Fig. 1. Equilibrium binding of ¹²⁵I-DIP-uPA to MDA-MB-231 cells. MDA-MB-231 cells were acid-washed and then incubated with increasing concentrations of ¹²⁵I-DIP-uPA for 4 hours at 4°C. The specific binding isotherm is shown in panel A. Each point represents the mean ± s.e.m. of results from two separate experiments, each with triplicate determinations. The Scatchard transformation of the same data is shown in panel B. B/F, bound/free.