Ph.D Thesis

Ph.D StudentPerl Sivan
SubjectRobust Spherical Proteins for Chemical Applications
DepartmentDepartment of Nanoscience and Nanotechnology
Supervisors PROFESSOR EMERITUS Ehud Keinan
PROF. Noam Adir
Full Thesis textFull thesis text - English Version


There are few protein nanoplatforms that offer the simultaneous control over size, shape, and biocompatibility. Among them, there is a family of cage-like proteins, which are amenable to both chemical and genetic manipulations. In addition to their self-assembling ability, they form very narrow size distribution complexes. The small heat shock proteins (sHSPs) are a highly conserved family of stress-response proteins, which are over-expressed at extreme temperatures, salinity and oxidative stress. Small HSP16.5 is a cage-like, hollow spherical protein comprised of 24 monomeric units. The sphere’s outer and inner diameters are 120Å and 65Å, respectively. In this research the protein's interior is being modified to include metal binding ligands. Both genetic and chemical manipulations were carried out, in order to introduce into the protein sequence metal binding residues. These residues are bidentatic ligands, such as bipyridine or diphosphine derivatives. The resulting metallated HSP16.5 serves as a nano-reactor that catalyzes chemical reactions. The engineered HSP 16.5 was used as an artificial metalloenzyme, shown to catalyze the transfer hydrogenation of trifluoroacetophenone with conversion rates exceeding 80% in 23 hrs. In addition, the modified protein was designed to contain anchors for the binding of gold nanoparticles within the spherical protein cavity. The encapsulated gold nanoparticles were designed to serve as labels for imaging technique such as electron tomography. Both demonstrations of catalysis and binding of gold nanoparticles represent proof of concepts and confirmation of the assumption that HSP16.5 can be converted to useful machines upon appropriate modification. These observations pave the way for the future applications of this and other heat-shock proteins as thermally stable catalysts in various other reactions, as well as imaging and patterning of metal nanoparticles.