'Viropore-Membranes' - Talk II: Multifunctional plant virus-based nanopore adapters for bionically 'self-sealing' high-performance bio-inorganic hybrid membranesThursday (22.03.2018) 12:00 - 12:20 Part of:
Tobacco mosaic virus (TMV)-based soft-matter nanorings cemented into conical solid-state membrane (SSM) pores by means of silica as 'bionic glue': Such bio-inorganic hybrids may afford an advantageous new way towards filtration devices with high selectivity or even biofunctionality. Proof-of-concept 'pore-in-pore' membranes have become possible through short RNA-scaffolded helical assemblies of ≈68 TMV coat protein (CP) subunits with a central 4 nm hole (i.e. perforated 18 nm wide 'disks' of ≈9 nm length), used as genetically encoded nanopore fittings in free-standing SSM templates (see project talk I, Gliemann et al.). The nanorings were efficiently prepared by help of structure-guiding 204-nucleotide RNAs containing the TMV origin of assembly, and were well dispersed in the technically relevant pH range up to 9. Distinct selectively addressable CP types with anchor groups could be combined in individual 'disks', allowing the display of effector molecules on their outer rim. These included mineralization-guiding peptides re-designed to direct the deposition of thin silica sheaths around the protein cores. This was established for full TMV particles by use of tetraethoxysilane (TEOS) precursors and adapted to the TMV-derived disks and the narrow annular gaps between them and the SSM pores by employing hydrolyzed TEOS derivatives of low condensation degree (silanols or silicic acid) and thus size as precursors. The efficacy of electrophoretic insertion of the TMV-based nanorings into SSMs surpassed that of merely diffusive implantation. Hence, TMV 'pore adapters' with protruding nucleic acid leashes were fabricated by help of elongated, DNA-blocked RNA scaffolds, further increasing the nanoobjects' electrophoretic mobility. To modulate the biopores' charge- and size-specific permeability, two engineered TMV CP variants were produced, which led to nanorings with altered chemical groups lining their pores. Finally, the RNAs' 5'-ends could be covalently biotinylated prior to their incorporation into nanorings, resulting in a single biotin adjacent to every protein nanopore. This renders possible the installation of streptavidin-conjugated molecules such as enzymes to achieve bioconversion capability. Functional characterization of the novel hybrid layouts realized by the 'synthetic virology' approach is on its way, to delimit first applications that might benefit from such pore-in-pore membranes, from molecular sorting up to enrichment of high-value compounds.