Figure 1.

Pre-incubation of purified hERα with E₂-BSA competes for estradiol binding. Purified ERα was incubated with E₂ (solid line) or E₂-BSA (dotted line) for four hours before (a) or concurrently with (b) the addition of labeled E₂. Incubation was continued for another 2 h at room temperature, and at the end of this period, specific binding was determined by adsorption, removal, and counting of free labeled E₂.