2018
DOI: 10.1038/s41598-018-30286-z
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Charged giant unilamellar vesicles prepared by electroformation exhibit nanotubes and transbilayer lipid asymmetry

Abstract: Giant unilamellar vesicles (GUVs) are increasingly used as a versatile research tool to investigate membrane structure, morphology and phase state. In these studies, GUV preparation is typically enhanced by an externally applied electric field, a process called electroformation. We find that upon osmotic deflation, GUVs electroformed from charged and neutral lipids exhibit inward pointing lipid nanotubes, suggesting negative spontaneous curvature of the membrane. By quenching a fluorescent analog of the charge… Show more

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Cited by 98 publications
(115 citation statements)
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References 56 publications
(73 reference statements)
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“…Lira, R. Dimova, K.A. Riske, unpublished data; see also (44)). This effect is negligible for high POPG mol%, at which fusion is very efficient.…”
Section: Discussionmentioning
confidence: 78%
See 1 more Smart Citation
“…Lira, R. Dimova, K.A. Riske, unpublished data; see also (44)). This effect is negligible for high POPG mol%, at which fusion is very efficient.…”
Section: Discussionmentioning
confidence: 78%
“…GUVs were formed by the electroformation method with few modifications (43); see Supporting Materials and Methods. The vesicles were used fresh (the same day), and thus for vesicles made of POPC and POPG mixtures, slightly higher POG concentration on the vesicle surface may be expected (44). Alternatively, the gel-assisted method (45) was used for GUVs with 100 mol% POPG.…”
Section: Methodsmentioning
confidence: 99%
“…We incorporated CSL into giant unilamellar vesicles (GUV-CSL) or giant hybrid unilamellar vesicles (GHUV-CSL) prepared by electroformation, since their micrometric size is better adapted to confocal microscopy [20]. Their morphological alterations upon global decrease of pH was experimentally examined under confocal microscopy ( Figures S6-S9, Supplementary Materials) and posteriorly categorized as vesicles with inward or outward structures (tubular protrusions, membrane-attached aggregation), internalized vesicles, or membrane fluctuation (non-round shaped vesicles) [23] and assembled in a table with values presented as the relative percentage of total vesicles counted (Table 2). As previously, non-switchable giant unilamellar vesicles (GUV-POPC) or giant hybrid unilamellar vesicles (GHUV-POPC) were used as control.…”
Section: Confocal Observationsmentioning
confidence: 99%
“…GUV-CSL 20% and GUV-CSL 50% vesicles responded to acidification by projecting outward tubular protrusions, since 20% and 14% of the vesicles analyzed presented such structures, respectively (Table 2). Membrane-derived structures pointing outward are commonly referred as positive curvatures [23], whilst negative curvature denotates membrane-arisen structures pointing inward. In the images, we could observe positive membrane curvatures in GUV-CSL 20% and 50% as a result of treatment with HCl but not NaCl ( Table 2, Figures S6 and S7, Supplementary Materials).…”
Section: Confocal Observationsmentioning
confidence: 99%
“…spontaneous curvature, may be generated in many ways, 20 such as by an asymmetric concentration of lipids in each of the monolayers, 21,22 or by asymmetric concentrations of particles in solution that create adsorption or depletion layers near the membrane. 21,23,24 Thus, spontaneous formation of nanotubes has been observed for membranes with lipid asymmetry, 25 in particular of lipids with bulky headgroups such as GM-1; 26,27 for asymmetric concentrations of ions or sugars in the inner and outer aqueous solutions; 28,29 for asymmetric concentrations of polymers such as PEG that adsorb to the membrane; 30,31 or for membranes in contact with specialized curvature-inducing proteins such as BAR domains. 32 Importantly, it has been shown 26 that these artificial membrane reservoirs confer cell-like mechanical responses to the vesicles, such as the liquid-droplet-like instability in micropipette aspiration undergone by white blood cells.…”
Section: Introductionmentioning
confidence: 99%