Turning Proteins To Gold
Ivan J. Dmochowski, University of Pennsylvania CHE-0548188
Proteins come in a variety of shapes that range from 1-20 nm in size. Properties, such as metal binding, can be tuned by changing the constituent amino acids, and most soluble proteins can be characterized at atomic resolution by x-ray crystallography. Thus, proteins are versatile building blocks for synthesizing and assembling inorganic materials into highly ordered structures.
Our lab is studying ferritin proteins, which mineralize a wide range of metals. Twenty-four 4-helix bundles self assemble to form a spherical ferritin with large central cavity. We have recently found that citrate-capped Au nanoparticles can be encapsulated very efficiently within a thermophilic ferritin. This protein normally exists as a 4-helix bundle dimer at low salt concentrations, and assembles to form the 24mer at 600 mM NaCl (top right). Remarkably, a 10-nm citrate-capped Au nanoparticle can template ferritin assembly at low salt. In capsule form (bottom right), the protein stabilizes the internal gold particle and provides new routes for particle functionalization and assembly.