Rate of γ-dimer and α-polymer formation in fibrin 1 versus fibrin 2. Reaction was initiated by adding thrombin (0.5 U/mL, final) to factor XIII-containing (100 Loewy U/mL) fibrinogen 1 or fibrinogen 2 in TBS containing 5 mM CaCl₂. Fibrin 1 γ-dimer (□); fibrin 2 γ-dimer (○); fibrin 1 α-polymer (▪); fibrin 2 α-polymer (○). Inset shows the first 1.5 minutes of cross-linking.