Affinity of factor VIII C1 domain mutants for plasma VWF. Wild-type factor VIII (●) and mutants 2159 (■), 2042/2043 (▾), 2090/2091 (◇), and 2092/2093 (♦) were incubated with various concentration of purified plasma VWF for 60 minutes before placement in microtiter wells coated with mAb BO2C11. Bound factor VIII was detected with biotinylated mAb ESH8. Because VWF competes for the BO2C11 epitope,²⁵  it leads to decreased bound factor VIII. Displayed values are normalized to the maximum signals measured for each type of factor VIII in the absence of added VWF. The quantity of factor VIII used was 0.4 unit/mL for wild-type factor VIIII and mutants. Data are the average of 3 experiments. The molar concentration of VWF subunits, indicated on the abscissa, was obtained by dividing the VWF concentration by the molecular weight of a single VWF subunit.