Bio-mediated self-assembly of nanoscale structures using the M13 bacteriophage

The M13 bacteriophage is ~1 μm long, with a capsid comprised of five coat proteins. Small peptides can be displayed upon the coat proteins. The aim of this work was to use the phage display of small peptides for the purpose of fabricating a self-assembling molecular transistor with the M13 bacteriophage acting as the scaffold. Each aspect of this fabrication was considered. Firstly, a 50 nm long microphage particle was re-created and used to produce a 215 nm long phage particle. These smaller phage particles could be used to make the transistor 100 nm in size. To create the scaffold, selenocysteine was displayed on the coat protein pIII and used to self-assemble two to four phage particles around 10 nm gold nanoparticles or quantum dots. These higher order structures were then purified using a linear sucrose gradient. So that the transistor could be directed to a specific area of an existing electronic circuit, the coiled-coil pair ACID:BASE was used. ACID was displayed on the coat protein pIX whilst a BASE peptide containing a Cvterminal cysteine was immobilised onto a gold surface. It was shown that ACID and BASE form a coiled-coil when the BASE is immobilised on a surface and that the M13 bacteriophage, displaying ACID, can be anchored to the surface via coiled-coil formation. Finally, tyrosine was displayed on the major coat protein pVlIl so that gold could be specifically reduced onto the M13 phage particle scaffold to create the gold electrodes of the transistor. Although within solution, and on a carbon surface, gold was reduced onto the phage particles, when the particles were adsorbed onto an Si02 surface there was no gold deposition. Therefore, although much progress was made towards the goal of a self assembling transistor, the aspects devised within this study need to be combined.