Yoshiro Kaneko

Novel Gelling Systems of κ-, ι- and λ-Carrageenans and their Composite Gels with Cellulose Using Ionic Liquid

Gels of three types of carrageenans (kappa-, iota- and lambda-), as well as their composite gels with cellulose, were prepared using an ionic liquid, 1-butyl-3-methylimidazolium chloride (BMIMCl), by a heating-cooling process. kappa-Carrageenan gave the formation of hard gel while the other two carrageenans gave the formation of softer gels with BMIMCl. The gels were characterized by X-ray diffraction (XRD), thermal analysis (TGA and DSC), scanning electron microscope (SEM) and compressive testing. The results indicated that, among the three types of carrageenans, kappa- and iota-carrageenans gave better miscible gels with BMIMCl, followed by lambda-carrageenan. On the other hand, lambda-carrageenan gave a better miscible composite gel with cellulose and BMIMCl, followed by iota- and kappa-carrageenans. The stress-strain curves indicated that the mechanical properties of the above gel systems on the compressive mode were much better than those of the hydrogels of kappa- and iota-carrageenans as well as the cellulose gel with BMIMCl.

Molecular arrangement of rhodamine 6G cations in the films of layered silicates: the effect of the layer charge

Montmorillonite nanocor saturated with Li+ cations was used for the synthesis of reduced charge montmorillonites (RCMs). The films of RCMs with intercalated rhodamine 6G (R6G) were prepared by adsorption of the dye on montmorillonite film deposited on a quartz slide. Penetration of the dye into the interlayer spaces of silicates was monitored by elemental analysis and X-ray diffraction measurements of the prepared R6G/silicate films. Polarized UV-Vis spectroscopy was used for the characterization of the molecular orientation of dye cations on silicate surface. There were several species of R6G cations in the interlayer spaces of the inorganic host, which was easily resolvable by the polarized spectra. The cations forming H-aggregates and absorbing light at low wavelengths were oriented in nearly perpendicular fashion, which was observed as a strongly positive dichroism, i.e., the increase of the dichroic ratio with film tilting. Adsorbed isolated dye cations were inclined at low angles with respect to the plane of the silicate surface. The layer charge of the inorganic host affected only partially the orientation of dye cations in the H-aggregates, but rather it controlled the extent of aggregation and in this way the number of nearly perpendicularly oriented cations.

Synthesis of ion-exchangeable layered polysiloxane by sol–gel reaction of aminoalkyltrialkoxysilane: a new preparation method for layered polysiloxane materials

An ion-exchangeable layered polysiloxane containing alkylammonium groups was synthesized by sol–gel reaction of 3-aminopropyltrimethoxysilane (APTMOS) catalyzed by hydrochloric acid; the present reaction system provides a new method for the preparation of layered polysiloxane materials.

Synthesis of nanostructured bio-related materials by hybridization of synthetic polymers with polysaccharides or saccharide residues

In the first part of this review, we describe the synthesis of nanostructured hybrid materials composed of polysaccharides and synthetic polymers. Amylose–synthetic polymer inclusion complexes were synthesized by amylose-forming polymerization using phosphorylase enzyme in the presence of synthetic polymers such as polyethers and polyesters. Alginate–polymethacrylate hybrid materials were prepared by free-radical polymerization of cationic methacrylate in the presence of sodium alginate. These methods allow the simultaneous control of the nanostructure with polymerization, giving well-defined hybrid materials. In the second part of this review, we describe the synthesis of novel glycopolymers with rigid structures. Polyaniline-based glycopolymers were synthesized by means of oxidative polymerization of N-glycosylaniline. Polysiloxane-based glycopolymers were prepared by means of introduction of sugar-lactone to the rodlike polysiloxane. These glycopolymers had regular higher-ordered structures due to their rigid polymer backbones, resulting in control of the three-dimensional array of sugar-residues.

Molecular orientation of methylene blue cations adsorbed on clay surfaces

Abstract Cationic dye, methylene blue (MB), was intercalated into films of expandable clay minerals with low, moderate and high layer charges (saponite, montmorillonite and synthetic expandable mica-fluorohectorite, respectively) . Tilted orientation of the dye cations on the silicate surface was observed by polarized ultraviolet-visible (UV-Vis) transmission spectroscopy. The tilting angle of the dye cations increased with the formation of high-order H-aggregates that absorb light at 525 μm. These dye species were formed only on the surface of fluorohectorite, which has the highest layer charge, and exhibited dichroism. Models for the orientation of MB cations on a clay surface were proposed based on MB orientation models previously reported, and compared with the basal spacings determined by X-ray diffraction.

Acetylation of α-chitin in ionic liquids

Acetylation of alpha-chitin using acetic anhydride in an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), was performed. First, a mixture of chitin and AMIMBr (2% w/w) was heated at 100 degrees C for 24h for dissolution. Then, acetic anhydride (5-20 equiv) was added to the solution and the mixture was heated with stirring at desired temperatures for 24h. The product was precipitated by the addition of the reaction mixture into methanol. The IR spectrum of the product indicated the progress of acetylation. The degrees of substitution (DS), which were determined from the IR spectra, increased with increasing the amounts of acetic anhydride used for the reaction. The highest DS was 1.86, which was obtained by the reaction using 20 equiv of acetic anhydride at 100 degrees C. The product with this DS value was soluble in DMSO, and thus the structure of the product was further confirmed by (1)H NMR spectroscopy in DMSO-d(6). The DS value estimated by the integrated ratio of signals due to acetyl protons to a signal due to anomeric protons was in good agreement with that determined from the IR spectrum.

Preparation of cage-like octa(3-aminopropyl)silsesquioxane trifluoromethanesulfonate in higher yield with a shorter reaction time

Cage-like octa(3-aminopropyl)silsesquioxane trifluoromethanesulfonate (OAP-POSS-CF3SO3) was prepared in higher yield (ca. 93%) with a shorter reaction time (ca. 5–6 h), when the hydrolytic condensation of 3-aminopropyltrimethoxysilane was performed using the superacid trifluoromethanesulfonic acid as a catalyst. The structure of the resulting OAP-POSS-CF3SO3 was confirmed mainly by 29Si NMR, MALDI-TOF MS, ESI MS, and IR measurements. It is suggested that the lower pKa of the acid catalyst is an important factor leading to the improved yield for the preparation of OAP-POSS-CF3SO3.

Preparation of temperature-induced shapeable film material from guar gum-based gel with an ionic liquid

A temperature-induced shapeable film material was prepared from guar gum-based gel with an ionic liquid, 1-butyl-3-methylimidazolium chloride, by soaking and compression techniques.

Nitric oxide release in human aortic endothelial cells mediated by delivery of amphiphilic polysiloxane nanoparticles to caveolae.

Microdomains such as lipid raft and caveolae are organized as functional compartments in plasma membrane of cells. In this study, we note the functional platform of caveolae with dual functions, internalization of external substances and cell signalings leading to nitric oxide release, and hypothesize that the switching of enzyme activity of endothelial nitric oxide synthase can be achieved by targeting caveolae with nanoparticles. We prepared polysiloxane nanoparticles and studied cellular uptake of the nanoparticles and its concomitant influence on the nitric oxide release in human aortic endothelial cells. We found that polysiloxane nanoparticles were endocytosed via caveolae in human aortic endothelial cells and that enhanced nitric oxide release was followed by the cellular uptake of the nanoparticles. Furthermore, we confirmed that endothelial nitric oxide synthase was activated during cellular uptake of the nanoparticles. These findings support our idea that delivery of the polymeric nanoparticles to endothelial cells can lead to the induction of nitric oxide release.

Enzymatic α-glucosaminylation of maltooligosaccharides catalyzed by phosphorylase

This paper describes phosphorylase-catalyzed enzymatic alpha-glucosaminylation for the direct incorporation of a 2-amino-2-deoxy-alpha-D-glucopyranose unit into maltooligosaccharides. When the reaction of 2-amino-2-deoxy-alpha-D-glucopyranosyl 1-phosphate as the glycosyl donor with maltotetraose as a glycosyl acceptor was performed in the presence of phosphorylase, glucosaminylated oligosaccharides were produced, which were characterized by MALDI-TOF MS measurement after N-acetylation of the crude products. The N-acetylated derivative of the main product in this system was isolated by using HPLC, and its structure was confirmed by MS and (1)H NMR spectra. Furthermore, glucoamylase-catalyzed reaction of the isolated compound provided support that the alpha-glucosamine unit is positioned at the non-reducing end of the oligosaccharide.