1D 1H NMR titrations of MycPu22 DNA with indenoisoquinolines and 7-azaindenoisoquinolines. Imino proton regions of the titration spectra of MycG4 with compound 5 (A), 6 (B), 13 (C), 9 (D), 12 (E), and 17 (F) are shown. In Figure 5A, the imino proton signals from the 5′ G-tetrad (Figure 1B) are labeled in red, the middle G-tetrad in black, and the 3′ G-tetrad in green. Conditions: 150 μM DNA, 25 °C, pH 7, 100 mM K+.