| In nature, biominerals are formed under the control of organic components such as proteins and polysaccharides at ambients pHs and temperatures. Yet up until recently, there has been little success in utilizing such constituents as templates for biomimetic silica synthesis. Our recent studies here at UCSB of the proteins occluded within silica needles of the sponge, Tethya aurantia, demonstrate that the proteins which we've named silicateins (silica proteins), have the capability of acting as catalysts for the hydrolysis of silicon alkoxides at physiological pH and temperature, while also serving as scaffolds to organize the resulting silica or silisequioxane products. It is well understood among silica chemists that silicon alkoxides normally must undergo acid or base hydrolysis prior to condensation to silicon dioxide and is therefore normally very stable of pH 7. The understanding of the mechanism of these silicateins arose from mutagenesis studies of the proteins and it was from these results that block copolypeptides were designed. These polymers could not only accelerate the polycondensation of silica from silicon alkoxides at neutral pH but also contained self assemblying features, either through hydrogen, ionic or covalent bonding. It was discovered that the utilization of these varying polypeptides allowed us to successfully synthesize ordered silica structures ranging from transparent silica spheres to bundles of lathelike silica structures at ambient temperature, pressure and pH. |
