Inhibition of SC54701 binding to _IIbβ₃ by group II antagonists. Washed platelets (1 × 10⁹/mL) were incubated with 1 μmol/L SC54701 for 30 minutes at room temperature, and then varied concentrations of group II antagonists (Ro44-9883 or MK383) were added to the mixtures as a competitor and incubated for 30 minutes at room temperature. Biotinylated AP5 (5 μg/mL) was incubated with the mixtures, followed by adding FITC-conjugated streptavidin (1:320 dilution). AP5 binding to platelets was analyzed by flow cytometry. Mean fluorescence intensity (MFI) is the value obtained by subtracting AP5 binding in the absence of any antagonists. These results are the average of two separate experiments.