Figure 6.

Unfolding probability (P_u) as a function of the applied force for the I27₁₂ polyprotein (●) and the I28₈ polyprotein (■). P_u is calculated by counting the number of unfolding events that have occurred up to a given force. For example, there are 24 unfolding events observed in Fig. 5A. The occurrence of event 12 marks the force at which P_u = 0.5. ● correspond to data obtained from the engineered I27₁₂ polyprotein (49 steps from six experiments). ■ correspond to data obtained from the engineered I28₈ polyprotein (31 steps from four experiments). Both sets of data were fitted with a simple two-state model of unfolding that considers that the applied force increases linearly with time (solid lines; see text).