Seminar über aktuelle Fragen zur Dynamik komplexer Fluide: Mechanical properties of vesicle membranes in asymmetric buffer conditions
10:15 - 11:15
Max Planck Institute of Colloids and Interfaces, Potsdam
Max-Planck-Institut für Dynamik und Selbstorganisation (MPIDS)
Biological membranes consist of molecular bilayers which are intrinsically asymmetric in nature. This asymmetry can be induced not only by leaflet composition but also by the difference in the cytosolic and periplasmic solutions containing macromolecules and ions. Membranes are surrounded by aqueous buffers inside and outside the cell exhibiting strong concentration asymmetry of various ions such as sodium, potassium and chlorine ions. There has been a long quest to understand the effect of these ions on the physical and morphological properties of membranes. Ion-lipid interactions and, in particular, the effect of ion trans-membrane asymmetry is crucial not only for the membrane phase state but also influences the mechanical properties of membranes. In the current work, we set to explore the changes inflicted on the mechanical properties of membranes exposed to asymmetric buffer conditions. As a model membrane, we employed giant unilamellar vesicles (GUVs) with asymmetric salt and sugar solutions across the membrane. To assess the membrane mechanical properties, we used a combination of two different techniques which are the micropipette aspiration for holding the vesicles and controlling the membrane tension, and optical tweezers for trapping the beads as a handle to pull the tube. The assay allows us to measure the spontaneous curvature and the bending rigidity of the bilayer in the presence of different ions and sugar. Our findings point to the membrane reshaping the role of alkali ions in asymmetric conditions which are crucial in real cells.