PubMed · 508329
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P I Lelkes. 1979-09-27. Potential dependent riigidity changes in lipid membrane vesicles.. https://doi.org/10.1016/0006-291x(79)91285-3
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Phospholipid hydroperoxides and phospholipid alcohols are two of the major forms of oxidatively modified phospholipids produced during oxidant stress and lipid peroxidation. The process of lipid peroxidation is known to affect the physiological function of membranes. We, therefore, investigated the effects of lipid peroxidation products on the molecular interactions in membranes. Our study was specifically focused on the effects of lipid peroxidation products on static membrane structure (molecular orientational order) and on the reorientational dynamics of the probe molecules in lipid bilayers. The study was done by performing angle-resolved fluorescence depolarization measurements (AFD) on the fluorescent probe diphenylhexatriene (DPH) and by performing angle-resolved electron spin resonance (A-ESR) measurements on cholestane (CSL) nitroxide spin probes embedded in macroscopically oriented planar bilayers consisting of 2-10% 1-palmitoyl-2-(9/13-hydroperoxylinoleoyl)phosphatidylcholine (PLPC-OOH) or 1-palmitoyl-2-(9/13-hydroxylinoleoyl)phosphatidylcholine (PLPC-OH) in 1-palmitoyl-2-linoleoylphosphatidylcholine (PLPC) or dilinoleoylphosphatidylcholine (DLPC). Both probe molecules have rigid cylindrical geometries and report on the overall molecular order and dynamics. However, being more polar, the nitroxide spin probe CSL is preferentially located near the surface of the membrane, while the less polar fluorescent probe DPH reports preferentially near the central hydrophobic region of the lipid bilayers. The results show that the presence of relatively small amounts of oxidatively modified phospholipids within the PLPC or DLPC membranes causes pronounced structural effects as the molecular orientational order of the probe molecules is strongly decreased. In contrast, the effect on membrane reorientational dynamics is minimal.
The sensitivity of the fluorescence lifetime of 1,6-diphenyl- 1,3,5-hexatriene (DPH) to the dielectric constant of its environment has been used to detect oxidative damage to phospholipid membranes induced by ionizing radiation. The DPH fluorescence decay in phospholipid vesicles is described well by a continuous distribution of lifetime values, reflecting the various DPH depths in the bilayer and related to the gradient of the dielectric constant. Ionizing radiation oxidizes unsaturated acyl residues of phospholipids, altering the dielectric constant across the bilayer, sharpening the distribution of DPH lifetimes and increasing the centre of the distribution. Ionizing radiation doses between 22 and 110 Gy were used, and were effective only in the presence of oxygen. A model based on the formation of packing defects in the bilayer describes the phenomenon.
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