Shape transformation of giant phospholipid vesicles at high concentrations of C12E8 (original) (raw)
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Abstract Shape transformation of giant phospholipid vesicles at high concentrations of C 12E 8
2008
Giant unilamellar phospholipid vesicles were prepared by the method of electroformation from 1-palmitoyl-2-oleoyl-sn-glycero-3phosphatidylcholine (POPC). We studied the influence of different concentrations of the surfactant octaethyleneglycol dodecylether (C12E8) on the spontaneous shape transformations of POPC vesicles at room temperature. In accordance with previous results, we observed that low concentration of C 12E 8 increased the speed of the characteristic vesicle shape transformation, starting from the initial shape with thin tubular protrusion, through beaded protrusion where the number of beads gradually decreased, to final spherical shapes with invagination, whereby the average mean curvature of the vesicle membrane monotonously decreased. In contrast, higher concentration of C12E8 initially induced the shape transformation in the ‘‘opposite direction’’: in the protrusion, the number of beads gradually increased and eventually a tube was formed whereby the average mean c...
Chem. Phys. Lipids, 2009
The interaction of two types of vesicle systems was investigated: micrometer-sized, giant unilamellar vesicles (GUVs) formed from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and submicrometer-sized, large unilamellar vesicles (LUVs) formed from oleic acid and oleate, both in a buffered aqueous solution (pH=8.8). Individual POPC GUVs were transferred with a micropipette into a suspension of oleic acid/oleate LUVs, and the shape changes of the GUVs were monitored using optical microscopy. The behavior of POPC GUVs upon transfer into a 0.8 mM suspension of oleic acid, in which oleic acid/oleate forms vesicular bilayer structures, was qualitatively different from the behavior upon transfer into a 0.3 mM suspension of oleic acid/oleate, in which oleic acid/oleate is predominantly present in the form of monomers and possibly non-vesicular aggregates. In both cases, changes in vesicle morphology were observed within tens of seconds after the transfer. Vesicle initially started to evaginate. In 60% of the cases of transfer into a 0.8 mM oleic acid suspension, the evagination process reversed and proceeded to the point where the membrane formed invaginations. In some of these cases, several consecutive transitions between invaginated and evaginated shapes were observed. In the remaining 40% of the cases of transfer into the 0.8 mM oleic acid uspension and in all cases of vesicle transfer into the 0.3 mM oleic acid suspension, no invaginations nor subsequent evaginations were observed. An interpretation of the observed vesicle shape transformation on the basis of the bilayer-couple model is proposed, which takes into account uptake of oleic acid/oleate molecules by the POPC vesicles, oleic acid flip-flop processes and transient pore formation.
Chemistry and Physics of Lipids, 2000
Several methods for the preparation of giant unilamellar vesicles (GUVs) using synthetic phosphatidylcholine phospholipids were evaluated. We compared the physical characteristicsin terms of lamellarity and morphology -of the whole lipid sample for each different lipid preparation using the sectioning capability of the two-photon excitation fluorescence microscope. From the evaluation of the entire lipid sample we determined that vesicle size, internal shape and shell thickness distributions depend on the vesicle's preparation method.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2004
Vesicle shape transformations caused by decreasing the difference between the equilibrium areas of membrane monolayers were studied on phospholipid vesicles with small volume to membrane area ratios. Slow transformations of the vesicle shape were induced by lowering of the concentration of lipid monomers in the solution outside the vesicle. The complete sequence of shapes consisted of a string of pearls, and wormlike, starfish, discocyte and stomatocyte shapes. The transformation from discocyte to stomatocyte vesicle shapes was analyzed theoretically to see whether these observations accord with the area difference elasticity (ADE) model. The membrane shape equation and boundary conditions were derived for axisymmetrical shapes for low volume vesicles, part of whose membranes are in contact. Calculated shapes were arranged into a phase diagram. The theory predicts that the transition between discocyte and stomatocyte shapes is discontinuous for relatively high volumes and continuous for low volumes. The calculated shape sequences matched well with the observed ones. By assuming a linear decrease of the equilibrium area difference with time, the ratio between the nonlocal and local bending constants is in agreement with reported values.
Journal of Membrane Biology, 2005
A microscopic study has allowed the analysis of modifications of various shapes acquired by phospholipid vesicles during a hydrostatic pressure treatment of up to 300 MPa. Giant vesicles of dimyristoylphosphatidylcholine / phosphatidylserine (DMPC/PS) prepared at 40°C mainly presented a shape change resembling budding during pressure release. This comportment was reinforced by the incorporation of 1,2-dioleyl-sn-glycero-3-phosphatidylethanolamine (DOPE) or by higher temperature (60°C) processing. The thermotropic main phase transition (Lα to Pβ′) of the different vesicles prepared was determined under pressure through a spectrofluorimetric study of 6-dodecanoyl-2-dimethylamino-naphtalene (Laurdan) incorporated into the vesicles’ bilayer. This analysis was performed by microfluorescence observation of single vesicles. The phase transition was found to begin at about 80 MPa and 120 MPa for DMPC/PS vesicles at, respectively, 40°C and 60°C. At 60°C the liquid-to-gel transition phase was not complete within 250 MPa. Addition of DMPE at 40°C does not significantly shift the onset boundary of the phase transition but extends the transition region. At 40°C, the gel phase was obtained at, respectively, 110 MPa and 160 MPa for DMPC/PS and DMPC/PS/DOPE vesicles. In comparing volume data obtained from image analysis and Laurdan signal, we assume the shape change is a consequence of the difference between lateral compressibility of the membrane and bulk water. The phase transition contributes to the membrane compression but seems not necessary to induce shape change of vesicles. The high compressibility of the Lα phase at 60°C allows induction on DMPC/PS vesicles of a morphological transition without phase change.
Langmuir, 2002
We have designed and synthesized a peptide, WLFLLKKK (peptide-1), which has positive charges and a segment partitioned into the electrically neutral lipid membrane interface, and investigated its effect on the stability of the phosphatidylcholine (PC) membrane. Spacing of multilamellar vesicles of palmitoyloleoyl-PC increased greatly with an increase in peptide-1 concentration. The addition of 5 µM peptide-1 through a micropipet near the giant unilamellar vesicle (GUV) of dioleoylphosphatidylcholine induced several kinds of shape changes; for example, a discocyte was changed to two spheres connected by a neck, and small vesicles were budded into the outside of the spherical GUV. These results indicate that the de novo designed peptide-1 can be partitioned into the PC membrane interface and have a large effect on its structure and properties.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1989
Extrusion of multilamellar vesicles under moderate pressures through filters of defined pore size is a convenient method for generation of large unilamellar vesicles of variable size (Hope et al, (1986) Chem. Phys. Lipids 40, 89-108). To date, this technique has been applied primarily to unsaturated phosphoUpids in the liquid-crystalline state. In this work we extend this procedure to include saturated phosphatidylcholines of chain lengths varying from C 14 (dimyristoylphosphatidylcholine) to C2o (diaraehidoyl phosphatidy!eholine). It is shown that whereas gel-state lipids cannot be extruded at convenient pressures, systems incubated at temperatures above the gei-to-liqaid.crystalline transition (To) can be readily extruded through filters with pore sizes ranging from 30 nm to 200 nm to produce homogeneously sized systems.
Chemistry and Physics of Lipids, 2003
We studied spontaneous shape transformations and burst of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) vesicles with exogeneously added non-ionic detergent octaethylene-glycol dodecylether C 12 E 8 . The addition of C 12 E 8 increased the speed of the vesicle shape transformation, so that we were able to study for the first time the complete sequence of POPC vesicle shapes starting from initial spherical vesicle with long thin tubular protrusion to final shape with invagination(s). The average mean curvature of the vesicle membrane continuously decreases during this process. The shape of the invaginations is usually spherical, however also non-spherical shapes of invaginations were observed. C 12 E 8 increases amplitudes of the fluctuations of the vesicle membrane. At higher concentrations in the membrane, C 12 E 8 induces the membrane leakage and burst of the vesicles.
Langmuir, 2019
This study provides insights into dynamic nanostructural changes in phospholipid systems during hydrolysis with phospholipase C, the fate of the hydrolysis products, and the kinetics of lipolysis. The effect of lipid restructuring of the vesicle was investigated using smallangle X-ray scattering and cryogenic scanning electron microscopy. The rate and extent of phospholipid hydrolysis were quantified using nuclear magnetic resonance. Hydrolysis of two phospholipids, phosphatidylethanolamine (PE) and phosphatidylcholine (PC), results in the cleavage of the molecular headgroup, causing two strikingly different changes in lipid self-assembly. The diacylglycerol product of PC escapes the lipid bilayer, whereas the diacylglycerol product adopts a different configuration within the lipid bilayer of the PE vesicles. These results are then discussed concerning the change of the lipid configuration upon the lipid membrane and its potential implications in vivo, which is of significant importance for the detailed understanding of the fate of lipidic particles and the rational design of enzyme-responsive lipid-based drug delivery systems.