Date of Award

Spring 1-1-2010

Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry & Biochemistry

First Advisor

Daniel L. Feldheim

Second Advisor

Bob Sievers

Third Advisor

Gordana Dukovic

Abstract

Biomolecules have evolved in nature with the ability to synthesize materials with uniquely interesting properties in response to environmental stress. Bio-mediated materials are often synthesized under conditions of neutral pH and ambient temperature and pressure from a limited set of biologically available metals. This thesis presents work done in an effort to 1) identify biomolecules capable of mediating the synthesis of nanomaterials in vitro, 2) further understand the circumstances that promote bio-mediated materials synthesis and 3) apply the knowledge gained to a novel intracellular protein labeling scheme.

In vitro selection experiments involving RNA, phagemids, or whole cells can identify biomolecules that bind tightly to or mediate the formation of inorganic materials. Through this work, iterative cycles of RNA selections have identified RNAs that mediate the formation of metal oxide nanoparticles. The selection pressure required RNA-mediated assembly of Co and/or Fe into a solid that responded to a magnetic field under ambient conditions.

The ability of peptides selected via phage display to mediate the formation of inorganic nanoparticles is now well established. However, the atomic-level interactions between the selected peptides and the metal ion precursors remain largely obscure. We identified a new peptide that is capable of mediating the formation of Ag nanoparticles. Surprisingly, nanoparticle formation required the presence of peptide, HEPES buffer, and light. Peptide epitope mapping indicated crucial residues for particle formation. Additionally, once immobilized onto a surface, the peptide formed Ag nanoparticles or high-aspect ratio nanowires as a function of immobilization concentration.

Finally, we explored biomolecule-mediated formation of nanomaterials by investigating protein chimeras. We engineered and expressed proteins that included peptides known to bind silver or iron. The Ag and Fe binding peptide-based protein chimeras successfully demonstrated in vitro activity. Additionally the iron binding proteins were capable of scavenging trace iron from Luria-Bertaini broth during protein expression, creating nanoparticles in vivo. These results have lead toward developing genetically clonable tags, where specific proteins are labeled with a biomolecule capable of mediating the synthesis of a nanomaterial, and the unique nanomaterial is used to uniquely identify the protein of interest.

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