title: The interaction of metal ions with nucleic acids. NMR, EPR, CD and spectrophotometric study of the copper (II) interaction with 6-ketopurine ribosides.
abstract: The copper (II)-inosine system in water-DMSO solutions was investigated as a function of pH and the molar ratio between the ligand and copper(II) ion by the EPR, NMR, CD and visible absorption spectrometric methods. It was concluded that a simple M.[-N]L copper(II)-inosine 1:1 complex is formed over the pH range 1.4-5.0, while M.[-N]L2 complexes are present in the solutions of pH 5.0-6.2. From pH 6.2 to 7.8 a diamagnetic, hydroxybridged complex M2.(OH)2.[-N]L4 dominates. At pH values of 7.8-9.2 an insoluble, oxybridged species (M.O.[-N]L)n is formed in addition to the soluble paramagnetic M.[-N-1)L4 complex. Above pH 9.1 the nitrogenbridged polymeric complex (M.[-N-1].M[-N-7] )n is formed which is stable up to pH 12.5, and above pH 12.5 the only species found is the M.[-OH]L2 chelate complex in which inosine is coordinated to copper through the two ionized hydroxyl groups.
mesh_terms: D002942:Circular Dichroism; D003300:Copper / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D007288:Inosine / Q000031:analogs & derivatives* / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009584:Nitrogen; D009696:Nucleic Acids / Q000032:analysis*; D012995:Solubility; D013053:Spectrophotometry
chemical_list: D007202:Indicators and Reagents; D009696:Nucleic Acids; D007288:Inosine; D003300:Copper; D009584:Nitrogen