An Organogermanium Compound Enhances the Initial Reaction Rate of Alkaline Isomerization of an Aldose into a Ketose through Enediol Complex Formation

We previously demonstrated that the organogermanium compound 3-(trihydroxygermyl)propanoic acid (THGP) enhances the enzymatic and alkaline isomerization of an aldose to a ketose through cis-diol complex formation by multiple mechanisms. Its higher affinity for the ketose than the aldose protects the ketose complex from alkaline decomposition. Furthermore, it has been reported that the aldose-ketose alkaline isomerization pathway includes 1,2-enediol. Therefore, we speculated that the complex-forming ability of THGP could also be applied to enediol, a transient intermediate of alkaline isomerization. To test this prediction, we analyzed the initial rates of glucose or lactose isomerization in a region where there was no substantial difference in pH with and without THGP addition. The results showed that THGP enhanced the rate of fructose or lactulose formation per unit time by approximately 2-fold compared to the control. This finding indicated that THGP could form a complex with the transition state of aldose-ketose alkaline isomerization.     

Poly(4-diphenylaminostyrene) with a well-defined polymer chain structure: Controllable optical and electrical properties

The effect of polymer chain structure on the optical and electrical properties are reported for poly(4-diphenylaminostyrene) (PDAS), which was prepared by the living anionic polymerization of 4-diphenylaminostyrene (DAS) with the benzyllithium (BzLi)/N,N,N′,N′-tetramethylethylenediamine (TMEDA) system. The optical properties of PDAS are strongly affected by the stereoregularity of the PDAS polymer chain; intramolecular excimer-forming fluorescence was observed from PDAS with a syndiotactic-rich configuration. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PDAS were approximately −5.4 and −2.0 eV, respectively, regardless of the polymer chain structure. The hole and electron drift mobilities for PDAS were in the order of 10⁻⁴ to 10⁻⁵ (cm²/V s) and 10⁻⁵ (cm²/V s), respectively, with negative slopes. The distance of each triphenylamino (TPA) group in the polymer chain was a major factor influencing the drift mobility of PDAS. The current-voltage (I-V) characteristics of PDAS were controllable according to the polymer chain structure of PDAS.     

Piezoelectric Film Response Studied with Finite Element Method

It is difficult to measure accurately the piezoelectric constant, d ₃₃, of either a thin or thick film on a substrate, because piezoelectric deformation of a film is small. The measured value of d ₃₃ for the film is often smaller than the value of d ₃₃ for the bulk material. This is partly because of bending of the sample and side clamping of the film. However, we used finite element method (FEM) to simulate common experimental conditions and show that inner local deformation was more significant than either bending or side clamping. Using our FEM results, we propose optimum conditions for making unbiased d ₃₃ measurements.     

Ketones from carboxylic acids over supported magnesium oxide and related catalysts

Silica-supported alkaline earth oxides revealed excellent activity to convert acetic acid selectively into acetone in a vapor-phase fixed-bed flow system. Acetone was obtained through the cyclic formation of alkaline earth acetate followed by decomposition. Magnesium oxide should be supported on the silica surface without formation of magnesium silicate, which was inactive for the present reaction. Attempted syntheses of benzophenone and acetophenone are also described.     

Sintering of Ceria-Doped Tetragonal Zirconia Crystallized in Organic Solvents, Water, and Air

Amorphous CeO₂–ZrO₂ gels were prepared by coprecipitation in ammonia solutions. The onset of crystallization of the gels, from calcining in air, was 420°C, while 200° to 250°C in the presence of water and organic solvents such as methanol and ethanol. The sintering behaviors of CeO₂–ZrO₂ powders were sensitive to the crystallizing conditions, since hard agglomerates formed when the precipitated gels were crystallized by normal calcination in air, whereas soft agglomerates formed when they were crystallized in water or organic solvents. CeO₂–ZrO₂ powders crystallized in methanol and water at 250°C were sintered to full theoretical density at 1150° and 1400°C, respectively, whereas that crystallized by calcination in air at 450°C was sintered to only 95.2% of theoretical density, even at 1500°C.     

Graded‐index plastic optical fiber with high mechanical properties enabling easy network installations. I

A doped poly(methyl methacrylate) (PMMA)–based graded‐index plastic optical fiber (GI POF) with high mechanical strength is reported for the first time. Although the POF is generally believed to have a good mechanical flexibility even if it has a large‐core diameter, such a high mechanical strength has been provided by making the polymer chains in the POF highly oriented in its axial direction. If such an orientation of polymer chains is eliminated, the POF becomes brittle, which is similar to silica‐based fibers. On the other hand, too high an orientation of the polymer chains induces fiber deformation in a high‐temperature atmosphere resulting from orientation relaxation. This study reports how high mechanical strengths such as the tensile strength and the large elongation are provided to the GI POF. By selecting the optimum heat‐drawing conditions, the GI POF has a mechanical strength comparable to that of the commercially available step index (SI) POF. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 404–409, 2004     

Glycoconjugated polymer 6. Synthesis of poly[styrene-<Emphasis Type="Italic">block</Emphasis>-(styrene-<Emphasis Type="Italic">graft</Emphasis>-amylose)] via potato phosphorylase-catalyzed polymerization

Summary The potato phosphorylase-catalyzed polymerization of α-D-glucose-1-phosphate (G-1-P) onto poly[styrene-block-(4-vinylbenzyl maltohexaoside)] (1) was performed at the molar ratios of [G-l-P]₀ and [maltohexaose]₀ of 35, 80, and 250. The product was found to be soluble in dimethyl sulfoxide, which was a good solvent for amylose, and showed the complex-formation with iodine, indicating that the product was assignable to poly[styrene-block-(styrene-graft-amylose)] (2). The quantitative analysis of the liberated phosphoric acid gave the average degree of polymerization o f the glucose unit (n) as 27, 5 1, and 180 for 2-I, 2-II, and 2-III, respectively. Received: 29 November 2002/Accepted: 22 December 2002 Correspondence to Toyoji Kakuchi     

Effect of Grain Boundaries on Thermal Conductivity of Silicon Carbide Ceramic at 5 to 1300 K

The thermal conductivity of a SiC ceramic was measured as 270 W·m⁻¹·K⁻¹ at room temperature. At low temperatures ( T < 25 K), the decrease in the conductivity was proportional to T ³ on a logarithmic scale, which indicated that the conductivity was controlled by boundaries. The calculated phonon mean free path in the ceramic increased with decreased temperature, but was limited to ∼4 μm, a length almost equal to the grain size, at temperatures below 30 K. We concluded that the thermal conductivity of the ceramic below 30 K was influenced significantly by grain boundaries and grain junctions.     

Direct conversion mechanism of fluorine-GIC into poly(carbon monofluoride), (CF)n

The reaction mechanisms of a stage-1 fluorine-graphite intercalation compound (GIC), C_2.5F, with 0.10 MPa of fluorine gas have been studied at 573-773 K. The original stage-1 structure of C_2.5F with semi-ionic C-F bonds and planar sp² carbon sheets is maintained in most part of the compound after the reaction at 573 K, although a large number of covalent C-F bonds are formed on the surface. This compound is partially or completely converted to poly(carbon monofluoride), (CF)_n, with covalent C-F bonds and puckered sp³ carbon sheets at 673 or 773 K, respectively. Single-phase (CF)_n obtained at 773 K possesses remarkably small BET specific surface area, 61 m²/g carbon, almost unchanged from the value of the precursor C_2.5F (69 m²/g carbon). In this reaction, the accommodation of fluorine atoms supplied from the atmosphere into the galleries of C_2.5F is facilitated by the rearrangement of originally intercalated fluorine atoms in the GIC, forming (CF)_n with fewer defects compared to those by the conventional direct fluorination of graphite.     

Surfactant-Assisted Purification of Hydrophobic DNA Nanostructures

Purification of functional DNA nanostructures is an essential step in achieving intended functions because misfolded structures and the remaining free DNA strands in a solution can interact and affect their behavior. However, due to hydrophobicity-mediated aggregation, it is difficult to purify DNA nanostructures modified with hydrophobic molecules by conventional methods. Herein, we report the purification of cholesterol-modified DNA nanostructures by using a novel surfactant-assisted gel extraction. The addition of sodium cholate (SC) to the sample solution before structure folding prevented aggregation; this was confirmed by gel electrophoresis. We also found that adding sodium dodecyl sulfate (SDS) to the sample inhibited structural folding. The cholesterol-modified DNA nanostructures prepared with SC were successfully purified by gel extraction, and their ability to bind to the lipid membrane surfaces was maintained. This method will facilitate the purification of DNA nanostructures modified with hydrophobic molecules and expand their applicability in the construction of artificial cell-like systems.