Silicateins—A Novel Paradigm in Bioinorganic Chemistry: Enzymatic Synthesis of Inorganic Polymeric Silica

The inorganic matrix of the siliceous skeletal elements of sponges, that is, spicules, is formed of amorphous biosilica. Until a decade ago, it remained unclear how the hard biosilica monoliths of the spicules are formed in sponges that live in a silica‐poor (<50 μM ) aquatic environment. The following two discoveries caused a paradigm shift and allowed an elucidation of the processes underlying spicule formation; first the discovery that in the spicules only one major protein, silicatein, exists and second, that this protein displays a bio‐catalytical, enzymatic function. These findings caused a paradigm shift, since silicatein is the first enzyme that catalyzes the formation of an inorganic polymer from an inorganic monomeric substrate. In the present review the successive steps, following the synthesis of the silicatein product, biosilica, and resulting in the formation of the hard monolithic spicules is given. The new insight is assumed to open new horizons in the field of biotechnology and also in biomedicine.     

Reactivity of bis-vinylphosphates obtained from imide derivatives. Synthesis of 2,6-disubstituted 1,4-dihydropyridines

The Pd-catalyzed functionalization of lactam-derived vinyl phosphates has become an important tool in the last decade for the synthesis of nitrogen-containing heterocycles. By using this method, we were able to introduce alkenyl, aryl and heteroaryl groups on bis-vinylphosphate derivatives to provide efficient access to 2,6-disubstituted 1,4-dihydropyridines.     

Calcite and apatite coatings on titanium

A new method was used to deposit coatings containing calcium carbonate and calcium phosphates onto titanium. The presence of calcite and hydroxyapatite crystals in specimens as the major phases was proved by X-ray diffraction analysis, IR spectroscopy, elemental analysis, and electron microscopy. The inorganic coatings were revealed to have good adhesion to titanium and be stable in aqueous solutions.     

Biological and medical significance of calcium phosphates

The inorganic part of hard tissues (bones and teeth) of mammals consists of calcium phosphate, mainly of apatitic structure. Similarly, most undesired calcifications (i.e. those appearing as a result of various diseases) of mammals also contain calcium phosphate. For example, atherosclerosis results in blood-vessel blockage caused by a solid composite of cholesterol with calcium phosphate. Dental caries result in a replacement of less soluble and hard apatite by more soluble and softer calcium hydrogenphosphates. Osteoporosis is a demineralization of bone. Therefore, from a chemical point of view, processes of normal (bone and teeth formation and growth) and pathological (atherosclerosis and dental calculus) calcifications are just an in vivo crystallization of calcium phosphate. Similarly, dental caries and osteoporosis can be considered to be in vivo dissolution of calcium phosphates. On the other hand, because of the chemical similarity with biological calcified tissues, all calcium phosphates are remarkably biocompatible. This property is widely used in medicine for biomaterials that are either entirely made of or coated with calcium phosphate. For example, self-setting bone cements made of calcium phosphates are helpful in bone repair and titanium substitutes covered with a surface layer of calcium phosphates are used for hip-joint endoprostheses and tooth substitutes, to facilitate the growth of bone and thereby raise the mechanical stability. Calcium phosphates have a great biological and medical significance and in this review we give an overview of the current knowledge in this subject.     

Thermal Analysis of Ba(II)–Sr(II) Cyclo-Tetraphosphates(V)

The synthesis of new inorganic pigments has been investigated with the goal of preparing heat stable and anticorrosive pigments. The synthesis is based on a thermal procedure making use of the reversible transformation of cyclo-tetraphosphates(V) to higher linear phosphates(V). New binary condensed phosphates were synthesized based on the results of thermal analysis. These compounds represent new environmentally-friendly special pigments. This revised version was published online in August 2006 with corrections to the Cover Date.     

TiO2 synthesis inspired by biomineralization: control of morphology, crystal phase, and light-use efficiency in a single process

Hydroxyapatite is mineralized along the long axis of collagen fiber during osteogenesis. Mimicking such biomineralization has great potential to control inorganic structures and is fast becoming an important next-generation inorganic synthesis method. Inorganic matter synthesized by biomineralization can have beautiful and functional structures that cannot be created artificially. In this study, we applied biomineralization to the synthesis of the only photocatalyst in practical use today, titanium dioxide (TiO(2)). The photocatalytic activity of TiO(2) mainly relates to three properties: morphology, crystal phase, and light-use efficiency. To optimize TiO(2) morphology, we used a simple sequential peptide as an organic template. TiO(2) mineralized by a β-sheet peptide nanofiber template forms fiber-like shapes that are not observed for mineralization by peptides in the shape of random coils. To optimize TiO(2) crystal phase, we mineralized TiO(2) with the template at 400 °C to transform it into the rutile phase and at 700 °C to transform it into a mixed phase of anatase and rutile. To optimize light-use efficiency, we introduced nitrogen atoms of the peptide into the TiO(2) structure as doped elemental material during sintering. Thus, this biomineralization method enables control of inorganic morphology, crystal phase, and light-use efficiency in a single process.     

Selective determination of orthophosphate and total inorganic phosphates in detergents by flow injection photometric method

A flow injection photometric system was developed for the determination of orthophosphate and total inorganic phosphates in detergents. While orthophosphate was directly determined in the presence of other phosphates by utilizing the kinetic discrimination of flow injection analysis, total inorganic phosphates was analyzed after on-line hydrolysis of polyphosphates in 2.5 mol l(-1) sulfuric acid for 50 s under 145 degrees C. Sodium dodecyl sulfate (SDS) was added to mask the interference of non-ionic surfactants. The detection limits and the sampling rates were 2.5 mg l(-1) P(2)O(5) and 40 h(-1) for total inorganic phosphates, and 1.0 mg l(-1) P(2)O(5) and 80 h(-1) for orthophosphate determination. The proposed method was applied to analyze orthophosphate and total inorganic phosphates in washing powders. The experimental results are in good agreement with those obtained by the Chinese national standard methods.     

Layered Group(IV) Metal Phosphates as Catalysts for MTBE Synthesis

Layered group(IV) metal phosphates and their phenylsulfonic acid derivatives were used as catalysts for the synthesis of methyl tert-butyl ether (MTBE) from methanol and isobutene. Because zirconium and titanium phosphates have only moderate acidic strength, relatively high temperatures are required to activate their Brønsted acidic sites. The optimal activity was obtained at ca. 443 K. Their phenylsulfonic acid derivatives, however, demonstrated higher acidic strength by giving much higher activity toward MTBE formation at relatively low temperaures. The catalysts were characterized in terms of their structure, thermal stability, surface area and acidic strength.     

Mcrowave-Assisted Rapid Solid-State Chemistry of Phosphate Materials

Abstract

The present work reports some applications of microwave processing in the synthesis of inorganic condensed phosphates.     

Enantioselective Synthesis of L- and D-Carboranylalanine

The enantioselective synthesis of L- and D-carboranylalanine is reported. Imides 13 and 14 are treated with titanium tetrachloride, DIEA, and NBS to introduce a bromo functionality in 98:2 ratio at the alpha-center. Azide displacement with TMGA, displacement of the oxazolidinone template with titanium tetrabenzyloxide, and subsequent hydrogenolysis permits L- or D-carboranylalanine to be isolated in high stereoselectivity and 35-40% yields overall.     

One-dimensional inorganic nanostructures: synthesis, field-emission and photodetection

One-dimensional inorganic nanostructures have drawn prime attention due to their potential for understanding fundamental physical concepts and constructing nanoscale electronic and optoelectronic devices. This critical review mainly focuses on our recent research progresses in 1D inorganic nanostructures, including their rational synthesis and potential applications, with an emphasis on field-emitter and photodetector applications. Firstly, we will discuss the rational design of synthetic strategies and the synthesis of 1D nanostructures via a vapour phase approach. Secondly, we will present our recent progresses with respect to several kinds of important inorganic nanostructures and their field-emission and photoconductivity characteristics. Finally, we conclude this review with some perspectives/outlook and future research in these fields (212 references).     

Polymerization Behaviour of Organically Modified Titanium Alkoxides in Solution

Modified titanium alkoxides with polymerizable organic ligands allow the synthesis of copolymers consisting of hybrid organic/inorganic networks. In this work titanium based-precursors were characterized in relation to the polymerization behaviour of the organic matrix. Alkoxide sols were prepared by reaction of methacrylic acid, itaconic acid anhydride, isoeugenol, p-vinylbezoic acid, p-vinylphenylacetic acid, and acetoxyacetomethacrylate with titanium tetraisopropoxide and titanium tetraethoxide. Polymerization reactions were carried out in solution using UV-irradiation and a redox-system of dibenzoylperoxide/N, N-dimethyl-p-toluidine as radical initiators. Especially for chemical activation some complexes showed high reactivity similar to silica-based methacrylates. The systems investigated are capable of acting as adhesive promoters between metal and polymer in dental applications.     

锌配位聚合物的制备与表征——推荐一个无机化学综合实验

介绍了一个无机化学综合型新实验——锌配位聚合物的制备与表征。通过有机配体的合成、金属有机框架材料的制备及其相关结构和性能表征,使学生了解金属有机框架这一科研前沿领域,在引导学生进行实验操作、解释及归纳的过程中,提升学生的综合及创新能力。本实验综合了无机、有机和分析化学知识点的学习与实验操作能力的培养,建议纳入高年级综合型化学实验课。     

Coated gas bubbles for the continuous synthesis of hollow inorganic particles

We present a microfluidic approach for the controlled encapsulation of individual gas bubbles in micrometer-diameter aqueous droplets with high gas volume fractions and demonstrate this approach to making a liquid shell, which serves as a template for the synthesis of hollow inorganic particles. In particular, we find that an increase in the viscosity of the aqueous phase facilitates the encapsulation of individual gas bubbles in an aqueous droplet and allows control of the thickness of a thin aqueous shell. Furthermore, because such droplets contain a finite amount of water, uncontrolled hydrolysis reactions between reactive inorganic precursors and bulk water can be avoided. We demonstrate this approach by introducing reactive inorganic precursors, such as silane and titanium butoxide, for sol-gel reactions downstream from the formation of the bubble in a droplet and consequently fabricate hollow particles of silica or titania in one continuous flow process. These approaches provide a route to controlling double-emulsion-type gas-liquid microstructures and offer a new fabrication method for thin-shell-covered microbubbles and hollow microparticles.     

多酸配位聚合物的制备与表征——推荐一个综合化学实验

介绍了一个综合化学新实验--多酸配位聚合物的制备与表征。通过杂多酸和有机配体的合成、多酸配位聚合物的制备和性能表征,使学生了解多酸配位聚合物这一无机合成化学前沿领域,在引导学生进行材料合成及性质表征的过程中,提高学生对已学知识融会贯通的能力,提升学生学习化学的兴趣。本实验综合了无机、有机化学知识点以及实验、仪器操作和数据分析能力的培养,可纳入高年级综合化学实验。     

成对电合成技术

本 文主要 介绍作者 在成对电 合成技 术的研究 成果,结 合研究实 例,介绍 了工艺条 件如电极材 料、电流 密度及电 解温度 等的优化 选择以 为同行参 考;并 将成 对电 合成 技术 归纳 分类, 开拓成对有 机电合 成思路,促 进有机 电合成技 术的发 展．     

Analysis of sugar phosphates in plants by ion chromatography on a titanium dioxide column with pulsed amperometric detection

This paper describes the development of a practical method for the analysis of sugar phosphates from the model higher plant Arabidopsis thaliana by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The extraction method of sugar phosphates from higher plants was first optimized for HPAEC-PAD analysis. In order to improve the resolution in HPAEC-PAD, a column packed with titanium dioxide resin was used. The titanium dioxide column was used as a trap-column for sugar phosphates and nucleotides, for the removal of sample matrices. Sample pretreatment was achieved in-line and automatically using a six-port valve placed after the injection valve.     

Template engineering through epitope recognition: a modular, biomimetic strategy for inorganic nanomaterial synthesis

Natural systems often utilize a single protein to perform multiple functions. Control over functional specificity is achieved through interactions with other proteins at well-defined epitope binding sites to form a variety of functional coassemblies. Inspired by the biological use of epitope recognition to perform diverse yet specific functions, we present a Template Engineering Through Epitope Recognition (TEThER) strategy that takes advantage of noncovalent, molecular recognition to achieve functional versatility from a single protein template. Engineered TEThER peptides span the biologic-inorganic interface and serve as molecular bridges between epitope binding sites on protein templates and selected inorganic materials in a localized, specific, and versatile manner. TEThER peptides are bifunctional sequences designed to noncovalently bind to the protein scaffold and to serve as nucleation sites for inorganic materials. Specifically, we functionalized identical clathrin protein cages through coassembly with designer TEThER peptides to achieve three diverse functions: the bioenabled synthesis of anatase titanium dioxide, cobalt oxide, and gold nanoparticles in aqueous solvents at room temperature and ambient pressure. Compared with previous demonstrations of site-specific inorganic biotemplating, the TEThER strategy relies solely on defined, noncovalent interactions without requiring any genetic or chemical modifications to the biomacromolecular template. Therefore, this general strategy represents a mix-and-match, biomimetic approach that can be broadly applied to other protein templates to achieve versatile and site-specific heteroassemblies of nanoscale biologic-inorganic complexes.     

Open-Framework Inorganic Materials

Aluminosilicate zeolites such as UTD-1 (structure shown) belong to a family of nanoporous inorganic materials that find utility in catalysis, separation, and ion exchange. During the last decade, the rate of discovery of new open-framework materials based, for example, on phosphates, sulfides, halides, nitrides, and coordination compounds has increased dramatically. The synthesis, structures, and properties of this remarkable class of materials are reviewed.