INFLUENCE OF THE REDOX STATE OF UBIQUINONES AND PLASTOQUINONES ON THEORDER OF LIPID BILAYERS STUDIED BY FLUORESCENCE ANISOTROPY OF DIPHENYLHEXATRIENE AND TRIMETHYLAMMONIUM DIPHENYLHEXATRIENE

The measurements of diphenylhexatriene (DPH) and trimethylammonium dip henylhexatriene (TMA-DPH) fluorescence anisotropy in egg yolk lecithin (EYL) and of DPH anisotropy in dipalmitoylphosphatidylcholine (DPPC) liposomes containing different concentrations of oxidized and reduced ubiquinone (UQ) and plastoquinone (PQ) homologues have been performed. All the oxidized UQ homologues strongly induced ordering of EYL membr ane structure, whereas in DPPC liposomes, above the phase transition t emperature, the most pronounced effect showed UQ-4. PQ-2 and PQ-9 were less effective than the corresponding ubiquinones in this respect. Th e reduced forms of UQ and PQ homologues increased the order of membran e lipids to a smaller extent than the corresponding quinones both in t he interior of the membrane and closer to its surface. Nevertheless, t he investigated prenylquinols showed stronger increase in the membrane order than alpha-tocopherol or alpha-tocopherol acetate, which could be connected with binding of prenylquinol head groups to phospholipid molecules by hydrogen bonds. The strong ordering influence of ubiquino nes on the membrane structure was attributed to methoxyl groups of the UQ quinone rings.