The Structure, Spectra, and Reactivity of Visual Pigments

Recent chemical and physical studies have clearly shown that visual pigments are an integral part of a lipoprotein membrane whose apparent role is to initiate cation exchange flow across its boundaries, when illuminated, giving rise, thereby, to a neural receptor potential. As membrane structures visual pigments are unique in that they contain, as the principal prosthetic group, a chromophore whose rather singular absorption spectrum serves as a sensitive probe of its molecular environment and whose spectral changes provide an essentially non-perturbative method of monitoring molecular events occurring within the membrane.