Fig. 9. Dose-PWR response curves for G_i1 protein binding to agonist-bound human cannabinoid CB₁–myc-His₆ receptor conformations.

PWR spectra were measured after addition of increasing concentrations of GDP-bound G_i1 heterotrimer (1:1 mixture of recombinant myristoylated G_iα1 and purified βγ-subunits from bovine brain) to the aqueous compartment of the PWR resonator containing WIN 55,212-2 (■) or CP 55,940 (▲)-bound epitope tagged CB₁ receptors. PWR spectra were obtained with p-polarized light; similar dose-response curves were obtained using s-polarization (not shown). Lines through the data points were obtained by a hyperbolic fit; K_D values are given in the text. The spectra are representative from three independent experiments.