Dependence of EPI (1 μM) fluorescence intensity at 540 nm on the G-quadruplex sequences (1 μM) in 0.1 M K+ solution (pH 7.5): [Q] (1), A[Q] (2), T[Q] (3), TA[Q] (4), AT[Q] (5), AA[Q] (6), TT[Q] (7), TA[Q]A (8), TA[Q]T (9), TTA[Q] (10), TTA[Q]TT (11), AAA[Q]AA (12), TA[Q]TT (13), [Q]T (14), [Q]TA (15), mPu22 (16), 1XAV (17), PS2.M (18), T30695 (19), 2O3M (20), T3TT (21), T3TT3 (22), and T3T3T3 (23). Inset: Excitation and emission spectra of EPI in the absence (a) and presence (b) of TA[Q].