FIGURE 3.

Force-ramp unfolding of P5GA hairpin. (A) An example of FEC at the loading rate r_f = 45 pN/s (k_s = 0.07 pN/nm, v = 0.64 μm/s). The data points are recorded every 50 μs (gray), but for better illustration the running average is displayed every 500 μs (red). (B) The end-to-end distance (R) as a function of time. (C) Time-dependence of f. The loading rate r_f = df/dt is nearly a constant. (D) Distribution of unbinding forces from 100 trajectories at four loading rates , , , and 10 ((k_s = 0.7 pN/nm, v = 6.4 μm/s)). The red star is the rupture force value (f* = 12.5 pN) at r_f = 45 pN/s. (E) Plot f*, the most probable unfolding force, as a function of r_f. The position of transition state is computed using . The inset shows the variation of as a function of r_f.