VWF dose dependency. Increasing amounts of ¹²⁵I-VWF were added to fibrin strands formed from 0.75 mg/mL fibrinogen (37 μg fibrinogen on filter) and 10 nM thrombin. Specific binding, calculated from total binding and nonspecific binding, eg, in the absence of fibrin, is plotted versus the free VWF concentration. The solid line is the result of a nonlinear regression analysis that fits the data points of 3 independent experiments to a Langmuir binding model. Error bars indicate SEM.