Figure 3.

Characterization of secondary structure by NMR with site-specific labeling. a, site-specific assignments of imino proton resonances of hT25 hairpin structure. The 1D ¹⁵N-edited HMQC spectra of 8% ¹⁵N-enriched oligonucleotide samples were shown with assignments to the labeling sites. b, 2D NMR spectra of hT25 hairpin form. The recorded NOESY spectrum with mixing time of 300 ms showed two major GC correlations. c, proposed scheme of hairpin orientation of the hT25 with two G-C hydrogen-bonding pairs. d, site-specific assignments of imino proton resonances of hT25-m2 quadruplex structure. The 1D ¹⁵N-edited HMQC spectra of 8% ¹⁵N-enriched oligonucleotide samples are shown with assignments to the labeling sites. e, 2D NMR spectra of hT25-m2 quadruplex form. The recorded NOESY spectrum with mixing time of 250 ms showed the H1-H1 correlations. f, proposed scheme of quartet orientation of the hT25-m2 with two quartets of G-G-G-C configurations.