of damage induced in DNA by ionizing radiation. Emphasis was placed in this work on the measurement of four oxidized pyrimidine bases, including 5- (hydroxymethyl)uracil (5-HMUra), 5-formyluracil (5-ForUra), 5-hydroxy- cytosine (5-OHCyt), and 5-hydroxyuracil (5-OHUra), in isolated DNA upon exposure to γ radiation in aerated aqueous solution. For this purpose, both high performance liquid chromatography associated with electrochemical detection (HPLC-EC) and gas chromatography coupled to mass spectrometry (GC- MS) were used. Conditions of hydrolysis of the N-glycosidic bond were carefully checked in order to achieve a quantitative release of the lesions. We showed that 60% formic acid treatment leads to the decomposition of the four lesions studied. On the other hand, hydrolysis based on the use of either 88% formic acid or 70% hydrogen fluoride in pyridine (HF/Pyr) allowed the quantitative release of the modified bases, with the exception of 5- HMUra when the latter reagent was utilized. A dose course study of the radiation-induced formation of 5-HMUra and 5-ForUra in DNA by using the GC- MS assay showed that the latter lesion was produced in a 2.1-fold higher yield than the former one. HF/Pyr and 88% formic acid hydrolysis provided similar results for 5-ForUra, indicating the reliability of both techniques for the measurement of this lesion. For 5-OHUra and 5-OHCyt, the level of modification determined by GC-MS analysis was higher after 88% formic acid treatment than upon HF/Pyr hydrolysis. When DNA was enzymatically digested and analyzed by HPLC-EC for 5-OHdCyd and 5-OHdUrd, the results were very close to those obtained by GC-MS following HF/Pyr treatment. It was concluded that additional amounts of both 5-OHUra and 5-OHCyt are produced during the 88% formic acid treatment from radiation-induced 5,6-saturated pyrimidine precursors. It is likely that cytosine and uracil diols are involved in this reaction. The radiochemical yields of formation (in μmol · J-1) for the products studied are in the following decreasing order: 5-ForUra (0.0083) > 5-OHCyt (0.0046) > 5-HMUra (0.0039) > 5-OHUra (0.0035).
- Douki, Thierry,Delatour, Thierry,Paganon, Frederique,Cadet, Jean
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p. 1145 - 1151
(2007/10/03)
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- Oxidation of nucleic acid related compounds by the peroxodisulfate ion
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The treatment of nucleic acid bases, nucleosides, and nucleotides with peroxodisulfate ion in a phosphate buffer solution at pH 7.0 or water at 70-75°C was investigated. The reaction of thymine and 5-methylcytosine nucleosides and nucleotides resulted in the oxidation of the 5-methyl groups. The oxidation products from 1,3-dimethyluracils and the time-course of the reaction of uracils led to two plausible reaction mechanisms for the oxidation of uracils.
- Itahara,Yoshitake,Koga,Nishino
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p. 2257 - 2264
(2007/10/02)
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- The Kinetics of the Rearrangement of Some Isopyrimidines to Pyrimidines studied by Pulse Radiolysis
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Isopyrimidines are formed as a result of the oxidation of the 6-yl radicals derived by .OH attack on pyrimidines and dihydropyrimidines.The kinetics of the rearrangement of the isopyrimidines into the corresponding pyrimidines has been followed by pulse radiolysis.The rearrangement of isouracil into uracil is proton-catalysed (k 1.8E7 l mol-1 s-1).Around pH 7 a spontaneous reaction, k 3000 s-1, is observed.On increasing the pH the isouracil deprotonates at N(3) (pKa ca. 9.4).The spontaneous rearrangement of the isouracil anion is considerably slower (k -1).At pH > 10.5 an OH(1-)-catalysed reaction sets in (k 4.9E5 l mol-1 s-1) which involves a second deprotonation, at C(5).Similar results have been obtained for the rearrangement of 5-hydroxyisouracil into isobarbituric acid.On blocking the N(3) position as in 3-methylisouracil, the OH(1-)-induced rearrangement sets in at a much lower pH (pH-1 s-1) than that observed in the other two systems.
- Schuchmann, Man Nien,Al-Sheikhly, Mohamed,Sonntag, Clemens von,Garner, Anthony,Scholes, George
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p. 1777 - 1780
(2007/10/02)
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- Reactions of some Free Radicals Derived from Uracil with Nickel(II) Compounds
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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)+).
- Bhattacharyya, Sudhindra N.,Mandal, Parikshit C.
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p. 1205 - 1216
(2007/10/02)
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- EFFECT OF COPPER(II) IONS ON THE γ-RADIOLYSIS OF URACIL
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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.
- Bhattacharyya, Sudhindra N.,Mandal, Parikshit C.
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p. 2613 - 2630
(2007/10/02)
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- Application of the Elbs Persulfate Oxidation to the Preparation of 5-Hydroxypyrimidines
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The use of potassium persulfate in cold sodium hydroxide solution has been shown to give the pyrimidin-5-yl hydrogen sulfates in cases where the pyrimidine has at least two electron-releasing groups in the 2, 4 or 6 positions.However, the reaction has been unsuccessful in a number of cases.The pyrimidin-5-yl hydrogen sulfates are hydrolysed to the corresponding 5-hydroxypyrimidines by hydrochloric acid.
- Hurst, Derek T.
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p. 1285 - 1289
(2007/10/02)
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- The Radiolysis of Uracil in Oxygenated Aqueous Solutions. A Study by Product Analysis and Pulse Radiolysis
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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.
- Schuchmann, Man Nien,Sonntag, Clemens von
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p. 1525 - 1532
(2007/10/02)
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- One-Electron Redox Potentials of Phenols. Hydroxy- and Aminophenols and Related Compounds of Biological Interest
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The rate constants for reversible electron transfer between a series of substituted phenolate ions and anilines and various substituted phenoxyl or anilino radicals in aqueous solution were measured by observing the formation or depletion of the radicals involved.Nonequilibrium concentrations of the radicals were produced in the presence of the corresponding phenols or anilines by using the pulse radiolysis technique.The relaxation of the system to equilibrium was monitored by optical detection methods.From the equilibrium constants for one-electron transfer, the one-electron redox potentials (E2) for 38 phenolic or anilino type compounds were determined, many of which are natural products.The redox potentials are strongly influenced by electron-donating or -withdrawing substituents at the aromatic system.
- Steenken, S.,Neta, P.
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p. 3661 - 3667
(2007/10/02)
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- Analysis of Radiolysis Products of Aqueous Uracil + N2O Solutions
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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.
- Ali, Khondoker M. Idris,Scholes, George
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p. 449 - 456
(2007/10/02)
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- The sonolysis of uracil
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The sonolysis of uracil (1) has been studied at 630 kHz in the presence of air, oxygen, nitrogen and argon.The degradation products were identified by gc-ms analysis.Under aerated conditions the following products were found: uracil glycols (7), isobarbituric acid (8), N-formyl-N'-glyoxylurea (6), 5-hydroxyhydantoin (9), dialuric acid (10), alloxan monohydrate (12), parabanic acid (13), and oxaluric acid (14).In deaerated solutions 6, 13, and 14 were not observed but either 6-hydroxy-5,6-dihydrouracil (17) or its isomer (18) were detected in addition to 7, 8, 9, 10, and 12.The observed products have been used to develop a possible mechanism for the sonolytic degradation and the results are similar to those obtained in radiolysis.The sonolytic degradation of 5-bromouracil (19) is also reported: the products observed were 5-bromobarbituric acid (20), 12, 13, 14, and 9 and these can be rationalized by a similar mechanism scheme.
- Yu, Tain-Jen,Sutherland, Ronald G.,Verrall, Ronald E.
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p. 1909 - 1915
(2007/10/02)
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