(633j) Biomimetic Synthesis of Magnetic Nanocrystals Mediated By Protein Mms6

The synthesis of magnetic nanoparticles with uniform size has attracted a lot of research interest due to their applications in biomedical devices and high-density data storage. Uniform superparamagnetic magnetite nanocrystals, with a size of about 30 nm, were synthesized in vitro in the presence of a recombinant Mms6 protein, which is found in the magnetosomes of magnetotactic bacteria. Mms6 was shown to have two phases of iron binding: one high affinity and stoichiometric and the other low affinity, high capacity, and cooperative with respect to iron. Iron can also induce a protein structure change in solution, as shown by small angle X-ray scattering. Nanoparticle fabrication studies showed that the nanoparticles synthesized by the wild type Mms6 differ greatly compared to the mutants, indicating that the number and placement of charged groups in the protein were very critical for its function. We explore the bio-inspired synthesis of magnetite nanoparticles on gold surfaces as well. Self-assembled monolayers on gold were used to study the effect of the surface hydrophobicity on the protein surface aggregates and the resulting magnetite nanoparticle size and morphology. It was shown that the Mms6 formed larger aggregates on hydrophobic surfaces, leading to larger magnetite nanoparticles. These studies are very important in understanding the mechanism by which Mms6 promotes the formation of the uniformly sized nanoparticles under mild conditions, and for using the bio-inspired magnetic materials for different applications.