Lipid Bilayers on Planes and in Micropipettes - Two model systems to study binding of DivIVA to flat and negatively curved membranes

Abstract: The aim of this thesis work was to form and characterize model systems of cell membranes on planar supports and in micropipettes. Firstly, supported lipid bilayers (SLBs) were formed on glass slides after an existing experimental procedure. It was shown possible to obtain fluid SLBs from different kinds of lipids as well as on glass slides that were cleaned with different techniques. Custom-written Matlab scripts were used to assess the mobilities of the lipids. It was found that all SLBs showed diffusivities within the same order of magnitude independent of the lipid used, while the fraction of lipids that were immobile within the SLB were higher for Escherichia coli (E. coli) compared to POPC lipids. Secondly, a new protocol was established for the lipid-coating of pipettes, which was successfully demonstrated as well. Using again a custom-written Matlab program to analyze the mobility of the lipids, it was found that they diffused significantly slower than on the planar SLBs. It is suggested that this was due to deficient cleaning or that it could be inherent to the geometry of the lipid bilayer. Additionally, both model systems were used to investigate the membrane binding behavior of the protein DivIVA which is known to localize to regions of high negative curvature in the cell. The results indicated that besides curvature, lipid charge and composition are also features that affect the membrane binding behavior of the protein. Overall, this work presents the groundwork for a cheap model system of the curved cell membrane, which also allows to investigate many different curvature radii at the same time.