PK activation by FXIIa and clotting assays. (A-D) PK activation. PK (60 nM) was incubated with 60 pM of FXIIa, βFXIIa, HGFA^HC/FXIIa^LC, or activated forms of the FXII-HCD chimeras shown in Figure 2C in the absence (A-B) or presence (C-D) of poly-P (70 μM). At the indicated times, aliquots were removed and tested for PKa generation by chromogenic assay. (E) aPTT assays. Shown are average clotting times (±1 standard deviation) for normal plasma (NP) or FXII-deficient plasma supplemented with recombinant proteins to a final concentration of 400 nM.