93] Fluorine-labeled retinals and rhodopsins

Abstract

Publisher Summary This chapter discusses the fluorine (F)-labeled retinals and rhodopsins. The use of F as a label to probe for structural information of complex biomolecules by nuclear magnetic resonance (nmr) spectroscopy is an established technique. Its advantages over other NMR active nuclei are several. Among them is the absence of background signals from proteins or detergents. The disadvantages associated with the method are the synthetic difficulties sometimes encountered in introducing the fluorine labels at strategic positions and the possibility that the highly electronegative fluorine atom might change the overall properties of the biomolecules of interest. The absorption maxima of isomers of several fluorinated rhodopsins are listed in the accompanying table along with those of the corresponding retinals. That the selectivity of fluororetinal isomers in their reaction with cattle opsin is virtually the same as the parent retinals suggests that the fluorine substituents do not exert a vastly different steric effect.