FIGURE 4.
Effect of HD22 on the affinity of thrombin for γA/γA-fibrin clots. 20 nm 125I-YPR-α-thrombin and 5 nm α-thrombin were added to a series of microcentrifuge tubes containing 0–12.5 μm γA/γA-fibrinogen and 2 mm CaCl2 in the absence (♦) or presence of 20 μm HD22 (●). After incubation for 45 min, fibrin was pelleted by centrifugation, and free 125I-YPR-α-thrombin in the supernatant was used to calculate the bound fraction. Data are plotted as the relative amount of thrombin bound to the fibrin clot versus the γA/γA-fibrin concentration and represent the means ± S.E. of three experiments, each done in duplicate, while the lines represent non-linear regression analysis of the data. The affinity of 125I-YPR-α-thrombin for γA/γA-fibrin is 6-fold lower in the presence of HD22 than it is in its absence (Kd values of 12.6 ± 1.4 and 2.1 ± 0.7 μm, respectively).