Direct Observation of Guanine Radical Cation Deprotonation in Duplex DNA Using Pulse Radiolysis
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- Kazuo Kobayashi
- Contribution from The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki Osaka 567-0047, Japan
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- Seiichi Tagawa
- Contribution from The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki Osaka 567-0047, Japan
書誌事項
- 公開日
- 2003-08-01
- DOI
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- 10.1021/ja036211w
- 公開者
- American Chemical Society (ACS)
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説明
The dynamics of one-electron oxidation of guanine (G) base mononucleotide and that in DNA have been investigated by pulse radiolysis. The radical cation (G+*) of deoxyguanosine (dG), produced by oxidation with SO(4)-*, rapidly deprotonates to form the neutral G radical (G(-H)*) with a rate constant of 1.8 x 10(7) s(-1) at pH 7.0, as judged from transient spectroscopy. With experiments using different double-stranded oligonucleotides containing G, GG, and GGG sequences, the absorbance increases at 625 nm, characteristic of formation of the G(-H)*, were found to consist of two phases. The rate constants of the faster ( approximately 1.3 x 10(7) s(-1)) and slower phases ( approximately 3.0 x 10(6) s(-1)) were similar for the different oligonucleotides. On the other hand, in the oligonucleotide containing G located at the 5'- and 3'-terminal positions, only the faster phase was seen. These results suggest that the lifetime of the radical cation of the G:C base pair (GC+*), depending on its location in the DNA chain, is longer than that of free dG. In addition, the absorption spectral intermediates showed that hole transport to a specific G site within a 12-13mer double-stranded oligonucleotide is complete within 50 ns; that is, the rate of hole transport over 20 A is10(7) s(-1).
収録刊行物
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- Journal of the American Chemical Society
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Journal of the American Chemical Society 125 (34), 10213-10218, 2003-08-01
American Chemical Society (ACS)
