A Carbon-13 Nuclear Magnetic Resonance Study of Binding of Copper(II) to Pyrimidine Nucleotides and Nucleosides

The influence of paramagnetic Cu2+ ions on the proton decoupled 13C n.m.r. spectra of pyrimidine nucleosides and nucleotides has been studied. For 5′-CMP, the C5 resonance is broadened first on the addition of Cu2+ ions followed by the C2, C4, and C1′ resonances. From a comparison of the transverse and longitudinal relaxation rates of the base carbon nuclei due to the presence of Cu2+ ions, binding of Cu2+ to the N3 nitrogen of 5′-CMP is predicted. A similar broadening behavior is observed for 5′-UMP, 5′-TMP, cytidine, and uridine. This indicates that the Cu2+ ion is located near the N3 nitrogen in these Cu2+-nucleoside and -nucleotide complexes.