Figure 27.

Reversible unfolding of single RNA hairpins pulled between two light-scattering 2 μm beads. (a) RNA hairpins are attached to beads through 500 bp hybridized RNA/DNA handles. (b) Force vs extension curves show differences in extension behavior for RNA/DNA handles with (black) and without (red) a hairpin loop sequence. (c) Average unfolding force calculated based on 36 sequential unfolding/refolding events in a single molecule. (d) Length vs time traces at constant forces show hopping between folded and unfolded states at forces from 14.0−14.6 pN. (e) Calculation of unfolding equilibrium constant based on applied force. Adapted from ref (301).