Substituting Both the N-Terminal and “Cord” Regions of a Xylanase from <Emphasis Type="Italic">Aspergillus oryzae</Emphasis> to Improve Its Temperature Characteristics

To improve the temperature characteristics of AoXyn11A, a mesophilic glycoside hydrolase family (GHF) 11 xylanase from Aspergillus oryzae CICC40186, its N-terminal and “cord” regions were selected to be substituted by means of the computer-aided analysis and calculation. In brief, one mutant, named ATX11A⁴¹, possessing the lowest root-mean-square deviation (RMSD) value was designed based on the molecular dynamics (MD) simulation by substituting the N-terminal 41 amino acids of AoXyn11A with the corresponding 42 ones of pXYL11, a thermophilic GHF11 xylanase from Thermobifida fusca. On the basis of the primary structure alignment of pXYL11 with ATX11A⁴¹ (or AoXyn11A), another mutant, named ATX11A^41/cord, was designed by substituting the cord region (⁹³GTYNPGSGG¹⁰¹) of ATX11A⁴¹ with the corresponding one (⁹³GTYRPTG⁹⁹) of pXYL11. Both mutant-encoding genes, ATx11A⁴¹ and ATx11A^41/cord, were constructed as designed theoretically by a megaprimer PCR technique and were expressed in Pichia pastoris GS115. The specific activities of recombinant (re) AoXyn11A, ATX11A⁴¹, and ATX11A^41/cord were 2916.7, 2667.6, and 2457.0 U/mg, respectively. The analysis of temperature characteristics displayed that the temperature optimum (T_opt) of reATX11A⁴¹ or reATX11A^41/cord was 65 °C, which was 15 °C higher than that of reAoXyn11A. The thermal inactivation half-life (t_1/2) values of reATX11A⁴¹ and reATX11A^41/cord at 60 °C were 55 and 83 min, respectively, whereas that of reAoXyn11A was only 18 min at 50 °C. The melting temperature (T_m) values of reAoXyn11A, reATX11A⁴¹, and reATX11A^41/cord were 54.2, 66.7, and 71.9 °C, respectively. In conclusion, the above findings indicated that the substitution of both the N-terminal and cord regions of a mesophilic AoXyn11A greatly contributed to its improved temperature characteristics.     

Determination of Dynamic History of Impact Loadings Using Polyvinylidene Fluoride (PVDF) Films

We propose a simple experimental method for determining dynamic history of impact loadings on flexible structures using polyvinylidene fluoride (PVDF) films. The dynamic impact history obtained from the proposed method is verified with impact hammers with inbuilt force sensors. The performance of the proposed method is demonstrated with FEM computations based on the acquired impact history to predict the transient responses of a flexible cantilever beam.     

Urine analysis in microfluidic devices

Microfluidics has attracted considerable attention since its early development in the 1980s and has experienced rapid growth in the past three decades due to advantages associated with miniaturization, integration and automation. Urine analysis is a common, fast and inexpensive clinical diagnostic tool in health care. In this article, we will be reviewing recent works starting from 2005 to the present for urine analysis using microfluidic devices or systems and to provide in-depth commentary about these techniques. Moreover, commercial strips that are often treated as chips and their readers for urine analysis will also be briefly discussed. We start with an introduction to the physiological significance of various components or measurement standards in urine analysis, followed by a brief introduction to enabling microfluidic technologies. Then, microfluidic devices or systems for sample pretreatments and for sensing urinary macromolecules, micromolecules, as well as multiplexed analysis are reviewed, in this sequence. Moreover, a microfluidic chip for urinary proteome profiling is also discussed, followed by a section discussing commercial products. Finally, the authors' perspectives on microfluidic-based urine analysis are provided. These advancements in microfluidic techniques for urine analysis may improve current routine clinical practices, particularly for point-of-care (POC) applications.     

Organosilanes in Free Radical Cyclizations Reactions (1)

A study on the intramolecular free radical cyclization reactions mediated by diphenylsilane is described.     

Use of two‐step split‐operator approach for 2D shallow water flow computation

The objective of this paper is to present a methodology of using a two‐step split‐operator approach for solving the shallow water flow equations in terms of an orthogonal curvilinear co‐ordinate system. This approach is in fact one kind of the so‐called fractional step method that has been popularly used for computations of dynamic flow. By following that the momentum equations are decomposed into two portions, the computation procedure involves two steps. The first step (dispersion step) is to compute the provisional velocity in the momentum equation without the pressure gradient. The second step (propagation step) is to correct the provisional velocity by considering a divergence‐free velocity field, including the effect of the pressure gradient. This newly proposed method, other than the conventional split‐operator methods, such as the projection method, considers the effects of pressure gradient and bed friction in the second step. The advantage of this treatment is that it increases flexibility, efficiency and applicability of numerical simulation for various hydraulic problems. Four cases, including back‐water flow, reverse flow, circular basin flow and unsteady flow, have been demonstrated to show the accuracy and practical application of the method. Copyright © 1999 John Wiley & Sons, Ltd.     

Syntheses and Characterization of Organoimido Complexes of Niobium(V); Potential CVD Precursors

New niobium imido complexes (RN)Nb(NEt₂)₃ (R = Prⁿ, Prⁱ and Bu^t), potential precursors to grow niobium containing thin films by chemical vapor deposition (CVD), were prepared by reacting the corresponding (RN)NbCl₃py₂ complexes (R = Prⁿ, Prⁱ and Bu^t; py = pyridine) with LiNEt₂ in hydrocarbon solvents. The structures of (RN)NbCl₃py₂ (R = Prⁱ and Bu^t), determined by X-ray crystallography, are mononuclear with distorted octahedral geometries, For each complex, three chloride ligands are cis to the imido ligand and occupy meridional positions. One of two py ligands is cis to and the other is trans to the imido ligand. For (PrⁱN)NbCl₃py₂, the Nb=NPrⁱ bond distance (Å) is 1.733(3) and the ∠Nb=N-Prⁱ angle (°) is 178.0(3). Crystal data: monoclinic, space group P2₁/n, a = 8.805(2), b = 14.930(4), c = 13, 407(3) Å, β = 93.37(2)°, V = 1759.5(7) ų, Z = 4, D_c = 1.565 g cm³. For (Bu^tN)NbCl₃py₂, the Nb=NBu^t bond distance (Å) is 1.734(4) and the ∠Nb=N-Bu^l angle (°) is 174.8(4). Crystal data: monoclinic, space group P2₁/c, a = 9.609(1), b = 13.591(6), c = 14.615(2) Å, β = 90.05(1)°, V = 1908.5(9) ų, Z = 4, D_c = 1.492 g cm^?3.     

Palladium-Catalyzed Direct C-3 Alkynylation of Indolizines with (2,2-Dibromovinyl)arenes

The direct C-3 alkynylation of indolizines with (2,2-dibromovinyl)arenes in the presence of palladium catalyst has been developed. This novel protocol showed wide substrate scope with respect to both indolizines and dibromoalkenes. Also this method was characterized with high efficiency and good functional group tolerance.