Fibrin clot formation is dependent on the initial prothrombin concentration.

The model plasma system was incubated with 2 mg/mL fibrinogen and the level of prothrombin (0% ○, 1% ■, 10% ⋄, 50% ▵, 100% ●, 150% ▪, 200% ♦, and 300% ▴ of plasma levels) was varied. Clot formation was monitored by an increase in optical density. Data shown are representative of 10 experiments.