Direct evidence for the formation of thymine radical cations from the reaction of sulfate (SO4.cntdot.-) with thymine derivatives:  A pulse radiolysis study with optical and conductance detection

Deeble, David J.; Schuchmann, Man Nien; Steenken, S.; Sonntag, Clemens von

doi:10.1021/j100384a038

Cited by 101 publications

(98 citation statements)

References 3 publications

(3 reference statements)

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“…Vinyl polymerization of freshly distilled acrylonitrile monomer in deaerated reaction mixture in the present study confirms free radical pathway. It may be interesting to draw a formal analogy between the oxidative chemical damage observed in this study and the ionizing radiation induced direct effect of the pyrimidine bases both involving the intermediacy of the radical cations of the biomolecules [4]. Recently some studies involving laser-flash induced ionization of nucleobases mimicking the direct effect of ionizing radiation via their radical cations have been camed out [27].…”

Section: Resultsmentioning

confidence: 87%

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Kinetics of oxidation of certain pyrimidines by Ce(IV)

Lakshmi¹,

Renganathan²

1996

Int. J. Chem. Kinet.

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The kinetics of the oxidation of certain biologically important pyrimidine bases (Uracil, Thymine, and 6‐Methyluracil) by Ce(IV) in aqueous H2SO4 has been investigated. A first‐order dependence of rate each on [Ce(IV)], [pyrimidine], and an inverse first‐order dependence on [H2SO4] has been observed. Rate and activation parameters for the oxidation of these pyrimidines have been computed. A suitable rate law and a mechanism consistent with the kinetic observations and product analysis have been proposed. © 1996 John Wiley & Sons, Inc.

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Section: Resultsmentioning

confidence: 87%

“…Photophysical investigations involving the binding of certain complexes like Ru( bpy ii' with DNA have been carried out [3]. Investigations on the oxidative degradation of nucleobases involving their radical cation intermediates bearing significance in relation to the direct effect of ioniLinp radiation on DNA have been performed [4].…”

Section: Introductionmentioning

confidence: 99%

Kinetics of oxidation of certain pyrimidines by Ce(IV)

Lakshmi¹,

Renganathan²

1996

Int. J. Chem. Kinet.

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“…(63) In our hands, the SO 4·-system has yielded very interesting results regarding the spectra, PKa values and reactions of the pyrimidine radical cations (see Ref. 63 for additional references). …”

Section: Reactions Of the Nucleobase Radical Cationsmentioning

confidence: 93%

The Chemistry of Free-Radical-Mediated DNA Damage

Sonntag

1991

Physical and Chemical Mechanisms in Molecular Radiation Biology

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In the living cell, ionizing radiation can cause DNA damage by the direct effect (ionization of DNA) and the indirect effect (reaction of radicals formed in the neighborhood of DNA with DNA, e.g., OH, e~q' H, protein-and glutathione-derived radicals). Properties of the base radical cations have been studied in model systems using S04 radical to oxidize the nucleobases in aqueous solution. The pK a values of some nucleobase radical cations are reported, so are the ensuing reactions of the thymidine radical cation with water. The products of reactions are compared with those formed by OH radical attack. The reaction of e~q with the nucleobases yields radical anions. Protonation at heteroatom sites and at carbon are discussed, and some recent results regarding the electron transfer to adjacent nucleobases as well as to 5-bromouracil are reported. A brief account is given on the reaction of carbon-centered radicals with the nucleobases. These reactions may mimic the reactions of protein-derived radicals with DNA. Glutathione is present in cells at rather high concentrations and is expected to act as an H-or electron-donor in repairing radiation-induced DNA damage (chemical repair). As thiyl radicals are known to also undergo the reverse reaction, i.e., H-abstraction from suitable solutes, some experiments are reported which probe this type of reaction with dilute DNA solutions.In some polynucleotides radical transfer from the base radical to the sugar moiety occurs with the consequence of strand breakage and base release. Some currently held mechanistic concepts are discussed.Attention is drawn to some important open questions which should be addressed in the near future.

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“…The pulse radiolysis experim ents do n ot reveal w hether the observed build-up (k = 2.2 x 104 s" 1 at 320 nm) is due to the transform ation o f an S 0 4 adduct into the radical cation (reaction (29) [15], those o f m ethoxylated benzenes are stable against hydrolysis on the pulse radiolysis time-scale [9], The photoionization o f phenylalanine has recently been studied [50]. Spectroscopic d a ta th a t w ould allow to discrim inate between an S 0 4"-adduct and the radical cation have ap p arently never been re ported.…”

Section: So -Induced Reactionsmentioning

confidence: 97%

“…The hy droxycyclohexadienyl-type radicals thus form ed are readily oxidized to phenols by strong oxidants such as Fe(CN)g_, w ith the obsious exception o f the O H adducts at the position ipso to a given su b stituent [3][4][5][6][7], The S 0 4 " radical is a very p o ten t oxid an t (E 0 = 2.8 V [8]) and has been proven to oxidize aro m atic com pounds [9 -1 4 ] and D N A -nucleobases [15,16] to the corresponding radical cations. H ere as well, an adduct m ight be considered as a very sh o rt * R eprint requests to Prof. D r. C. von Sonntag.…”

Section: Introductionmentioning

confidence: 99%

Phenylalanine: Its ˙OH and SO₄˙⁻-Induced Oxidation and Decarboxylation. A Pulse Radiolysis and Product Analysis Study

Wang

Schuchmann

Sonntag

1993

Zeitschrift Für Naturforschung B

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A m ino Acid. Phenylalanine, Pulse R adiolysis, Peroxyl R adicals, Sulfate Radical Phenylam ine has been oxidized by radiolytically g enerated hydroxyl and sulfate radicals, the ensuing interm ediates an d th eir reactions have been studied by pulse radiolysis an d p ro d uct analysis in the absence and presence o f oxid an ts such as Fe(C N )^" and 0 2. U p o n O H ra d i cal attack, hydroxycyclohexadienyl-type radicals are m ainly form ed while H -ab stractio n reac tions can be neglected. In the presence o f Fe(C N )^" these radicals are for the m ost p a rt oxi dized to the corresponding tyrosines (80% ), except fo r the z/«o-O H -adduct radicals (= 2 0 % ). U p o n S 0 4'--attack, decarb o x y latio n becom es a m ajo r process (33% o f S 0 4'~) alongside the production o f tyrosines (43% ). H ere, w ith F e(C N )|~ as the o x id an t the fo rm atio n o f p -Tyr (18.5% ) and ra-Tyr (16.5% ) is preferred over o-T yr fo rm atio n (8.5% ). It is believed th a t in analogy to oth er systems a radical cation is form ed im m ediately u p o n S 0 4'~-attack which either reacts with w ater u n d er the fo rm atio n o f hydroxycyclohexadienyl-type (" O H -a d d u c t" ) radicals, o r decarboxylates after in tram o lecu lar electron transfer. T he radical cation can also arise indirectly through H +-catalysed w ater elim ination from the O H -ad d u ct radicals. A t pH 2 and a dose rate o f 0.0046 G y s_1 C O , fo rm atio n m atches the O H radical yield w hen O H is the attacking radical. Below pH 2, G (C Ö 2) decreases w ith falling pH . This indicates the oc currence o f another, unim olecular, p ath w ay u n d er these conditions com peting effectively with decarboxylation. This ap p ears to be a relatively slow d e p ro to n a tio n reactio n o f the carboxylp ro to n ated phenylalanine radical catio n w hich gives rise to the benzyl-type radical.

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Direct evidence for the formation of thymine radical cations from the reaction of sulfate (SO4.cntdot.-) with thymine derivatives: A pulse radiolysis study with optical and conductance detection

Cited by 101 publications

References 3 publications

Kinetics of oxidation of certain pyrimidines by Ce(IV)

Kinetics of oxidation of certain pyrimidines by Ce(IV)

The Chemistry of Free-Radical-Mediated DNA Damage

Phenylalanine: Its ˙OH and SO₄˙⁻-Induced Oxidation and Decarboxylation. A Pulse Radiolysis and Product Analysis Study

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Direct evidence for the formation of thymine radical cations from the reaction of sulfate (SO4.cntdot.-) with thymine derivatives: A pulse radiolysis study with optical and conductance detection

Cited by 101 publications

References 3 publications

Kinetics of oxidation of certain pyrimidines by Ce(IV)

Kinetics of oxidation of certain pyrimidines by Ce(IV)

The Chemistry of Free-Radical-Mediated DNA Damage

Phenylalanine: Its ˙OH and SO4˙⁻-Induced Oxidation and Decarboxylation. A Pulse Radiolysis and Product Analysis Study

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Phenylalanine: Its ˙OH and SO₄˙⁻-Induced Oxidation and Decarboxylation. A Pulse Radiolysis and Product Analysis Study