Fig. 4.
The unfolding probability of ubiquitin. Frequency histogram of unfolding forces (ntotal = 538) measured from force-ramp experiments like that shown in Fig. 3. We obtained the unfolding probability distribution (Pu·; green line) by integrating and normalizing the frequency histogram. A fit of the unfolding probability, Pu, with Eq. 3, gave α0 = 0.0375 s-1, a = 103 pN/s, and Δx = 0.14 nm. A plot of Eq. 4, evaluated with these parameters, resulted in the dotted line that accurately describes the unfolding force frequency histogram.