VWF self-association kinetics as a function of free VWF concentration and shear stress. (A) Scheme for VWF self-association. Top: A primary VWF molecule tethered on the substrate at the large open triangle is shown with secondary VWF molecules tethered at small closed triangles. Bottom: Key for the tension within each VWF molecule. (B) Average time course of VWF self-association after wall shear stress increase from 80 to 240, 480, or 960 dyn cm⁻² (red arrows) and then decrease to 80 dyn cm⁻² (black arrows) with 1, 5, 10, or 50 μg mL⁻¹ free VWF. Different sets of tethered VWF molecules (in independent flow channels) were measured for each free VWF concentration; at each free VWF concentration, the same set of tethered VWF molecules was measured at each shear stress. Data were from 67, 70, 93, and 57 VWF molecules for 1, 5, 10, and 50 μg mL⁻¹ free VWF, respectively. Data for 10 μg mL⁻¹ free VWF are the same as in Figure 1C. Flow pattern, imaging exposure time, and frame rates are described in supplemental Tables 1 and 2.