Characteristics of FX, FXa, FIXa, and prothrombin distribution on the surface of procoagulant-activated platelets. Platelets (5 × 10⁴ μL⁻¹) were activated with 100 nM thrombin plus 20 μg/mL CRP, incubated for 5 minutes with either 250 nM FX, 30 nM FХa, 60 nM FIXa, or 60 nM prothrombin, and imaged with confocal microscopy. (A-B) Representative confocal images of DIC, FITC (green) fluorescence of FX, FXa, FIXa, and prothrombin, and overlay are shown for procoagulant platelets (A) and nonprocoagulant ones (B). Scale bars, 5 μm. (C-F) The quantities of factor molecules bound to the “cap” (red bar) and to the “balloon” (black bar) are shown. Mean ± SD in (C-F) were determined for 30 to 70 procoagulant platelets analyzed in each experiment.