Model systems for photosynthesis IV. Photosensitization by chlorophyllamonolayers at a lipid/water interface

Abstract

Multilayers of chlorophyllaand plant quinones have been constructed on solid surfaces and their absorption spectra have been characterized. Chlorophyllafluorescence quenching by quinones was studied by using a Cd2+1:1 stearate:oleate layer diluent and Cd2+arachidate layers as spacers. The linear dependence of fluorescence yield on separation of the pigments indicates that the quinone can diffuse through arachidate layers. Photosensitized redox reactions have been studied by means of ascorbate-tetrazolium blue and ascorbate-methyl red pairs incorporated in an aqueous solution adjacent to chlorophyllamonolayers. Photoreduction of the dye occurred with light absorbed only by the chlorophyll. A quinone layer adjacent to the chlorophyll layer enhanced the rate of photoreduction by a factor of three, whereas incorporation of quinone in the chlorophyll layer inhibited the photoreduction.