Investigation of structure and particle fabrication of ferritin

Abstract

In this thesis, we demonstrate ferritins and ferritin-like proteins are ideal model systems to investigate protein quaternary structure and to fabricate nanomaterials. Ferritins and ferritin-like proteins self-assemble into hollow, nanoscale cages with octahedral symmetry and tetrahedral symmetry respectively. Although they share little sequence homology, they have homologous tertiary structure—both fold into a four-helix bundle structure. Despite their structural similarity, these monomers assemble into nanocages with different symmetries. To understand how the information stored in protein primary and tertiary structure defines the protein-protein interactions which govern quaternary structure formation, mutants were produced by mixing key domains from ferritin and ferritin-like protein. These mutants were studied by a number of biophysical techniques to determine their folding stability, self-assembling ability, and nanostructure. We also describe our attempts to fabricate gold nanoparticles within the cavities of native ferritin cages utilizing a novel approach. The key step is to fabricate gold nanoclusters within the ferritin and the clusters can initiate the formation of particles. We characterized the resulting nanoparticles utilizing a series of techniques. We confirmed that highly monodisperse nanoparticles are formed within intact protein shells and the size of the nanoparticles correlates with the interior diameter of the cages. These gold mineralized ferritin protein cages can be further utilized in bioimaging.