Motonari Shibakami

Microtubule-Cyclodextrin Conjugate: Functionalization of Motile Filament with Molecular Inclusion Ability

A microtubule-β-cyclodextrin conjugate was prepared on a kinesin-adsorbed glass surface by chemical and biochemical means. Fluorescence microscope observation and a motility assay indicated that the conjugate simultaneously expressed an inherent motor function and an inclusion property.

Activation of diacylglycerol acyltransferase expressed in Saccharomyces cerevisiae: overexpression of Dga1p lacking the N-terminal region in the ∆snf2 disruptant produces a significant increase in its enzyme activity

We previously found that overexpression of DGA1 encoding diacylglycerol acyltransferase (DGAT) in the ∆snf2 disruptant of Saccharomyces cerevisiae caused a significant increase in lipid accumulation and DGAT activity. The present study was conducted to investigate how Dga1p is activated in the ∆snf2 disruptant. To analyze the expression of Dga1p in wild type and the ∆snf2 disruptant, we overexpressed Dga1p with a 6x His tag at the N-terminus and a FLAG tag at the C-terminus. Immunoblotting using anti-6x His and anti-FLAG antibodies revealed that, in addition to full-length protein, Dga1p lacking the N-terminus was produced only in the ∆snf2 disruptant. Full-length Dga1p and N-terminally truncated Dga1p were separated and purified from the lipid body fraction by using anti-FLAG M2 agarose and TALON metal affinity resin. Major DGAT activity was recovered in the purified fraction of N-terminally truncated Dga1p, indicating that proteolytic cleavage at the N-terminal region is involved in DGAT activation in the ∆snf2 disruptant. Analysis of the cleavage site of N-terminally truncated Dga1p revealed a major site between Lys-29 and Ser-30. We then overexpressed truncated Dga1p variants that lacked different N-terminal amino acids and had a FLAG tag at the C-terminus. The homogenate and lipid body fraction of the ∆snf2 disruptant overexpressing Dga1p lacking the N-terminal 29 amino acids (Dga1∆N2p) had higher DGAT activity than that overexpressing Dga1p, indicating that Dga1∆N2p is activated Dga1p. Dga1∆N2p-FLAG(C-terminus) was purified to near homogeneity by anti-FLAG M2 agarose chromatography and maintained significant DGAT activity. These results provide a new strategy to engineer expression of DGAT.

The synthesis of perfluoroamine using nitrogen trifluoride

Abstract The reactions of nitrogen trifluoride ( 1 ) with hexafluoropropene ( 2 ) in the presence of cesium fluoride (CsF) gave 2- ( 3 ) and 1-heptafluoropropyldifluoroamine ( 4 ) in moderate yields. Tetrafluoroethylene ( 6 ) and octafluoro-2-butene ( 8 ) similarly reacted with 1 to give corresponding products.

Polysaccharide nanofiber made from euglenoid alga.

We have fabricated a polysaccharide nanofiber made from paramylon (β-1,3-glucan), a storage polysaccharide stored as a micrometer-sized particle in the cell of euglenoid alga. Preparation of this nanofiber primarily hinges on the bottom-up approach. First, paramylon, which is originally present in the form of a bundle of nanofibers in a particle, was fibrillated to a randomly coiled polymer by dissolving the particle in a 1.0-mol/L NaOH aqueous solution. Second, the randomly coiled polymer was allowed to self-assemble into a triplex as the NaOH concentration was reduced to 0.25-0.20mol/L. Third, a 20-nm-width nanofiber made from the triplex emerged in the solution when the NaOH concentration was reduced to approximately 0.20mol/L.

Stereoselective glycosylations using benzoylated glucosyl halides with inexpensive promoters.

Reactions of O-benzoylated glucopyranosyl halide (I, Br), isolated or generated in situ from per-benzoylated glucose (8a) and trimethylsilyl halide, with various alcohols were efficiently promoted by zinc halide (Cl, Br) or N-bromosuccinimide with a catalytic ZnI(2) to give the corresponding 1,2-trans-beta-glucosides in good to high yields. When the anomeric halogenation of 8a was carried out in the presence of reactive alcohols, 1,2-cis-alpha-glucosides were selectively formed.

Preparation of carboxylic acid-bearing polysaccharide nanofiber made from euglenoid β-1,3-glucans

This paper introduces a new strategy for creating surface modified polysaccharide nanofibers. To demonstrate proof of principle, the synthesis, structure, and self-assembly behavior of a carboxylic acid-bearing polysaccharide made from paramylon (β-1,3-glucan) and succinic anhydride were investigated. Examination by a combination of NMR, FT-IR, and SEC-MALLS confirmed that successful preparation of the desired succinylated paramylon without significant depolymerization. NMR, SEC-MALLS, visible absorption and CD spectroscopic analyses indicated that the paramylon derivative forms the triplex structure in solutions. SEM observation revealed that succinylated paramylon forms a nanofiber that has carboxylic acid on the surface.

Thermoplasticization of euglenoid β-1,3-glucans by mixed esterification

We experimentally demonstrated that paramylon, a storage polysaccharide of Euglena gracilis, is efficiently thermoplasticized by adding acyl groups that differ in alkyl chain length. Glass transition temperature of mixed paramylon esters was higher than those of plant-based polylactic acid (PLA), poly 11-aminoundecanoic acid (PA11), and petroleum-based acrylonitrile-butadiene-styrene (ABS) resin and was comparable to that of cellulose acetate stearate (CAS). Their thermoplasticity was equivalent to or higher than those of these reference plastics. The bending strength and bending elastic modulus of injection molded test specimens made from mixed paramylon esters were comparable to those of the reference plastics. While their impact strength was lower than that of specimens made from ABS resin and CAS, it was comparable to those of PLA and PA11. Euglenoid β-1,3-glucans are thus a potential component of thermoplastic materials.

Deaminative Fluorination of Anilines with Silicon Tetrafluoride: Utility of Silicon Tetrafluoride as a Fluorine Source

Application of silicon tetrafluoride to deaminative fluorination of anilines as a fluorine source is investigated. A diazotization of anilines proceeds with silicon tetrafluoride and t-butyl nitrite under mild condition and the following fluoro-dediazoniation affords fluoroarenes in good yields.

Potassium dihydrogen trifluoride: a novel fluorinating reagent for ring-opening of epoxides

Abstract It has been found that potassium dihydrogen trifluoride is an efficient and easy-to-handle solid reagent for the ring-opening reaction of epoxides giving fluorohydrins regio- and stereo-selectively. The reaction proceeds via cis -addition of HF to the epoxide.

One-pot synthesis of thermoplastic mixed paramylon esters using trifluoroacetic anhydride.

Mixed paramylon esters prepared from paramylon (a storage polysaccharide of Euglena), acetic acid, and a long-chain fatty acid by one-pot synthesis using trifluoroacetic anhydride as a promoter and solvent were shown to have thermoplasticity. Size exclusion chromatography indicated that the mixed paramylon esters had a weight average molecular weight of approximately 4.9-6.7×10(5). Thermal analysis showed that these esters were stable in terms of the glass transition temperature (>90°C) and 5% weight loss temperature (>320°C). The degree of substitution of the long alkyl chain group, a dominant factor determining thermoplasticity, was controlled by tuning the feed molar ratio of acetic acid and long-chain fatty acid to paramylon. These results implied that the one-pot synthesis is useful for preparing structurally-well defined thermoplastic mixed paramylon esters with high molecular weight.