Fig. 3: Experimental and simulation results from the optical tweezers.
a Experimental force-extension curves in chronological order from a medium ramp experiment, showing non-history dependent switching between strong (red) and weak (blue) rupture events for the hook9/9-jaw 8/18 construct shown in Fig. 2b. Traces end when the hook unbinds. Fishing attempts that do not yield single tethers are not shown. b The same force-extension curves in (A), but with theoretical worm-like chain curves overlaid for the two possible states (dashed lines). The distribution of ΔLc (inset) from all medium pulls with a jaw opening event, as compared with the theoretical ΔLc of 20.20 nm. c Rupture force distributions at three pulling rates compared to the Monte-Carlo simulation. The slow pulling rate has a higher proportion of hook unzipping, while the fastest pulling rate has a higher proportion of hook shearing. d Rupture force plotted against force loading rate for the three ramps, calculated at the moment of rupture. Due to the long DNA handles, each pulling speed (nm s−1) has a range of loading rates (pN s−1) obtained from the worm-like chain model. e The proportion of open-jawed constructs as a function of pulling rate compared to the simulation. Two additional catch bonds were tested in addition to the one shown in the rest of Figs. 2 and 3 (h9/9j8/18), one with an 11/11 CG content hook (h11/11j8/18; yellow; n = 101, 178, 130 for slow, medium, and fast ramp speed) and one with a 10/18 CG content jaw (h9/9j10/18; green; n = 253, 490, 187 for slow, medium, and fast ramp speed). Error bars are the 95% confidence interval of the proportion; n = 1000 for each simulated point.
