Identification of the alpha and beta 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.

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-beta-D-erythro-pentofuranosyl) oxaluric acid (beta-dOx) and thymidylyl-(3'-5')-1-(2-deoxy-beta-D-erythro-pentofuranosyl) oxaluric acid (Tpbeta-dOx), respectively. In aqueous solution the modified beta-deoxyribonucleoside is slowly converted to the alpha-anomer, generating alpha-dOx and Tpalpha-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 alpha-dOx and Tpalpha-dOx slowly convert back into the modified beta-deoxyribonucleoside, indicating that the furanosidic anomers are in dynamic equilibrium. Relative to TpdG, the rate of hydrolysis of Tpbeta-dOx and Tpalpha-dOx by spleen phosphodiesterase is greatly reduced. Hot piperidine (1.0 M, 90 degrees C, 30 min) destroys Tpbeta-dOx and Tpalpha-dOx. Riboflavin-mediated photosensitization of TpdG in D2O instead of H2O has no detectable effect on the yield of Tpbeta-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'-deoxyguanosine.
Authors	Garry W Buchko, Jean Cadet
Journal	Photochemistry and photobiology (Photochem Photobiol) 2006 Jan-Feb Vol. 82 Issue 1 Pg. 191-9 ISSN: 0031-8655 [Print] United States
PMID	16489851 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S.)
Chemical References	Dinucleoside Phosphates Photosensitizing Agents Solutions thymidylyl-(3',5')-2'-deoxyguanosine Guanine Deoxyguanosine Thymine Oxygen Riboflavin
Topics	Deoxyguanosine (chemistry) Dinucleoside Phosphates (chemistry) Guanine (chemistry) Kinetics Oxygen Photosensitizing Agents Riboflavin (chemistry) Solutions Stereoisomerism Thymine (chemistry)

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