Syntheses of Metal and Metal Oxide Particles by Genetically-Engineered Protein Templates

S. Behrens,^a A. Heyman,^b S. Essig,^a O. Shoseyov^b

Institute for Technical Chemistry, Karlsruhe Institute of Technology, Postfach 3640, 76021 Karlsruhe, (Germany) ^a; The Robert H. Smith Institute of Plant Science and Genetics, The Faculty of Agriculture; The Hebrew University, Rehovot (Israel)^b

Protein superstructures have been used to synthesize particles and nanowires, providing unique inorganic-biomolecule hybrids with multifunctional properties derived from both the inorganic and the biological material. We report the synthesis of metal nanoparticles and metal oxide particles using genetically modified stable proteins (SP1). SP1 is a homo-dodecamer ring protein expressed during drought in aspen plants (populus tremula) demonstrating an extremely high thermal and chemical stability. Material specific hexapeptides were genetically fused to the N-terminus of SP1 thus obtaining variants with 12 peptidic aptamers facing the inner-pore of the protein ring structure. We here demonstrate chemical processes that allow the synthesis of monodisperse Pd nanoparticles and TiO₂ particles in the presence of the genetically-engineered SP1 mutants. The resulting hybrids were investigated, e.g. by electron microscopy (TEM/REM) and CD spectroscopy. Our studies demonstrate that these stress-related protein mutants are not only appealing templates for synthesizing monodisperse particles, but the generated particles also provide a mortar to construct novel geometrical architectures of hybrid nanoparticle – protein complexes.