Specific binding of ¹²⁵I SDF-1α to immobilized Fn shows a 40 nmol/L K_d.

(A) Typical equilibrium-binding isotherm for ¹²⁵I–SDF-1α to Fn-coated tubes. ○: ¹²⁵I–SDF-1α binding to Fn. ▵: ¹²⁵I–SDF-1α binding to noncoated tubes. Values reported are the mean of 4 independent assays for each concentration ±1 SD. Inset: Scatchard transform of the data in the main panel, showing a calculated K_d of approximately 40 nmol/L. (B) Binding is inhibited by “cold” SDF-1α. Two concentrations of ¹²⁵I–SDF-1α (60 or 95 nmol/L) were incubated in Fn-coated tubes with increasing concentrations of cold SDF-1α. Values reported for both panels are the mean of 4 independent assays for each concentration ±1 SD.