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CHLOROPHYLL PHOTOSENSITIZED ELECTRON TRANSFER REACTIONS IN LIPID BILAYER VESICLES: GENERATION OF PROTON GRADIENTS ACROSS THE BILAYER COUPLED TO QUINONE REDUCTION AND HYDROQUINONE OXIDATION
Author(s) -
Zhao ZhanGong,
Tollin Gordon
Publication year - 1992
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1992.tb04284.x
Subject(s) - bilayer , chemistry , hydroquinone , photochemistry , quinone , vesicle , lipid bilayer , electron transfer , flash photolysis , proton , analytical chemistry (journal) , membrane , kinetics , stereochemistry , chromatography , organic chemistry , biochemistry , reaction rate constant , physics , quantum mechanics
— A chlorophyll‐containing small unilamellar lipid bilayer vesicle system with a sulfonated quinone molecule (MQS) in one aqueous compartment and a sulfonated hydroquinone molecule (H 2 QS) in the other has been investigated, using laser flash photolysis and steady‐state irradiation, as a means of storing light energy in the form of a proton gradient across the lipid bilayer. Under optimal conditions, an efficiency of 39% based on the chlorophyll triplet state quenched has been achieved for vectorial electron transfer across the bilayer; this corresponds to a quantum yield of 23% based on absorbed photons. As a consequence of irradiation by a single laser flash, 0.2 μ M of protons were taken up by quinone reduction (MQS → H 2 MQS) in the outer compartment. The same number of protons were released in the inner compartment by hydroquinone oxidation (H 2 QS → QS). Since the volume occupied by the vesicles was only 1/1000 of the total volume of the sample, the local concentration of protons in the inner compartment was 1000 times larger ( i.e. ≅ 200 μ M ), resulting in the generation of an appreciable proton gradient across the bilayer.