Compared with F13a^+/+clots, F13a^+/−clots have delayed FXIII activation and fibrin crosslinking. PRP was clotted with TF/CaCl₂ and quenched at the indicated time points. FXIII activation (generation of FXIII-A′) and fibrin crosslinking were analyzed by SDS-PAGE with western blotting. (A) Representative western blots and (B) quantitation of FXIII-A′ over time for clot formation in F13a^+/+ and F13a^+/− PRP. Data show mean ± SEM (n = 3-5). (C-D) Representative western blots for fibrin crosslinking in F13a^+/+and F13a^+/− PRP clots. (E-F) Quantification of γ-γ (E) and HMW (F) crosslinked fibrin species formation. Data show mean ± SEMs (n = 3-5). A.F.U., arbitrary fluorescence units.