Premium
CHLOROPHYLL PHOTOSENSITIZED ELECTRON TRANSFER REACTIONS IN LIPID BILAYER VESICLES: VECTORIAL ELECTRON TRANSFER ACROSS THE BILAYER FROM REDUCED CYTOCHROME c IN THE INNER COMPARTMENT TO OXIDIZED FERREDOXIN IN THE OUTER COMPARTMENT
Author(s) -
Zhao ZhanGong,
Tollin Gordon
Publication year - 1991
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.1751-1097.1991.tb01993.x
Subject(s) - chemistry , electron transfer , photochemistry , redox , vesicle , electron transport chain , biophysics , bilayer , compartment (ship) , photosynthetic reaction centre , cytochrome , aqueous solution , photosystem i , ferredoxin , lipid bilayer , p700 , membrane , photosynthesis , photosystem ii , biochemistry , biology , inorganic chemistry , organic chemistry , enzyme , geology , oceanography
A negatively charged large unilamellar vesicle system containing a membrane‐bound photo‐sensitizer (chlorophyll, Chi), a reduced redox protein [cytochrome c , cyt c(red)] in the inner aqueous compartment, an oxidized redox protein [ferredoxin, Fd(ox)] in the outer aqueous compartment, and propylene diquat (PDQ 2+ ) as a mediator, was investigated using both flash and steady‐state photolysis techniques. The results demonstrate that the light‐generated triplet state of Chi ( 3 Chl) was initially quenched by PDQ 2+ at the outer membrane surface to form Chi cation radical (Chl + ) and the reduced diquat (PDQ + ). This was succeeded by a biphasic recombination between Chi + and PDQ + . The slow phase of the recombination process, which represents reverse electron transfer between Chl + and those PDQ + molecules which escaped from the membrane surface, could be suppressed effectively both by the reduction of Chl^ in the inner monolayer of the vesicles by cyt c (red), and by the reoxidation of PDQ + by Fd(ox) in the outer aqueous compartment. These reactions lead to the permanent accumulation of oxidized and reduced product proteins, i.e. cyt c (ox) in the inner compartment and Fd(red) in the outer compartment. The yields of such accumulation were 11%, based on the 3 Chl quenched, and 1.4%, based on absorbed quanta, under the conditions used in the present study. This system mimics one of the key events in natural photosynthesis and results in an appreciable storage of electromagnetic energy in the reaction products.