EXAFS and XANES studies of Cu(II) complexes formed with adenosine or uridine in solution at different hydrogen ion concentrations

摘要

The interactions between adenosine or uridine and Cu(II) ion were studied by means of CuK-XANES and EXAFS measurements at different hydrogen ion concentrations in water-DMSO solutions. The EXAFS spectra suggested that the Cu(II)-equatorial O bond (ca. 191 pm) in the Cu(II) complexes are almost the same as those in the hexaaqua Cu(II) ion or other Cu(II)-sugar complexes (195 pm). The EXAFS Fourier transforms clearly revealed a peak ascribed ot non-bonding Cu...C interactions, indicating the formation of chelate rings of the D-ribose moiety of the nucleosides around Cu(II) ion at higher hydrogen ion concentrations. On the basis of earlier EPR and NMR measurements and the results of the present studies, the most likely structures of the Cu(II)-nucleosides complexes are proposed.