Immobilization of glutaryl-7-aminocephalosporanic acid acylase on silica gel and enhancement of its stability

Glutaryl-7-aminocephalosporanic acid (GL-7-ACA) acylase isan enzyme that converts GL-7-ACA to 7-aminocephalosporanic acid, a starting material for semisynthetic cephalosporin antibiotics. In this study, optimal conditions for the immobilization of GL-7-ACA acylase were determined by experimental observations and statistical methods. The optimal conditions were as follows: 1.1 M phosphate buffer (pH 8.3) as buffer solution, immobilization temperature of 20°C, and immobilization time of 120 min. Unreacted aldehydegroups were quenched by reaction with a low-molecular-weight material such as l-lysine, glycine, and ethanolamine after immobilization in order to enhance the activity of immobilized GL-7-ACA acylase. The activities of immobilized GL-7-ACA acylase obtained by using the low-molecular-weight materials were higher than those obtained by immobilized GL-7-ACA acylase not treated with low-molecular-weight materials. In particular, the highest activity of immobilized GL-7-ACA acylase was obtained using 0.4% (v/v) ethanolamine. We also investigated the effect of sodium cyanoborohydride in order to increase the stability of the linkage between the enzyme and the support. The effect on operational stability was obvious: the activity of immobilized GL-7-ACA acylase treated with 4% (w/w) sodium cyanoborohydride remained almost 100% after 20 times of reuse.     

Self-aggregates of hydrophobically modified poly(2-hydroxyethyl aspartamide) in aqueous solution

Dehydrocholic acid (DHA) grafted poly(2-hydroxyethyl aspartamide) (PHEA)s were successfully synthesized and their self-aggregates in aqueous solution were characterized by fluorescence spectra and light scattering. PHEA was obtained by a simple reaction of ethanolamine with synthesized poly(succinimide) (PSI), and then PHEA-g-DHA was synthesized through an ester linkage between DHA and PHEA. The degree of substitution (DS) of DHA groups, defined by grafted mole%, was determined from both ¹H-NMR and elemental analysis. The grafting reaction of DHA was retarded up to almost 10 mole% feed ratio of DHA/PHEA, but increased linearly above the threshold ratio. Nano-size self-aggregates in aqueous solution were examined with four DSs less than 10. As DS increased, the critical aggregation concentrations (CAC) of polymers were continuously reduced and the size of primary aggregates reduced to as small as 40 nm in diameter. When stored, the sonicated aggregates of high DS were destabilized, apparently forming large aggregates with small curvatures. The formation of irreversible interfused secondary structures would be induced by the curvature change or aggregation of primary particles. A simple calculation indicates that a small change of separation between grafted DHA groups may induce the large curvature shift, in fact, sphere-to-planar surface transition.     

Heterogeneous Photocatalytic Degradation of Disulfoton in Aqueous TiO2 Suspensions: Parameter and Reaction Pathway Investigations

The photocatalytic degradation of organophosphorus insecticide disulfoton is investigated by having titanium dioxide (TiO₂) as a photocatalyst. About 99% of disulfoton is degraded after UV irradiation for 90 min. The effects of the solution pH, catalyst dosage, light intensity, and inorganic ions on the photocatalytic degradation of disulfoton are also investigated, as well as the reaction intermediates which are formed during the treatment. Eight intermediates have been identified and characterized through a mass spectra analysis, giving insight into the early steps of the degradation process. To the best of our knowledge, this is the first study reporting the degradation pathways of disulfoton. The results suggest that possible transformation pathways may involve in either direct electron or hole transfer to the organic substrate. The photodegradation of disulfoton by UV/TiO₂ exhibits pseudo‐first‐order reaction kinetics and a reaction quantum yield of 0.267. The electrical energy consumption per order of magnitude for photocatalytic degradation of disulfoton is 85 kWh/(m³ order).     

Stereoselective determination of ginsenosides Rg3 and Rh2 epimers in rat plasma by LC‐MS/MS: Application to a pharmacokinetic study

We developed and validated an accurate and sensitive LC–MS/MS method for the simultaneous quantitation of ginsenoside Rg3 and Rh2 epimers (R‐Rg3, S‐Rg3, R‐Rh2, and S‐Rh2) in rat plasma. Analytes were extracted from 0.1 mL aliquots of rat plasma by liquid–liquid extraction, using 2 mL of ethyl acetate. In this assay, dioscin (500 ng/mL) was used as an internal standard. Chromatographic separation was conducted using an Acclaim RSLC C₁₈ column (150 × 2.1 mm, 2.2 μm) at 40°C, with a gradient mobile phase consisting of 0.1% formic acid in distilled water and in acetonitrile, a flow rate of 0.35 mL/min, and a total run time of 20 min. Detection and quantification were performed using a mass spectrometer in selected reaction‐monitoring mode with negative electrospray ionization at m/z 783.4 → 161.1 for R‐Rg3 and S‐Rg3, m/z 621.3 → 161.1 for R‐Rh2 and S‐Rh2, and m/z 867.2 → 761.5 for the internal standard. For R‐Rg3 and S‐Rg3, the lower limit of quantification was 5 ng/mL, with a linear range up to 500 ng/mL; for R‐Rh2 and S‐Rh2, the lower limit of quantification was 150 ng/mL, with a linear range up to 6000 ng/mL. The coefficient of variation for assay precision was less than 10.5%, with an accuracy of 86.4–112%. No relevant cross‐talk or matrix effect was observed. The method was successfully applied to a pharmacokinetic study after oral administration of 400 mg/kg and 2000 mg/kg of BST204, a fermented ginseng extract, to rats. We found that the S epimers exhibited significantly higher plasma concentrations and area under curve values for both Rg3 and Rh2. This is the first report on the separation and simultaneous quantification of R‐Rg3, S‐Rg3, R‐Rh2, and S‐Rh2 in rat plasma by LC‐MS/MS. The method should be useful in the clinical use of ginseng or its derivatives.     

Mastoid Obliteration Using Three‐Dimensional Composite Scaffolds Consisting of Polycaprolactone/β‐Tricalcium Phosphate/Collagen Nanofibers: An In Vitro and In Vivo Study

Two different composite scaffolds, solid‐freeform‐fabricated PCL/β‐TCP supplemented with and without collagen nanofibers are fabricated. These scaffolds are evaluated whether a combination of collagen nanofibers with PCL/β‐TCP can promote osteogenesis in a mastoid obliteration. To assess the effects of the cellular activities of osteoblast‐like‐cells (MG63), SEM images and MTT assays are conducted. Experimental mastoid obliteration is performed using guinea pigs that are divided group A (PCL/β‐TCP/collagen‐nanofiber scaffold) and group B (PCL/β‐TCP scaffold). The results reveal that PCL/β‐TCP/collagen scaffold provide much broader cell attachment sites than PCL/β‐TCP scaffold. The µ‐CT and fluorescent microscopy results reveal that the acceleration of early new bone formation within the pores and scaffold itself at week 4 post‐operation is more effective in group A. In addition, based on the results of the histological and µ‐CT at 12 weeks post‐surgery, the effective regeneration of bone in the PCL/β‐TCP/collagen scaffold is appeared.

     

Characterization of chemical information and morphology for in‐depth oxide layers in decarburized electrical steel with glow discharge sputtering

A combination of scanning electron microscopy, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy with a sampling method by glow discharge sputtering was successfully employed to characterize the chemical information and microscopic features of oxide layers formed during decarburization annealing of electrical steel in the depth direction at high resolution. The discontinuous surface oxides consisted of SiO₂, (Fe,Mn)SiO₃/(Fe,Mn)₂SiO₄, and FeO. SiO₂ embedded in the (Fe,Mn)₂SiO₄ at the surface may be developed by the preferential nucleation and growth kinetics. The discrete or often relatively spherical oxides of internal oxidation by the energetically favorable surface effect were identified as a mixture of SiO₂ and (Fe,Mn)₂SiO₄ at a depth of ~0.5 µm from the surface. The oxides of networks and small particles at a depth greater than ~1 µm were solely silica, of which the morphologies were possibly caused by the enhanced diffusion of oxygen atoms and Si atoms at grain boundaries or sub‐grain boundaries. The equilibrium and kinetic considerations served by theoretical calculations were introduced to understand the formation and behavior of the observed in‐depth oxidation. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of 5-ortho-Carboranylsalicylaldehyde and an Indolinospirobenzopyran

5-ortho-Carboranylsalicylaldehyde was prepared from 5-iodosalicylaldehyde in six steps in 18% overall yield, and also from 5-iodosalicylic acid in seven steps in 45% overall yield. The reaction of 5-ortho-carboranylsalicylaldehyde with Fischer's base gave a spiropyran in 63% yield.     

APUSM technology for the production of BTX and LPG from pyrolysis gasoline using metal promoted zeolite catalyst

SK Corporation developed an advanced pyrolysis gasoline (pygas) upgrading (APU^SM) technology based on a catalytic process for producing valuable benzene, toluene and xylenes (BTX) and liquefied petroleum gas (LPG) from pygas containing aromatics and non-aromatic hydrocarbons. Hydrodealkylation of heavy aromatics and hydrocracking of non-aromatic hydrocarbons occurred with facility in the conversion of pygas over a proprietary catalyst, metal promoted zeolite. This catalytic process produced benzene and toluene with high purity corresponding to chemical grade while giving mixed xylenes with reduced ethylbenzene. In the present study, we described novel features of the APU^SM technology in terms of the process and catalyst. The influence of the process conditions was also examined. This technology has been commercially proven, and hence is available for licensing through Axens, which is a major engineering and licensing company.     

Performance of pyrophyllite and halloysite clays in the catalytic degradation of polystyrene

Summary The performance of pyrophyllite and halloysite clays in the degradation of polystyrene (PS) was investigated. The degradation was carried out in a semi-batch reactor with a mixture of polystyrene and catalysts at 400-450^oC. The catalysts showed good catalytic activity for the degradation of PS with high selectivity to aromatics liquids. Styrene is the major product, and ethylbenzene is the second most abundant one in the liquid product. The catalytic degradation showed much less production of styrene dimers and higher selectivity to ethylbenzene than the thermal degradation did. High degradation temperature favored the production of styrene monomer, but it decreased the ethylbenzene production.     

Preparation of a Reduced Graphene Oxide Wrapped Lithium‐Rich Cathode Material by Self‐Assembly

A lithium‐rich cathode material wrapped in sheets of reduced graphene oxide (RGO) and functionalized with polydiallyldimethylammonium chloride (PDDA) was prepared by self‐assembly induced from the electrostatic interaction between PDDA–RGO and the Li‐rich cathode material. At current densities of 1000 and 2000 mA g^?1, the PDDA–RGO sheet wrapped samples demonstrated increased discharge capacities, increasing from 125 to 155 mA h g^?1 and from 82 to 124 mA h g^?1, respectively. The decreased resistance implied by this result was confirmed from electrochemical impedance spectroscopy results, wherein the charge‐transfer resistance of the pristine sample decreased after wrapping with the PDDA–RGO sheets. The PDDA–RGO sheets served as a protective layer sand as a conductive material, which resulted in an improvement in the retention capacity from 56 to 81 % after 90 cycles.