Biomacromolecules in recent phosphate-shelled brachiopods: identification and characterization of chitin matrix

Abstract

Phosphate-shelled brachiopods differ in filter-feeding lifestyle, with Lingula anatina an active infaunal burrower, and Discinisca tenuis a shallow marine epibenthic animal. The shells of these animals are built of organophosphatic constituents, the organic fibres/sheets reinforced with calcium phosphate to provide a sophisticated ultrastructural robustness. This investigation examined the nature of the organic fibres in order to improve understanding of how living organisms produce hierarchically structured biomaterials. Unlike powdered samples commonly used in previous studies, organic fibres were isolated for the first time and the shell fractions were purified, in order to study the content and nature of the biopolymer fibres. Biochemical methods including Calcofluor staining revealed a chitin matrix. Ultrastructural analysis, thermal gravimetric analysis, and spectroscopic analyses show that the core polysaccharide framework is composed of layers of β-chitin sheets and/or fibrils that are coated with a fibrous organic matrix. There is more chitin matrix in the L. anatina shells (26.6 wt.%) compared to the D. tenuis shells (12.9 wt.%). Taken together, the data show that the chitin matrix contributes to increased skeletal strength, making L. anatina highly adapted for life as an active burrower. In comparison, D. tenuis contains less chitin and lives as attached epibenthos in a shallow marine environment. Graphical abstract First spectroscopic evidence of β-chitin sheets in recent organophosphatic brachiopods

Dissolution of Phosphate and Precipitation of Carbonate in the Biomineralization of the Bivalve Shell Limnoperna fortunei

“…The presence of an amorphous organic phase in the shells seems to be essential for its flexibility and its ability to adapt to the narrow and irregular holes in which these beings live. The complex hierarchical organization of chitin+protein (17,18) organic fibrils and lamellae in the shells of inarticulate brachiopods may thus indicate evolutionary competencies.…”

“…Starting with the concentrations of calcium phosphate (approximately 50-60%), which are much lower compared to the concentrations of calcium carbonate commonly found in bivalve shells (approximately 95%). Recent work (17) with brachiopod shells indicates the existence of hierarchical structures, at the nano, micro, and macro levels, besides very sophisticated mechanical and rheological behavior (viscoelastic). These features are especially attributed to the concentration of nonbiomineralized organic components.…”

A natural biogenic fluorapatite as a new biomaterial for orthopedics and dentistry: antibacterial activity of lingula seashell and its use for nanostructured biomimetic coatings

“…67,68 The organic fraction, which comprises the remaining 32% of the shell weight, is composed of proteins, glycosaminoglycans and chitin. 67,69,70 At the micron scale, the shell has a laminated structure made of alternating layers of predominantly organic and predominantly mineral phases. The L. anatina shell is of particular interest to orthopedics and dentistry, as its inorganic composition is close to that of bone and enamel, and it contains ion dopants (magnesium, zinc, sodium, manganese) that are important to promote bone regeneration but difficult to incorporate into synthetically produced hydroxyapatite.…”

Raman Technology for Process Control: Waste Shell Demineralization for Producing Transparent Polymer Foils Reinforced with Natural Antioxidants and Calcium Acetate By-Products

“…Summarized Raman bands observed in spectra of the demineralized, chitin-based foil products derived from the three crustacean species, compared to the pure α-chitin[29][30][31][32].…”