Biominerals composites

Many questions still exist concerning the physico-chemical and vital factors affecting biomineral composition in the modern environment. Because of these uncertainties, it is hazardous to use chemical, mineralogical, and isotopic data on... 

Functional Hydrogel-Biomineral Composites Inspired by Natural Bone... 

Bone, shell, and coral are not, however, the only biominerals created by living organisms. The kidney and liver of animals, for example, often synthesize biominerals in the form of pathological stones (known as calculi) of varied composition (mostly of calcium oxalate, calcium phosphate, or... 

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... 

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). 

New insights on biomineralization may be revealed by measuring Ca isotope variations in shell secreting organisms (e.g. Griffith et al. 2008). Two factors influence the Ca isotope composition of shells (1) the chemistry of the solution, in which the organisms live and (2) the process by which Ca is precipitated. 

Once formed, crystals can interact with or adhere to other components. Adhesion can occur directly between crystals to form larger structures which may act as the nidus for further mineralization. Crystals can also interact with metabolites and/or tissues to form such structures. These interactions can and do alter the stereochemical course of crystal assembly, and molecular recognition probably accounts for the striations and intricate geometries adopted by biomineralized structures. The role and composition of metabolites comprising the matrix may be useful to understanding the local and large-scale structure of biominerals. 

G.L. Grandjean, E. (eds.) Mdssbauer spectroscopy applied to inorganic chemistry. Plenum Publ. Corp., 3 417-444 Webb, J. Macey, D.J. Mann, S. (1989) Biomineralization of iron in molluscan teeth. In Mann, S. Webb, J. Williams, R.J.P. (eds.) Biomineralization Chemical and biochemical perspectives. VCH Weinheim, 345-387 Webster, J.G. Swedlund, P.J. Webster, K.S. (1998) Trace metal adsorption onto an acid mine drainage iron(lll) oxy hydroxy sulfate. Environ. Sci.Techn. 32 1361-1368 Wedepohl, K.H. (1969) Composition and abundance of common igneous rocks. In Wedepohl, K.H. (ed.) Handbook of geochemistry. Springer, Berlin, 1 227-249 Wedepohl, K.H. (1969a) Composition and abundance of common sedimentary rocks. 

The inorganic phase of bones or teeth is mainly hydroxyapatite (HA), and deviation in Ca/P ratio from common HA (Ca/P = 1.667) is explained by the presence of amorphous phosphates3). The biogenetic HA resembles in size crystals of HA prepared by precipitation from aqueous solutions. The chemical composition of biominerals is similar to HA. However, crystals in bone, dentine and enamel can vary... 

Our understanding of the mechanisms of biomineralization is superficial435. In the past 20 years, most researchers have concentrated upon the extracellular concepts of epitaxy, matrix composition and solubility products while recently the role of cellular organelles and enzymes have attracted more attention. But there are some accepted principles which necessarily carry theoretical implications445. ... 

Looking at the literature in the field of biomineralization, one notices, that the majority of articles is descriptive in nature. On the basis of electron micrographs or thin section studies, the intricate relationships between mineral phase and organic matrix are investigated. Other papers deal with the chemical composition of the mineralized tissue and the minerals. Only a few authors address themselves to the question of metal ion transport mechanisms in cellular systems and the solid state principles involved in mineral deposition on organic substrates. All three sets of information, however, are essential to understand calcification processes. It appears, therefore, that information on the functionality of metal ions in living systems and their role in mineral deposition are particularly desired in this area of research. 

A most remarkable result in the chemical study of ancient morphologies is the complex chemical composition, comprizing carbonaceous materials and different inorganic materials such as carbonates, iron sulphides and iron oxides. It can be shown that most of the inorganic constituents are biominerals produced directly or indirectly by the life activity of the involved organisms. So also these products are chemical fossils and, therefore, merit adequate consideration in our analyses. 

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