A model for the effect of lipid oxidation on diphenylhexatriene fluorescence in phospholipid vesicles.
We have determined by means of a standard spectrophotometric assay that lipid oxidation occurred at a significant rate in large, multilamellar vesicles containing egg phosphatidylcholine under normal experimental conditions. We have also observed that the fluorescence intensity of the vesicle-associated probe, 1,6-diphenyl-1,3,5-hexatriene, decreased with time in vesicles containing such oxidizing lipids. The spectrophotometric data utilized to monitor lipid oxidation were found to fit an apparent first-order kinetic model. The loss of diphenylhexatriene fluorescence intensity in oxidizing liposomes was analyzed in terms of a first-order event superimposed (and thus presumably dependent) upon the ongoing formation of oxidized lipid. These and other data were used to conclude that the oxidation-induced loss of diphenylhexatriene fluorescence intensity was due to chemical modification of the fluorophore rather than to excited-state quenching or ground-state complex formation. Finally, the loss of fluorescence intensity in oxidizable membranes was found to alter drastically the 'microviscosity' parameter as derived from diphenylhexatriene fluorescence anisotropy and relative intensity measurements.
D002784:Cholesterol / Q000378:metabolism; D004161:Diphenylhexatriene / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism*; D008433:Mathematics; D008560:Membrane Fluidity; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000378:metabolism*; D011090:Polyenes / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013997:Time Factors
D008081:Liposomes; D010713:Phosphatidylcholines; D011090:Polyenes; D004161:Diphenylhexatriene; D002784:Cholesterol