Figure 2.

1D ¹⁵N filtered HSQC spectra of sl21 with 8% ¹⁵N-residue specifically labeled residues. Imino region of 1D ¹H NMR spectrum of sl21 and assignment of guanine imino resonances is shown on top. Stars indicate signals of minor species. All spectra were recorded in 90% H₂O, 10% ²H₂O at 0°C, 120 mM KCl and 20 mM phosphate buffer with pH 7.2 on 600 or 800 MHz spectrometers. Oligonucleotide concentrations were between 0.3 and 0.6 mM per strand.