Dynamic Control of Nanoparticle Assembly Using Solid-Binding Proteins

Thesis (Master's)--University of Washington, 2021Solid binding peptides (SBPs) are short sequences of amino acids selected by combinatorial techniques for their ability to bind to inorganic or synthetic surfaces. SBPs can be genetically encoded within the framework of larger polypeptides to produce solid-binding proteins that retain biological function while gaining the ability to organize inorganic components into hybrid materials. In this project, we build on previous efforts showing that derivatives of superfolder green fluorescent protein (sfGFP) fitted with oppositely located Car9 silica-binding peptides drive repeated cycles of silica nanoparticle assembly and disassembly when the solution pH is toggled between 7.5 and 8.5. We explore how aggregate size is influenced by the substitution of two lysine residues in the Car9 sequence by alanine, and how the location of the mutant sequence on the sfGFP framework, the solution pH, and the chemical fatigue associated with the accumulation of sodium ions upon alkalinization, impact colloidal formation and dispersion. Furthermore, we describe progress in the construction, expression and purification of de novo designed trimeric and tetrameric proteins modified with a Car9 extension which might prove useful to organize silica nanoparticles into defined architectures