(A) Plasma PK (60 nM) was incubated with 50 pM fXIIa in the absence (○) or presence (●) of 60 nM HK; in the absence of nucleic acids (No Nucleic Acids), in the presence of 5 μg/ml DNA, or in the presence of 1 μg/ml RNA. (B) Plasma PK (60 nM) incubated in the absence (○) or presence (●) of 60 nM HK, without fXIIa or nucleic acids. For panels A and B, at the indicated time points, aliquots were tested for kallikrein activity by chromogenic assay. (C) Western blot for HK using samples from the reaction containing HK in the left-hand image in panel A. Positions of standard for HK and HKa are indicated at the right of the image. (D and E) Same for panels A and B, respectively except that HK was replaced with 60 nM HKa. For panels A, B, D and E, error bars are +/− one SD.