A spectrophotometric study of the interaction of VO2+ with cytosine in nucleotides

The interaction of VO2+ with cytidine-monophosphate, -diphosphate, and -triphosphate has been investigated at different pH values and metal-to-ligand ratios by differential UV-absorption spectroscopy. It is shown that at pH values between 3 and 5 and for metal-to-ligand ratios up to 0.5, the cytosine ring is involved in coordination. On the other hand, measurements performed at pH = 7 show the absence of this type of interaction. Some comments on the possible structural characteristics of the generated complexes are made on the basis of the known coordination behavior of cytosine. Similar spectroscopic measurements with the systems VO2+/PO43-, VO2+/P2O74-, and VO2+/D-ribose were also performed in order to complement the analysis of the experimental results.