Photo-Induced Electron Transfer in Chlorophyll Containing Liposomes

Walter Oettmeier, James R. Norris, Joseph J. Katz
1976 Zeitschrift für Naturforschung C - A Journal of Biosciences  
Liposomes (lipid, ᴅʟ-α-dipalmitoyl-phosphatidylcholine) containing chlorophyll a (ratio lipid to chlorophyll 30:1) exhibit an absorption maximum at 670 nm. Upon oxidation with iodine these liposomes yield a chlorophyll radical that shows a ESR signal with a line width (peak to peak) ⊿Y = ~0.1 G and a g-value of 2.0022, consistent with the presence of monomeric chlorophyll. Under anaerobic conditions, in the absence of acceptors, no light induced ESR signal is observed, whereas under aerobic
more » ... s under aerobic conditions the chlorophyll free radical is generated in the light. Acceptors having access to the lipid membrane, like Fe3+ -pyrophosphate and methylviologen, give rise to chlorophyll radical formation, or, like quinones, form a semiquinone radical in the light. Non-permeable acceptors, such as ferricyanide, NADP, FMN and cytochrome c do not act as acceptors and no chlorophyll radicals can be produced by light. Furthermore, light dependent and completely reversible electron transfer from N,N,N′,N′-tetramethyl-p-phenylenediamine to ubiquinone can be demonstrated. Liposomes containing chlorophyll, therefore, can serve as a model system for photosynthetic electron transport.
doi:10.1515/znc-1976-3-413 fatcat:y4cssytqyjhb7mhxi7rbww3tl4