Scanning electron micrographs (EM) and laser scanning confocal microscopy (LSCM) of BβArg448 and BβLys448 fibrin clots. Panels A and B represent EM of clots prepared from recombinant fibrinogen Arg448 and Lys448, respectively, at a concentration of 1.3 μM in the presence of 2.5 mmol CaCl₂ and 0.5 U/mL thrombin (magnification, ×10 000). Panels C and D represent LSCM of clots prepared from recombinant fibrinogen Arg448 and Lys448, respectively, at 1.3 μM using 5 mmol CaCl₂ and 0.5 U/mL thrombin. Scale bars on all micrographs indicate 5 μm. Complete microscopy information can be found in “Methods.”