Tissue factor–stimulated thrombin generation in factor IX–deficient plasma supplemented with 1%, 5%, 10%, and 100% levels of recombinant factor IX wild-type, R170A, and R233A. Thrombin generation was initiated with 0.2 pM of human tissue factor, 8.3 μM of PC:PS vesicles, and 40 μg/mL of CTI (plasma concentrations) in factor IX–deficient plasma supplemented with 0%, 1% (0.9 nM), 5% (4.5 nM), 10% (9 nM), and 100% (90 nM) levels of recombinant factor IX wild-type (A), R170A (B), or R233A (C). The time course of thrombin generation was measured as described in “Fluorogenic method for detection of plasma thrombin generation.” Thrombin generation curves representing the mean fluorescent data from replicate determinations (n = 10) are shown. Curves are identified by representative points. Peak thrombin concentration (D) and velocity index of thrombin generation (E) for each recombinant protein are plotted for comparison. Error bars represent SE.