Figure 2.

Contribution of enthalpy and entropy changes to ligand binding to A₁ adenosine receptors under different incubation conditions. Equilibrium binding experiments with A₁ adenosine receptor ligands had been conducted in 50 mM Tris-HCl pH 7.4 with membranes not pretreated or pretreated with NEM or in 50 mM Tris-HCl pH 7.4, 2 mM triethanolamine, 1 mM EDTA, 5 mM MgCl₂, 100 mM NaCl, 1 mM dithiothreitol and 0.5% bovine serum albumin or, alternatively, in the same incubation medium containing in addition 10 μM GDP. Thermodynamic parameters were calculated from van't Hoff plots. Data for K_H values are represented by filled symbols, data for K_D and K_L values are shown as open symbols.