Figure 6.

Unfolding and refolding force-extension traces of D34. (A) The unfolding and refolding traces of D34 obtained by AFM. Unfolding force peaks were fitted with worm-like chain curves (persistence length ∼0.7 nm). Note the pronounced refolding force peaks. (B) The unfolding and refolding traces of another D34 molecule obtained by AFM. (Dotted-line trace) The unfolding trace in panel A is superimposed. Note the absence of pronounced refolding force peaks. (C) The unfolding and refolding traces of another D34 molecule obtained by AFM. (Dotted-line trace) The unfolding trace in panel A is superimposed. Note that the unfolding force peaks at the extension >40 nm match reasonably well with the force peaks of the unfolding trace shown in panel A. (D) Histograms of the contour length increment ΔL_c and unfolding forces F_unfold with Gaussian distribution fits. The average ΔL_c of unfolding force peaks was 8.8 ± 4.9 nm, the average F_unfold was 57 ± 27 pN (number of observations, N = 1123). (E) Histograms of the contraction length ΔL_c and the refolding forces F_refold with Gaussian distribution fits. The average ΔL_c of refolding was 8 nm, 16 nm, and 24 nm. The average F_refold was 26 ± 11 pN (number of observations, N = 543).