Hydrophobic Tagged Dihydrofolate Reductase for Creating Misfolded Glycoprotein Mimetics

In the endoplasmic reticulum (ER), nascent glycoproteins that have not acquired the native conformation are either repaired or sorted for degradation by specific quality‐control systems composed by various proteins. Among them, UDP‐glucose:glycoprotein glucosyltransferase (UGGT) serves as a folding sensor in the ER. However, the molecular mechanism of its recognition remains obscure. This study used pseudo‐misfolded glycoproteins, comprising a modified dihydrofolate reductase with artificial pyrene–cysteine moiety on the protein surface (pDHFR) and Man₉GlcNAc₂‐methotrexate (M9‐MTX). All five M9‐MTX/pDHFR complexes, with a pyrene group at different positions, were found to be good substrates of UGGT, irrespective of the site of pyrene modification. These results suggest UGGT's mode of substrate recognition is fuzzy, thus allowing various glycoproteins to be accommodated in the folding cycle.     

Pervaporation separation of water/ethanol mixtures through polysaccharide membranes. II. The permselectivity of chitosan membrane

The separation of water/alcohol mixtures through chitosan membrane was investigated. The degree of the deacetylation of chitosan did not affect the selectivity of the membrane in the separation of the water/ethanol mixture. The selectivity of the chitosan membrane was affected by the specific salts such as CoSO₄, ZnSO₄, and MnSO₄ and it increased when the salts were present in the feed mixture or the membrane was pretreated with the salt solution. This behavior would be explained by the contraction of the “holes” produced by the thermal motion of polymer chains and this contraction would be correlated with the conformation change of chitosan molecule due to the formation of complexes with metal ions.     

Improved direct bonding method of Nd:YVO4 and YVO4 laser crystals

We succeeded in the fabrication of bonded laser crystals composed of a neodymium-doped YVO₄ laser crystal (Nd:YVO₄) and its host crystals YVO₄ by a newly developed dry etching technique using an argon ion beam. The optical distortion caused by the bonded interface of size 5 mm × 6 mm was estimated to be 0.05λ at 633 nm. From the comparison of laser performance pumped by a laser diode, the bonded crystals could increase the laser output power by nearly twice that of the non-bonded crystals with the same degree of polarization of 99.2%. To analyze the mechanism of the enhanced reduction of the thermal load in the bonded crystals, numerical simulations with a finite-element method were also performed.     

Active sites of Cu-ZSM-5 for the decomposition of acrylonitrile

The catalytic decomposition of acrylonitrile (AN) over Cu-ZSM-5 prepared with various Cu loadings was investigated. AN conversion, during which the nitrogen atoms in AN were mainly converted to N₂, increased as Cu loading increased. N₂ selectivities as high as 90–95% were attained. X-ray diffraction measurements (XRD) and temperature-programmed reduction by H₂ (H₂-TPR) showed the existence of bulk CuO in Cu-ZSM-5 with a Cu loading of 6.4 wt% and the existence of highly dispersed CuO in Cu-ZSM-5 with a Cu loading of 3.3 wt%. Electron spin resonance measurements revealed that Cu-ZSM-5 contains three forms of isolated Cu²⁺ ions (square-planar, square-pyramidal, and distorted square-pyramidal). The H₂-TPR results suggested that in Cu-ZSM-5 with a Cu loading of 2.9 wt% and below, Cu⁺ existed even after oxidizing pretreatment. The activity of AN decomposition over Cu/SiO₂ suggested that CuO could form N₂, but, independent of the CuO dispersion, nitrogen oxides (NO_x) were formed above 350 °C. Cu⁺ and the square-pyramidal and distorted square-pyramidal forms of Cu²⁺ showed low activity for AN decomposition. Temperature-programmed desorption of NH₃ suggested that N₂ formation from NH₃ proceeded on Cu²⁺, resulting in the formation of Cu⁺. The Cu⁺ ions were oxidized to Cu²⁺ at around 300 °C. Thus, high N₂ selectivity over Cu-ZSM-5 with a wide range of temperature was probably attained by the reaction over the square-planar Cu²⁺, which can be reversibly reduced and oxidized.     

Preparation and Properties of Carbon/Zeolite Composites with Corrugated Structure

Composites of carbon/zeolite with corrugated structures were prepared by carbonization, steam activation and/or hydrothermal treatment of corrugated paper. No zeolite formation resulted from conventional hydrothermal treatment of the carbonized and activated samples in NaOH solution but zeolite Na P1 was formed by addition of silica to the solution. By contrast, zeolites Na P1 and Na A were formed by the in-situ crystallization method (hydrothermal treatment of solid samples impregnated with NaOH solution). With higher impregnating NaOH concentrations, longer reaction times and higher reaction temperatures, the products changed to sodalite- and cancrinite-type compounds. Hydrothermal treatment was effective in increasing the specific surface area of the products by the formation of zeolite from amorphous calcium aluminosilicate, and also increased the mechanical strength by gluing together the carbon fibers in the samples. The resulting samples showed enhanced adsorption for polar molecules such as ammonia, water vapor and methanol due to the formation of composites of activated carbon with hydrophilic zeolites.     

Hot Corrosion Behavior and Microstructural Change of Al-Gradient CoNiCrAlYSi Coatings, Produced by LVPS and Diffusional Processes

Conventional and gradient CoNiCrAlYSi coatings were produced by using low vacuum plasma spray and an additional step of diffusional over aluminizing (pack cementation) techniques on an Inconel-738 substrate. Hot corrosion of these coatings was investigated using Na₂SO₄–20wt%NaVO₃ molten salt at 880?°C for 800?h. Hot corrosion rate was determined by measuring the weight gain of the specimens at regular intervals for a duration of 20?h. X-ray diffraction, field emission scanning electron microscopy and electron probe micro analysis techniques were used to determine the nature of phases, investigation of the thermally grown oxide, examination of the surface attack and determination of the elemental distribution. The gradient coating showed better performance by re-healing alumina scale due to its possession of more β phase as Al reservoir. Results indicated that pack cementation process caused an increase in amount of aluminum-rich β phase and better hot corrosion properties of gradient coatings owing to the Al enrichment in the outer layer and rapid formation of protective oxide on the surface.     

Multi-walled carbon nanotube-reinforced copper nanocomposite coating fabricated by low-pressure cold spray process

Multi-walled carbon nanotube (MWCNT)-reinforced copper (Cu) nanocomposite coatings were successfully deposited on aluminum (Al) substrate by a cold spraying process at a low pressure. The microstructure and the Raman spectrum of the low-pressure-cold-sprayed MWCNT–Cu nanocomposite coating showed that the MWCNTs maintained their tube structure in the Cu matrix, even though structural damage to the MWCNTs increased slightly. MWCNT–Cu nanocomposite-coated Al exhibits higher thermal diffusivity than pure-Cu-coated Al with a comparable hardness. The higher thermal diffusivity of the MWCNT–Cu coating could be explained by the dispersion of MWCNTs within the clean and closed CNT/Cu interfaces, which were achieved with the aid of compressive stress during the cold spraying.     

In situ X-ray diffraction of surface oxide on type 430 stainless steel in breakaway condition using synchrotron radiation

Changes in the crystal structure of type 430 stainless steel and the oxides on its surface were studied in situ at 1373 K using a high-intensity synchrotron X-ray source provided by SPring-8 in Japan. The surface of the steel was initially covered with Cr₂O₃, which was then converted to FeCr₂O₄, and finally Fe₃O₄ and Fe₂O₃ formed on it. These results indicated that the reason for the breakaway oxidation in type 430 stainless steel is Cr depletion beneath Cr₂O₃ layer and the subsequent ionisation of Fe, not the simple mechanical failure of Cr₂O₃.     

High Resistance of Cu–Ferrierite to Coke Formation During NH3-SCR in the Presence of n-Decane

Selective catalytic reduction of NO _x by NH₃ over Cu–FER and Cu–ZSM-5 in the presence of n-decane and SO₂ was investigated. NO _x conversion over Cu–ZSM-5 decreased in the presence of n-decane, owing to inhibition of the active sites by coke formation. In contrast, coke formation was negligible over Cu–FER, which maintained its NO _x conversion activity even in the presence of decane. Coke formation was negligible over H–ZSM-5 and H–FER supports, which suggests that Cu species were involved in coke formation. Temperature-programmed reduction by H₂ and electron spin resonance spectroscopy indicated that [Cu–O–Cu]²⁺ was probably the Cu species involved in coke formation over Cu–ZSM-5.