Thrombin (0.5 nM) or factor Xa (0.5 nM) inactivation by antithrombin (5 nM) was monitored at increasing concentrations of heparin (●), high- (■) or low- (□) molecular-weigth sulfated galactan in TS/PEG buffer, containing either 10 mM CaCl2 (A and C) or 20 mM EDTA (B and D). After 60 s, the remaining thrombin or factor Xa activity was determined by the addition of S-2238 or S-2765, respectively, as described in the legend of Fig. 3. The panels show mean±SD, n=3.