Figure 1.

Sequences and NMR characterization of G-quadruplex forming KRAS oligonucleotides. (A) Sequences of the wild type 32R-3n and its truncated 5q and 3q analogues corresponding to 5′- and 3′-end quadruplex forming region, respectively. Red guanines are involved in Hoogsteen hydrogen bonding, while blue guanines and cytosines form Watson–Crick base pairs. (B) Imino regions of 1D ¹H NMR spectra of 32R-3n, 5q and 3q oligonucleotides with assignments. Spectra were acquired at 25°C with oligonucleotide concentrations in the range between 0.5 and 2.0 mM in 10% ²H₂O, 80 mM KCl and 20 mM K phosphate buffer (pH 7).