The interaction of metal ions with nucleic acids. A nuclear magnetic resonance relaxation time study of the copper(II)-inosine 5'-monophosphate system in solution.

The nature of binding between copper ions and inosine 5'-monophosphate was studied using 13C, 1H, and 31P nuclear magnetic resonance techniques. The results imply that at least two species are present in the solution with the metal to ligand ratio of 1:1 and 1:2 (termed, respectively, ML and ML2); however, the ML complex predominates in the Cu(II)-IMP system. The results indicate that the copper ions bind directly to two different sites on the inosine ring i.e., to N7 and to N1. The distribution of the species MLRP7 and MLRP1 is nearly equal. The relative dipolar and scalar contributions to the proton and carbon-13 transverse relaxation have been assessed.