|About the Book|
While many industrial processes to form nanostructured metal-oxides require extreme temperatures, pressures, and caustic chemicals, Nature is able to form such structures under ambient conditions. The use of these inorganic structures by organisms isMoreWhile many industrial processes to form nanostructured metal-oxides require extreme temperatures, pressures, and caustic chemicals, Nature is able to form such structures under ambient conditions. The use of these inorganic structures by organisms is known as biomineralization. A deeper understanding of biomineralization, particularly the chemistry underlying these processes, offers potential for the development of biomimetic methods in materials chemistry. The work presented in this thesis investigates both the use and the biomimetic formation of mineralized titanium oxide structures.-Two organisms were studied for their apparent affinity towards titanium dioxide. The foraminiferan Bathysiphon argenteus was found to incorporate needles of rutile TiO2 into its shell. These needles were presumed to be detrital and collected from the environment. The Gram-positive bacteria Rhodococcus ruber was found to have three dominant cell-surface proteins that adhered strongly to TiO2. Preliminary experiments identified them as Elongation Factor G, dihydrolipoamide dehydrogenase, and Elongation Factor EF1A.-The R5 peptide, poly(allylamine), spennidine, and spermine were used to study the formation of micro- and nanostructured titanium oxide at the molecular level. All of the biomolecules studied induced the formation of micro- and nanostructured titanium oxide. The solid formed with poly(allylamine) was a titanium phosphate solid, while the solids formed with the R5 peptide, spermidine, and spermine were titanium dioxide. The green fluorescent protein was encapsulated in the solid precipitated with poly(allylamine) only. The effects of temperature and pH were studied in all cases. The kinetics and the mechanism of reaction were studied for the reactions with spermidine and spermine.-Titanium mineralization was also investigated using the iron-storage protein, ferritin. Oxidative and hydrolytic mineralization reactions were studied by the direct addition of Ti(III) and Ti(IV) precursors to ferritin. The reactions were monitored by using transmission electron microscopy, UV-Vis spectroscopy, mass spectrometry, and competition experiments. Preliminary results from a photoreductive method revealed a shift associated with a change in molecular weight upon mineralization as evidenced by using analytical ultracentrifugation.-Finally, the photoreduction of high-valent titanium precursors was studied. The photoreduction of Ti(IV) citrate was evidenced by the formation of a purple color due to a ligand-to-metal charge transfer. The citrate ligand was oxidatively decarboxylated to form acetone dicarboxylic acid, which spontaneously decarboxylated to form acetoacetic acid and, ultimately, acetone. These photoproducts were detected by using nuclear magnetic resonance. The photoreduction of TiBALDH was evidenced by the formation of a bright blue color, although no photoproducts were detected.