Silk Fibroin-Regulated Crystallization of Calcium Carbonate

Authors

  • Cheng Cheng,

    1. Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Advanced Materials Laboratory, Department of Macromolecular Science, Fudan University Shanghai 200433 (P. R. China)
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  • Zhengzhong Shao,

    Corresponding author
    1. Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Advanced Materials Laboratory, Department of Macromolecular Science, Fudan University Shanghai 200433 (P. R. China)
    • Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Advanced Materials Laboratory, Department of Macromolecular Science, Fudan University Shanghai 200433 (P. R. China).
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  • Fritz Vollrath

    1. Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS (UK)
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  • This work was supported by the National Natural Science Foundation of China (NSFC 20525414), as well as the Program for New Century Excellent Talents in University of China (NCET), the Program for Changjiang Scholars and Innovative Research Team in Fudan University and the international exchange program of the Royal Society of London. C. C. was further supported by the European Commission (COOP.CT-2005-018060) while F. V. was supported by US-AFOSR (F49620-03-1-0111). The authors further thank Dr. Y. Z. Huang and F. Cullen (University of Oxford) for the technical support on FIB and XRD. Supporting Information is available online from Wiley InterScience or from the authors.

Abstract

Mollusk shell is one of the best studied of all calcium carbonate biominerals. Its silk-like binder-matrix protein plays a pivotal role during the formation of aragonite crystals in the nacre sheets. Here, we provide novel experimental insights into the interaction of mineral and protein compounds using a model system of reconstituted Bombyx mori silk fibroin solutions serving as templates for the crystallization of calcium carbonate (CaCO3). We observed that the inherent (self-assembling) aggregation process of silk fibroin molecules affected both the morphology and crystallographic polymorph of CaCO3 aggregates. This combination fostered the growth of a novel, rice-grain-shaped protein/mineral hybrid with a hollow structure with an aragonite polymorph formed after ripening. Our observations suggest new hypotheses about the role of silk-like protein in the natural biomineralization process, but it may also serve to shed light on the formation process of those ‘ersatz’ hybrids regulated by artificially selected structural proteins.

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