Polyphosphate increases final clot turbidity but does not alter clotting time over a wide range of thrombin concentrations. Clotting reactions contained 2.6 mg/mL of citrate-free fibrinogen, which was preincubated for 15 minutes in the presence of 2.5 mM CaCl2, with or without polyphosphate (polyP), before clot initiation by thrombin. (A) Clotting times of reactions containing 1 mM polyP (▼) or no polyP (○) as a function of various thrombin concentrations. Data are mean plus or minus SE (n = 3). (B) Time courses of fibrin formation (turbidity increase) in reactions containing 0 (▲), 188 μM (◇), 375 μM (■), 750 μM (▼), or 1.5 mM (●) polyP, with clotting initiated by 3 nM thrombin. Data are from a representative experiment. (C) Maximum fibrin clot turbidities in reactions containing 1 mM polyP (▼) or no polyP (○) as a function of various thrombin concentrations. Data are mean plus or minus SE (n = 3).
