Fluorescence anisotropy of diphenylhexatriene and its cationic Trimethylamino derivative in liquid dipalmitoylphosphatidylcholine liposomes: opposing responses to isoflurane (original) (raw)
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Nanosecond fluorescence anisotropy decays of 1,6-diphenyl-1,3,5-hexatriene in membranes
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1979
Nanosecond decays of the fluorescence anisotropy, r, were studied for the emission of 1,6-diphenyl-l,3,5-hexatriene (DPH) embedded in a series of mixed multilamellar liposomes containing egg yolk phosphatidylcholine, phosphatidylethanolamine and cholesterol in varying molar ratios, as well as in membranes of intact cells and in virus envelopes.
Biochimica Et Biophysica Acta-biomembranes, 1993
Glyceryl trinitrate (GT) and pentaerythritol tetranitrate (PT) are two vasodilatory drugs. The physical properties of the membrane lipid matrix, which determine the structure and function of the membrane-bound proteins, generally control the pertubation mechanism of these drugs. Thus, physical interaction of these drugs with membrane lipids is very crucial for their clinical use, different cellular processes, as well as for targetted drug delivery systems. In the present paper, we have reported for the first time the interaction between these drugs and the lipid molecules in the liposomal system of dipalmitoylphosphatidylcholine (DPPC), as measured by steady-state fluorescence anisotropy using 1,6-diphenyl-1,3,5-hexatriene (DPH) as fluorescent probe. Our results show that by dissolving in the lipid matrix these two drugs effectively stabilise the liposomal membrane: the effect being more in case of GT than in PT, indicating that the rigidifying effect is independent of the number of nitrate groups of the two drugs. This effect increases with the increase in drug concentration, implying solubilisation of all drug molecules. Though our in vitro study has more physical significance than a physiological one, the results obtained here may be used to interpret the effects that are observed in vivo.
Biophysical Journal, 2003
The structural modifications of the dipalmitoylphosphatidylcholine (DPPC) organization induced by increasing concentration of the volatile anesthetic enflurane have been studied by differential scanning calorimetry, small-angle, and wideangle x-ray scattering. The interaction of enflurane with DPPC depends on at least two factors: the enflurane-to-lipid concentration ratio and the initial organization of the lipids. At 258C (gel state), the penetration of enflurane within the lipids induces the apparition of two different mixed lipid phases. At low anesthetic-to-lipid molar ratio, the smectic distance increases whereas the direction of the chain tilt changes from a tilt toward next-neighbors to a tilt between next-neighbors creating a new gel phase called L b9
Chemistry and physics of lipids, 2016
The molecular mechanism underlying the action of local anesthetics remains elusive. Phenylethanol (PEtOH) is an ingredient of essential oils with a rose-like odor and has been used as a local anesthetic. In this work, we explored the effect of PEtOH on organization and dynamics in membranes representing various biologically relevant phases using differentially localized fluorescent membrane probes, DPH and TMA-DPH. We show here that PEtOH induces disorder in membranes of all phases (gel/fluid/liquid-ordered). However, the extent of membrane disorder varies in a phase-specific manner. Maximum membrane disordering was observed in gel phase, followed by liquid-ordered membranes. The disordering was minimal in fluid phase membranes. Interestingly, our results show that the disordering effect of PEtOH in gel phase is sufficiently large to induce phase change at higher PEtOH concentrations. Our results are relevant in the context of natural membranes and could be useful in understanding t...
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1988
The sudace density of the fluorescent probe N-(lissamine Rbodamine B sulfonyl)dipalmitoylphosphatidylcholine is the same in the two lipid leaflets of phosphatidylcholine bilayers containing the probe. In the liquid-crystalline state, the probe molecules aggregate above a threshold amount, approximately 0.2 mol/mol phospholipids. Above this threshold value, the surface density of the free probe molecules is constant, and all probe molecules added are incorporated in the aggregated form. The aggregation of the probe increases by approximately 20% when the medium pH is lowered to 4. In the gel state, the probe aggregation is higher than tlmt in the liquid-crystalline state, and the free probe molecules distribute unevenly in the bilayer surface. Even though the results obtained in our model system cannot be directly extrapolated to all model systems, we point out that care is to be taken in the use of the probe. In fact, only in membranes in the liquid-crystalline state in which the amount of probe molecules to phospholipid molecules is lower than 1 : 7 the fluorescence response of the probe is independent of the pH changes and of the molecular aggregation.
Chemistry and Physics of Lipids, 1984
The steady state fluorescence anisotropy (r s) of l-acyl-2-cis parinaroyl phosphatidylcholine (PnPC) was compared with that of diphenylhexatriene (DPH) in a variety of model-and biological membrane systems. The fluorescence anisotropy of both probes responded similarly to temperature changes and variations in the acyl chain composition in phosphatidylcholine (PC) liposomes. The presence of proteins and cholesterol increased r s for both DPH and PnPC in the biological membranes as compared to the isolated polar membrane lipids. Comparison of DPH and PnPC in dipalmitoyl-PC-liposomes with and without 50 mol% cholesterol, showed at temperatures above the phase transition of pure dipalmitoyl-PC the presence of cholesterol increased the rs-value for DPH strongly, whereas the rs-value for PnPC was much less affected. In the cholesterol-rich erythrocyte membrane as well as in microsomes from Morris hepatoma 7787, which have an increased cholesterol content as compared to normal rat liver microsomes, the r s of DPH was higher than that of PnPC. No large differences between the rs-values of both probes were evident in the normal cholesterol-poor rat liver microsomes. These effects are discussed in terms of structural differences between the probes and variation of cholesterol content. Alterations in the fatty acid composition of PC present in human erythrocyte membranes were introduced with the aid of a PC-specific transfer protein. Fluorescence anisotropy values of both probes hardly changed upon enrichment of the red cell membrane with either dipalmitoyl PC or 1-paimitoyl-2-arachidonyl PC.
Photochemical & Photobiological Sciences, 2006
The partitioning efficiency of neutral and anionic prototropic forms of 1-hydroxypyrene in liposome suspensions has been studied. The high partition coefficient value of 1-hydroxypyrene indicates an easy incorporation of the molecule into the lipid bilayer. Detailed pH studies indicate that only the neutral form of 1-hydroxypyrene partitions into the membrane and appreciable spectral changes are observed in the pH range of 9.0-11.5 in Tris-NaOH buffer. However, at pH 11 the spectral changes are maximum. The possibility of using 1-hydroxypyrene as a fluorescent molecular probe for lipid bilayer membranes in alkaline media has been examined, by employing fluorescence intensity and fluorescence anisotropy as probe parameters. The neutral form fluorescence intensity as well as fluorescence anisotropy is sensitive to the changes in the membrane properties and is capable of sensing the phase-transition. This is also capable of monitoring the changes in the membrane due to incorporation of cholesterol and the ethanol-induced interdigitation. The time resolved fluorescence data and the quenching experiments show that 1-hydroxypyrene occupies the water inaccessible interior of the liposome. The high anisotropy value of 1-hydroxypyrene in liposome suggests that it resides in a considerably rigid environment and is very sensitive to the temperature-induced changes in the liposome.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2007
The conjugated phenyltetraene PTE-ET-18-OMe (all-(E)-1-O-(15′-phenylpentadeca-8′,10′,12′,14′-tetraenyl)-2-O-methyl-rac-glycero-3-phosphocholine) is a recently developed fluorescent lysophospholipid analog of edelfosine, (Quesada et al. (2004) J. Med. Chem. 47, 5333-5335). We investigated the use of this analog as a probe of membrane structure. PTE-ET-18-OMe was found to have several properties that are favorable for fluorescence anisotropy (polarization) experiments in membranes, including low fluorescence in water and moderately strong association with lipid bilayers. PTE-ET-18-OMe has absorbance and fluorescence properties similar to those of diphenylhexatriene (DPH) probes, with about as large a difference between its fluorescence anisotropy in liquid disordered (Ld) and ordered states (gel and Lo) as observed for DPH. Also like DPH, PTE-ET-18-OMe has a moderate affinity for both gel state ordered domains and Lo state ordered domains (rafts). However, unlike fluorescent sterols or DPH (Megha and London (2004) J. Biol. Chem. 279, 9997-10004), PTE-ET-18-OMe is not displaced from ordered domains by ceramide. Also unlike DPH, PTE-ET-18-OMe shows only slow exchange between the inner and outer leaflets of membrane bilayers, and can thus be used to examine anisotropy of an individual leaflet of a lipid bilayer. Since PTE-ET-18-OMe is a zwitterionic molecule, it should not be as influenced by electrostatic interactions as are other probes that do not cross the lipid bilayer but have a net charge. We conclude that PTE-ET-18-OMe has some unique properties that should make it a useful fluorescence probe of membrane structure.