Fibrinopeptide release from thrombin-treated γA/γA and γA/γ′ fibrinogen. Purified fibrinogen γA/γA and γA/γ′ (0.77 mg/mL each) were incubated with 1 IU/mL thrombin and release of FpA and FpB was analyzed by reverse-phase HPLC using a silica C18 column. The fraction of the concentration of the fibrinopeptides at a given time point divided by that at maximum release ([Fp]/[Fp]_max, so that full release equals 1) is plotted against time. FpA released from γA/γA fibrinogen is represented by •, FpB from γA/γA by ▵, FpA from γA/γ′ by ⋄, and FpB from γA/γ′ by ▪. Release of FpB was slower in γA/γ′ compared with γA/γA fibrinogen. Inset in the figure shows a typical chromatogram from HPLC, with the injection peak followed by 2 major peaks representing FpA and then FpB.