Search results for "Biomineral"
showing 10 items of 139 documents
Bioengineering of the silica-polymerizing enzyme silicatein-alpha for a targeted application to hydroxyapatite.
2009
Since its discovery, numerous biotechnological approaches have aimed to explore the silica-polymerizing catalytic activity of the enzyme silicatein. In vivo, silicatein catalyzes polymerization of amorphous silica nanospheres from soluble precursors. In vitro, it directs the formation of nanostructured biosilica. This is of interest for various applications that strive to benefit from both the advantages of the biological system (i.e., silica synthesis under physiological conditions) and the cell mineralization-stimulating effect of biosilica. However, so far immobilization of silicatein has been hampered by the complex multistep procedure required. In addition, the chemical surface modific…
Molluscan biomineralization: The proteinaceous shell constituents of Pinna nobilis L.
2005
Abstract The shell of molluscs is a remarkable example of a natural composite biomaterial, synthesized at ambient temperature. Consequently, many consider it as a model for trying to develop at little cost new biomimetic materials of superior mechanical properties. The peculiar resistance of shells to fracture lies in an organic matrix, which is closely associated with the mineral phase. This matrix regulates the crystal growth, by allowing nucleation of the crystals only where appropriate, by favoring crystal elongation in privileged directions, and by inhibiting their growth. This matrix is a mixture of glycoproteins and polysaccharides, the primary structure and function of which are poo…
Oil-Water Interface Templating of Mesoporous Macroscale Structures
1996
Ordered mesostructured porous silicas that are also macroscopically structured were created by control of the interface on two different length scales simultaneously. Micellar arrays controlled the nanometer-scale assembly, and at the static boundary between an aqueous phase and an organic phase, control was achieved on the micrometer to centimeter scale. Acid-prepared mesostructures of silica were made with the p6, Pm3n, and the P63/mmc structures in the form of porous fibers 50 to 1000 micrometers in length, hollow spheres with diameters of 1 to 100 micrometers, and thin sheets up to 10 centimeters in diameter and about 10 to 500 micrometers in thickness. These results might have implicat…
Marine biominerals: perspectives and challenges for polymetallic nodules and crusts.
2009
Deep sea minerals in polymetallic nodules, crusts and hydrothermal vents are not only formed by mineralization but also by biologically driven processes involving microorganisms (biomineralization). Within the nodules, free-living and biofilm-forming bacteria provide the matrix for manganese deposition, and in cobalt-rich crusts, coccolithophores represent the dominant organisms that act as bio-seeds for an initial manganese deposition. These (bio)minerals are economically important: manganese is an important alloying component and cobalt forms part of special steels in addition to being used, along with other rare metals, in plasma screens, hard-disk magnets and hybrid car motors. Recent p…
Nonclassical crystallization in vivo et in vitro (I): Process-structure-property relationships of nanogranular biominerals.
2016
A distinct nanogranular fine structure is shared by a wealth of biominerals from several species, classes and taxa. This nanoscopic organization affects the properties and behavior of the biogenic ceramic material and confers on them attributes that are essential to their function. We present a set of structure-relationship properties that are rooted in the nanogranular organization and we propose that they rest on a common pathway of formation, a colloid-driven and hence nonclassical mode of crystallization. With this common modus operandi, we reveal the most fundamental and wide spread process-structure-property relationship in biominerals. With the recent increase in our understanding of…
Fractal-related assembly of the axial filament in the demosponge Suberites domuncula: relevance to biomineralization and the formation of biogenic si…
2007
Abstract The siliceous spicules of sponges (Porifera) show great variations of sizes, shapes and forms; they constitute the chief supporting framework of these animals; these skeletal elements are synthesized enzymatically by silicatein. Each sponge species synthesizes at least two silicateins, which are termed − α and − β . In the present study, using the demosponge Suberites domuncula , we studied if the silicateins of the axial filament contribute to the shape formation of the spicules. For these experiments native silicateins have been isolated by a new Tris/glycerol extraction procedure. Silicateins isolated by this procedure are monomeric (24 kDa), but readily form dimers through non-…
Enzyme-accelerated and structure-guided crystallization of calcium carbonate: Role of the carbonic anhydrase in the homologous system
2014
Abstract The calcareous spicules from sponges, e.g. from Sycon raphanus, are composed of almost pure calcium carbonate. In order to elucidate the formation of those structural skeletal elements, the function of the enzyme carbonic anhydrase (CA), isolated from this species, during the in vitro calcium carbonate-based spicule formation, was investigated. It is shown that the recombinant sponge CA substantially accelerates calcium carbonate formation in the in vitro diffusion assay. A stoichiometric calculation revealed that the turnover rate of the sponge CA during the calcification process amounts to 25 CO2 s−1 × molecule CA−1. During this enzymatically driven process, initially pat-like pa…
A hydrated crystalline calcium carbonate phase: Calcium carbonate hemihydrate.
2019
Hydrous CaCO 3 gets a new structure Calcium carbonate (CaCO 3 ) forms important minerals on Earth and is a model system for understanding crystal nucleation. Three different structures of CaCO 3 are known, along with two structures that are hydrated. Zou et al. found a third hydrated CaCO 3 structure formed from amorphous CaCO 3 in the presence of magnesium ions. The discovery illustrates the importance of amorphous precursors for producing new materials. Science , this issue p. 396
Nanostructure, composition and mechanisms of bivalve shell growth
2008
Abstract Freshwater and marine cultured pearls form via identical processes to the shells of bivalves and can therefore serve as models for the biomineralization of bivalve shells in general. Their nanostructure consists of membrane-coated granules (vesicles) which contain amorphous calcium carbonate (ACC) at the beginning of the biomineralization sequence, preceding the crystallization of aragonite and vaterite. In contrast to the commonly accepted view, crystallization of ACC occurs rapidly and within the granular nano-compartments mediated by organic molecules much earlier than platelet formation. The interlamellar organic sheets in nacre that form the platelet structure of nacre themsel…
Pmarg-pearlin is a matrix protein involved in nacre framework formation in the pearl oyster Pinctada margaritifera.
2011
11 pages; International audience; The shell of pearl oysters is organized in multiple layers of CaCO(3) crystallites packed together in an organic matrix. Relationships between the components of the organic matrix and mechanisms of nacre formation currently constitute the main focus of research into biomineralization. In this study, we characterized the pearlin protein from the oyster Pinctada margaritifera (Pmarg); this shares structural features with other members of a matrix protein family, N14/N16/pearlin. Pmarg pearlin exhibits calcium- and chitin-binding properties. Pmarg pearlin transcripts are distinctively localized in the mineralizing tissue responsible for nacre formation. More s…