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October 7, 2003


Dr. Dan Feldheim
Department of Chemistry
North Carolina State University
"The Interface of Solid-State Chemistry and Molecular Biology: from RNA-Mediated Evolution of Materials to Nanoparticle Electronics"

Abstract.  This talk will discuss potential uses of biological macromolecules in the synthesis of solid-state materials and surface assemblies. Inorganic materials and biology have a long and intimate past together. In fact, the two date back literally to the origin of life, when the most complex forms of organic matter were comprised of amino acids, fatty acids, sugars, purines, and pyrimidines. It has been hypothesized that in this “RNA world” catalytic reactions necessary for achieving the functional macromolecules necessary for life (proteins and enzymes) were performed by RNA. Yet the active RNA molecules themselves likely would not have formed or been stable enough to “survive” degradation processes had it not been for inorganic materials present at the time. Montmorillonite clay, for example, polymerizes adenylate, a building block of RNA (G. F. Joyce Nature 2002, 481, 214). More recently, biological organisms from humans to bacteria have exploited biopolymers such as proteins to construct elaborate structural, magnetic, and photoresponsive inorganic materials including those found in bone, teeth, and shells. Magnetotactic bacteria, for example, use biopolymers to construct 1-dimensional chains of iron oxide nanoparticles that are used for navigation. Thus, what began as a relationship in which an inorganic material synthesized a biomolecule has evolved into just the reverse-biomolecules now stabilize the formation of useful materials.While there are many examples in the recent literature of protein-mediated growth of solid-state materials, RNA and DNA have not been used previously in inorganic synthesis. (A particularly useful review is found in: Whitling, Spreitzer, Wright Adv. Mater. 2000, 12, 1377). RNA is an exciting polymer template for crystal engineering because it is a highly structured biopolymer that can reproducibly fold into intricate 3D structures that are conformationally distinct and dictated by their sequence.  Our group has employed RNA in vitro selection techniques to find RNA sequences capable of synthesize new materials. Using these methods, sequences have been isolated from a large random library of RNA (1014 unique sequences) that are capable of catalyzing the synthesis of new materials with unusual shapes or physical properties. Ferromagnetic palladium platelets and spinel ferrite wires are two examples that will be presented. The use of DNA duplex formation to assemble particles on surfaces for electronic characterization will also be described. 

Vanderbilt University