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Carina Drechsler

Carina Zorzin

Asymmetric Liposomes as Model Membranes for Protein-Lipid Interactions

Principal investigator: Prof. Dr. Heiko Heerklotz

Institute of Pharmaceutical Sciences
Pharmaceutical Technology and Biopharmacy
Hermann-Herder-Str. 9
79104 Freiburg

Phone: +49 (0) 761-203-4912
carina.drechsler@pharmazie.uni-freiburg.de

Abstract

Liposomes are a great tool for modeling protein-lipid interactions. In some cases, it is important to mimic not only the lipid composition but also the structure of a biological membrane as good as possible.

For instance, most biological membranes show a lipid asymmetry between the outer and the inner leaflet. Nevertheless, it is not fully understood how asymmetry influences the behavior of embedded proteins.

In order to have a better insight in this matter, we want to prepare asymmetric liposomes using two different methods.

On the one hand, a soluble form of the Phosphatidylserine Decarboxylase is used to create phosphatidylserine asymmetric vesicles showing the asymmetry of mammalian plasma membranes.

Methyl-beta-cyclodextrin, on the other hand, is used as a carrier for different lipids. This way, we can enrich the outer layer of preformed liposomes with new lipids, thus creating asymmetric vesicles. Preformed phosphatidylcholine vesicles, for example, can be enriched with negatively charged phosphatidylglycerol which allows for more realistic model membranes that carry negative charges exclusively in their outer leaflets to study processes that involve bacterial membranes.

 

Methods

Liposome preparation, zeta potential and size measurements of nanoparticles, size exclusion chromatography, high performance thin layer chromatography (HPTLC), protein purification, protein reconstitution into liposomes

 

Publications

Wang, F., Beck-Garcia, K., Zorzin, C., Schamel, W.W.A., and Davis, M.M. (2016). Inhibition of T cell receptor signaling by cholesterol sulfate, a naturally occurring derivative of membrane cholesterol. Nature immunology 17, 844–850.

Vogtle, F.-N., Keller, M., Taskin, A.A., Horvath, S.E., Guan, X.L., Prinz, C., Opalinska, M., Zorzin, C., van der Laan, M., Wenk, M.R., Schubert, R., Wiedemann, N., Holzer, M., and Meisinger, C. (2015). The fusogenic lipid phosphatidic acid promotes the biogenesis of mitochondrial outer membrane protein Ugo1. The Journal of cell biology 210, 951–960.

Beck-García, K., Beck-García, E., Bohler, S., Zorzin, C., Sezgin, E., Levental, I., Alarcón, B., and Schamel, Wolfgang W A (2015). Nanoclusters of the resting T cell antigen receptor (TCR) localize to non-raft domains. Biochimica et biophysica acta 1853, 802–809.