Materials Science

Crayfish Crystals

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Science  07 Apr 2006:
Vol. 312, Issue 5770, pp. 21-23
DOI: 10.1126/science.312.5770.21d

A number of studies have shown that biomineralization can occur through the sudden transformation of amorphous calcium carbonate (ACC) into its crystalline forms. In crayfish, for example, the exoskeleton consists primarily of a composite of chitin and protein microfibrils and calcium carbonate. Sugawara et al. examine the role of a recently isolated crayfish peptide, known as CAP-1, on the formation of calcium carbonate crystals. Chitin was spun-coated onto glass, where it formed a layer of fibrils and was then covered with a supersaturated solution of calcium carbonate and a small amount of CAP-1. The authors observed the growth of micrometer-sized crystals that were composed of assemblies of nanocrystals and were all found to have the same c-axis orientation. The crystals were connected to the chitin through CAP-1 and formed a nanocomposite. Crystallization occurred within the first 5 min after mixing, indicating that a sudden transformation of ACC occurs in the presence of CAP-1. By removing the lone phosphoserine residue of the peptide, the authors observed oriented crystal growth but with larger crystals, indicating that the phosphate group may play a role in limiting crystal growth through the stabilization of the ACC. — MSL

Angew. Chem. Int. Ed. 45, 10.1002/anie.200503800 (2006).

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