Etude de la fragmentation de derives de L'uracile et de la thymine par Spectrometrie de masse

Ulrich, J.; Téoule, R.; Massot, R.; Cornu, A.

doi:10.1002/oms.1210021202

Cited by 54 publications

(28 citation statements)

References 8 publications

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“…5-HydroxymethyluraciI (16) and 5,6-dihydroxy-5,6-dihydrothymine (17) were prepared by literature procedures. These procedures give the cis isomer only (18). A mixture of isomers was obtained by refluxing an aqueous solution of the cis isomer at 90 "C for 4 h (18).…”

Section: Methodsmentioning

confidence: 99%

The Ultrasonic Degradation of Thymine

Mead¹,

Sutherland²,

Verrall³

1975

Can. J. Chem.

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Chemical reactions that occur in liquids subjected to ultrasonic irradiation (insonation) of sufficient intensity to induce cavitation, have been attributed (1) to a number of processes; the reactive species produced in water and aqueous solutions during cavitation are hydroxyl radicals (2), hydrated electrons (3), hydroperoxyl radicals (4), and hydrogen atoms (5). These species are also produced during the radiolysis of water and in this paper we show that the sonolysis of thymine may be correlated with its radiolytic degradation.The radiolysis of aqueous thymine solutions has been the subject of numerous investigations and studies by Teoule and co-workers (6-11) identified more than 26 products formed during 60Co-y irradiation. Hydroxyl radicals produced by ionizing radiation react with thymine to give 6-hydroxy-5,6-dihydro-5-thyml and 5-hydroxy-5,6-dihydro-6-thymyl radicals; hydrogen atoms (or e,,-+ H,O+) react with thymine to give (5-uracyl)methyl, 5,6-dihydro-5-thyml, and 5,6-dihydro-6-thyml radicals (1 1). These radicals react. very rapidly with dissolved oxygen (e.g. K(TOH + 0,) = 1.5 x lo9 M -,l S-l (12) to produce hydroperoxide radicals which are reduced to the hydroperoxyhydroxydihydro products ( Fig. 1) (5 and 6) and the hydroperoxide products (7, 5-hydroperoxy-5,6-dihydrothymine, cis-and trans-6-hydroperoxy-5,6-dihydrothy-'For a preliminary communication see ref. 27. mine). The peroxide products are relatively unstable (11) and decompose to give various alcohols (cis-and trans-9, 8, 5-hydroxy-5,6-dihydrothymine, cis-and trans-6-hydroxy-5,6-dihydrothymine). In addition, the hydroxyhydroperoxides decompose to give 5-hydroxy-5-methylbarbituric acid and N-formyl-N'-pyruvylurea and the remaining products result from decomposition of N-formyl-N'-pyruvylurea to give pyruvylurea, urea, and formylurea.El'piner (1) was the first to investigate the effect of ultrasound on purine and pyrimidine bases. He insonated (500 kHz) aqueous solutions of the bases at an intensity of 5 W cm-2 in the presence of various gases. In the U.V. spectra of the insonated bases, the absorption maxima were reduced and the minima shifted to longer wavelengths. Uracil was found to be the most sensitive, adenine and guanine less so. In a later study, El'piner and Sokol'skaya (13) insonated aqueous solutions of cytosine, uracil, thymine, and adenine and investigated the products of sonolysis chromatographically but no degradation products were identified. The reduction in intensity of the U.V. absorption band of the various purines and pyrimidines was attributed to ring cleavage (1). Since the effect was considerably reduced in the presence of gases other than oxygen, it was suggested that molecular oxygen played an important role and a smaller oxidative role was assigned to hydroxyl radicals.This study was undertaken to reinvestigate the sonolysis of aerated aqueous thymine solutions Can. J. Chem. Downloaded from www.nrcresearchpress.com by 34.210.69.67 on 05/11/18For personal use only.

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Section: Methodsmentioning

confidence: 99%

The Ultrasonic Degradation of Thymine

Mead¹,

Sutherland²,

Verrall³

1975

Can. J. Chem.

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“…This is probably due to the accurate energy scale calibration using photon excitation where resonant transitions of rare gas absorption lines are used for that purpose. To our knowledge, the first EI mass spectra of NABs and their derivatives were recorded in 1965 by Rice et al [27,28], followed by others [29][30][31][32]. More recently, Denifl et al used a hemispherical electron monochromator to study the threshold electron impact ionization of uracil and two of its chlorine derivatives [33,34].…”

Section: Electron Impact Ionization Measurements On Nabsmentioning

confidence: 99%

Photoionization Spectroscopy of Nucleobases and Analogues in the Gas Phase Using Synchrotron Radiation as Excitation Light Source

Schwell

Hochlaf

2014

Topics in Current Chemistry

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We review here the photoionization and photoelectron spectroscopy of the gas phase nucleic acid bases adenine, thymine, uracil, cytosine, and guanine, as well as the three base analogues 2-hydroxyisoquinoline, 2-pyridone, and δ-valerolactam in the vacuum ultraviolet (VUV) spectral regime. The chapter focuses on experimental work performed with VUV synchrotron radiation and related ab initio quantum chemical calculations of higher excited states beyond the ionization energy. After a general part, where experimental and theoretical techniques are described in detail, key results are presented by order of growing complexity in the spectra of the molecules. Here we concentrate on (1) the accurate determination of ionization energies of isolated gas phase NABs and investigation of the vibrational structure of involved ionic states, including their mutual vibronic couplings, (2) the treatment of tautomerism after photoionization, in competition with other intramolecular processes, (3) the study of fragmentation of these molecular systems at low and high internal energies, and (4) the study of the evolution of the covalent character of hydrogen bonding upon substitution, i.e., examination of electronic effects (acceptor, donor, etc.).

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“…The fragmentation of thymine followinge nergy uptake and ionization has been observed by using different "energy sources". Fragmentation spectra were recordedu pon electron ionization, [20][21][22][23] ion impact [24][25][26][27][28] as well as after VUV photoionization, [15] core ionization, [29] and multiphoton ionization. [30] Wolf et al recently reported an ovel experiment in which ultrafast thymine fragmentation was inducedb yr esonance-enhanced three-photon ionization using 4.65 eV photons, that is, at a total energy of 13.95 eV,f ollowed by a5 70 eV free-electron laser pulse to produce an oxygen 1s hole, after whicht he Augers pectrum was recorded.T hey showed how the Auger spectrum of isocyanic acid (HNCO)d evelopsa safunction of delay time between 200 and 1500 fs.…”

Section: Introductionmentioning

confidence: 99%

Valence Photoionization of Thymine: Ionization Energies, Vibrational Structure, and Fragmentation Pathways from the Slow to the Ultrafast

Majer

Signorell

Heringa

et al. 2019

Chemistry A European J

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The photoionization of thymine has been studied by using vacuum ultraviolet radiationa nd imaging photoelectronp hotoion coincidences pectroscopy after aerosol flash vaporization andb ulk evaporation.T he two evaporation techniquesh ave been evaluated by comparison of the photoelectrons pectra and breakdown diagrams. The adiabatic ionization energies for the first four electronic states were determined to be 8.922 AE 0.008,9 .851 AE 0.008, 10.30 AE 0.02, and 10.82 AE 0.01 eV.V ibrational features have been assigned for the first three electronic states with the help of Franck-Condon factor calculations based on densityf unctional theory and wave function theory vibrational analysis within the harmonic approximation. The breakdown diagram of thymine, as supported by composite methoda bi nitio cal-culations,s uggestst hat the main fragment ions are formed in sequential HNCO-, CO-, and H-loss dissociation steps from the thymine parenti on, with the first step corresponding to ar etro-Diels-Alder reaction. The dissociation rate constants were extractedf rom the photoion time-of-flight distributions and used together with the breakdown curvest oc onstruct as tatistical model to determine 0K appearance energies of 11.15 AE 0.16 and 11.95 AE 0.09 eV for the m/z 83 and 55 fragment ions, respectively.T hese results have allowedu st o revise previously proposed fragmentation mechanismsa nd to proposeamodel for the final, nonstatistical H-losss tep in the breakdown diagram, yielding the m/z 54 fragment ion at an appearance energy of 13.24 eV.

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Etude de la fragmentation de derives de L'uracile et de la thymine par Spectrometrie de masse

Cited by 54 publications

References 8 publications

The Ultrasonic Degradation of Thymine

The Ultrasonic Degradation of Thymine

Photoionization Spectroscopy of Nucleobases and Analogues in the Gas Phase Using Synchrotron Radiation as Excitation Light Source

Valence Photoionization of Thymine: Ionization Energies, Vibrational Structure, and Fragmentation Pathways from the Slow to the Ultrafast

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