Fig 4. Short-chain polyphosphates accelerate the inhibition of TFPIα by FXIa.

(A) FXa (0.5 nM)-induced clotting time of FX-depleted plasma was measured in the presence of vehicle or 5 nM TFPIα pretreated with 1 nM FXIa + 25 μM Zn²⁺ for 30 min in the presence of 0, 0.6, 1.25, 2.5,5 or 10 μM SCP. After 30 min of incubation with FXIa, aprotinin (50 μM) and polybrene (16 μM) were added to stop the reaction. (B) FXa (0.5 nM)-induced clotting time of FX-depleted plasma was measured in the presence of vehicle or 5 nM TFPIα pretreated with 0.06, 0.125, 0.25, 0.5 or 1 nM FXIa for 30 min in the presence of 10 μM SCP and 25 μM Zn²⁺. After 30 min of incubation with FXIa, aprotinin (50 μM) and polybrene (16 μM) were added to all samples to stop the reaction. Data are mean ± SE (n = 3).