Influence of the Extrapallial Fluid of Pinctada fucata on the Crystallization of Calcium Carbonate and Shell Biomineralization

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• 作者：Jun Xie ; Jian Liang ; Juan Sun ; Jing Gao ; Sirui Zhang ; Yangjia Liu ; Liping Xie ; Rongqing Zhang
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：February 3, 2016
• 年：2016
• 卷：16
• 期：2
• 页码：672-680
• 全文大小：621K
• ISSN：1528-7505

文摘

Extrapallial fluid (EPF) is located between the shell and the mantle, and it is believed to play key roles in shell biomineralization in Pinctada fucata. However, few studies have been performed on the biomineralization effect of EPF. In this work, CaCO₃ crystallization experiments showed that EPF proteins could not only control the morphology but also regulate the phase transition of calcium carbonate through the different proteins specific binding to calcite or aragonite. In crystal growth inhibition experiments, when the final concentration of CaCl₂ and NaHCO₃ reduced from 50 to 5 mM, the function of EPF proteins (50 μg/mL) transferred from significantly improving over the number of CaCO₃ crystals (448 ± 28) upon the control (128 ± 20) to inhibiting the precipitation of CaCO₃. The precipitation rate of CaCO₃ was also inhibited by EPF proteins. In vivo, once EPF was extracted daily for 20 days, the nacre platelet in the nacreous layer was disturbed, and calcite deposited randomly due to the reduction of EPF proteins. Furthermore, EPF also acted as an external signal to induce the expression variation of shell-related genes to regulate nacre and prism formation. In conclusion, our findings demonstrate that EPF proteins not only take part in the nucleation, morphology, inhibition, and phase transition of CaCO₃ but also play a dual role in both shell biomineralization and prism–nacre transition, which is mediated by different proteins and their secondary structure and conformational changes.