Fig. 5.

Step-size analysis of the mechanical unfolding of ubiquitins. (A) A frequency histogram of the unfolding length step sizes shows one predominant peak at 20.3 ± 0.9 nm and two smaller peaks at 8.1 ± 0.7 nm and 12.4 ± 1.0 nm (n_total = 821). (Inset) Color-coded cartoon representation of the structure of ubiquitin (1UBI). The blue- and green-colored regions match structural features in the ubiquitin fold and would account for an intermediate unfolding step of either 8 or 12 nm (see Deviations from Two-State Unfolding). (B) The most typical examples of length vs. time recordings of ubiquitin unfolding.