Figure 4.

Conformational dynamics of a 6 bp DNA hairpin. A,B) Force-extension data at full measurement bandwidth collected with A) ten-helix bundles or B) conventional dsDNA linkers. C) Fluctuation amplitude in the data from (A,B) or when the linkers were connected directly (gray). D) Solid line: extension data for constant trap distance at full measurement bandwidth for the ten-helix bundles. Dashed line: fitted two-state hidden Markov transition trajectory. E) As in (D) but with conventional dsDNA. F) Force-dependent folding (falling branch) and unfolding (rising branch) rate constants as determined from dwell-time analysis of constant distance data as in (D) acquired at different loads. Vertical and horizontal bars indicate errors. G,H) Histogram of the deflection states visited by the system at constant trap distance for G) the ten-helix bundles or H) conventional dsDNA. Solid lines: fits using a single Gaussian (red) or a linear combination of two Gaussians (gray). The average force load on the folded and unfolded states was 6.5 pN and 6.0 pN in (G), respectively. I) Free-energy landscape reconstructed from the data in (G).