ULVWF binds recombinant CUB polypeptides under static and flow conditions. (A) Static assay: ULVWF was incubated with immobilized wild-type ADAMTS13 or CUB domain polypeptides for 30 minutes and bound ULVWF was detected using a polyclonal VWF antibody. The data are expressed as mean ± SEM (Student t test, n = 5, ^*P < .001 for each peptide compared with BSA). (B) Flow assay: Polystyrene beads coated with ADAMTS13 or CUB polypeptides were allowed to settle on immobilized ULVWF and then perfused with buffer for 2 minutes. The beads remaining adherent were counted (▪). The wall shear stress was then increased to 50 dyn/cm² for 2 minutes perfusion and the beads that remained were again counted (□). The data are mean ± SEM of beads bound in 10 random × 400 review fields (Student t test, n = 4, ^*P < .001 compared with BSA beads).