AN F-NMR-STUDY OF BIS(TRIFLUOROMETHYL)PHENYL BACTERIORHODOPSIN ANALOGS

Two bis-trifluoromethylated phenylretinal bacteriorhodopsin (bR) analo gs were prepared and studied by F NMR and UV-vis spectroscopy. In cont rast to those of visual pigments, only one fluorine signal was observe d for the doubly labeled bR analogs. After considering different possi ble explanations, we believe the result probably reflects a more open hydrophobic pocket for the bR analogs allowing rapid equilibration (at the NMR scale) of the double labels. The extent of protein perturbati on at the ortho position is different from that at the meta position.