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Tuning the Mg Content of Mg Calcite by Shell Matrix Macromolecules of Pinctada Fucata

Author: ZhuFangJie
Tutor: XieLiPing
School: Tsinghua University
Course: Marine biology
Keywords: P. fucata Biomineralization Magnesium calcite Crystal impurities
CLC: S917.4
Type: Master's thesis
Year: 2010
Downloads: 28
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Abstract

Calcite is the most widely distributed, by far the most studied a biological minerals. Sea water contains a lot of the Mg ^{2 , marine biological mineralization formed calcite are containing Mg calcite. Mg calcite main impurity elements, the calcite lattice integration of Mg atoms have a significant effect on its stability. The study showed that the Mg content subject to strict physiological regulation of biological origin calcite. About the source of the regulation, the general view is that, the organisms directly change the composition of the crystallization solution to achieve the regulation. Based on the experimental results of the present work, we propose another regulation mechanisms may exist, i.e. the Mg content of the crystallization solution in the regulation of biological macromolecules calcite. The Pinctada oyster (Pinctada fucata) shell prismatic layer containing Mg calcite. Shell mineralization process regulation largely from the crystalline biological macromolecules in solution, the shell matrix, therefore, the mother-of-pearl the Beibei shell EDTA soluble matrix macromolecules (ESM) for the study to test the in vitro calcite formed in the crystallization system containing the impact of the amount of Mg. For X-ray spectroscopy (EDS) and X-ray diffraction (XRD), the experimental results show that the prismatic layer ESM is present in the solution, the formation of calcite bulk Mg content significantly reduced the presence of nacre ESM, calcite phase Mg content occur only minor changed. X-ray photoelectron spectroscopy (XPS) analysis results show that the prismatic layer ESM solution can significantly reduce the Mg content of the calcite surface, nacre ESM can significantly increase the Mg content of the calcite surface. In addition, the the prismatic layer ESM reduce calcite Mg content in effect with the prism layer was observed to low Mg calcite characteristics coincide. These results suggest that the natural biological macromolecules in solution can be directly regulated by the impurity elements of the crystal. Biomineralization process, the mechanism may be organisms for precise adjustment of biological mineral properties. The initial mechanism studies have shown that the shell prismatic layer ESM the nacre ESM inhibition of calcite crystallization process is similar, but the magnesium content of calcite is significantly different. In addition, the experimental concentration ESM solution Mg / Ca ratio did not significantly affected. Thus, the role of the Mg content of the ESM changed calcite, not by affecting the rate of crystallization or adjusting the solution in Mg, Ca ions relative activity to achieve.}

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