Materials Research Science and Engineering Centers  The National Science Foundation

Research Highlight #3:

Nonequilibrium Synthesis and Assembly of Hybrid Inorganic-Protein Nanostructures Using an Engineered DNA Binding Protein

Haixia Dai, Woo-Seok Choe, Corrine K. Thai, Mehmet Sarikaya, Beth A. Traxler, François Baneyx, and Daniel T. Schwartz;
Chemical Engineering, Materials Science & Engineering, and Microbiology, University of Washington

We show that a protein with no intrinsic inorganic synthesis activity can be endowed with the ability to control the formation of inorganic nanostructures under thermodynamically unfavorable (nonequilibrium) conditions, reproducing a key feature of biological hard-tissue growth and assembly. The nonequilibrium synthesis of Cu2O nanoparticles is accomplished using an engineered derivative of the DNA-binding protein TraI in a room temperature precursor electrolyte. The functional TraI derivative (TraIi1753::CN225) is engineered to possess a cysteine-constrained 12-residue Cu2O binding sequence, designated CN225, that is inserted into a permissive site in TraI. When TraIi1753::CN225 is included in the precursor electrolyte, stable Cu2O nanoparticles form, even though the concentrations of [Cu,+] and [OH] are at 5% of the solubility product (Ksp,Cu2O). Negative control experiments verify that Cu2O formation is controlled by inclusion of the CN225 binding sequence. Transmission electron microscopy and electron diffraction reveals a core–shell structure for the nonequilibrium nanoparticles: a 2 nm Cu2O core is surrounded by an adsorbed protein shell. Quantitative protein adsorption studies show that the unexpected stability of Cu2O is imparted by the nanomolar surface binding affinity of TraIi1753::CN225 for Cu2O (Kd=1.2x10–8 M), which provides favorable interfacial energetics (–45 kJ/mol) for the core-shell configuration. The protein shell retains the DNA-binding traits of TraI, as evidenced by the spontaneous organization of nanoparticles onto circular double stranded DNA.

nanoparticles onto circular double stranded DNA

Contact D. Schwartz for more details,

Journal of the American Chemical Society, 127(44), 15637-15643, 2005.