Potency, Efficacy, and Curves

Around 500 compounds representing various clusters were submitted for screen to provide full concentration response curves in the human GPR81 cAMP TRF assay in addition to the described counterscreen. This included most of the singletons and a large nimiber of representatives from larger compound clusters. 

Steep curve behavior can also be seen for covalently binding compounds or very potent inhibitors with the value below the target protein concentration of the assay. For enzymes, this is known as zone behavior [28,29]. By applying the mass action law, inhibition becomes a linear function of the enzyme concentration if the Kd value of the inhibitor is far below the enzyme concentration. The steepness of the concentration response curve also increases with the amount of enzyme added. 

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