Figure 5.

1H NMR spectroscopy on the G-quadruplex at BCL2 MBR. (A) NMR spectrum of the wild-type sequence (23 mer, G_S) at 5°C. The spectrum was recorded on a Bruker Avance 800 MHz spectrometer with a cryo probe and analyzed by TOPSPIN 2.0 software. (B) NMR spectra recorded at different temperatures for G_S. (C) NMR spectrum of the mutant with a 2-nt loop (G_{2 loop}) at 5°C. In all the panels A–C, the resonance peaks between 10.8 and 12.2 ppm represent those resulting from the imino hydrogen present in the G-quadruplex structure. The resonance peaks at ∼13 and 14.5 ppm result from A…T and G…C Watson–Crick base pairing.