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

Crystal Chemistry of the Saccharinato Complexes of Trivalent Lanthanides and Yttrium

The term ‘organic minerals’ means naturally occurring crystalline organic compounds including metal salts of formic, acetic, citric, mellitic, methanesulfonic and oxalic acids. As for the rest of t...

Crystal chemistry of organic minerals – salts of organic acids: the synthetic approach

The powder Fourier transform (FT) infrared and Raman spectra of the new isotypic diarsenates RbScAs2O7, TlScAs2O7, and (NH4)ScAs2O7 are discussed with a factor group analysis, on the basis of their known structural characteristics. The spectroscopic behavior clearly reflects all the structural peculiarities and also confirms the rotational quenching of the NH4+ cation in (NH4) ScAs2O7. The crystal structure of TlScAs2O7 is also reported for the first time and is briefly discussed. Copyright © 2006 John Wiley & Sons, Ltd.

Vibrational spectra of three new diarsenates containing scandium(III)

Single crystals of manganese(II) fluorophosphate dihydrate, Mn(PO3F)(H2O)2, were grown in a metathesis reaction from aqueous solutions of MnCl2 and (NH4)2(PO3F). The crystal structure [P, Z = 2, a = 5.5280(7), b = 5.6357(7), c = 8.2570(10) A, α = 81.279(2), β = 75.156(2), γ = 71.722(2)°, 1345 structure factors, 86 parameter, R[F2 > 2σ(F2)] = 0.0322, wR(F2 all) = 0.0771] consists of [MnO4(H2O)2] octahedra that share a common edge to form isolated double octahedra of the type [Mn2O2/2O4/1(H2O)4/1]. Each double octahedron is bridged by the oxygen atoms of six (PO3F) tetrahedra to six neighboring double octahedra into a layered arrangement parallel to (001). Adjacent layers are held together through weak O–H···O hydrogen bonds, and no significant hydrogen bonding interactions of the type O–H···F are observed. Vibrational spectra are discussed in terms of a site-symmetry approximation for the (PO3F)2– anion. The thermal decomposition of Mn(PO3F)(H2O)2 starts above 130 °C. In a multi-stage mechanism the end-product Mn2P2O7 is formed at temperatures above 500 °C. Magnetic measurements suggest an antiferromagnetic ordering of Mn(PO3F)(H2O)2 at 3.4 K.

Enrique J. Baran

Papers

Crystal Chemistry of the Saccharinato Complexes of Trivalent Lanthanides and Yttrium

Crystal chemistry of organic minerals – salts of organic acids: the synthetic approach

Vibrational spectra of three new diarsenates containing scandium(III)

Synthesis, Crystal Structure, and Properties of Mn(PO3F)(H2O)2 †‡

Vibrational spectra of Zn(II) complexes of the amino acids with hydrophobic residues.