Fibrinogen Beta Chain (FGB) is the beta subunit of the coagulation factor fibrinogen, which is a component of the blood clot. Following vascular injury, fibrinogen is cleaved by thrombin to form fibrin which is the most abundant component of blood clots. Fibrinogen Alpha Chain (FGA) has been identified as an interactor of FGB. Thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human FGB and recombinant mouse FGA. Briefly, FGB was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to FGA-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-FGB pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µL stop solution to the wells and read at 450/630 nm immediately. The binding activity of recombinant human FGB and recombinant mouse FGA was shown in Figure 1, the EC50 for this effect is 0.03 ug/mL.