Chitin and collagen as universal and alternative templatesin biomineralization

摘要

Biomineralized structures and tissues are composites, containing a biologicallyproduced organic matrix and nano- or microscale amorphous or crystalline minerals.Two main examples of organic matrices – the amino-polysaccharide chitin and theasymmetric protein collagen – are presented and discussed as the basic structuralmodules and organo-templates for calcium and silica biomineralization in nature. Bothserve as templates, providing preferential sites for nucleation and controlling the loca-tion and orientation of mineral phases. Here, for the first time, chitin and collagen areanalysed from evolutionary, structural, and functional points of view with respect totheir templating properties in calcification and silicification phenomena, using both invivo and in vitro data. It is proposed that these biopolymers be characterized asfundamental templates in biomineralization, inasmuch as they are very ancient from anevolutionary point of view, common to many species and biological systems with aglobal distribution. The two polymers also exhibit very similar hierarchical structuralorganizations, in spite of the possible alternatives they provide in chemical nature andorigin. In addition, the phenomenon of multi-phase mineralization – where two miner-als, amorphous and crystalline CaCO3, form from one biomolecule, chitin – is alsodescribed, analysed, and discussed for the first time.