Nitrogen-15 NMR spectroscopy of N-metallated nucleic acids:: insights into 15N NMR parameters and N-metal bonds

It was recently demonstrated spectroscopically that RNA/DNA nucleobases can bind to metal cations in aqueous solution through coordination bonds and covalent bonds. Nitrogen-15 (N-15) NMR spectroscopy was employed and shown to be a powerful tool for determining the mode of metal ion binding to nitrogen atoms in RNA/DNA molecules. This review describes N-15 NMR spectroscopic characteristics in accordance with the mode of metal ion binding to nitrogen atoms. The general rules for N-15 chemical shift changes, which are applicable to the determination of the metal ion binding mode of N-metallated compounds, are also described.