6.1.2. Aqueous V(III) Chemistry 877 6.1.3. Oxidation State of Vanadium in Tunicates 878 6.1.4. Uptake of Vanadate into Tunicates 879 6.1.5. Vanadium Binding Proteins: Vanabins 879 6.1.6. Model Complexes and Their Chemistry 880 6.1.7. Catechol-Based Model Chemistry 880 6.1.8. Vanadium Sulfate Complexes 881 6.2. Fan Worm Pseudopotamilla occelata 883 7. Vanadium Nitrogenase 883 7.1. Nitrogenases 883 7.2. Biochemistry of Nitrogenase 884 7.3. Clusters in Nitrogenase and Model Systems: Structure and Reactivity 885

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The chemistry and biochemistry of vanadium and the biological activities exerted by vanadium compounds.

Starting with the history of the fundamental science of the relation of structure to composition delineated completely by Goldschmidt, we use the perovskite structure to illustrate the enormous pow...

The perovskite structure—a review of its role in ceramic science and technology

Calcium oxalate (CaOx) crystals are distributed among all taxonomic levels of photosynthetic organisms from small algae to angiosperms and giant gymnosperms. Accumulation of crystals by these organisms can be substantial. Major functions of CaOx crystal formation in plants include high-capacity calcium (Ca) regulation and protection against herbivory. Ultrastructural and developmental analyses have demonstrated that this biomineralization process is not a simple random physical-chemical precipitation of endogenously synthesized oxalic acid and environmentally derived Ca. Instead, crystals are formed in specific shapes and sizes. Genetic regulation of CaOx formation is indicated by constancy of crystal morphology within species, cell specialization, and the remarkable coordination of crystal growth and cell expansion. Using a variety of approaches, researchers have begun to unravel the exquisite control mechanisms exerted by cells specialized for CaOx formation that include the machinery for uptake and accumulation of Ca, oxalic acid biosynthetic pathways, and regulation of crystal growth.

CALCIUM OXALATE IN PLANTS: Formation and Function

I. Introduction A FUNCTIONAL relationship between cell growth and the initiation and progression of events associated with differentiation has been a fundamental question challenging developmental biologists for more than a century. In the case of bone, as observed with other cells and tissue, the relationship of growth and differentiation must be maintained and stringently regulated, both during development and throughout the life of the organism, to support tissue remodeling. For many years, bone was defined anatomically and examined largely in a descriptive manner by ultrastructural analysis and by biochemical and histochemical methods. These studies provided the basis for our understanding of bone tissue organization and orchestration of the progressive recruitment, proliferation, and differentiation of the various cellular components of bone tissue. Now, complemented by an increased knowledge of molecular mechanisms that are associated with and regulate expression of genes encoding phenotypic compone...

Molecular mechanism mediating proliferation, defferentiation interralationships during progressie development of the osteoblast phenotype

Chitin, the second most important natural polymer in the world, and its N-deacetylated derivative chitosan, have been identified as versatile biopolymers for a broad range of applications in medicine, agriculture and the food industry. Two of the main reasons for this are firstly the unique chemical, physicochemical and biological properties of chitin and chitosan, and secondly the unlimited supply of raw materials for their production. These polymers exhibit widely differing physicochemical properties depending on the chitin source and the conditions of chitosan production. The presence of reactive functional groups as well as the polysaccharide nature of these biopolymers enables them to undergo diverse chemical modifications. A complete chemical and physicochemical characterization of chitin, chitosan and their derivatives is not possible without using spectroscopic techniques. This review focuses on the application of spectroscopic methods for the structural analysis of these compounds.

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Application of Spectroscopic Methods for Structural Analysis of Chitin and Chitosan

Structural and spectroscopic behaviour of YSr2Cu3-xMxO7±y phases with M = Ti, Fe, Co, Al, Ga, Pb

Abstract Solid products obtained from calcium hydroxylapatite suspensions in diluted VO2+ solutions, under different experimental conditions, were investigated by means of X-ray powder diffractometry and IR and ESR spectroscopy. It is demonstrated that the VO2+ cation cannot be incorporated into the apatite-lattice but is strongly adsorbed on the surface of the material. Different aspects of this adsorption were thoroughly investigated. The ESR spectra suggest an inhomogeneous distribution of the adsorbed species and the generation of O = V (O)4 moieties, which show a high stability towards oxidation.

Über die Wechselwirkung des Vanadyl(IV)-Kations mit Calcium-Hydroxylapatit

Es wurde das Verhalten von Sn3PO4F3 in wasrigen Losungen unter verschiedenen experimentellen Bedingungen untersucht. Dabei wurde festgestellt, das diese Phase eine sehr hohe hydrolytische Stabilitat besitzt. Das thermische Verhalten wurde mittels TG/DTA-Messungen untersucht und die Zersetzungsprodukte rontgenographisch und durch 119Sn-Mosbauer-Spektroskopie charakterisiert. Eine eingehende Untersuchung des SnF2/H3PO4-Systems erlaubte weiterhin, neue Darstellungsmethoden fur Sn3PO4F3 und monoklines Sn3(PO4)2 auszuarbeiten.



Hydrolytic and Thermal Behaviour of Sn3PO4F3



The behaviour of Sn3PO4F3 in aqueous solutions, has been investigated under different experimental conditions. It is shown that the compound possesses a high hydrolytic stability. The thermal behaviour has been analyzed by means of TG/DTA measurements and the decomposition products have been characterized by X-ray diffraction and 119Sn-Mossbauer spectroscopy. A detailed study of the SnF2/H3PO4 system, allows the formulation of new preparative procedures for Sn3PO4F3 and monoclinic Sn3(PO4)2.

Hydrolytisches und thermisches Verhalten von Sn3PO4F3

Crystallographic data for the oxoapatites of general formula Ca8Ln2(PO4)6O2 withLn=La, Pr-Ho) have been obtained from X-ray powder data. The vibrational spectra, which are also discussed, allow to make a proposal about the location of the lanthanide cations present in these lattices.

Kristallographische Daten und Schwingungsspektren einiger Oxoapatite der Seltenen Erden des Typs Ca8Ln2(PO4)6O2

Mean amplitudes of vibration for IOF5 have been recalculated from known spectroscopic data using the “Method of the Characteristic Vibrations”. The obtained values are in excellent agreement with those obtained from electron diffraction and microwave measurements and give also a correct picture of the molecular geometry.

Enrique J. Baran

Papers

Structural and spectroscopic behaviour of YSr2Cu3-xMxO7±y phases with M = Ti, Fe, Co, Al, Ga, Pb

Über die Wechselwirkung des Vanadyl(IV)-Kations mit Calcium-Hydroxylapatit

Hydrolytisches und thermisches Verhalten von Sn3PO4F3

Kristallographische Daten und Schwingungsspektren einiger Oxoapatite der Seltenen Erden des Typs Ca8Ln2(PO4)6O2

Mittlere Schwingungsamplituden und Molekulargeometrie von IOF5