Affinity constants for binding of the different ligands to the hDOR obtained in these studies using PWR and from previous literature
Kd values were obtained from plotting the resonance minimum position (Y) for the PWR spectra as a function of ligand concentration (X) and fitting to the following hyperbolic function that describes the binding of a ligand to a receptor: Y = (BmaxX)/(Kd + X). Bmax represents the maximum concentration bound, and Kd is the concentration of ligand required to reach half-maximal binding.
| Ligands | Kd Obtained from PWR Experiments | Ligand Affinities Obtained from Literature | |
|---|---|---|---|
| p-Polarization | s-Polarization | ||
| nM | nM | ||
| DPDPE | 14 ± 3 | 18 ± 5 | 16 (Mosberg et al., 1983) |
| pCl-DPDPE | 2.9 ± 0.7 | 3.3 ± 0.8 | 1.6 (Toth et al., 1990) |
| Deltorphin II | 0.88 ± 0.05 | 1.2 ± 0.3 | 0.7 (Misicka et al., 1991) |
| SNC80 | 52 ± 8 | 57 ± 12 | 56 (Hosohata et al., 2001) |
| Tan 67 | 3.2 ± 1.2 | 3.7 ± 1.5 | 6 (Nagase et al., 1998) |
| TIPP | 1.1 ± 0.1 | 1.2 ± 0.1 | 1.22 (Schiller et al., 1999) |
| NTI | 0.025 ± 0.001 | 0.023 ± 0.004 | 0.028 (Knapp et al., 1994) |
| Naloxone | 8 ± 3 | 8 ± 1 | 10 (Lewanowitsch et al., 2003) |
| TMT-L-Tic | 2.5 ± 0.3 | 3.2 ± 0.2 | 9 (Liao et al., 1997) |
| Morphine | 520 ± 30 | 1101 (Gharagozlou et al., 2002) | |
| Ethorphine | 0.3 ± 0.1 | 0.2 (Gharagozlou et al., 2002) | |
Empty cells indicate that no net spectral shifts were obtained for this ligand using s-polarized light.