Fig. 3.
Long and stable ddFLN4 folding and unfolding traces close to equilibrium. (A) Force dependence of the rates for complete unfolding (circles) and refolding (triangles) as determined in Fig. 2 D and E. The intersection of the linear fits predicts the equilibrium force Fequi ∼ 7.3 pN, at which the probabilities of ddFLN4 being in the folded and unfolded state are equal. (B) 55-h-long extension vs. time trace of a ddFLN4 tether subjected to a constant force of 7.5 pN and zooms into indicated segments of the trace. (C) Zooms show not only full unfolding and folding transitions, but also transitions from the native to the intermediate state and back. Dashed lines indicate average extension levels corresponding to the native (N), intermediate (I), and unfolded (U) states, respectively. Red lines indicate positions of transitions between states and extension levels in each state, as determined by the step-finding algorithm employed for the analysis.