Figure 3.

The competitive effect of ZPI derivatives on the heparin-catalyzed inhibition of thrombin by antithrombin. The competitive effect of ZPI derivatives (0–250 nM) on the inhibition of thrombin (0.5 nM) by antithrombin (2.5 nM) was monitored in the presence of heparin (5 nM) for 2–3 min in TBS/Ca²⁺ containing 0.1 mg/mL BSA and 0.1% PEG 8000 as described under “Materials and Methods”. The symbols are: ZPI-WT (○), ZPI-3A (●), ZPI-des-NT (□), ZPI-D-helix^α1-PI (■), and ZPI-CD-helix^α1-PI (△). Solid lines are best fits of inhibition data to a hyperbolic equation. Data are derived from at least three independent measurements ±S.D.