Kinetics of thrombin-mediated release of fibrinopeptides from the primary fibrinogen layers adsorbed on polystyrene. The amounts of FpA (□) and FpB (■) released from the primary fibrinogen layers adsorbed from the high (500 μg/mL, 30 minutes) and low (20 μg/mL, 150 minutes) fibrinogen concentrations (A and B, respectively) and from fibrinogen in solution (C) was determined by HPLC, as described in “Methods.” The concentration of thrombin in all experiments was 2.5 U/mL. Each point represents a mean value obtained from 3 independent experiments in which the total amount released in one well at the indicated time interval was measured. Inserts in panels a and b show an illustrative arrangement of fibrinogen molecules adsorbed in the end-on and side-on orientations, respectively, and in panel C fibrinogen in solution.