Heteronuclear two‐dimensional ¹⁵N‐ and ¹³C‐nmr studies of DNA oligomers and their netropsin complexes using indirect proton detection

Heteronuclear multispin coherence proton‐detected two‐dimensional nmr spectroscopic experiments were used to obtain information on protonated carbons and nitrogens of the self‐complementary d (G‐G‐T‐A‐T‐A‐C‐C) and d (G‐G‐A‐A‐T‐T‐C‐C) duplexes, with and without the drug netropsin dissolved in aqueous solution. Many correlations of protons coupled to ¹³C nuclei on the base and sugar rings of the octanucleotides were detected, allowing the carbon resonances to be assigned based on previous homonuclear proton two‐dimensional nmr studies. Imino nitrogen assignments can also be made using the proton assignments from previous one‐dimensional nuclear overhauser effect experiments. Imino nitrogen shifts may be useful indicators of changes in local hydrogen‐bonding interactions to base‐pair edges.