Fig. 6

Intermolecular NOE interactions indicate distinct binding modes for DC-34 at the 5′ and 3′ end of MYC G4. a Representative G-quadruplex structure for the MYC G4 with nucleic acid number indicated. The lowest energy structure displayed in Fig. 7 was used to make this figure. b Annotation of DC-34 indicating numbering scheme and ¹³C-labeling. c–f Expanded regions of a 2D NOESY spectrum acquired on MYC G4 with twofold molar excess unlabeled DC-34 at pH 6.4 in buffer A (25 mM Tris-d₁₁ and 50 mM KCl) with 90% H₂O/10% DMSO-d₆. H1–H1, H21/H22–H1, and H8/H2–H1 NOE interactions within MYC G4 are labeled (c, bottom panel), as are intermolecular NOE interactions between MYC G4 H1 and DC-34 methyl (c, top panel) or methanediyl (c, middle panel) groups. g Selected region from a ¹H, ¹³C half-filtered NOESY experiment acquired with MYC G4 and twofold molar excess DC-34 with selective ¹³C-labeling as indicated by red arrows in b. Intermolecular NOE interactions between the DC-34 methyl group and MYC G4 protons are displayed and labeled as are intramolecular NOE interactions involving ¹²C bound DC-34 protons. A breakthrough intramolecular signal from the DC-34 methyl group is indicated by a black asterisk. Labeling of NOEs in c–g is color coded with DC-34 in red (intermolecular) or pink (intramolecular) and MYC G4 in black, light blue (for the 5′ G-tetrad and flanking residues), or orange (for the 3′ G-tetrad and flanking residues)