Development of Decibel Stepped Attenuator for Automated Sound Level Meter Calibration

MAPAN - Parameter testing in the sound level meter calibration, such as frequency weighting and linearity, needs precise adjustment of sound level in the decibel (dB) unit. In the...     

Acceptor recognition of kojibiose phosphorylase from Thermoanaerobacter brockii: syntheses of glycosyl glycerol and myo-inositol

The glucosyl transfer reaction of kojibiose phosphorylase (KP; EC 2.4.1.230) was examined using glycerol or myo-inositol as an acceptor. In the case of glycerol, KP produced two main transfer products: saccharides A and B. The structure of saccharide A was O-alpha-D-glucopyranosyl-(1-->1)-glycerol and that of saccharide B was O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->1)-glycerol. These results show that KP transferred a glucose residue to the hydroxyl group at position 1 of glycerol. On the other hand, when myo-inositol was used as an acceptor, KP produced four transfer products: saccharides 1-4. The structures of saccharides 1 and 2 were O-alpha-D-glucopyranosyl-(1-->1)- and O-alpha-D-glucopyranosyl-(1-->5)-myo-inositol, respectively; those of saccharides 3 and 4 were O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->1)- and O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->5)-myo-inositol, respectively. KP transferred a glucose residue to the hydroxyl group at position 1 or 5 of myo-inositol. On the basis of the structures of their glucosyl transfer products, glycerol and myo-inositol were found to have a common structure with three hydroxyl groups corresponding to the hydroxyl group of the glucose molecule at positions 2, 3 and 4. The conformation of these three hydroxyl groups in the structure is equatorial. This structure is the substrate recognition site of KP. It has been suggested that KP strictly recognizes the structures of glycerol and myo-inositol, and catalyzes the transfer reaction of a glucose residue to the hydroxyl group at position 1 in glycerol, and at position 1 or 5 in myo-inositol, corresponding to position 2 in glucose.     

农药上市公司上半年走势分析与未来展望

1 上半年农药上市公司业绩同比大幅下滑 受经济危机及天气干旱等不利因素影响.今年上半年农药行业整体处于外需疲软、收入下降的不景气状态.从近期已公布的部分农药上市公司上半年业绩来看,业绩同比大幅度下降,平均每股收益为0.25元,较2008年下滑67.60%.进入二季度以来,行业业绩平稳于低部,平均每股收益增加0.03元.业绩下滑使得上市公司在证券市场走势偏弱.进入二季度后,行业指数明显走弱.     

Acceptor specificity of trehalose phosphorylase from Thermoanaerobacter brockii: production of novel nonreducing trisaccharide, 6-O-alpha-D-galactopyranosyl trehalose

We investigated the acceptor specificity of a thermostable trehalose phosphorylase from Thermoanaerobacter brockii ATCC 35047 (TbTP) was examined using beta-D-glucose-1-phosphate (beta-G1P) as a glucosyl donor and oligosaccharides as the acceptor. Oligosaccharides with a reducing-end glucose residue as the C-6 substituent (e.g., isomaltose, gentiobiose, melibiose, isomaltotriose, and isopanose) were found to be successful acceptors. The transfer products of isomaltose, gentiobiose, and melibiose were isolated and characterized as 6-O-alpha-D-glucopyranosyl trehalose (alpha-GlcTre), 6-O-beta-D-glucopyranosyl trehalose (beta-GlcTre), and 6-O-alpha-D-galactopyranosyl trehalose (alpha-GalTre), respectively. To produce alpha-GalTre, a novel nonreducing trisaccharide, the reaction conditions of alpha-GalTre were examined using trehalose as a glucosyl donor. As a result, the yield of alpha-GalTre reached 40.5%.     

Hyper expression of kojibiose phosphorylase gene and trehalose phosphorylase gene from Thermoanaerobacter brockii ATCC35047 in Bacillus subtilis and selaginose synthesis utilizing two phosphorylases

The kojibiose phosphorylase (KP) gene and trehalose phosphorylase (TP) gene from Thermoanaerobacter brockii ATCC35047 were intracellularly hyper-expressed under the control of the Bacillus amyloliquefaciens alpha-amylase promoter in Bacillus subtilis. The production yields were estimated to be 2.1 g of KP and 4.9 g of TP per liter of medium. Selaginose, non-reducing trisaccharide, was synthesized from trehalose utilizing the recombinant KP and TP from B. subtilis. Selaginose was not hydrolyzed by salivary amylase, artificial gastric juice, pancreatic amylase, or small intestinal enzymes.     

固相萃取-荧光猝灭法测定氧氟沙星

在pH=7.7的Tris-HCl介质中,当加入氧氟沙星(OFLX)时,羟丙基-β-环糊精(HP-β-CD)与中性红(NR)所产生的荧光会被猝灭,对于浓度较低的实际样品采取了固相萃取前处理的方法,据此建立了固相萃取荧光猝灭法测定氧氟沙星的新方法.在优化的实验条件下,氧氟沙星工作曲线的线性范围为0.8～6.0 mg/L,回...     

关于6西格玛的实施战略的讨论(一)

本文对实施6西格玛所涉及的组织工程,选择项目计划和人员及改进方式等一应问题作了探讨.     

Thermodynamic and experimental approach of electrochemical reduction of CO2 in molten carbonates

This work is dedicated to the feasibility of CO₂ dissolution and transformation into CO by an electroreduction process. It is first based on a predictive thermodynamic study, through the establishment of potential-oxoacidity diagrams, mainly focused on competing reduction processes (CO₂/CO, CO₂/C, H₂O/H₂, M⁺/M) relative to pure Li, Na and K carbonates, Li₂CO₃–K₂CO₃ (62–38 mol.%) and Li₂CO₃–Na₂CO₃ (52–48 mol.%) carbonate eutectics. Due to their lower melting points, only the Li–K and Li–Na eutectics are investigated experimentally by cyclic voltammetry at a gold flag or planar disk working electrode at temperatures from 575 °C to 650 °C. CO₂ reduction wave gives evidence for both eutectics, showing that CO₂/CO system is relatively slow in the present conditions. Re-oxidation of CO formed at the Au electrode only produces a very low intensity signal, indicating a lower solubility of this species. Microelectrolysis at a potential corresponding to the reduction wave of CO₂ increases the amount of CO and an oxidation wave probably corresponding to adsorbed CO can be observed. The whole electrochemical process is complex, involving both soluble and adsorbed CO₂, mostly adsorbed CO and probably other intermediate species.     

Effect of lateral forces on the movement of myosin-coated beads on actin cables studied using a centrifuge microscope

We developed an in vitro motility assay system, in which myosin-coated polystyrene beads were made to slide on actin filament arrays (actin cables) in giant algal cells and subjected to centrifugal forces, which were parallel to the direction of bead movement to serve as external loads on actin-myosin sliding (Oiwa et al. (1990) Proc Natl Acad Sci USA 87: 7893-7897), and succeeded in determining the steady-state force-velocity relation of ATP-dependent actin-myosin sliding. To give further information about the properties of actin-myosin sliding, we have applied centrifugal forces, in parallel with the plane of actin-myosin sliding but at right angles with the direction of bead movement, and have found that such "lateral" centrifugal forces reduced the velocity of bead movement. In addition, we have also found that the velocity of bead movement is reduced more markedly with lateral forces applied from the left side of the bead ("left" lateral forces) than those applied from the right side of the bead ("right" lateral forces). These results are discussed in connection with the direction of sliding force generated by the myosin heads on the bead which interact with the right-handed double helix of actin monomers constituting actin filaments.