BINDING OF CU(II) TO DNA IN THE PRESENCE OF LI(I), NA(I) AND MN(II)

Complexation of Cu(II) with DNA has been studied by EPR and UV techniques in the presence of Li(I), Na(I) and Mn(II) both in unoriented samples (solutions) and in partially oriented ones (fibres). This study shows that Cu(II) binding to the bases of DNA is influenced by the concentration and by the nature of the cations present. All the ions investigated cause a reduction of the amount of Cu(II) bound to the bases which is proportional to their concentration. The effect, at any given concentration of the ions, follows the order Mn(II)»Li(I) > Na(I). Since the stabilisation of DNA double helix by these ions follows the same order, it is suggested that Cu(II) binding to the bases depends on the possibility that the double helix can be deformed, at least locally. © 1979.