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Zusammenfassung:
Supported planar lipid bilayers (SLBs) prepared by spreading of unilamellar vesicles on hydrophilic substrates such as silicon dioxide are frequently used to investigate lipid-protein interactions by means of surface sensitive methods. In recent years, the receptor lipid PtdIns[4,5]P2 became particularly important as a significant number of proteins bind to this lipid at the inner leaflet of the plasma membrane. Here, we investigated how the lipid PtdIns[4,5]P2 distributes between the two leaflets of an SLB on SiO2 surfaces. We prepared SLBs on SiO2 by spreading small unilamellar vesicles and quantified the adsorption of PtdIns[4,5]P2 binding proteins providing information about the accessibility of PtdIns[4,5]P2. We compared protein binding to PtdIns[4,5]P2 in SLBs with that in lipid monolayers on a 1,1,1-trimethyl-N-(trimethylsilyl)silanamine-functionalized SiO2 surface using reflectometric interference spectroscopy and atomic force microscopy. Our results clearly demonstrate that the accessibility of PtdIns[4,5]P2 for protein binding is reduced in SLBs compared to that in supported hybrid membranes, which is discussed in terms of PtdIns[4,5]P2 distribution in the two leaflets of SLBs.
