Role of metal cations in colour transition and hydrolysis of the chromophores of retinal-binding photoreceptor proteins

Abstract

Rates of hydrolysis of a model retinylidene Schiff base chromophore, namely all- trans-N-retinylidene-β-naphthylamine ( 1), have been determined in tetrahydrofuran, CHCl 3, and CH 3CN, in the presence and absence of metal cations (Li +, Mg 2+) and trichloroacetic acid as the protonating agent. A mechanism for the hydrolysis of the Schiff base chromophore in visual pigments and a representation of the role of metal ions in maintaining the structure functions of bacteriorhodopsin have been proposed.