Figure 4.

Collagen proteolysis by trypsin is enhanced by force. (a) Collagen tethers rupture at higher rates in the presence of force and trypsin (solid blue circles) than in the absence of either, implying their force-induced denaturation. Data points represent the mean fraction of beads remaining at each time and error bars represent standard errors of this mean. Every 10th data point is shown for the experiments at 9 pN of force, for clarity. Each experimental condition is well described by a single-exponential decay process, with rate constants presented in Table 2. (b) Representative images of collagen-tethered beads at the beginning (left) and after 20 min (right) of incubation with trypsin. Top: no force (67 fN; gravitational force on beads), recorded using a conventional bright-field microscope. Bottom: 8.8 pN of force, recorded within MR.CFM. To see this figure in color, go online.