Solid Supported Model Membranes Containing Plant Glycolipids: A Tool to Study Interactions between Diatom Biomolecules and the Silicalemma in vitro
von Oliver Gräb
Datum der mündl. Prüfung:2017-06-13
Erschienen:2017-06-22
Betreuer:Prof. Dr. Claudia Steinem
Gutachter:Prof. Dr. Claudia Steinem
Gutachter:Prof. Dr. Daniel John Jackson
Gutachter:Prof. Dr. Burkhard Geil
Gutachter:Prof. Dr. Bert De Groot
Gutachter:Dr. Jochen Hub
Gutachter:Dr. Sebastian Kruss
Dateien
Name:Dissertation_Graeb.pdf
Size:6.81Mb
Format:PDF
Description:Dissertation
Zusammenfassung
Englisch
Silica biomineralization in diatoms is presumably controlled by a self-assembly of biomolecules inside membrane-enclosed silica deposition vesicles. The fine-patterned structure of the diatom’s cell wall is thereby determined by the morphology of the templating organic matrix. Several studies addressed self- or co-aggregation of silica-associated biomolecules in solution but no research focusing on the influence of the organelle surrounding lipid bilayer was published so far. This study aimed on the investigation of interactions between exemplary diatom biomolecules and lipid membranes in vitro. As a basis for all experiments, protocols for the preparation of solid supported model membranes, mimicking the overall lipid composition of diatoms and containing the three glycolipids monogalactosyldiacylglycerol, digalactosyldiacylglycerol and sulfoquinovosyl-diacylglycerol were established. Artificial model membranes were successfully prepared and characterized on hydrophobically functionalized gold and glass supports as well as on hydrophilic silicon dioxide and mica surfaces. These model systems were first applied to study the interactions of two exemplary recombinant cingulins with lipid membranes. Cingulins show structural similarities to silaffins and were recently identified as part of the organic matrix inside the diatom biosilica. Adsorption measurements revealed no significant interactions between these proteins and lipid membranes. In addition, long-chain polyamines (LCPA) marked a second class of biomolecules localized in the diatom biosilica and were used in this study as well. LCPA are known to aggregate in solution and catalyze silica precipitation. Herein, for the first time, synthetic LCPA with molecular masses matching the range of LCPA isolated from diatoms were investigated with regard to their interaction with lipid membranes. Upon adsorption of LCPA the formation of membrane stacks was observed and characterized. These stacks were formed from vesicles in solution and were proven to be connected to the underlying membrane. While stack formation was found to be independent of the membrane composition, a clear dependency on polyamine chain-length was observed since only LCPA with more than five amine groups mediated stack formation.
Keywords: Long-chain polyamine; Cingulin; Plant lipid; Solid supported membrane