Figure 4.

2AP substitution corroborates Hoogsteen bonding under H-DNA/triplex-forming conditions, and suggests loop formation under G4-DNA-forming conditions. Under H-DNA-forming conditions, the fluorescence emission of AP-A33hg is (A) quenched and follows a (B) temperature-dependent increase in fluorescence, comparable to that of a hairpin-forming structure, AP-HP. AP-longSS and AP-T11lp are the single-strand and loop controls, respectively. Under G4-DNA-forming conditions, (C) AP-A33hg is fluorescent and follows a (D) temperature-dependent decrease in fluorescence, suggestive of a loop conformation.