Figure 3. Capturing single protein refolding reactions using SMFS.

A) Cartoon diagram showing the equilibrium between folded (i) and unfolded states (ii) of a polyprotein controlled by an applied mechanical force. B) Refolding kinetics probed with a double-pulse protocol (inset). The force/extension traces of an I27₈ polyprotein obtained by consecutively stretching (sawtooth pattern; trace i), relaxing (trace ii) and re-stretching after 10 s relaxation time (iii). All of the domains unfolded in the first pull and spontaneously refolded during the relaxed period. Single molecule experiments show the stochastic nature of the process which is exhibited by small difference between unfolding forces in following pulls. Reproduced with permission from (48).