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

A new ReV oxo complex with tetramethylthiourea, [ReO(Me4tu)4](PF6)3, has been synthesized by reduction of perrhenate with tin(II) chloride in strongly acidic solution in the presence of excess tetramethylthiourea. The complex has been characterized by elemental analysis and electronic and FTIR spectroscopy. The molecular structure of the compound was determined by X-ray diffraction methods. The coordination polyhedron is a regular square pyramid with the substituted thiourea sulfur atoms in the equatorial positions [d(Re–S) = 2.339(3) A] and the oxo ligand located in the summit [d(Re–O) = 1.63(2) A]. Computational methods were employed to analyze the geometric and electronic structures of tetramethylthiourea and thiourea. Quantum mechanical studies suggest steric hindrance as the reason for the stabilization of the ReO3+ center instead of the ReIII one.

Synthesis, Characterization, and Crystal Structure of [ReO(Me4tu)4](PF6)3 (tu = thiourea)

A study of the electronic, infrared, Raman and pre-resonace Raman spectra of the solid complex tris(8-hydroxyquinolinato)vanadium(III) was performed. The excitation profiles of the vibrational modes that show preresonance on excitation with laser lines within the electronic bands in the visible region are reported and, on this basis and molecular orbital calculations, several vibrational and electronic absorption bands were assigned.

Vibrational and electronic properties of tris(8-hydroxyquinolinato)vanadium (III)

The infrared and laser-Raman spectra of crystalline Pb2V2O7 are reported and discussed with the aid of a “Site Symmetry”-analysis.

Das Schwingungsspektrum von Pb2V2O7

Perbromylfluorid, Br03F, wurde vor kurzem erstmalig dargestellt1 und eine darauffolgende schwingungsspektroskopische Untersuchung zeigte, daß dieses Molekül genauso wie C103F Csv-Symmetrie besitzt 2. Da wir vor einiger Zeit die Schwingungseigenschaften des Perbromat-Ions eingehend untersudit haben3, erschien es interessant, auch bei dem verwandten Br03F eine ähnliche Untersudiung durchzuführen. Die Berechnung der Kraftkonstanten erfolgte, wie iiblidi, durch Lösung der Säkulargleichung:

Notizen: Schwingungseigenschaften von Perbromylfluorid / Vibrational Properties of Perbromyl Fluoride

Abstract The principal force constants for the title anions have been calculated using the GVFF. Mean amplitudes of vibration, at different temperatures are also estimated. The results are briefly discussed and some comparisons with related species are made

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Enrique J. Baran

Papers

Synthesis, Characterization, and Crystal Structure of [ReO(Me4tu)4](PF6)3 (tu = thiourea)

Vibrational and electronic properties of tris(8-hydroxyquinolinato)vanadium (III)

Das Schwingungsspektrum von Pb2V2O7

Notizen: Schwingungseigenschaften von Perbromylfluorid / Vibrational Properties of Perbromyl Fluoride

Schwingungseigenschaften der XF63- Anione (mit X = AI, Ga, In, TI)