Crossing the Border: From Keto- to Imine Reduction in Short-Chain Dehydrogenases/Reductases

The family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDRs) comprises numerous biocatalysts capable of C=O or C=C reduction. The highly homologous noroxomaritidine reductase (NR) from Narcissus sp. aff. pseudonarcissus and Zt_SDR from Zephyranthes treatiae, however, are SDRs with an extended imine substrate scope. Comparison with a similar SDR from Asparagus officinalis (Ao_SDR) exhibiting keto-reducing activity, yet negligible imine-reducing capability, and mining the Short-Chain Dehydrogenase/Reductase Engineering Database indicated that NR and Zt_SDR possess a unique active-site composition among SDRs. Adapting the active site of Ao_SDR accordingly improved its imine-reducing capability. By applying the same strategy, an unrelated SDR from Methylobacterium sp. 77 (M77_SDR) with distinct keto-reducing activity was engineered into a promiscuous enzyme with imine-reducing activity, thereby confirming that the ability to reduce imines can be rationally introduced into members of the “classical” SDR enzyme family. Thus, members of the SDR family could be a promising starting point for protein approaches to generate new imine-reducing enzymes.     

Grid Computing: A Critical Discussion on Business Applicability

In the last decade, the Grid emerged from computing-intensive application domains. It has become very difficult to distinguish between "real" Grids, Web services, and simply a distributed computing environment. A critical discussion of Grid technologies points out the pros and cons of applying current Grid technologies in a business or enterprise environment.     

Excessive degradation of intracellular protein in macrophages prevents presentation in the context of major histocompatibility complex class II molecules

The endogenous major histocompatibility complex (MHC) class II presentation pathway allows biosynthesized, intracellular antigens access for presentation to MHC class II-restricted T cells. This pathway has been well documented in B cells and fibroblasts, but may not be universally available in all antigen-presenting cell types. This study compares the ability of different antigen-presenting cells, expressing endogenous C5 protein (fifth component of mouse complement) as a result of transfection, to present their biosynthesized C5 to MHC class II-restricted T cells. B cells and fibroblasts expressing C5 were able to present several epitopes of this protein with MHC class II molecules, whereas macrophages were unable to do so, but readily presented C5 from an extracellular source. However, macrophage presentation of endogenous C5 could be achieved when they were treated with low doses of the lysosomotropic agent ammonium chloride. In the presence of an inhibitor of autophagy, presentation of endogenous C5 was abrogated, indicating that biosynthesized C5 is shuttled into lysosomal compartments for degradation before making contact with MHC class II molecules. Taken together, this suggests that proteolytic activity in lysosomes of macrophages may be excessive, compared with fibroblasts and B cells, and destroys epitopes of the C5 protein before they can gain access to MHC class II molecules. Thus, there are inherent differences in presentation pathways between antigen-presenting cell types; this could reflect their specialized functions within the immune system with macrophages focussing preferentially on internalization, degradation, and presentation of extracellular material.     

Microstructure and mechanical properties of the superalloy ATI Allvac 718Plus™

ATI Allvac^® 718Plus™ is a novel nickel-based superalloy, which was designed for heavy-duty applications in aerospace turbines. In the present study the high-resolution investigation techniques, atom probe tomography, electron microscopy and in situ high-temperature small-angle neutron scattering were used for a comprehensive microstructural characterization. The alloy contains nanometer-sized spherical γ′ phase precipitates (Ni₃(Al,Ti)) and plate-shaped δ phase precipitates (Ni₃Nb) of micrometer size. The precipitation kinetics of the γ′ phase can be described by a classical model for coarsening. The precipitation strongly influences the mechanical properties and is of high scientific and technological interest.     

温室气体排放与钢铁工业--聚焦COREX(R)技术

采取措施减少温室气体(CO2)排放,对于工业领域、特别是钢铁工业这一最大的能源用户来说正变得日益重要.归纳了评估CO2排放率所必需的因数,比较了不同钢铁生产工艺的CO2排放指标.计算表明,基于COREX(R)工艺的生产路线比传统工艺具有更加满意的结果.     

Photodoping and relaxation of persistent photoconductivity in YBa2Cu3Ox studied byin-situ transport measurements

We report on in-situ resistivity and Hall-effect studies of partially oxygen-depleted YBa₂Cu₃O_x thin films during white light illumination. The measurements were performed at various temperatures between the superconducting transition and room temperature. At all temperatures the resistivity and the Hall coefficient decreased as a function of the illumination time. The Hall number p_H and the Hall mobility _H, calculated within a simple one-band model, showed an increase of p_H during the illumination without a saturation. At low temperatures, _H behaved similarly to p_H. At 200 K, however, _H became constant after several hours of illumination, while at 260 K and 290 K, we observed a short increase of _H followed by a long-term decrease. From the different time dependences of _H and p_H, we conclude that two mechanisms contribute to the photodoping effect. Additionally, we observed that after termination of the illumination at 290 K the photodoped values of p_H and _H relaxed with substantially different time constants.     

Photoinduced Changes of the Electrical Anisotropy in Oxygen-Depleted YBa2Cu3O x

Long-term photoexcitation experiments were performed on Y Ba ₂ Cu ₃ O _x (x6.6) thin films, prepared by pulsed-laser deposition on tilted SrTiO₃ substrates. From the anisotropic resistance of the samples, the in-plane and the out-of-plane resistivities were calculated. Photoexcitation was carried out with a He-Ne laser at various temperatures from 70 K to 305 K. We observed that the electrical anisotropy _c/_ab increased at low temperatures, but decreased at high temperatures. This unusual behavior resembles that of the in-plane Hall mobility in a previous study. Possible interpretations according to the models for the photodoping effect in YBa ₂ Cu ₃ O _x are discussed.     

Defining the grid: a snapshot on the current view

The term “Grid” was introduced in early 1998 with the launch of the book “The Grid. Blueprint for a new computing infrastructure”. Since that time many technological changes have occurred in both hardware and software. One of the most important ones seems to be the wide acceptance of Web services. Although the basic Grid idea has not changed much in the last decade, many people have different ideas about what a Grid really is. In the following article we report on a survey where we invited many people in the field of Grid computing to give us their current understanding.

A new epoxy resin/hardener system with variable processing and end properties

A combination of a standard bisphenol-A liquid epoxy resin and a zinc–pyrrolidone–carboxylate complex with a long chain poly(oxypropylene diamine) (Jeffamine D 2000) has been found to give variable processing and end properties over a very wide range, e.g., pot life < 1–70 days, Martens Heat-Distortion Temperature < 25–124°C and elongation at break 35–1%. The variation in properties is achieved simply by changing the epoxy/complex ratio. The very reactive high elongation formulation is thought to be the result of a very fast zinc catalyzed amine/epoxy polyaddition reaction and the low reactivity rigid formulation to be due to zinc-complex initiated anionic homopolymerization of the epoxy resin. The borderline concentrations are approximately 200 and 10 phr of the complex, respectively.