Biopolym. Cell. 2003; 19(3):242-246.
Structure and Function of Biopolymers
Interaction with carboxylate ion in anhydrous DMSO shifts keto-enolic prototropic equilibrium in nucleosides to enolic tautomeric form: 1H NMR spectroscopy data
1Samijlenko S. A., 1Kondratyuk I. V., 1Hovorun D. M.
  1. Institute of Molecular Biology and Genetics, NAS of Ukraine
    150, Akademika Zabolotnoho Str., Kyiv, Ukraine, 03680


The disappearance of signals of N3H aglycon protons and all hydroxyl protons of glycosylic fragment was observed in 1H NMR spectra of four nucleosides of uracil and thymine – U, dU, T and rT – in anhydrous DMSO in the presence of carboxylate ion. These changes were interpreted as a result of the N3H → O2H diketo-keto-enolic transition in the base residues under the formation of complex between nucleosides and ligand molecules: one carboxylate ion forms two H-bonds with groups O2H and O5'H, the other – two H-bonds with hydroxyl groups O2H and O3'H in the case of a riboside or one H-bond with group O3'H of a deoxyriboside. Orders of the complexes' stability were established according to which the canonical nucleosides U and T form more stable complexes with carboxylate ion, than metabolites dU and rT. Biological significance of the results obtained is pointed out.


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