MODE OF COORDINATION AND STABILITY OF CU(II) AND ZN(II) COMPLEXES WITH ADENOSINE, DEOXYADENOSINE, CYTIDINE AND DEOXYCYTIDINE

Stability constants of Cu(II) and Zn(II) complexes with nucleosides have been determined from a computer analysis of potentiometric titration results. Spectral investigations prove that in acidic solution adenosine coordinates to Cu(II) via its N1 or N7 atoms, while at pH > 7 only N7 is involved. Similar interactions are observed for dAdo complexes. Spectral and potentiometric studies suggest that Zn does not form stable complexes with dAdo. In the case of cytidine and deoxycytidine, the preferred site of coordination is the N3 atom of the nucleoside. Oxygen atoms from the carbonyl groups are not involved in Cu(II) or Zn(II) coordination. The results of the spectral investigation have excluded the ribose and deoxyribose moieties of all studied ligands from participation in the interactions. In general, the mode of coordination of nucleosides and deoxynucleosides with Cu(II) and Zn(II) has been found analogous.