Figure 5. Effect of Li⁺ on K⁺-induced G-quadruplex folding.

(A) CD spectra of the G-quadruplex sequence in Tris/HCl buffer, 100 mM KCl buffer, 100 mM LiCl buffer, and 100 mM KCl buffer with 100 mM LiCl. (B) Time-courses of the fluorescence intensity of FAM after the unfolded G-quadruplex DNA were rapidly mixed with different concentrations of KCl and 10 mM LiCl at room temperature (23°C). The solid lines are double-exponential fits of the data. (C) Total folding amplitude versus KCl concentration at different concentrations of LiCl. (D) Fast folding rate versus KCl concentration at different concentrations of LiCl.