Pre-1 (1.4μM) was incubated with either human or bovine FVa (10nM), CaCl2 (2.0mM), PCPS vesicles (20μM) and DAPA (3.0μM) in 0.02M HEPES, 0.15M NaCl, pH 7.4 and 0.01% (v/v) Tween-80, and its activation was initiated by the addition of FXa (2.5nM). Samples were withdrawn at various times, and were analyzed as in Figure 5.