Figure 5.

(A) An RPA flow experiment showing unfolding of a GQ by RPA in real time. As GQ is unfolded by RPA, FRET efficiency transitions from a high level, corresponding to the folded GQ structure, to a low level, corresponding to RPA-bound unfolded DNA. The bottom panel shows the section of the time trajectory that is in the vicinity of RPA binding and unfolding of the GQ. The unfolding time is marked by red arrows. We occasionally observed intermediate states during unfolding (green dotted line). (B) Example of an unfolding event in which the GQ molecule transitions back and forth between the folded and unfolded states. (C) Example of an unfolding event in which the transition from the folded to the unfolded state occurs gradually, without a distinct stable intermediate state. (D) Histograms of unfolding times (Δt) for L2–L5. (E) Histograms of unfolding times (Δt) for O1–O5. The red curves in D and E are Gaussian fits to the data. Interestingly all the constructs have similar unfolding times despite the large difference in their steady-state stability.