The interaction between RPA and different preformed G4 structures
(A) The schematic diagram of the experimental design. Preformed G4 substrates were anchored at the coverslip surface, and then different concentrations of RPA were added to unfold the G4 structures. For G4 substrates prepared in 100 mM KCl (or 100 mM NaCl), the reaction buffer of RPA is composed of 100 mM KCl (or 100 mM NaCl) and 5 mM MgCl2.
(B and C) The left panels are the FRET distributions of 2G4 in 100 mM KCl and 3G4L3 in 100 mM NaCl before and 4 min after the addition of 10 nM RPA. Washing the channels with buffer leads to little difference in the FRET distributions. The right panels are the representative traces. The red arrow indicates the addition of RPA.
(D–F) The left panels are the FRET distributions of 3G4L3, 3G4L4, and 3G4L5 in 100 mM KCl before and 4 min after the addition of 100 nM RPA. The right panels are the representative traces.