Reactivity of DNA guanyl radicals with phenolate anions.

Reactivity of DNA guanyl radicals with phenolate anions. Research Abstract Details 

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Reactivity of DNA guanyl radicals with phenolate anions. Abstract Text:

Anne Ly,Simona L Bandong,Nancy Q Tran,Kathrina J Sullivan,Jamie R Milligan,

Guanine bases are the most easily oxidized sites in DNA. Electron-deficient guanine species are major intermediates produced in DNA by the direct effect of ionizing radiation (ionization of the DNA itself) because of preferential hole migration within DNA to guanine bases. By using thiocyanate ions to modify the indirect effect (ionization of the solvent), we are able to produce these single-electron-oxidized guanine radical species in dilute aqueous solutions of plasmid DNA where the direct effect is negligible. The guanyl radical species produce stable modified guanine products. They can be detected in the plasmid by converting them to strand breaks after incubation with a DNA repair enzyme. If a phenol is present during irradiation, the yield of modified guanines is decreased. The mechanism is reduction of the guanine radical species by the phenol. It is possible to derive a rate constant for the reaction of the phenol with the guanyl radical. The pH dependence shows that phenolate anions are more reactive than their conjugate acids, although the difference for guanyl radicals is smaller than with other single-electron-oxidizing agents. At physiological pH values, the reduction of a guanyl radical entails the transfer of a proton in addition to the electron. The relatively small dependence of the rate constant on the driving force implies that the electron cannot be transferred before the proton. These results emphasize the potential importance of acidic tyrosine residues and the intimate involvement of protons in DNA repair.

Reactivity of DNA guanyl radicals with phenolate anions. Publishing Authors By Initials

A Ly,SL Bandong,NQ Tran,KJ Sullivan,JR Milligan,

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Reactivity of DNA guanyl radicals with phenolate anions. Journal Published:

PUBLICATION TYPE: Research Support, N.I.H., Extr

Journal: The journal of physical chemistry. B

VOLUME: 109

Page Numbers: 13368-74

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ISSN: 1520-6106

DAY: 14

MONTH: Jul

YEAR: 2005

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LANGUAGE: eng

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Grant and Affiliation Information for Reactivity of DNA guanyl radicals with phenolate anions.

AFFILIATION: Department of Radiology, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0610, USA.

Country: United States

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MEDLINETA: J Phys Chem B

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