ABSTRACT
The analog pigments have been used to ascertain the chromophore's role in the particular physiological activity of the respective pigment. This chapter discusses the contributions of the laboratory to the knowledge on the structure and function of rhodopsin and bacteriorhodopsin. Hubbard and Wald established that the addition of 11-cis-retinal to the pigment that had been exposed to light resulted in regeneration of the rhodopsin pigment. The acyclic pigments are stable to the addition of hydroxylamine and 11-cw-retinal over several hours, which demonstrates that the analogs are in the binding site. The electron spin resonance spectrum of the spin-labeled retinal shows the classic triplet expected for a nitroxide in a mobile environment. The bleaching of rhodopsin starts with the absorption of light by pigment. The metarhodopsin intermediates are late photoproducts in the bleaching process. In the intact eyecup preparation, visual sensitivity parallels rhodopsin concentration.
