Competition of nonlabeled VWF with ¹²⁵I-VWF.¹²⁵I-VWF (250 ng/mL) and increasing concentrations of unlabeled VWF were incubated in filters without and with fibrin (37 μg) for 2 hours at 37°C. Nonspecific binding in the absence of fibrin was subtracted from the total binding to obtain the specific binding. Results are expressed as percentages of specific binding of ¹²⁵I-VWF in the absence of nonlabeled VWF. Error bars indicate SEM.