Emax compares the structure of the complexes. A, the relationship of the percent energy transfer (E) from ERα-CFP in the ER·SRC-RID complex to the total amount of YFP-SRC2-RID (fluorescent units). This example shows measurements from a total of 720 cells treated with estradiol (closed boxes) or with vehicle (open boxes). Emax, maximal amount of ERα-CFP energy transfer at saturating YFP-SRC2-RID. B, Emax for the interaction of ERα-CFP with each of the YFP-tagged SRC1, -2, and -3 RIDs (mean ± S.D. from three independent experiments) and with ERα-YFP (nine independent experiments).