Engineered superoxide dismutase monomers for superoxide biosensor applications

Because of its high reaction rate and specificity, the enzyme superoxide dismutase (SOD) offers great potential for the sensitive quantification of superoxide radicals in electrochemical biosensors. In this work, monomeric mutants of human Cu,Zn-SOD were engineered to contain one or two additional cysteine residues, which could be used to bind the protein to gold surfaces, thus making the use of promotor molecules unnecessary. Six mutants were successfully designed, expressed, and purified. All mutants bound directly to unmodified gold surfaces via the sulfur of the cysteine residues and showed a quasi-reversible, direct electron transfer to the electrode. Thermodynamic and kinetic parameters of the electron transfer were characterized and showed only slight variations between the individual mutants. For one of the mutants, the interaction with the superoxide radical was studied in more detail. For both partial reactions of the dismutation, an interaction between protein and radical could be shown. In an amperometric biosensorial approach, the SOD-mutant electrode was successfully applied for the detection of superoxide radicals. In the oxidation region, the electrode surpassed the sensitivity of the commonly used cytochrome c electrodes by approximately 1 order of magnitude while not being limited by interferences, but the electrode did not fully reach the sensitivity of dimeric Cu,Zn-SOD immobilized on MPA-modified gold.     

Particle Adhesion to Drops

The adhesion of spheroidal particles to spherical drops is calculated and discussed in terms of an equilibrium-penetration index. The present study emphasizes the case of particles that are sufficiently large to affect the drop volume upon penetration. It is shown that the more elongated the particles, the steeper the dependence of the penetration index on the contact angle. The effect of line tension on nanoscale particles is considered. Positive line tensions increase the steepness of the dependence of penetration index on contact angle whereas negative line tensions decrease this dependence. In addition, the energy barrier caused by positive line tensions is presented and discussed.     

Development of a Hypersensitive Periodate‐Cleavable Amino Acid that is Methionine‐ and Disulfide‐Compatible and its Application in MHC Exchange Reagents for T Cell Characterisation

Incorporation of cleavable linkers into peptides and proteins is of particular value in the study of biological processes. Here we describe the synthesis of a cleavable linker that is hypersensitive to oxidative cleavage as the result of the periodate reactivity of a vicinal amino alcohol moiety. Two strategies directed towards the synthesis of a building block suitable for solid‐phase peptide synthesis were developed: a chemoenzymatic route, involving L ‐threonine aldolase, and an enantioselective chemical route; these led to α,γ‐diamino‐β‐hydroxybutanoic acids in diastereoisomerically mixed and enantiopure forms, respectively. Incorporation of the 1,2‐amino alcohol linker into the backbone of a peptide generated a conditional peptide that was rapidly cleaved at very low concentrations of sodium periodate. This cleavable peptide ligand was applied in the generation of MHC exchange reagents for the detection of antigen‐specific T cells in peripheral blood cells. The extremely low concentration of periodate required to trigger MHC peptide exchange allowed the co‐oxidation of methionine and disulfide residues to be avoided. Conditional MHC reagents hypersensitive to periodate can now be applied without limitations when UV irradiation is undesired or less practical.     

Produktivitätssteigerung durch integrierte Produktionstechnik und Verfahrens-Know-how

Increasing Productivity through Integrated Production Engineering and Processing Expertise The future of production engineering is interdisciplinary. Between product innovation and product marketing there lies a design process which has to be optimised and which is interdisciplinary in character. The design process has to satisfy the demands of global markets on chemical products, which lead, for example, to shorter and shorter product life cycles, and to demands for low production costs, high and consistent product quality, and faster market launches.     

ELECTROPORATION: BIO-ELECTROCHEMICAL MASS TRANSFER AT THE NANO SCALE

This article provides a brief review of the field of electroporation and introduces a new microdevice that facilitates studies to test theories, gain understanding, and control this important biomedical technology. Electroporation, a bio-electrochemical process whose fundamentals are not yet understood, is a means of permeating the cell membrane by applying a voltage across the cell and forming nano-scale pores in the membrane. It has become an important field in biotechnology and medicine for the controlled introduction of macromolecules, such as gene constructs and drugs, into various cells. It is viewed as an engineering alternative to biological techniques for the genetic engineering of cells. To study and control electroporation, we have created a low-cost microelectroporation chip that incorporates a live biological cell with an electric circuit. The device revealed an important behavior of cells in electrical fields. They produce measurable electrical information about the electroporation state of the cell that may enable precise control of the process. The device can be used to facilitate fundamental studies of electroporation and can become useful in providing precise control over biotechnological processes.     

新型电磁式电压互感器

介绍了一种新型电磁式电压互感器,阐述了电磁式和电容式电压互感器技术特性的区别.     

Photochemistry of Nanostructured Materials for Energy Applications

A number of major disciplines have separately developed as distinctfields of energy research utilizing nanostructure materials: i.Heterogeneous photocatalysis; ii. Photoelectrochemistry—includingelectrochemical photovoltaic cells; iii. Photochemistry in zeolites andintercalated materials; iv. Photochemistry of thin films andmembranes—including self assembled structures; and v. Supramolecularphotochemistry. Photophysical properties of small particles, in the angstromto nanosized regime—depending on specific material, resulting in bandgap broadening as compared to bulk properties, and corresponding phenomenawith organic dyes as a function of aggregate size having relevance to energyrelated applications are discussed, as are dielectric confinement effectscontrolling the geometric distribution of light absorption within aparticle, aggregate or adsorbed molecular deposit. Synergism among fieldshas emerged, as for example with transition metal oxide photocatalysts andphotoelectrodes, combined with supramolecular spectral sensitizingtransition metal ligand complexes used to harvest light and vectoriallytransfer photo-generated electrons and holes along selected energeticpathways. Two systems have already demonstrated potential for significantlyreducing reliance on fossil fuels and concomitant environmental stress.These are: i. Pollution remediation with wide band gap semiconductingparticulate and nanoporous photocatalysts; and ii. Electrochemicalphotovoltaic cells utilizing nanoporous semiconducting electrodes fabricatedby lightly sintering nanosized TiOÄ2É particulates, followed byspectral sensitization with tri-nuclear ruthenium ligand dyes.Heterojunction contacts between inorganic photoconducting particulates,termed photocatalytic diodes, and three phase systems, termed photocatalytictransistors, have been demonstrated to increase photocatalytic conversionefficiency in catalytic processes and to increase light sensitivity ofanalogous silver halide photographic systems. Research being carried out inlaboratories throughout the world, aimed at improving the efficiency andunderstanding of the multi-disciplinary processes involved are described.Suggested areas of investigation for achievement of short (5 years) andlong term (5–20 years) goals are reviewed.     

On O16–O18 Isotope Effects in Manganese Perovskites

Large isotope effects which have been found by others [1,2] in some colossal magneto resistance manganite perovskites, AMnO₃, are evidence of unusually strong interactions between the lattice and magnetism. We offer a model which is based upon the approximate degeneracy of two Mn⁺³ states: one with high spin S = 2, and the other with low spin S = 1. These states have different radii and different electron form factors. They thus have different force constants governing the interaction with neighboring oxygen ions which provide the sought for link between magnetism and oxygen mass. The experiments can be understood with the reasonable assumption that the LS has greater force constants than HS. The dependence of changes in T_c with isotopic substitution as a function of the A-ion radius, the metal insulator transitions and the Mossbauer effect changes, are discussed in terms of this model.     

三电平和两电平逆变器效率分析与比较

在分析、计算二极管箝位型三电平逆变器和两电平逆变器的通态损耗、开关损耗以及输出滤波电感损耗的基础上,对这两种逆变器的损耗、效率进行了比较。     

新型高压油浸组合互感器的研制与运用

文章阐述了几种组合互感器的特点,介绍了组合互感器的误差特性。较详细地介绍了由1台倒立式电流互感器和1台具有开放式铁心的电磁式电压互感器组合而成的新型高压组合互感器（VAU型）的基本特征及主要性能,测量结果表明,VAU型组合互感器误差特性好,瓷套管上电场强度沿高度分布均匀,体积小,占空间少,制造成本低,而且还可防铁磁谐振,现在的最高设备电压已达550kV。