FIGURE 3.

Evaluation of competition binding experiments. The calculations were performed using Model 2 (see “Experimental Procedures”). A, inhibition of monovalent p85 C-SH2 domain binding to Tyr(P)⁷⁵¹ of PDGF β-receptor by different competitor peptides as indicated. Fig. 6A of Ref. 17 was recapitulated with S_T = K_D,C1 = 10 nm and K_D,C2 = 75 nm, where S_T is the total concentration of C-SH2. B, inhibition of p85 tandem SH2 construct by different competitor peptides as indicated. In the case of the bisphosphorylated competitor, the value of χ is varied as indicated. Fig. 6 (B and C) of Ref. 17 compares favorably with these results when χ > 10 μm.