Macroscopic lysis velocity of fibrin clots formed from recombinant BβArg448 and BβLys448. Fibrinolysis was assessed directly after completion of polymerization (1.3 μmol/L fibrinogen, 2.5 mmol CaCl₂ and 0.5 U/mL thrombin) at 60 minutes, and results are corrected for maximum absorbancy at the time of addition of plasminogen and tPA at 0.05 g/L and 10 nmol/L, respectively. Fibrinolysis was observed every 2 minutes for 7 hours. There was no difference in lysis rates of Lys448 (□) compared with the Arg448 variant (■; P > .1). In contrast, the addition of the recombinant protein to fibrinogen-depleted plasma resulted in prolongation of lysis rate, which was more pronounced with the Lys448 variant (red □) compared with Arg448 (blue □), a difference that was statistically significant (P < .001). Error bars represent SEM.