Self-assembly und structure formation of spider silk proteins in (ultra-)thin films

• Applicants: Professor Dr. Andreas Fery; Professor Dr. Thomas Scheibel
• Subject Area: Polymer Materials ; Preparatory and Physical Chemistry of Polymers
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 410872515

The preparation of (ultra) thin spider silk films (d = 2 – 100 nm) in combination with the design of various (new) recombinant spider silk proteins offers the unique possibility to investigate the structure formation and self-assembly behavior of silk proteins in thin films at defined interfaces and allows to compare these processes to those in bulk solution. The coating of the substrates and preparation of the films is achieved by deposition from aqueous solution. By self-assembly as well as surface interaction phase separated structures with domains in the nanoscale are formed. This proposal aims at the elucidation of structure formation within spider silk proteins in dependence of their amino acid sequence (amino acid composition as well as sequence of defined amino acid modules). The general question of this proposal addresses the modalities of deposition and orientation of spider silk-related films as well as the influence of primary structure (i.e. sequence), of amino acid charge, and of the molecular weight of spider silk proteins in (ultra-)thin films, as well as the influence of surface chemistry and topography of the used support materials. The size of the gained structural nano-sized domains will be controlled via the sequence of the modules. The following aims are tackled in detail:• Time course (kinetics, dynamics) of the folding (secondary structure) and orientation of the structural elements in spider silk protein films at surfaces• Influence of charge (exchange of amino acid E by K, from C- to Kappa-module) and its relation to salinity and pH• Role of the typically major fraction of the random coil/alpha-helix rich hydrophilic amorphous phase concerning the formation of the minor fraction of beta-sheet rich hydrophobic crystalline phases within spider silk materials (embedding) • Role of the aqueous (buffer, pH, salinity) respectively organic solvent• Role of mechanical textures, orientation and surface properties of substrates concerning structure formation and orientation of the domainsThe characterization of the orientation of secondary structural elements by polarised FTIR spectroscopy and of the separation of spider silk peptide blocks by high resolution atomic force microscopy techniques allows to draw conclusions with respect to the mechanism of structure formation and to create a general assembly model of spider silk based thin films.

• DFG Programme: Research Grants
• Co-Investigator: Privatdozent Dr. Martin Müller