Identification and Characterization of D‐Succinylase,and a Proposed Enzymatic Method for D‐Amino Acid Synthesis

Chiral amino acids are important intermediates for the pharmaceutical industry. We have developed a novel one‐pot enzymatic method for D ‐amino acid synthesis by the dynamic kinetic resolution of N‐succinyl‐dl ‐amino acids using D ‐succinylase (DSA) and N‐succinylamino acid racemase (NSAR, EC 4.2.1.113). The DSA from Cupriavidus sp. P4‐10‐C, which hydrolyzes N‐succinyl‐D ‐amino acids enantioselectively to their corresponding D ‐amino acids, was identified for the first time by screening soil microorganisms. Subsequently, the DSA gene was cloned and overexpressed in Escherichia coli. DSA was shown to comprise two subunits with molecular masses of 26 kDa and 60 kDa. Additionally, the NSAR gene from Geobacillus stearothermphilus NCA1503, which racemizes N‐succinylamino acids, was also cloned and overexpressed in E. coli. The highly purified DSA and NSAR prepared from each recombinant E. coli were characterized and used for D ‐amino acid synthesis. A one‐pot enzymatic method converted 100 mM N‐succinyl‐dl ‐phenylalanine to D ‐phenylalanine in 91.1% conversion with 86.7% ee. This novel enzymatic method may be useful for the industrial production of many D ‐amino acids.

     

The Effect of Physical and Chemical Cues on Hepatocellular Function and Morphology

Physical topographical features and/or chemical stimuli to the extracellular matrix (ECM) provide essential cues that manipulate cell functions. From the physical point of view, contoured nanostructures are very important for cell behavior in general, and for cellular functions. From the chemical point of view, ECM proteins containing an RGD sequence are known to alter cell functions. In this study, the influence of integrated physical and chemical cues on a liver cell line (HepG2) was investigated. To mimic the physical cues provided by the ECM, amorphous TiO₂ nanogratings with specific dimensional and geometrical characteristics (nanogratings 90 nm wide and 150 nm apart) were fabricated. To mimic the chemical cues provided by the ECM, the TiO₂ inorganic film was modified by immobilization of the RGD motif. The hepatic cell line morphological and functional changes induced by simultaneously combining these diversified cues were investigated, including cellular alignment and the expression of different functional proteins. The combination of nanopatterns and surface modification with RGD induced cellular alignment and expression of functional proteins, indicating that physical and chemical cues are important factors for optimizing hepatocyte function.     

Complementation analysis reveals a potential role of human ARV1 in GPI anchor biosynthesis

ARV1 is involved in regulating lipid homeostasis but also in the biosynthesis of glycosylphosphatidylinositol (GPI) in Saccharomyces cerevisiae. Here, we examined whether human ARV1 can complement the role of yeast ARV1 in GPI biosynthesis. Overexpression of human ARV1 could rescue the phenotypes associated with GPI anchor synthesis defect in the yeast arv1Δ mutant. The results suggest that Arv1 function in GPI biosynthesis may be conserved in all eukaryotes, from yeast to humans. Copyright © 2015 John Wiley & Sons, Ltd.     

In Situ Observation of Wear Process Before and During Scuffing in Sliding Contact

In this study, a direct observation of a point contact area was conducted to understand the scuffing phenomenon. The contact area was produced between a rotating sapphire disc and a stationary steel ball and it was lubricated using n-hexadecane. The image detected by a colour digital CCD camera, load, and friction were synchronously recorded by a computer during the test. It was found that wear debris produced in the contact area played an important role in the wear process, which includes running-in and scuffing. In the test, debris particles accumulated in the inlet zone, and some particles entered the contact area to cause abrasive wear of the ball surface, even in the light-load stages. During the running-in process, the abrasive wear by debris particles changed the conformity between the sliding surfaces. In the high-load stage, just before the occurrence of scuffing, the whole contact area was flattened at once. When scuffing occurred, the contact area suddenly expanded. The conformity of the contact area was dramatically changed during its expansion. The flattening of the whole contact area and dramatic expansion with changing the conformity seemed to play important roles in scuffing.     

基于结构强震记录的结构时变模态参数识别

为研究结构在地震过程中动力特性变化和损伤过程，为结构地震损伤评估提供可靠依据，采用递归式在线系统辨识算法RARX模型，利用结构强震记录识别了结构时变模态参数。以一座6层钢筋混凝土框架结构为例，识别了其时变自振频率、阻尼比和等效刚度。结果发现：在小地震动作用下，结构自振频率随时间几乎不发生改变；在大地震动作用的整个时间过程中，结构自振频率随时间逐渐降低，降低到一定程度到达最低点后，频率开始回升，直至地震结束，但最后不能回升到初始值，说明经历大震发生损伤的结构在震后性能会有所恢复；结构等效刚度变化趋势和自振频率相同，但在大震中下降比频率下降大的多；结构阻尼比在经历大震发生损伤后增大。结果可供结构地震损伤预测及结构震后安全鉴定参考。     

THE SEPARATION OF NEPTUNIUM AND TECHNETIUM IN AN ADVANCED PUREX PROCESS

ABSTRACT

An advanced PUREX process has been developed which can reduce TRU waste volume and the environmental hazard risk due to long-lived nuclides. The separation of neptunium and technetium from plutonium and uranium solutions has been studied before the U/ Pu partitioning step in the PUREX process. The effectiveness of normal-butyraldehyde as a reductant of Np( VI) to Np( V) and of high acid scrubbing of technetium was shown in a basic study and a chemical flowsheet study.     

Construction of an error map of rotary axes on a five-axis machining center by static R-test

This paper proposes an efficient and automated scheme to calibrate error motions of rotary axes on a five-axis machining center by using the R-test. During a five-axis measurement cycle, the R-test probing system measures the three-dimensional displacement of a sphere attached to the spindle in relative to the machine table. Location errors, defined in ISO 230-7, of rotary axes are the most fundamental error factors in the five-axis kinematics. A larger class of error motions can be modeled as geometric errors that vary depending on the angular position of a rotary axis. The objective of this paper is to present an algorithm to identify not only location errors, but also such position-dependent geometric errors, or “error map,” of rotary axes. Its experimental demonstration is presented.     

A Simplified Õ(nm) Time Edge-Splitting Algorithm in Undirected Graphs

Let G=(V,E) be a multigraph which has a designated vertex s ∈ V with an even degree. For two edges e ₁ = (s,u ₁ ) and e ₂ = (s,u ₂ ) , we say that a multigraph G' is obtained from G by splitting e ₁ and e ₂ at s if two edges e ₁ and e ₂ are replaced with a single edge (u ₁ ,u ₂ ) . It is known that all edges incident to s can be split without losing the edge-connectivity of G in V-s . This complete splitting plays an important role in solving many graph connectivity problems. The currently fastest algorithm for a complete splitting [14] runs in O(n(m+n log n) log n) time, where n = |V| and m is the number of pairs of vertices between which G has an edge. Their algorithm is first designed for Eulerian multigraphs, and then extended for general multigraphs. Although the part for Eulerian multigraphs is simple, the rest for general multigraphs is considerably complicated. This paper proposes a much simpler O(n(m+n log n) log n) time algorithm for finding a complete splitting. A new edge-splitting theorem derived from our algorithm is also presented. Received March 13, 1997; revised October 10, 1997.     

日本水坝的安全管理和地震安全评价

日本是一个地震多发的国家,而特殊的地形又决定了水坝在其经济社会发展中具有重要的地位,因此水坝的安全管理和地震安全评价就成为一个至关重要的方面.     

Evaluation of inelastic constitutive models under plasticity-creep interaction for steel at 600°C

Uniaxial tests to identify plasticity-creep interaction in steel at 600°C were carried out as the Benchmark Project by the Subcommittee on Inelastic Analysis and Life Prediction, JSMS. The purpose of this paper is to present recent experimental data and predictions of constitutive models obtained in the project. Ten types of constitutive models were utilized to compare analytical predictions to sixteen benchmark experiments which are grouped into four categories: (I) tensile and creep tests under monotonic loading, (II) mixed mode tests under plastic and creep loading, (III) ratcheting deformation tests under program loads, and (IV) cyclic deformation tests under the combination of different strain rates. The benchmark tests in Group IV are used to estimate the creep-fatigue life of steel; the results will be published in a separate paper.