Figure 2.

¹⁹F NMR and ¹H NMR spectra of ¹⁹F labeled RNA. (A) Chemical structure of ¹⁹F labeled telomere RNA bearing 3,5 bis(trifluoromethyl)phenyl group at the 5΄ terminal. (B) ¹⁹F NMR spectra of ¹⁹F labeled telomere RNA at different concentrations. The peaks of the dimeric and two-subunits stacked G-quadruplex are marked with red and green spots, respectively. Concentrations of RNA indicated on the right. (C)¹⁹F NMR of ¹⁹F labeled RNA at different temperatures. Red and green spots indicated dimer and two-subunits stacked G-quadruplex. The peaks of single strand are marked with black spots. Temperatures indicated on the right. Condition: 3 mM RNA in 50 mM KCl and 10 mM Tris-HCl buffer (pH 7.0). The sample is kept for 10 min at each temperature. (D) ¹⁹F NMR of ¹⁹F labeled RNA at different temperatures and concentrations. The peaks of dimer G-quadruplex are red spots. The peak of two-subunits stacked G-quadruplex is green spot. The peaks of single strand are marked with black spots. (E) ¹H imino proton NMR of ¹⁹F labeled RNA corresponding to ¹⁹F NMR at different temperatures and concentrations. The peaks characteristic of the dimeric and two-subunits stacked G-quadruplex are marked with red and green spots, respectively.