Identification of the α and β Anomers of 1-(2-Deoxy-d-Erythro-Pentofuranosyl)-Oxaluric Acid at the Site of Riboflavin-mediated Photooxidation of Guanine in 2′-Deoxyguanosine and Thymidylyl-(3′-5′)-2′-Deoxyguanosine

Authors

  • Garry W. Buchko,

    1. Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA
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  • Jean Cadet

    Corresponding author
    1. Laboratoire ‘Lésions des Acides Nucléiques,’ DRFMC/LCIB UMR-E no. 3 CEA/UJF, CEA/Grenoble, F-38054 Grenoble cedex 9, France
    • To whom correspondence should be addressed: Laboratoire ‘Lésions des Acides Nucléiques,’ DRFMC/LCIB UMR-E No. 3 CEA/UJF, CEA/Grenoble, F-38054 Grenoble cedex 9, France, Fax: 33 04 38 78 50 90; e-mail: jcadet@cea.fr

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  • This paper is part of a special issue dedicated to Professor J. C. (Tito) Scaiano on the occasion of his 60th birthday.

ABSTRACT

Products of riboflavin-mediated photosensitization of 2′-deoxyguanosine (dG) and thymidylyl-(3′-5′)-2′-deoxyguanosine (TpdG) by 350-nm light in oxygen-saturated aqueous solution have been isolated and identified as 1-(2-deoxy-β-d-erythro-pentofuranosyl) oxaluric acid (β-dOx) and thymidylyl-(3′-5′)-1-(2-deoxy-β-d-erythro-pentofuranosyl) oxaluric acid (Tpβ-dOx), respectively. In aqueous solution the modified β-deoxyribonucleoside is slowly converted to the α-anomer, generating α-dOx and Tpα-dOx. These modified nucleosides and dinucleoside monophosphates have been isolated by HPLC and characterized by proton and carbon NMR spectroscopy, fast atom bombardment mass spectrometry, and enzymatic analyses. Both α-dOx and Tpα-dOx slowly convert back into the modified β-deoxyribonucleoside, indicating that the furanosidic anomers are in dynamic equilibrium. Relative to TpdG, the rate of hydrolysis of Tpβ-dOx and Tpα-dOx by spleen phosphodiesterase is greatly reduced. Hot piperidine (1.0 M, 90°c, 30 min) destroys Tpβ-dOx and Tpα-dOx. Riboflavin-mediated photosensitization of TpdG in D2O instead of H2O has no detectable effect on the yield of Tpβ-dOx, suggesting that oxaluric acid is generated through a Type-I reaction mechanism, likely through the intermediary on initially generated 8-oxo-7,8-dihydro-2′-de-oxyguanosine.

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