Fig. 5.

a Seven successive elongations of a single P pilus in the presence of 2.8 μM PapD. Whereas the response from the first elongation has the conventional plateau, indicative of sequential uncoiling, a sigmoid like response was observed for subsequent elongations, indicating the presence of entropy, which in turn originates from stochastic (non-sequential) opening of the TT-bonds. b–d Force versus elongation curves for a single P pilus in the presence of 2.8 μm BSA, FimC, and IGFBP-5 respectively. Elongation of the pilus was stopped when the pilus had become fully uncoiled and the elongation had proceeded into region III; this was followed by retraction, giving rise to a recoiling of the pilus. This procedure was repeated seven times on the same pilus