Figure 2.

(A) A G-tetrad with detectable H1–H1 and H1–H8 NOE connectivity. (B) Imino H1 and aromatic H8 proton assignments of Pu30_3T4AA by 1D ¹⁵N-filtered experiments using site-specific labeled oligonucleotides at 25 °C. (C) Schematic drawing of the folding topology of the major G-quadruplex 1245G4 formed in the BCL-2 promoter sequence Pu30 (G = red, A = green, C = yellow). (D) H1–H1 region and (E) H1–H8 region of the 2D-NOESY spectrum of Pu30_3T4AA in H₂O at 5 °C with a mixing time of 200 ms. The proton assignments are shown on the sides. Intratetrad NOEs are in red, intertetrad NOEs in blue, sequential intertetrad NOEs in black, and NOEs with flanking bases in green. Conditions: 25 mM K-phosphate, 70 mM KCl, pH 7.0.