Ligand-quadruplex interactions. a: CD spectra of ligands 1 (black hashed), 2 (red) and 3 (blue) at 4 μM in 110 mM of K+ at pH 7.0 using the h-Tel sequence 5′-d[AGGG(TTAGGG)3]-3′ are compared to the ligand free h-Tel (black) spectra. b: The ability of ligands 1, 2 and 3 to induce an anti-parallel conformation in the absence of K+ ions. c: The quadruplex stabilising effects of ligands 1, 2 and 3 was carried out by monitoring the h-Tel thermal unfolding at 290 nm. d: Schematic representation of the intramolecular folded structure of the h-Tel sequence 5′-d[AGGG(TTAGGG)3]-3′ anti-parallel (2 + 2) basket form and anti-parallel (3 + 1) hybrid form. The arrows indicate strand direction from 5′ to 3′.