Figure 1. Atomic force spectroscopy used to probe tether length.

Schematic illustrating the single molecule approach to probing the short (a) and long (b) polyethylene glycol (PEG) tethers. As the cantilever is retracted upwards the force due to the tension in the linker causes the lever to be deflected, which is measured as a force. (c) Representative force-extension traces for short, medium, and long linkers. The dashed line represents the force required to activate integrins (43pN). Histograms of distances taken to reach the 43pN threshold force for short (d), medium (e) and long (f) length tethers together with Gaussian fits to the data and peak lengths (n = 300 for each).