Towards a thermodynamic definition of efficacy in partial agonism: The thermodynamics of efficacy and ligand proton transfer in a G protein-coupled receptor of the rhodopsin class

Enthalpy differences between agonist (ΔHijx + ΔHτ) and antagonist (ΔHrs) component binding of a partial agonist, prenalterol, on the β1-adrenoreceptor can be coincident with the energetics of ligand proton delivery to an aspartate ion on α-helix II.