Free-Radical Damage of Nucleic Acids and Their Components: The Direct Absorption of Energy

Myers, L.S.

doi:10.1016/b978-0-12-566504-9.50010-6

Cited by 5 publications

(1 citation statement)

References 53 publications

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“…The reactions of the OH' radical with purines and pyrimidines have been studied intensively because of interest in radiation-induced cell death (Myers et al . 1970, Schmidt and Borg 1971, Michaels and Hunt 1973, Masuda et al 1975, Willson et al 1974, van Hemmen 1975, Schmidt and Borg 1976, Myers 1980, Fujita and Steenken 1981, O'Neill 1983, Santamaria et al 1984, Cadet and Berger 1985, Vieira and Steenken 1987a, b, Steenken 1987, von Sonntag 1987, Steenken 1989, Vieira and Steenken 1990 . The main sites of purine attack by OH' are C4, C5 and C8, by addition to double bonds on the purine ring .…”

Section: Introductionmentioning

confidence: 99%

Gamma and Pulse Radiolysis Study of Pentoxifylline, a Methylxanthine

Pasquier

Franzini

Abedinzadeh

et al. 1991

International Journal of Radiation Biology

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Pentoxifylline (Ptx) is a tri-substituted purine with anti-inflammatory properties which are thought to be due, in part, to oxygen radical scavenging. This paper reports an investigation of the reaction of Ptx with the hydroxyl radical [OH.], superoxide anion, azide radical and hydrogen peroxide generated by pulse and gamma-radiolysis, which was carried out to determine the scavenging properties of Ptx towards oxygen radicals. The superoxide anion, azide radical and hydrogen peroxide did not react with Ptx, whereas OH. reacted rapidly. In gamma-radiolysis, the action of OH. on Ptx at pH 7.4 gave rise to an end-product separated by high-performance liquid chromatography and identified by nuclear magnetic resonance and mass spectrometry as C-8-OH-Ptx (yield 0.12 x 10(-6) mol J-1). The reaction of Ptx with OH. after pulse radiolysis at pH 7-7.4 occurred with a rate constant of (7.7 +/- 1.0) x 10(9) mol-1 s-1, forming time-dependent transient radicals. The initial spectrum (2 microseconds after the pulse) showed three maxima (310, 338 and 500 nm). A decrease in the absorbance around 500 nm and an increase around 310 nm reflected a first-order reaction, suggesting a unimolecular rearrangement. It was shown by redox titration that at least two OH-adducts were formed, one with reducing and the other with oxidizing properties. These results suggest that the reducing radical may be (C-8-OH-Ptx)(.).

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Section: Introductionmentioning

confidence: 99%

Gamma and Pulse Radiolysis Study of Pentoxifylline, a Methylxanthine

Pasquier

Franzini

Abedinzadeh

et al. 1991

International Journal of Radiation Biology

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Neurodegenerative disorders in humans: the role of glutathione in oxidative stress-mediated neuronal death

Bains

Shaw

1997

Brain Research Reviews

669

376

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Site of OH Radical Attack on Dihydrouracil and Some of Its Methyl Derivatives

Schuchmann

Steenken

Wroblewski

et al. 1984

International Journal of Radiation Biology and Related Studies

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The site of attack of OH radicals on dihydrouracil and five of its methylated derivatives was determined by pulse radiolysis using N,N,N',N'-tetramethylphenylenediamine (TMPD) to detect oxidizing radicals and tetranitromethane (TNM) as well as K3Fe(CN)6 to detect reducing radicals. In the case of dihydrouracil OH radicals abstract preferentially an H atom at C(6) to give the 6-yl radical (greater than or equal to 90 per cent) which at pH approximately 6.5 reduces TNM and K3Fe(CN)6 at almost diffusion-controlled rates. Only a small fraction of OH radicals abstract the H atom at C(5) (less than or equal to 10 per cent). The resulting 5-yl radical oxidizes TMPD to TMPD+ at pH 7-8. With the methylated derivatives of dihydrouracil, OH radicals react less selectively, especially in the case of N(1)-methyl derivatives. This methyl group is activated to a similar degree as the methylene group at C(6). In 1-Medihydrouracil the yield of N(1)-CH2 radicals is about 29 per cent, which has been deduced from the yield of formaldehyde formed after oxidation of this radical by TNM at pH approximately 6.5 and the subsequent hydrolysis. Radicals at the other methyl substituents are generated to a lesser extent (less than or equal to 10 per cent) and are relatively unreactive towards oxidizing agents such as TNM and K3Fe(CN)6 as well as towards the reducing agent TMPD. Although methyl substitution opens new routes for OH attack the preferred site of H abstraction remains C(6) (greater than 60 per cent).

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Free-Radical Damage of Nucleic Acids and Their Components: The Direct Absorption of Energy

Cited by 5 publications

References 53 publications

Gamma and Pulse Radiolysis Study of Pentoxifylline, a Methylxanthine

Gamma and Pulse Radiolysis Study of Pentoxifylline, a Methylxanthine

Neurodegenerative disorders in humans: the role of glutathione in oxidative stress-mediated neuronal death

Site of OH Radical Attack on Dihydrouracil and Some of Its Methyl Derivatives

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