#03 - Buds, Necklaces, Tubes - Shape Instabilities of Asymmetric Membranes of Giant Unilamellar Vesicles

Tripta Bhatia (Max Planck Institute of Colloids and Interfaces, Potsdam)

Monday, 30 Nov 21:15 - 22:00 CET

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Abstract

Title: Buds, Necklaces, Tubes - Shape Instabilities of Asymmetric Membranes of Giant Unilamellar Vesicles

Author(s): Tripta Bhatia^a, Simon Christ^a, Jan Steinkühler^b, Jaime Agudo-Canalejo^c, Tom Robinson^a, Rumiana Dimova^a, and Reinhard Lipowsky^a

Affiliations: ^aMax Planck Institute of Colloids and Interfaces, Potsdam; ^bNorthwestern University, Chicago; ^cMax Planck Institute for Dynamics and Self-Organization, Göttingen

Giant unilamellar vesicles (GUVs) represent biomimetic and biocompatible compartments with linear dimensions of many micrometers [1,2]. The bilayer membranes with a thickness of only a few nanometers, can respond sensitively to changes in their composition [3] as well as in local aqueous environment [4]. We discuss two different examples of the vesicle walls consisting of, i) asymmetric leaflets facing symmetric aqueous solution and ii) symmetric leaflets facing asymmetric aqueous solution to demonstrate that GUVs can amplify the nanoscopic responses to larger scales, thereby attaining many different shapes such as membrane inward and outward buds and tubes. We are particularly interested in multi-sphere morphologies, consisting of one membrane that forms several spheres connected by closed membrane necks. These necklaces can transform to tubes if the length is increased further and vice-versa as confirmed by solution exchange using microfluidics and optical microscopy [5]. The spontaneous curvature provides a quantitative measure for the asymmetry between the two leaflets of the bilayers. The stability of the necks is governed by relatively simple conditions that allow us to estimate the spontaneous curvature directly from the shape of the necks [2,4,6]. In the context of cell biology, shape transformation of membranes represents an essential step in many biological processes such as the transport and storage of materials across cellular compartments, engulfment by endo- or exocytosis, protein crowding and the division of cells by cytokinesis [6,7]. The work was supported by the Max Planck Society and the German Federal Ministry of Education and Research (BMBF) via the MaxSynBio consortium.

References

[1] Dimova, Rumiana, Carlos Marques, and Carlos Marques. The Giant Vesicle Book. CRC Press, 2019. https://doi.org/10.1201/9781315152516.

[2] Lipowsky, Reinhard. “Chapter Three - Understanding and Controlling the Morphological Complexity of Biomembranes.” In Advances in Biomembranes and Lipid Self-Assembly, edited by Reinhard Lipowsky, 30:105–57. Multiresponsive Behavior of Biomembranes and Giant Vesicles. Academic Press, 2019. https://doi.org/10.1016/bs.abl.2019.10.002 .

[3] Bhatia, Tripta, Jaime Agudo-Canalejo, Rumiana Dimova, and Reinhard Lipowsky. “Membrane Nanotubes Increase the Robustness of Giant Vesicles.” ACS Nano 12, no. 5 (May 22, 2018): 4478–85. https://doi.org/10.1021/acsnano.8b00640.

[4] Bhatia, Tripta, Simon Christ, Jan Steinkühler, Rumiana Dimova, and Reinhard Lipowsky. “Simple Sugars Shape Giant Vesicles into Multispheres with Many Membrane Necks.” Soft Matter 16, no. 5 (February 5, 2020): 1246–58. https://doi.org/10.1039/C9SM01890E.

[5] Bhatia, Tripta, Tom Robinson, and Rumiana Dimova. “Membrane Permeability to Water Measured by Microfluidic Trapping of Giant Vesicles.” Soft Matter 16, no. 31 (August 12, 2020): 7359–69. https://doi.org/10.1039/D0SM00155D.

[6] Steinkühler, Jan, Roland L. Knorr, Ziliang Zhao, Tripta Bhatia, Solveig M. Bartelt, Seraphine Wegner, Rumiana Dimova, and Reinhard Lipowsky. “Controlled Division of Cell-Sized Vesicles by Low Densities of Membrane-Bound Proteins.” Nature Communications 11, no. 1 (February 14, 2020): 905. https://doi.org/10.1038/s41467-020-14696-0.

[7] Bassereau, Patricia, Rui Jin, Tobias Baumgart, Markus Deserno, Rumiana Dimova, Vadim A Frolov, Pavel V Bashkirov, et al. “The 2018 Biomembrane Curvature and Remodeling Roadmap.” Journal of Physics D: Applied Physics 51, no. 34 (August 2018). https://doi.org/10.1088/1361-6463/aacb98.