VWF binding to fibrin. Increasing concentrations of fibrinogen were mixed with 10 nM thrombin for 15 minutes at 37°C on the membrane of spin-X tubes. The fibrin strands were washed, and thrombin bound to fibrin was neutralized with PPACK. ¹²⁵I-VWF (250 ng/mL) was then added to the filter cups and incubated for 2 hours at 37°C. After washing, binding percentages were determined by gamma counting of the filters and the supernatants. Error bars indicate SEM.