The effect of the N-linked glycans on structural features and physicochemical functions of soybean β-conglycinin homotrimers

β-Conglycinin is a trimeric protein consisting of three subunits, α,α′,and β, which are N-glycosylated. The α and α′ subunits contain extension regions in addition to core regions common to all subunits. We purified homogeneous trimers consisting of only α, α′, or β from mutant soybean cultivars containing β-conglycinin lacking one or two subunits: α homotrimers from an α′-lacking mutant, α′ homotrimers from an α-lacking mutant, and β homotrimers from an α-and α′-lacking mutant. Structural features and physicochemical functions of the three homotrimers were examined and compared with those of recombinant homotrimers having no N-linked glycans. The native homotrimers have secondary structures very similar to those of the recombinant ones. In analogy with the recombinant homotrimers, the native ones exhibit different thermal stabilities from one another (β>α′>α), and the native α and α′ homotrimers exhibit better solubility, emulsifying ability, and heat-induced association than the native β homotrimer. Further, the N-linked glycans contribute to solubilities of the three subunits at low ionic strength (μ=0.08) and to the emulsifying ability of the native β homotrimer. N-Linked glycans also prevent heat-induced associations of the native α and α′ homotrimers but do not contribute to the secondary structure and the thermal stability of β-conglycinin.     

Gibbs Energy Change of Carbothermal Nitridation Reaction of Al2O3 to Form AlN and Reassessment of Thermochemical Properties of AlN

The experimental method for the high-temperature reaction equilibria in the AlN-Al₂O₃ system has been established. The equilibrium N₂-CO gas compositions coexisting with AlN- Al₂O₃-graphite have been successfully measured by quadrupole mass spectrometry and gas chromatography. From the obtained results, the standard Gibbs energy change of the forming reaction of AlN by carbothermal nitridation is determined at temperatures ranging from 1723 to 1899 K:
From the obtained result, the standard Gibbs energy of formation of AlN and the third-law enthalpy of formation of AlN at 298.15 K are derived as
The disagreement between the present results and values in the NIST–JANAF thermodynamic table is discussed.     

Template-free synthesis and adsorption properties of microporous crystal AlPO4-H3

A microporous aluminophosphate molecular sieve, AlPO₄-H3, was prepared without using organic templates. It was crystallized at temperatures as low as 90 °C from aluminophosphate gels with a molar ratio of Al₂O₃/P₂O₅1; the addition of seed crystals was essential. AlPO₄-H3 was topotactically and irreversibly converted into AlPO₄-D at 300 °C, which adsorbed water up to 0.2 ml/g at 25 °C, although nitrogen gas was hardly adsorbed at liquid nitrogen temperature.     

Epitaxially grown free-standing diamond platelet

We obtained an epitaxially grown free-standing diamond platelet utilizing epitaxial diamond film formed on a {100} iridium surface using a d.c. plasma CVD process. Iridium was selected as a suitable substrate material for the heteroepitaxy of diamond based on original criteria. Confocal Raman spectroscopy revealed that the diamond platelet contained little or no non-diamond carbon. The obtained diamond platelet is transparent to visible light and cleavable along the 110 direction on the surface. The angles between the top surface and the cross-sectional surfaces are approximately 55°, almost equal to the theoretical angle of 54.74° between {100} and {111} planes in cubic crystals. Therefore, the cross-sectional surfaces would be {111} planes of a typical facet for single-crystalline diamond. This means that the diamond platelet we have formed has relatively good crystallinity.     

Aerosol-to-liquid collection: A method for making aqueous suspension of hydrophobic nanomaterial without adding dispersant

This article introduces an aerosol-based technique to make aqueous suspension of hydrophobic nanomaterial without adding dispersant. The method is intended for making a test-sample for evaluating the toxicities of nanomaterial by intra-tracheal administration. The method can wet the surface of hydrophobic nanomaterial within a few seconds. After the wetting process five to ten minutes of sonication assisted with manual stirring can fully disperse the hydrophobic nanomaterials in water. Two types of TiO₂ nanomaterial were used in this study; Tayca JMT-150IB whose surfaces are coated with negatively charged hydrophobic functional group, and P25 whose surfaces are naturally hydrophilic. Nanomaterials are aerosolized by a dry-method and become micrometer-sized agglomerates. Then supersaturated water vapor is condensed onto these airborne agglomerates by using a growth tube collector. The collected suspension (CS) of hydrophobic nanomaterial (JMT-150IB) is prepared in two steps; airborne agglomerates are collected onto a flat surface then transferred to liquid-water and subsequently sonicated for complete dispersion. This method works equally well for making the CS of hydrophilic nanomaterial. Size distribution measurements of the CS show that airborne agglomerates of TiO₂ dissociate into smaller units of agglomerates once they are captured into water, and the sizes of the agglomerates are in the nanometer to sub-micrometer range. Light scattering technique is used to show that a short sonication process can reproduce the particle number concentration of the CS after long storage.

Copyright © 2017 American Association for Aerosol Research     

Dehydrogenation of ethane to ethylene via radical pathways enhanced by alkali metal based catalyst in oxysteam condition

The dehydrogenation of ethane to ethylene in the presence of oxygen and water was conducted using Na₂WO₄/SiO₂ catalyst at high temperatures. At 923 K, the conversion rate without water was proportional to ethane pressure and a half order of oxygen pressure, consistent with a kinetically relevant step where an ethane molecule is activated with dissociated oxygen on the surface. When water was present, the ethane conversion rate was drastically enhanced. An additional term in the rate expression was proportional to a quarter of the oxygen pressure and a half order of the water pressure. This mechanism is consistent with the quasi‐equilibrated OH radical formation with subsequent ethane activation. The attainable yield can be accurately described by taking the water contribution into consideration. At high conversion levels at 1073 K, the C₂H₄ yield exceeded 60% in a single‐pass conversion. The C₂H₄ selectivity was almost insensitive to the C₂H₆ and O₂ pressures. © 2016 American Institute of Chemical Engineers AIChE J, 63: 105–110, 2017     

Phase transformation and interface segregation behavior in Si3N4 ceramics sintered with La2O3–Lu2O3 mixed additive

Microstructure and mechanical property of silicon nitride (Si₃N₄) ceramic are strongly dependent on the selection of sintering additives. When rare‐earth (RE) oxide is used as the sintering additive, segregation of RE ions at interface between Si₃N₄ grain and intergranular glassy film (IGF) is believed to play a critical role. Although the ionic radius of RE ion is known to be an empirical parameter to modify the mechanical property, the correlation between the segregated ions and their ionic radii is still under controversy. In order to address this issue, (i) rate of α‐β phase transformation and (ii) segregation behavior at the interface were studied for Si₃N₄ ceramics sintered using mixture of La₂O₃ and Lu₂O₃ as additives in this study. Specimens of Lu content 30% and higher exhibited lower activation energies for the α‐β phase transformation as compared with those of Lu content 20% and lower. In terms of the segregation behavior, La was preferably segregated at one site and Lu at the other site along β‐Si₃N₄/IGF interface in the specimens of Lu content 30% and higher. It is understood from these results that Lu segregation site should be more closely related with grain growth.     

Application of Poly(acetic Acid)–Based Graft Copolymer as a Compatibilizer for Poly(L-lactic Acid)/Poly(butylenesuccinate) Blend System

Poly(L-lactic acid) (PLLA) was blended with poly(butylenesuccinate) (PBS) using a single-screw extruder to modify the poor characteristics of these polymers. Furthermore, when both polymers were blended, the graft copolymer that was synthesized by partially saponified poly(vinyl alcohol) (PSPVA) and ?-caprolactone (?-CL) was used as a novel compatibilizer. The structure of the synthesized compatibilizer was determined by ¹H or ¹³C NMR. From this result, the ring-opening polymerization of the ?-CL occurred at the hydroxyl group of PSPVA. The structures of the PLLA/PBS solvent-cast blended films could be observed via an optical microscope. From the optical microscopic observation, the structures of the solvent-cast blended films with the synthesized compatibilizer were more homogeneous than those of the solvent-cast blended films without the compatibilizer. The mechanical properties of the PLLA/PBS extruded blended films were determined by a tensile test. The result showed the tensile strength of the blended films with the synthesized compatibilizer was greater than that of the blended films without the compatibilizer.     

LIQUID-PHASE PHOTOCATALYTIC REACTION ON TiO22 THIN FILM

The photocatalytic decomposition process on TiO₂ thin films, was modeled by taking the decay of illumination intensity via Lambert-Beer law into account. For the sake of experimental verification of the proposed model, Ti02 thin films were prepared on a glass substrate by a dip-coating method combined with a sol-gel process and the photocatalyuc activity of the thin films was evaluated by the decomposition of 2-propanol (IPA) in an aqueous solution under illumination of UV light source. The film thickness up to 1.4 μm increased with the withdrawal speed raised to the power 0.6 and was proportional to the number of application (i.e., repetition of dip-coating process). The TiO₂ gel films prepared by a dip-coating technique, were subject to firing at 500°C. The photocatalytic decomposition rate could be expressed apparently as first-order with respect to IPA concentration. The observed relationship between apparent first-order rate constant of decomposition and the film thickness could satisfactorily be explained by the proposed model.