Solid‐phase microextraction Arrow for the volatile organic compounds in soy sauce

A novel solid‐phase microextraction Arrow was used to separate volatile organic compounds from soy sauce, and the results were verified by using gas chromatography with mass spectrometry. Solid‐phase microextraction Arrow was optimized in terms of three extraction conditions: type of fiber used (polydimethylsiloxane, polyacrylate, carbon wide range/polydimethylsiloxane, and divinylbenzene/polydimethylsiloxane), extraction temperature (40, 50, and 60°C), and extraction time (10, 30, and 60 min). The optimal solid‐phase microextraction Arrow conditions were as follows: type of fiber = polyacrylate, extraction time = 60 min, and extraction temperature = 50°C. Under the optimized conditions, the solid‐phase microextraction Arrow was compared with conventional solid‐phase microextraction to determine extraction yields. The solid‐phase microextraction Arrow yielded 6–42‐fold higher levels than in solid‐phase microextraction for all 21 volatile organic compounds detected in soy sauce due to the larger sorption phase volume. The findings of this study can provide practical guidelines for solid‐phase microextraction Arrow applications in food matrixes by providing analytical methods for volatile organic compounds.     

Enthalpic effect of polyacrylonitrile on the concentrated solutions in dimethyl sulfoxide: Strong thixotropic behavior and formation of bound solvents

The effect of dipole–dipole interaction by nitrile groups of PAN on the bound state of solvent molecules and the concentrated solution properties in DMSO was investigated. Variation of a solution viscosity exhibited three overlap concentrations, C1*, C2*, and C3*, at 2.7, 8.6, and 16.3 wt%, respectively, representing the transition of concentration regions in the order of dilute, unentangled‐semi dilute, entangled‐semi dilute, and concentrated regions. The two‐dimensional mapping of FT‐IR analysis and dielectric measurement confirmed that the intermolecular interaction of PAN was suddenly enhanced at the C*s, inducing polarization to DMSO. In the ice‐melting process of PAN solutions, two different melting peaks (T_m2 and T_m3) of DMSO newly appeared at each C2* and C3*, suggesting the different types of bound solvents. In the concentrated solutions, the saturated dielectric constant and the strongly delayed evaporation of the solvent even at the boiling point of DMSO along with strong thixotropic behavior were indicative of the stronger confinement state of bound DMSO than in the semidilute solutions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1080–1089     

Synthesis and halocyclization of 3-cyano-4,6-dimethyl-2-pyridone allyl derivatives

Chemistry of Heterocyclic Compounds - The sequence of condensation, alkylation, and halocyclization reactions during the synthesis of the target 2,3-dihydro[1,3]oxazolo[3,2-a]-pyridinium salts was...     

Acetic Anhydride as an Oxygen Donor in the Non-Hydrolytic Sol–Gel Synthesis of Mesoporous TiO2 with High Electrochemical Lithium Storage Performances

An original, halide-free non-hydrolytic sol–gel route to mesoporous anatase TiO₂ with hierarchical porosity and high specific surface area is reported. This route is based on the reaction at 200 °C of titanium(IV) isopropoxide with acetic anhydride, in the absence of a catalyst or solvent. NMR spectroscopic studies indicate that this method provides an efficient, truly non-hydrolytic and aprotic route to TiO₂. Formation of the oxide involves successive acetoxylation and condensation reactions, both with ester elimination. The resulting TiO₂ materials were nanocrystalline, even before calcination. Small (about 10 nm) anatase nanocrystals spontaneously aggregated to form mesoporous micron-sized particles with high specific surface area (240 m² g⁻¹ before calcination). Evaluation of the lithium storage performances shows a high reversible specific capacity, particularly for the non-calcined sample with the highest specific surface area favouring pseudo-capacitive storage: 253 mAh g⁻¹ at 0.1 C and 218 mAh g⁻¹ at 1 C (C=336 mA g⁻¹). This sample also shows good cyclability (92 % retention after 200 cycles at 336 mA g⁻¹) with a high coulombic efficiency (99.8 %). Synthesis in the presence of a solvent (toluene or squalane) offers the possibility to tune the morphology and texture of the TiO₂ nanomaterials.     

Ag/ZnO Catalysts with Different ZnO Nanostructures for Non‐enzymatic Detection of Urea

Silver coated ZnO nanorods and nanoflakes with different crystallographic orientations were synthesized by a combination of sputter deposition and solution growth process. Catalytic properties of morphology‐dependent Ag/ZnO nanostructures were then investigated for urea sensors without enzyme. Ag/ZnO nanorods on carbon electrodes exhibit a higher catalytic activity and an improved efficiency than Ag/ZnO nanoflakes on carbon electrodes. Ag/ZnO nanorod catalysts with more electrochemically surface area (169 cm² mg^?1) on carbon electrode facilitate urea electrooxidation due to easier electron transfer, which further promotes the urea electrolysis. The Ag/ZnO nanorod catalysts also show a significant reduction in the onset voltage (0.410 V vs. Ag/AgCl) and an increase in the current density (12.0 mA cm^?2 mg^?1) at 0.55 V vs Ag/AgCl. The results on urea electrooxidation show that Ag/ZnO nanostructures can be a potential catalyst for non‐enzymatic biosensors and fuel cells.     

Micropillar‐based microfluidic device to regulate neurite networks of uniform‐sized neurospheres

The inability of neurons to undergo mitosis renders damage to the central or peripheral nervous system. Neural stem cell therapy could provide a path for treating the neurodegenerative diseases. However, reliable and simple tools for the developing and testing neural stem cell therapy are still required. Here, we show the development of a micropillar‐based microfluidic device to trap the uniform‐sized neurospheres. The neurospheres trapped within micropillar arrays were largely differentiated into neuronal cells, and their neurite networks were observed in the microfluidic device. Compared to conventional cultures on glass slides, the neurite networks generated with this method have a higher reproducibility. Furthermore, we demonstrated the effect of thapsigargin on the neurite networks in the microfluidic device, demonstrating that neural networks exposed to thapsigargin were largely diminished and disconnected from each other. Therefore, this micropillar‐based microfluidic device could be a potential tool for screening of neurotoxins.     

Non-newtonian viscosity of polypeptides in the helix–coil transition region

The non-Newtonian intrinsic viscosities [η] of poly(γ-methyl L-glutamate) were measured in the helix–coil transition region under various conditions in this work. The helix content f_H, which represents the degree of conformational transition, was obtained by using a polarimeter. Our experimental results show that the non-Newtonian behavior of the polypeptide is markedly affected by its conformation; i.e., the non-Newtonian effect becomes larger as f_H increases. The effect of external pressure ΔP on [η] was studied carefully; [η] increases with f_H when ΔP < 1.5 psi, but it decreases when ΔP > 1.5 psi and f_H > 0.8. The reason for this result is considered in the text.     

Molecular cloning and expression of an endo-β-1,4-d-glucanase I (avicelase I) gene from Bacillus cellulyticus K-12 and characterization of the recombinant enzyme

Bacillus cellulyticus K-12 Avicelase (Avicelase I; EC 3.2.1.4) gene (ace A) has been cloned in Escherichia coli by using the vector pT7T3U19 and HindIII-HindIII libraries of the chromosomal inserts. The libraries were screened for the expression of avicelase by monitoring the immunoreaction of the antiavicelase (immunoscreening). Positive clones (Ac-3, Ac-5, and Ac-7) contained the identical 3.5-kb HindIII fragment as determined by restriction mapping and Southern hybridization, and expressed avicelase efficiently and constitutively using its own promoter in the heterologous host. From the immunoblotting analysis, a polypeptide that showed a carboxymethylcellulase (CMCase) activity with an M _r , of 64,000 was detected. The recombinant endo 1,4-β- _d -glucanase I was purified to homogeneity from an intracellular fraction of E. coli by DEAE-Toyopearl M650, Phenyl Toyoperal M650, and TSK gel HW50S chromatography. The enzyme had a monomeric structure, its relative molecular mass being 65 kDa by gel filtration and 64 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pI was 5.3 and the optimal pH was 4.6, and the enzyme was stable at pH 4.0–10.5. The enzyme had a temperature optimum of 50°C and was stable at 55°C for 48 h, and retained approx 20% of its activity after 30 min at 70°C. It showed high activity toward carboxymethylcellulose (CMC) as well as p-nitrophenyl-β-d-cellobioside, 4-methylumbelliferyl cellobioside, Avicel, filter paper, and some cellooligosaccharides. K _m values for CMC and Avicel were 7.6 and 85.2 mg/mL, respectively, whereas V _max values were 201 and 9.2 μmol · min⁻¹ · mg⁻¹, respectively. Cellotetraose (G4) was preferentially cleaved into cellobiose (G2) and cellopentaose (G5) was cleaved into G2 + cellotriose (G3), whereas cellohexaose (G6) was cleaved into G4 + G2 and, to a lesser extent, into G3 + G3. G3 was not cleaved at all. G2 was the main product of Avicel hydrolysis. G2 inhibited whereas Mg⁺⁺ stimulated the activity of CMCase and Avicelase. Hydrolysis of CMC took place with a rapid decrease in viscosity but a slow liberation of reducing sugars. Based on these results, it appeared that the cellulase should be regarded as endo type, although it hydrolyzed Avicel.     

Determination of breath alcohol using a differential-type amperometric biosensor based on alcohol dehydrogenase

A differential-type amperometric biosensor based on conventional thick-film technology has been developed for breath alcohol measurement. The amperometric breath alcohol biosensor utilizes the alcohol dehydrogenase (ADH) and nicotinamide adenine dinucleotide (NAD⁺) cofactor which produce reduced NADH as a product of the oxidation of alcohol. The biosensor was designed in a differential format consisting of a common Ag/AgCl reference electrode, an active working electrode containing the ADH, and the inactive working electrode containing only bovine serum albumin instead of the ADH. The differential signal between the active working electrode and the inactive working electrode minimized the interference from a large number of oxidizable species present in a person's breath. Prior to the amperometric measurement the biosensor was hydrated simply by dipping it into a phosphate buffer solution at pH 7.4. The NADH produced from the enzymatic reaction was oxidized at the working electrode biased at a potential of 470 mV vs. an on-board Ag/AgCl reference electrode. The biosensor can measure a person's breath alcohol over the concentration range 20–800 ppm routinely required in a test of drunken driving.     

Studies of gas-jet assisted RF-glow discharge atomic absorption spectrometry

The gas jet assisted glow discharge source has been employed for the RF-glow discharge atomic absorption spectrometry (RF-GDAAS). Data are described to illustrate the role of discharge power, pressure as well as gas flow rate on the sample loss rate, absorbance and self-bias potential. Results show that the optimum discharge conditions depend not only on the pressure and discharge power but also on the gas flow rate. The absorbance increases as much as 1 order of magnitude as the gas flow rate increases from 50 mL/min to 500 mL/min at a pressure of 3 mbar. The use of a gas-jet source allows the direct analysis of solids by RF-GDAAS.