The relevance of kinetic parameters in the determination of specific binding to the estrogen receptor

This paper illustrates how the kinetics of the interaction between steroid hormone and estrogen receptor influences binding parameter evaluation and determines biological activity. The relative binding affinities and amount of specific binding measured with two isomeric estrogen derivatives, R 2858 (moxestrol = 11β-methoxy-19-nor-1,3,5(10)-pregnatrien-20-yne-3,17-diol) and RU 16117 (11α-methoxy-19-nor-1,3,5(10)-pregnatrien-20-yne-3,17-diol), have been compared under different conditions and related to their respective association and dissociation rates.