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ENERGY TRANSFER AND ENERGY LOSSES IN BILAYER MEMBRANE VESICLES (LIPOSOMES)
Author(s) -
Mehreteab Ammanuel,
Strauss George
Publication year - 1978
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.1751-1097.1978.tb07720.x
Subject(s) - acceptor , chemistry , quenching (fluorescence) , liposome , fluorescence , vesicle , bilayer , photochemistry , membrane , förster resonance energy transfer , lipid bilayer , biochemistry , physics , quantum mechanics , condensed matter physics
. The efficiency of singlet‐singlet energy transfer was studied in bilayer lipid membrane vesicles (liposomes) for the following donor‐acceptor systems: (1) p ‐terphenyl (TP) and diphenyloctatetraene (DPO); (2) DPO and chlorophyll a (Chl a ); and (3) β‐carotene and Chl a. The energy transfer efficiency φ DA was measured by sensitized fluorescence of the acceptor. Fractional quenching of the donor φ Q was found from the donor fluorescence in absence and presence of the acceptor. For TP‐DPO and for DPO‐Chl a , the transfer efficiency increased with increasing acceptor concentration but was essentially independent of the donor concentration. No energy transfer from β‐carotene to Chl a could be detected. In liposomes, φ DA differed only slightly from φ Q at all donor and acceptor concentrations, thus demonstrating the absence of any appreciable energy losses. For solutions of the same donor‐acceptor pairs in cyclohexane φ Q was considerably larger than φ DA . The difference represents energy lost, principally by internal conversion, due to collisional quenching. The principal function of the lipid membrane appears to be the suppression of such losses. In addition, the rate of energy transfer in lipid membranes is about double that in solutions (at the same intermolecular distance) due to more favorable orientation.