Analytical Sciences

Structural and Spectral Characteristics of the Cross-linked Dimer Derived from Electrooxidation of Cyclic 1,N²-Propanoguanosine

Hiroya MURAKAMI, Yukihiro ESAKA, and Bunji UNO

Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan

The acetaldehyde-derived cyclic propano adduct of 2′-deoxyguanosine was easily oxidized electrochemically into the cross-linked dimer as an oxidative product. The structural and spectroscopic characteristics of the dimer were investigated by MS, ¹H and ¹³C-NMR, UV, and DFT calculations. The dimer formation was inferred from a molecular ionic peak of m/z 705 ([(2M–2H)+H]⁺, M being the molecular weight of the monomer) on the ESI-MS spectra and the chemical formula as C₂₈H₃₆N₁₀O₁₂ provided by the high-resolution ESI-MS results. The C2–N5 linkage between the two monomers in the dimer was deduced from the ¹H- and ¹³C-NMR spectral results. In addition, the correlations in the 2-dimensional NMR spectra (DQF-COSY and HMBC) were consistently explained by the structure of the C2–N5 cross-linked dimer. UV spectral measurements also support the C2–N5 linking in the dimer formation. The formation of the cross-link dimer as an oxidative lesion of the acetaldehyde-derived cyclic propano adduct of guanosine is expected to interfere with DNA replication and to contribute to acetaldehyde-mediated genotoxicity.

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