A Site-Specific Low-Enrichment ¹⁵N,¹³C Isotope-Labeling Approach to Unambiguous NMR Spectral Assignments in Nucleic Acids

We demonstrate that base and sugar protons within a DNA oligomer can be assigned unambiguously following site-specific 15N,13C isotope incorporation at levels as low as 1% enrichment. This simple and cost-effective methodology is demonstrated on the d(GGGTTCAGG) DNA sequence, which forms a dimeric G-quadruplex containing G.G.G.G tetrads sandwiched between G.(C-A) triads.