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.

     

Phase Separation in Chalcogenide Glasses: The System AgAsSSe

We report on visualization of a phase separation in Ag_x(As_0.33S_0.67)_100−x and Ag_x(As_0.33S_0.335Se_0.335)_100−x chalcogenide glasses by means of atomic force microscopy (AFM). Sufficient topographical contrast (~20 nm) was achieved by selective polishing of a phase-separated sample (Ag-poor, Ag-rich regions) and phase separation occurred within 0.5–20 at.% Ag and 2–18 at.% Ag in Ag_x(As_0.33S_0.67)_100−x and Ag_x(As_0.33S_0.335Se_0.335)_100−x systems, respectively. Homogenous regions were observed below and above the phase separation lower and upper limits. Direct comparison of scanning electron microscopy and atomic force microscopy sensitivity of phase separation detection is shown. In addition, concentration of silver in particular phases of AgAsS system was evaluated by NanoSIMS (secondary ion mass spectroscopy) and very similar concentration of silver was detected in the phases at boundaries of immiscibility region.     

A neck‐in model in extrusion lamination process

In this study, the experiment of the extrusion lamination process using high‐pressure process low‐density polyethylene (LDPE) was performed. The nonisothermal viscoelastic simulation of the extrusion lamination experiment was also carried out. The simulation results were in good agreement with the experimental data within wide range of take up velocity and air gap length. We developed the theoretical model based on force balance and deformation type of a film to predict the neck‐in behavior in the extrusion lamination or cast film process. It was suggested from the neck‐in model that the neck‐in correlates with the ratio of planar to uniaxial elongational viscosity. It was confirmed that the neck‐in model could predict the film edge shape and neck‐in properly for conventional LDPE. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Preparation of carbon-based transparent and conductive thin films by pyrolysis of silylated graphite oxides

Thin films of silylated graphite oxide were obtained from a chloroform/cyclohexane dispersion of n-hexadecylamine-intercalated silylated graphite oxide by a casting method at a low temperature. Carbon-based thin films were obtained from the pyrolysis of the resulting films under a reduced pressure at 500 °C or higher temperatures. The resulting samples were well adhered to the substrate because of the presence of silicon containing species as a “glue”. The resistivity decreased with an increase in the film thickness or a decrease in the transparency. Based on the data obtained for the samples prepared from graphite with different particle sizes and graphite oxide with different oxygen contents, the conduction of the electrons within each carbon sheet seemed important for large film thickness and conduction through the boundary seemed important when the film thickness was small. A low sheet resistance of 3.7 kΩ/sq for 80% of transmittance was achieved, when graphite oxide with a lower oxygen content was prepared from graphite with smaller particle sizes and the precursor film was heated at 500 °C. At 900 °C, it further decreased to a value of 700 Ω/sq.     

Migration of dehydroabietic and abietic acids from paper and paperboard food packaging into food-simulating solvents and Tenax TA

An investigation was undertaken to establish the concentration in paper products of dehydroabietic (DHA) and abietic (AA) resin acids, present in rosin, which are major toxicants of pulp- and paper-mill effluent. Their migration was studied from paper and paperboard products into various food-simulating solvents and the substitute fatty food simulant Tenax TA (modified polyphenylene oxide). DHA and AA were detected in five of 10 virgin paper products and in all 10 recycled paperboard products for food-contact use at concentrations of 14-500 and 110-1200 µg/g, respectively. In virgin paper products, the highest migration was into 95% ethanol or heptane, with negligible or no migration into other solvents. In recycled paperboard products, migration was highest into 95% ethanol, but was also observed into 20% ethanol, water and heptane. Migration to Tenax TA was also observed and the migration level increased with time. The maximum migration levels of DHA and AA into food simulants were 0.853 and 3.14 µg/g, respectively. The results suggest that, in the worst case, the daily intake of DHA and AA from paper and paperboard products was 50 times lower than the tolerable daily intake of rosin.     

Novel transdermal drug delivery system with polyhydroxyalkanoate and starburst polyamidoamine dendrimer

In search of an efficient transdermal drug delivery system (TDDS), a polyhydroxyalkanoate (PHA)-based system with a polyamidoamine dendrimer was examined. Tamsulosin was used as the model drug. The dendrimer was found to act as the weak enhancer. By adding the dendrimer, the dendrimer-containing PHA matrix achieved the clinically required amount of tamsulosin permeating through the skin model. This is also the first report of the application of PHA and dendrimer to the TDDS.     

Integrated protocol for optimized link state routing and localization: OLSR-L

Localization protocol is important for estimating node positions in a wireless multi-hop network. Routing protocol is also important for controlling paths. In previous research, localization and routing protocols have been discussed and evaluated separately. In this paper, we propose an integrated protocol for optimized link state routing (OLSR) and OLSR based localization (ROULA). Our protocol enables simultaneous localization and routing. ROULA’s localization is performed using OLSR overhead such as hello packets and routing tables. The routing overheads and the processing procedures can be efficiently integrated. We demonstrate that the integrated protocol for ROULA and OLSR enables simultaneous localization and routing.     

Calculations of heats of formation for nitroaromatics with PM3 and MM2

Abstract

We have attempted to calculate heats of formation (Δ H _f °) for various aromatic nitro compounds with the semi-empirical molecular orbital theory and the molecular mechanics. As the results we may say that PM3, a semi-empirical MO method, and MM2, molecular mechanics, can estimate Δ H _f ° of energetic materials with accuracy enough to use Δ H_f° for energy hazards prediction. In case of aromatic polynitro compounds, both methods may be able to calculate accurate Δ H_f°.