Investigation of Biopolymer - Mineral Interactions in the Natural Composite Material Nacre

Abstract

Nacre consists of platelets of aragonite, arranged in a regular manner. An organic matrix is intercalated between the mineral, necessary for the growth. Aspects of growth as well as properties of the organic matrix from nacre of Haliotis laevigata were investigated. The influence of the interlamellar matrix on CaCO3 formation was investigated. Crystallization under constant conditions and investigation with electron microscopy and X-ray diffraction revealed that interlamellar matrix nucleates flat aragonite crystals. The surface energy of the interlamellar matrix was determined with contact angle measurements. It is mainly of non-polar origin. The influence of soluble matrix proteins on precipitation rates was determined. Soluble proteins from nacre had a high influence on precipitation rates compared to other proteins. The soluble matrix was subject to an amino acid analysis. The result was dependent on the method protein purification. In general, pro, gly, leu and ala were dominant.