Voltammetric studies of purine bases and purine nucleosides with copper

Anodic stripping voltammetry with a hanging mercury drop electrode has been used to investigate the interaction of copper with the purines adenine, hypoxanthine, xanthine and purine nucleosides adenosine, guanosine and inosine at an ionic strength of 0.1 M in KNO3 and in the pH range 3.5-5.5. In all cases stabilisation of copper(I) occurs suggesting that the oxidation of copper(O) in the presence of excess ligand proceeds in two one-electron steps. Adsorption onto the electrode has been analysed and conditions where this is negligible were chosen for complexation studies. From the shift of the peak potential corresponding to Cu(O)/Cu(I) oxidation with increasing ligand concentration the stoichiometry of the complexes and their formation constants have been determined. The values obtained are discussed in terms of the ligand structure.