Carbonate biomineralization

Carbon 13c/12c 12C = 98.89 13C= 1.11 Organic matter, carbonates, biomineralized tissue, soil, C02 Diet, plant water-use efficiency, climate and habitat, provenance (ivory, marble)... 

Calcium carbide, 11 182-183 neutron diffraction studies on, 8 234 Calcium carbonate, biomineralization, 36 163-167... 

Another important point about calcium carbonate biomineralization is that more than one of the three polymorphs may be present in close proximity within an individual sample and each may be a different calcium carbonate polymorph (mollusks provide such an example), or the mineral may change over time. In many species the larval stage is aragonitic, while the adult biomineral is calcite. The different minerals in biomineralized tissues play specific roles in the proper functioning of the organism. 

Studies on the influence of polymers on the crystallization of calcium carbonates in vitro have shown that metastable liquid complexes with anionic polymers can be formed that subsequently transform to calcite. Studies of carbonate biomineralization have shown that amorphous calcium carbonate forms either transiently or as a stable phase. It has also been shown that absorbed proteins modify the fracture properties of carbonates. In particular, fracture surfaces show smooth conchoidal fracture, like glass, rather than the faceted fracture characteristic of normal crystals. This suggests that we have much to learn about the modification of the properties of crystals and amorphous solids by entrained polymer (see Fig. 3). There are parallels with the Lanxide process for... 

What Genes and Genomes Tell Us about Calcium Carbonate Biomineralization... 

Fricke M, Volkmer D (2007) Crystallization of Calcium Carbonate Beneath Insoluble Mono-layers Suitable Models of Mineral-Matrix Interactions in Biomineralization 270 1-41 Fujimoto D, see Tamura R (2007) 269 53-82... 

The bones and teeth of humans and other vertebrate animals, for example, consist mainly of a composite material made up of an organic substance, collagen, and a biomineral, calcium carbonate phosphate (see Textboxes 32 and 61). The latter, which makes up about two-thirds of the total dry weight of bone, is composed of calcium phosphate containing between 4-6% calcite (composed of calcium carbonate) as well as small amounts of sodium, magnesium, fluorine, and other trace elements. The formula Ca HPChXPChMCChXOH) approximately represents its composition its crystal structure is akin to that... 

As mentioned earlier, biological systems have developed optimized strategies to design materials with elaborate nanostructures [6]. A straightforward approach to obtaining nanoparticles with controlled size and organization should therefore rely on so-called biomimetic syntheses where one aims to reproduce in vitro the natural processes of biomineralization. In this context, a first possibility is to extract and analyze the biological (macro)-molecules that are involved in these processes and to use them as templates for the formation of the same materials. Such an approach has been widely developed for calcium carbonate biomimetic synthesis [13]. In the case of oxide nanomaterials, the most studied system so far is the silica shell formed by diatoms [14]. 

The collagen fibers leave small compartments where apatite nanocrystals are deposited during a controlled biomineralization process [20]. The collagen acts as a structural framework in which plate-like nanocrystals of carbonated hydroxyapatite (CHA) are embedded to strengthen the bone. The chemical formula of biological CHA can be represented as follows ... 

Oxygen 18o/16o 160 = 99.759 170 = 0.037 lsO = 0.204 Water, biomineralized carbonates and phosphates, sedimentary phosphates and carbonates, silicates, organic matter Climate, plant and animal water metabolism, ocean temperature, provenance (marble), chronostratigraphy... 

CALCIUM-BASED BIOMINERALS CALCIUM CARBONATES IN ASCIDIANS AND MOLLUSCS... 

Bone and teeth in mammals and bony fishes all rely on calcium phosphates in the form of hydroxyapatite [Ca5(P04)30H]2, usually associated with around 5% carbonate (and referred to as carbonated apatite). The bones of the endoskeleton and the dentin and enamel of teeth have a high mineral content of carbonated apatite, and represent an extraordinary variety of structures with physical and mechanical properties exquisitely adapted to their particular function in the tissue where they are produced. We begin by discussing the formation of bone and then examine the biomineralization process leading to the hardest mineralized tissue known, the enamel of mammalian teeth. 

Finally, it is intriguing that in terms of biomineralization, invertebrates have based their reliance on calcium carbonates, while vertebrates appear to have used almost exclusively calcium phosphate. We say almost, because, while the use of calcium phosphates for biomineralization is an invention of some vertebrates, they still use calcium carbonate for the formation of otoliths4 of the inner ear. It remains to be established if the equivalent of the gene starmaker required for otolith formation in zebrafish has homologues among invertebrates. 

Because of its relatively long mean residence time, ocean water has a constant isotope composition. Corals are about l%c and foraminifera are about 4.5%o lighter than ocean water. Thus significant Mg isotope fractionations occur during biomineralization of carbonate secreting organisms which is larger than for Ca isotopes (see Section 2.11). 

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