Biochemical characterization of the recombinant FVIII-R1645H (RH) variant. (A) SDS-PAGE results of 3 μg of FVIII-RH and FVIII-BDD staining with Coomassie blue before (−) and after (+) incubation with thrombin are shown. (B) The alignment of partial sequences of FVIII B domain from distinct species is shown. (C) The graph shows the decay of FVIII-RH and FVIII-BDD following thrombin activation. Purified proteins (20 nM) were activated in the presence of α-thrombin, and the residual activity of FVIII was determined by a 2-stage aPTT assay. (D) FVIII clotting activity was determined by 1-stage (without thrombin) or 2-stage (with thrombin) aPTT assay; data represent triplicated experiments.