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Charged giant unilamellar vesicles prepared by electroformation exhibit nanotubes and transbilayer lipid asymmetry

Jan Steinkuhler, Philippe De Tillieux, Roland L. Knorr, Reinhard Lipowsky and Rumiana Dimova

Article (2018)

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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 charged lipid, zeta potential measurements and experiments with the lipid marker annexin A5, we show that electroformed GUVs exhibit an asymmetric lipid distribution across the bilayer leaflets. The asymmetry is lost either after storing electroformed GUVs at room temperature for one day or by applying higher voltages and temperatures during electroformation. GUVs having the same lipid composition but grown via gel-assisted swelling do not show asymmetric lipid distribution. We discuss possible mechanisms for the generation and relaxation of lipid asymmetry, as well as implications for studies using electroformed vesicles. The observed effects allow to control the molecular assembly of lipid bilayer leaflets. Vesicle tubulation as reported here is an example of protein-free reshaping of membranes and is caused by compositional lipid asymmetry between leaflets.

Uncontrolled Keywords

Annexin A5/chemistry/metabolism; Cell Membrane/chemistry/metabolism; Electrochemical Techniques/instrumentation/*methods; Lipid Bilayers/*chemistry/metabolism; Microscopy, Confocal; Nanotubes/*chemistry; Phosphatidylcholines/chemistry/metabolism; Phosphatidylglycerols/chemistry/metabolism; Unilamellar Liposomes/*chemistry/metabolism

Subjects: 5100 Cell biology > 5100 Cell biology
Department: Department of Electrical Engineering
Funders: Deutsche Forschungsgemeinschaft (DFG), DAAD RIS, Federal Ministry of Education and Research of Germany, Max Planck Society
Grant number: IRTG 1524
PolyPublie URL: https://publications.polymtl.ca/5144/
Journal Title: Scientific Reports (vol. 8, no. 1)
Publisher: Nature
DOI: 10.1038/s41598-018-30286-z
Official URL: https://doi.org/10.1038/s41598-018-30286-z
Date Deposited: 04 Jul 2022 09:58
Last Modified: 09 Apr 2024 01:30
Cite in APA 7: Steinkuhler, J., De Tillieux, P., Knorr, R. L., Lipowsky, R., & Dimova, R. (2018). Charged giant unilamellar vesicles prepared by electroformation exhibit nanotubes and transbilayer lipid asymmetry. Scientific Reports, 8(1), 11838 (9 pages). https://doi.org/10.1038/s41598-018-30286-z

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