Figure A2.
3D graphs illustrating the connection between ligand concentration [L] and effect E (purple curves) via the concentration of active ligand‐bound receptors [LR*] (blue curves) and the transduction (response) function generating the effect (red curves). (A) Simple single‐state (Clark) model with linear response and affinity only (K d) as parameter; (B) operational (Black and Leff) model with high efficacy (high τ, low K τ) similar to the one shown in the original publication introducing this model (Black and Leff 1983); (C) operational model with low efficacy (low τ, high K τ; a case not illustrated in the original publication) – note that the response (red line) is below that of the linear one for much of the region and most of the hyperbolic response function is left unused; (D) present model with full agonist (ε = 1) and good amplification (γ >> 1); (E) present model with partial agonist (ε < 1) and low amplification (γ ≈ 1) – note that the response is always larger than the linear one and partial activation / effect is achieved via ε. With the present model, if all receptors are active ([LR*] = Rtot), the response always corresponds to E max.