FIGURE 2.
Effect of exosite-directed ligands on thrombin clotting times. γA/γA-Fibrinogen (2 μm) containing 2 mm CaCl2 was clotted with 2 nm α-thrombin in the absence or presence of exosite 2-directed ligands, HD22 (●), γ'-peptide (▴), or F2 (■) (A), or exosite 1-directed ligands, HD1 (○) or hirudin-(54–65) (▵), exosite 1-directed ligands (B). Absorbance was determined spectrophotometrically at 405 nm, and the time to reach half-maximal turbidity (clot time) was normalized with respect to that measured in the absence of ligands. Symbols represent the means ± S.E. of three experiments, each done in duplicate, while the lines represent non-linear regression analysis of the data.