ABSORPTION MAXIMA OF CATIONS RELATED TO RETINAL AND THEIR IMPLICATION TO MECHANISMS FOR BATHOCHROMIC SHIFT IN VISUAL PIGMENT*

Abstract— The cations resulting from eleven retinal-related polyenes by placing the latter in n-butanol-sulfuric acid were examined spectroscopically in an effort to explain the batho-chromic effect observed in visual pigments. A comparison of the Λ_max values, intensities and 1/2-band widths of the model carbonium ions with those of the visual pigments does not seem to justify the representation of the chromophore in visual pigments as a pure carbonium ion.