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Within this proposal, we aim at developing a platform of synthetic amphiphiles to be used in combination with and as mimetics of biological amphiphiles to study effects of membrane structure and dynamics. Recently we have introduced solid phase polymer synthesis, where we apply standard Fmoc-peptide coupling protocols to assemble novel tailor-made building blocks and obtain monodisperse, sequence-defined oligoamides or so-called precision macromolecules. This iterative process in combination with a library of building blocks allows for the straightforward variation of different structural parameters such as the site-selective introduction of functional groups, chain length and chain geometry. Preliminary studies have shown that this approach also gives access to amphiphilic precision macromolecules (AMs), e.g. through the introduction of fatty acids.
Within this project we aim at using AMs to selectively alter membrane properties and study the effect of such changes on proteins located within the membrane. Overall, three strategies to achieve this goal will be explored and tested in collaboration with our partners from biochemistry and biology. In a first subproject, special focus will be devoted to AMs for crowding membrane surfaces. Through variation of the geometry (linear vs. branched), composition (PEG-like or peptidoglycan-mimetic) and introduction of charges, the sterical demand as well as short and long-range interactions of AMs can be tuned and studied for their influence on protein-protein complex formation of membrane proteins. In a second subproject, we will additionally introduce crosslinkable units into the AMs. On the one hand, this allows for covalent linking of AMs with each other, thereby decreasing mobility of the membrane and thereby membrane proteins. On the other hand, AMs can be covalently linked to a membrane protein trying to fix its conformation and blocking protein-protein cluster formation. Finally, peptide-AM hybrid structures comprising of known binders or fragments of membrane proteins will be evaluated for their ability to induce protein-protein complex formation.
Figure: From building blocks to amphiphilic precision macromolecules to membrane variations.