title: The interaction of metal ions with nucleic acids. NMR study of the copper(II) interaction with inosine derivatives.
abstract: The interaction of copper(II) with inosine derivatives substituted at the purine ring, modified at the ribose residue, and with the syn conformation at the glycosidic bond was examined using 1H and 13C nuclear magnetic resonance techniques. The results imply that, in non-aqueous medium, the main site of copper(II) binding is N7 of inosine derivatives. No interaction with ribose hydroxyl groups was observed. CNDO/2 calculations performed for a copper(II) complex with 9-methyl-hypoxanthine support direct bonding of copper(II) ion to the ring. In aqueous medium, coordination of copper(II) with N1 and N7 of inosine is p2H-dependent: 98.7% of Cu(II) is bound with N7 at p2H 3.6, 49.4% at p2H 6.9, and only 35% at p2H 8.2 The relative dipolar and scalar contributions to the proton and carbon-13 transverse relaxation of the inosine derivatives nuclei have been assessed. The distances between the metal ion and the carbon and proton nuclei can not be estimated from T1 measurements because dipolar interaction contributing to relaxation is not only between the paramagnetic ion and the affected nucleus; there is also an important contribution from unpaired spin density on the ligand.
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003300:Copper; D006863:Hydrogen-Ion Concentration; D007288:Inosine / Q000031:analogs & derivatives*; D007291:Inosine Monophosphate; D009682:Magnetic Resonance Spectroscopy
chemical_list: D007291:Inosine Monophosphate; C012433:1-methylinosine; D007288:Inosine; D003300:Copper