Hierarchical self-assembly with viral coat proteins

Synopsis

Nature uses proteins as structural elements both as scaffolds and for controlling organization. Materials such as spider silk, which has been shown to have toughness superior to Kevlar, are made from relatively simple protein building blocks under ambient conditions. The appealing properties of these protein-based biological materials are directly influenced by the hierarchical organization of their protein sub-units from the nanoscale to the microscale and beyond. Viruses and viral proteins offer an exciting path towards protein-based self-assembling structured materials as the supramolecular chemistry guiding their capsid formation can inspire the design of macroscale materials with novel hierarchical structures. Tobacco mosaic virus (TMV) is of particular interest due to the well-characterized self-assembly of its capsid coat protein (TMVcp) into various conformations that can be controlled by solution conditions. Furthermore, native TMV virus particles exhibit lyotropic liquid crystal phases. This is exciting for materials fabrication, since recent work demonstrates that numerous biological materials use fluid protein condensates including liquid crystals as a malleable yet concentrated precursor phase that can be rapidly processed into solid materials with hierarchical organization.

Here, we report the successful formation of reproducible hierarchically structured macroscale structures from self-assembled recombinant TMVcp. In-situ experiments indicate the transition of the TMVcp suspension to a liquid crystal prior to final material formation which has not been previously seen for mixed-length rod assemblies. We also show that TMVcp structures can act as templates to organize nanoparticles, producing materials with novel optical and possibly magnetic properties through self-assembly. Ultimately, this research highlights the use of viral protein supramolecular chemistry in self-assembly for advanced material design as an alternative to fossil-fuel-based synthetic polymers using mild conditions.