FIGURE 4.

Determination of the degree of diffusional control in the coincident activation of hfX and bfII by extrinsic tenase and prothrombinase under flow conditions. The absolute concentrations of hfXa (●) generated under flow conditions reported in Fig. 3A and hfIIa (○) generated under flow conditions as reported in Fig. 3B are shown as a function of the linear flow rate on a double logarithmic plot. A linear regression (dotted line) of the bfIIa data has a slope of −0.9 ± 0.1, indicative of a dilution-mediated model (Equation 3). A linear regression of the hfXa data has a slope of −0.8 ± 0.1, suggesting that under these conditions, the activation of hfX deviates from a model of diffusion-mediated control (Equation 4).