| Summary: | 博士 === 國立清華大學 === 生命科學系 === 95 === Radulae of limpets are regarded as an ideal experimental material for studying biologically controlled mineral deposition for it possesses teeth in different mineralization stages. The possible mechanism of silica precipitation in the limpet Notoacmea schrenckii (Acmaeidae, Gastropoda) was explored in this study using electron microscopy, electron diffraction, energy-dispersive X-ray analysis, and ICP-MS. ICP-MS elemental analysis showed that iron and silica both infiltrate into the radulae in early stages during teeth development. Electron dense granules in nanometer size were observed in teeth ultrathin section specimen of early teeth formation stage, subsequent electron diffraction analysis indicates that silica is the primary component of these granules. Transmission electron microscopic images revealed the intimate association between silica granules and the organic matrix, which implied that the organic matrix may take more active roles in catalyzing other than merely functioning as physical constraints during mineral deposition. Low molecular weight peptides were harvested from cusp using HF extraction suggested the possibility of co-precipitation of the peptides together with silica. The amino acid composition result suggested that the peptides extracted from the cusps might be related to mitochondrial carrier protein family and thus might take part in silica transportation process. Milder NH4F treatment of the cusps to expose the peptides and the appearance of silica spheres following the application of silicate suggest that the low molecular weight peptides embedded within the minerals may assist silica precipitation.
|
|---|
