Figure 5.

(a) Fluorescence spectra of 200 nM F-32R-T in water (spectrum 1) or 50 mM Tris–HCl, pH 7.4, 50 mM KCl in the absence (spectrum 2) or presence of BSA (r = 10, spectrum 3) or Up1 (r = 0.5, 1, 3, 6, 10, spectra 4–8); (b) row FRET-melting curves (F₅₂₅ versus T) obtained with the iQ5 real-time PCR machine of quadruplex F-32R-T treated with A1/Up1 at various [protein]/[DNA] ratios, in 50 mM Tris pH 7.4, 50 mM KCl. As reference a melting curve of F-32R-T in the presence of BSA (r = 10) is reported. Bottom panels show the corresponding first derivative curves, –dF₅₂₅/dT versus T. The G-quadruplex was incubated with the protein for 30 min prior to melting; (c) schematic representation of the U-shape structure of the DNA–protein complex between F-32R-T and Up1.