Effect of Ganglioside GM3 Synthase Gene Knockout on the Glycoprotein N‐Glycan Profile of Mouse Embryonic Fibroblast

The structural and clinical significance of cellular glycoproteins and glycosphingolipids (GSLs) are often separately discussed. Considering the biosynthetic pathway of glycoconjugates, glycans of cell‐surface glycoproteins and GSLs might partially share functions in maintaining cellular homeostatis. The purpose of this study is to establish a general and comprehensive glycomics protocol for cellular GSLs and N‐glycans of glycoproteins. To test the feasibility of a glycoblotting‐based protocol, whole glycans released both from GSLs and glycoproteins were profiled concurrently by using GM3 synthase‐deficient mouse embryonic fibroblast GM3(?/?). GM3(?/?) cells did not synthesize GM3 or any downstream product of GM3 synthase. Instead, expression levels of o‐series gangliosides involving GM1‐b and GD1‐α increased dramatically, whereas a‐/b‐series gangliosides were predominantly detected in wild‐type (WT) cells. We also discovered that glycoprotein N‐glycan profiles of GM3(?/?) cells are significantly altered as compared to WT cells, although GM3 synthase is responsible only for GSLs synthesis and is not associated with glycoprotein N‐glycan biosynthesis. The present approach allows for high‐throughput profiling of cellular glycomes enriched by different classes of glycoconjugates, and our results demonstrated that gene knockout of the enzymes responsible for GSL biosynthesis significantly influences the N‐glycans of glycoproteins.     

A Unique Amino Transfer Mechanism for Constructing the β‐Amino Fatty Acid Starter Unit in the Biosynthesis of the Macrolactam Antibiotic Cremimycin

Cremimycin is a 19‐membered macrolactam glycoside antibiotic based on three distinctive substructures: 1) a β‐amino fatty acid starter moiety, 2) a bicyclic macrolactam ring, and 3) a cymarose unit. To elucidate the biosynthetic machineries responsible for these three structures, the cremimycin biosynthetic gene cluster was identified. The cmi gene cluster consists of 33 open reading frames encoding eight polyketide synthases, six deoxysugar biosynthetic enzymes, and a characteristic group of five β‐amino‐acid‐transfer enzymes. Involvement of the gene cluster in cremimycin production was confirmed by a gene knockout experiment. Further, a feeding experiment demonstrated that 3‐aminononanoate is a direct precursor of cremimycin. Two characteristic enzymes of the cremimycin‐type biosynthesis were functionally characterized in vitro. The results showed that a putative thioesterase homologue, CmiS1, catalyzes the Michael addition of glycine to the β‐position of a non‐2‐enoic acid thioester, followed by hydrolysis of the thioester to give N‐carboxymethyl‐3‐aminononanoate. Subsequently, the resultant amino acid was oxidized by a putative FAD‐dependent glycine oxidase homologue, CmiS2, to produce 3‐aminononanoate and glyoxylate. This represents a unique amino transfer mechanism for β‐amino acid biosynthesis.     

Electrical Properties of Pre-Alloyed Cu-P Containing Electrically Conductive Adhesive

In this study, a pre-alloyed Cu-P powder with a trace amount of P (0.002 at.%) was used as a metallic filler in a phenolic resin-based electrically conductive adhesive (ECA). The electrical property of the Cu-P-filled ECA was investigated for long-term stability and reliability by aging at high temperature exposure at 125°C and 85°C/85% RH for 1000 h, respectively. Results showed that the electrical resistivity of the Cu-P-filled ECA could be maintained consistently low after high temperature exposure at 125°C for 1000 h or aging at 85°C/85% RH for 1000 h, compared with the rapidly increased resistivity of Cu-filled ECA over time. A significantly low final resistivity at an order of magnitude of 10^?4 Ω·cm could be maintained in Cu-P-filled ECA even after aging at 85°C/85% RH for 1000 h.     

RADIOLYTIC DEGRADATION OF A CROWN ETHER FOR EXTRACT ABILITY OF STRONTIUM

ABSTRACT

Dicyclohexano- 18-crown-6 (DC18C6), dissolved in chloroform, 1-octanol, toluene or cyclohexane, was irradiated by ⁶⁰Co γ-rays. Radiolytic destruction of DC18C6, measured by gas chromatography, decreased in the order: chloroform > cyclohexane > 1-octanol > toluene. Distribution coefficients in the solvent extraction of strontium from nitric acid solution were measured. These distribution coefficients were minimally affected by γ-irradiation in toluene solution, but decreased with the absorbed dose in chloroform solution. It was suggested that the distribution coefficient for the liquid-liquid extraction system was influenced by radiolytic products. The effect of radiolytic products on the distribution coefficients was evaluated by considering DC18C6 remaining in the organic phase after irradiation. The distribution coefficient measured for the organic phase with radiolytic products was larger than that without radiolytic products. The radiolytic products were thus shown to contribute to the increase in the distribution coefficient.     

Development of AAS resin by the emulsion–suspension polymerization method

In order to improve the weatherability of acryonitrile—styrene—butadiene rubber graft polymer (ABS resin), an attempt was made to develop a resin (AAS resin) in which acrylic rubber of good weatherability was used instead of butadiene rubber. First, by copolymerizing dicyclopentenyl-methacrylate (DCP-MA,3%) with butyl acrylate, crosslinked acrylic rubber was obtained. This also introduced grafting sites into the rubber. Next, methods of graft copolymerizing styrene and acrylonitrile with this rubber were examined. An emulsion–suspension polymerization method was developed in which the initial stage of the polymerization, emulsion polymerization, changed into suspension polymerization during the process. By this method of polymerization, rubber particles were combined and enlarged, bringing about a graft-type resin with high impact resistance. This polymerization method is industrially useful because particle-shaped resins are obtained without the need of a salting-out process. The AAS resin, obtained in this way, has much improved weatherability over ABS resin and shows strength equal to that of ABS resin. © 1992 John Wiley & Sons, Inc.     

Modification of Rheological Properties Under Elongational Flow by Addition of Polymeric Fine Fibers

A new technique to provide melt elasticity using flexible fine fibers prepared from a polymer with high melting point is demonstrated. A polymer composite of poly(propylene) with a small amount of fine fibers of poly(butylene terephthalate) shows marked strain‐hardening behavior in elongational viscosity, i.e., a rapid increase in the transient elongational viscosity with time or strain. The blend also shows prominent normal stress difference at steady shear. These elastic properties have not been observed for polymer composites with rigid fibers and can be applicable to the modification of rheological properties and thus the improvement of processability.

     

Rapid evaluation of oxidation catalysis by gas sensor system: total oxidation, oxidative dehydrogenation, and selective oxidation over metal oxide catalysts

The rapid evaluation of catalysis is an indispensable technology for the success of combinatorial chemistry. A small-sized, less expensive, easily operating screening is desirable for parallel settings which dramatically shortens the evaluation time. Recent advances in gas sensors have enabled us to use them for the rapid evaluation of oxidation catalysis. Three typical catalytic oxidations over metal oxide catalysts were evaluated by gas sensor systems optimized for each catalytic system. The first one is the total oxidation of carbon monoxide in air. Five catalytic combustion-type gas sensors were used in a parallel reactor system to shorten the evaluation time. The second one is the oxidative dehydrogenation (ODH) of ethane over the mixed oxide of nickel and iron. The evaluation of the ODH catalysis was performed by a selective olefin sensor which determines the concentration of C₂H₄ in C₂H₆. The third one is the selective oxidation catalysis of propane over alkali modified Fe/SiO₂. The effluents including CO, CO₂, aldehydes and ketones in propane were analyzed by the CO, CO₂ and semiconductor-type gas sensors selective toward aldehydes and ketones. These evaluation results indicated that gas sensors have a good potential for the rapid evaluation of oxidation catalysts.     

Preparation of Morphology‐Controlled Plate‐Like Sodium Niobate Particles by Hydrothermal Synthesis

Sodium niobate (NaNbO₃) particles with plate‐like morphology and hexagonal unit cells were prepared by the hydrothermal method. The result of SEM showed that the hexagonal NaNbO₃ were characterized by plate‐like morphology with a diameter of 5–15 μm and a thickness of 1–2 μm. The crucial influences on the morphology and crystal phase of the NaNbO₃, such as concentration of [OH^?], surfactant, and K⁺:Na⁺ ratio, were established. By further calcination treatment, the plate‐like hexagonal NaNbO₃ particles could be completely transformed into perovskite structure without morphology change. The XRD and EBSD results indicate that the major face of the calcined particles is parallel to the crystallographic (001)_pc (pseudo cubic index) plane. Compared with the traditional high‐temperature molten salt method, this work provides a simpler way to prepare the template for fabricating textured ceramics.     

Insights from ab initio molecular dynamics simulations for a multicomponent oxide glass

It remains a challenge to establish structural models of multicomponent oxide glass systems. In this study, we have investigated 68.3SiO₂–16.1B₂O₃–4.2Al₂O₃–11.4Na₂O glass and melt structures by ab initio molecular dynamics (AIMD) simulations. The atomic configurations obtained from AIMD simulations were validated against ¹⁷O solid‐state NMR spectrum under 24.0 T and neutron diffraction data, and excellent agreement was achieved. The bond lengths, angles, and coordination geometries were statistically analyzed for each atomic species. Here we particularly address the role of minor atomic species such as five‐coordinate Si (Si^V) and Al (Al^V). The Si^V–O bond lengths and O–Si^V–O angle distribution in the glass indicated 1.718 Å and three peaks at 90°, 120°, and 175°, which are assigned to a coordination geometry of the trigonal bipyramidal structure. Ring statistic analysis revealed that Si^V and Al^V were found to preferentially contribute to the formation of small ring sizes.