Binding of recombinant 221*2 and 221*1 to fibrinogen. [¹²⁵I]-fibrinogen was incubated with 221*2 (A) and 221*1 (C) immobilized on Sepharose beads, and the amount of bound protein was determined as radioactivity associated with the beads following centrifugation and washing. Nonspecific binding was determined in the same way in the presence of a 20-fold molar excess of unlabeled fibrinogen. Specific binding is shown and was calculated by subtracting the nonspecific from the total bound. Each point represents the mean ± SD of 3 separate experiments. Scatchard plot of the data for 221*2 (B) and 221*1 (D). The best fit of the data was determined using the ligand program.³²  The correlation coefficients were 0.99.