Towards Patterned Protein Based Nanoparticle Arrays

To meet the exponential growth in the demand for data storage, capacity innovations in hard drive disk (HDD) technologies must be sought. A bit-pattern media (BPM) approach is the frontier of HDD storage technology. It consists of metallic nano-scale patterns of less than 10 nm with 20 nm periodicity and has the potential to significantly increase the data storage density, where each patterned island acts as a single bit. The conventional nano-scale manufacturing methods have so far failed to produce such patterns at scale. There are proteins in nature that can self-assemble into nano-patterns at the desired feature sizes without high energy input under ambient conditions. It is proposed here that a bio-inspired approach could provide useful input to the BPM field by constructing a nano-scale pattern using protein self-assembly exclusively. The project looks to the field of magnetic nanoparticle biomineralisation with attempts to functionalise the protein constructed patterns. The work here characterises a known, unusually rigid rod-like protein domain G52- E-G53 (originating from the SasG protein found in Staphyloccocus aureus) as a building block for protein pattern construction by creating extended linear assemblies through genetic fusion with two orthogonal pairs of coiled-coil forming a-helices. The assembly is validated through a robust series of biophysical and microscopy investigations. The G52-E-G53 coiled-coil constructs are also granted the ability to specifically interact with magnetite nanoparticles through a fusion with a known magnetite binding peptide. Initial work is also performed to create two-dimensional patterns using G52-E-G53 as a rigid linker. The work also shows strong evidence that a magnetite binding peptide and iron nucleation membrane protein Mms6 can be used as genetic fusions to impart improved biomineralisation/particle binding capacity to a well characterised S-layer protein SgsE. Modularity of a different magnetite binding peptide is also demonstrated with respect to different loop displaying scaffold proteins. Lastly, phage display is used to discover three new seven amino acid peptides for CoPt L10 nanoparticle binding and biomineralisation with one of the peptides showing evidence of improving magnetic properties of CoPt chemical synthesis products. Together this multi-pronged approach demonstrates substantial leads that could be the basis of a field of magnetic mineral templating on protein patterns using specific magnetic nanoparticle binding moieties.