Isolation and structure determination of a new marine toxin,neosurugatoxin, from the Japanese Ivory Shell, Babylonia japonica.

A new toxin, named neosurugatoxin, was isolated from the toxic Japanese Ivory Shell and its structure was determined by X-ray crystallographic analysis.     

Structure and crystallization of sub-elementary fibrils of bacterial cellulose isolated by using a fluorescent brightening agent

The structure and crystallization of carefully isolated sub-elementary fibrils (SEFs) of bacterial cellulose have been investigated using TEM, WAXD, and high-resolution solid-state ¹³C NMR. The addition of a suitable amount of fluorescent brightener (FB) to the incubation medium of Acetobacter xylinum effectively suppressed the aggregation of the SEFs into the microfibrils, as previously reported. However, this study confirmed for the first time that serious structural change in the SEFs occurs during the removal of excess FB by washing with buffer solutions having pH values higher than 6 or with the alkaline aqueous solution that was frequently used in previous studies. In contrast, the isolation of unmodified SEFs was successfully performed by utilizing a washing protocol employing pH 7 citrate–phosphate buffer solution containing 1% sodium dodecyl sulfate. High-resolution solid-state ¹³C NMR and WAXD measurements revealed that the SEFs thus isolated are in the noncrystalline state in which the pyranose rings of the almost parallel cellulose chains appear to be stacked on each other. The respective CH₂OH groups of the SEFs adopt the gt conformation instead of the tg conformation found in cellulose I _α and I _β crystals, and undergo significantly enhanced molecular motion in the absence of intermolecular hydrogen bonding associated with these groups. The main chains are also subject to rapid motional fluctuations while maintaining the parallel orientation of the respective chains, indicating that the SEFs have a liquid crystal-like structure with high molecular mobility. Moreover, the SEFs crystallize into cellulose I _β when the FB molecules that may adhere to the surface of the SEFs are removed by extraction with boiling 70 v/v% ethanol and 0.1N NaOH aqueous solution. On the basis of these results, the crystallization of the SEFs into the I _α and I _β forms is discussed, including the possible formation of the crystalline-noncrystalline periodic structure in native cellulose.     

Note Water Vapor Sorption by the Polyelectrolyte Complex of Poly (Acrylic Acid) and Poly (4-Vinyl-N-Ethylpyridinium Bromide)

A great number of studies of polyelectrolyte complexes have been carried out by various investigators; most of them concentrated on the reaction between oppositely charged polyelectrolytes [1-3]. The structure and properties of the resultant complexes have been investigated to a lesser extent, and the understanding of this new class of polymer materials is still insufficient. Thus, we have been investigating the sorption of water vapor by the complexes and the morphological changes caused by this sorption [4,5].     

Synthesis of end‐functionalized polyethers by phosphazene base‐catalyzed ring‐opening polymerization of 1,2‐butylene oxide and glycidyl ether

For the living ring‐opening polymerization (ROP) of epoxy monomers, the catalytic activity of organic superbases, tert‐butylimino‐tris(dimethylamino)phosphorane, 1‐tert‐butyl‐2,2,4,4,4‐pentakis(dimethylamino)‐2Λ⁵,4Λ⁵‐catenadi(phosphazene), 2,8,9‐triisobutyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo[3.3.3]undecane, and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phosphoranylidenamino]‐2Λ⁵,4Λ⁵‐catenadi(phosphazene) (t‐Bu‐P₄), was confirmed. Among these superbases, only t‐Bu‐P₄ showed catalytic activity for the ROP of 1,2‐butylene oxide (BO) to afford poly(1,2‐butylene oxide) (PBO) with predicted molecular weight and narrow molecular weight distribution. The results of the kinetic, post‐polymerization experiments, and MALDI‐TOF MS measurement revealed that the t‐Bu‐P₄‐catalyzed ROP of BO proceeded in a living manner in which the alcohol acted as the initiator. This alcohol/t‐Bu‐P₄ system was applicable to the glycidol derivatives, such as benzyl glycidyl ether (BnGE) and t‐butyl glycidyl ether, to afford well‐defined protected polyglycidols. The α‐functionalized polyethers could be obtained using different functionalized initiators, such as 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 6‐azide‐1‐hexanol. In addition, the well‐defined cyclic‐PBO and PBnGE were successfully synthesized using the combination of t‐Bu‐P₄‐catalyzed ROP and click cyclization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Electrical conductivity of SmS polycrystals

The electrical conductivity of SmS polycrystals has been studied in the temperature range 300?C870 K. It has been shown that, at 300 K ?? T ?? 700 K, the concentration of conduction electrons is determined by electron transfer from impurity donor levels, and at T > 700 K, by that from the samarium 4f levels.     

Synthesis of All Stereoisomers of Monomeric Spectomycin A1/A2 and Evaluation of Their Protein SUMOylation-Inhibitory Activity

A synthetic methodology to access all possible stereoisomers of spectomycin A1 (SMA1) and A2 (SMA2) has been established through late-stage diversification. The key reaction for the construction of all four diastereomers is an intramolecular cyclization based on the umpolung of π-allyl palladium species with bis(pinacolato)diborane (B₂(pin)₂). Silyl group assisted direct benzylic oxidation of each isomer enabled construction of the fragile β-hydroxytetralone skeleton to provide the SMAs. The relative and absolute stereochemistry of SMA2 was also determined, and the absolute stereochemistry of SMA1 was extrapolated based on the optical rotation of SMA2. The axial chirality of SMAs is discussed based on circular dichroism spectra and DFT calculations, and it is concluded that the M isomer is predominant in solution. Biochemical assessment of all isomers in vitro revealed that the C9 hydroxyl group and dimeric structure were both important for protein SUMOylation-inhibitory activity.     

Stereoselective analysis of flecainide enantiomers using reversed‐phase liquid chromatography for assessing CYP2D6 activity

Stereoselective analyses of flecainide enantiomers were performed using reversed‐phase high‐performance liquid chromatography (HPLC) equipped with a polysaccharide‐based chiral column (Chiralpak AS‐RH) and fluorescence detector. Excitation and emission wavelengths were set at 300 and 370 nm, respectively. Flecainide enantiomers in serum and urine were extracted using diethyl ether. The mobile phase solution, comprising 0.1 m potassium hexafluorophosphate and acetonitrile (65:35, v/v), was pumped at a flow rate of 0.5 mL/min. The recoveries of flecainide enantiomers were greater than 94%, with the coefficients of variation (CVs) <6%. The calibration curves of flecainide enantiomers in serum and urine were linear in the concentration range 5–500 ng/mL and 0.75–15 µg/mL (r > 0.999), respectively. CVs in intra‐day and inter‐day assays were 1.8–5.8 and 3.4–7.5%, respectively. In a pharmacokinetic study, the ratios of (S)‐ to (R)‐flecainide (S/R ratio) in the area under the curve and the amount of flecainide enantiomers excreted in urine were lower in a subject carrying CYP2D6*10/*10 than in subjects carrying CYP2D6*1/*2. The S/R ratio of trough serum flecainide concentration ranged from 0.79 to 1.16 in patients receiving oral flecainide. The present HPLC method can be used to assess hepatic flecainide metabolism in a pharmacokinetic study and therapeutic drug monitoring. Copyright © 2014 John Wiley & Sons, Ltd.     

Formation of polyketone particle structure by hexafluoroisopropanol solvent evaporation and effects of plasticizer addition

Few solvents are capable of dissolving polyketones (PKs). 1,1,1,3,3,3‐Hexafluoro‐2‐propanol (hexafluoroisopropanol, HFIP) is a better solvent than trifluoroethanol and m‐cresol. When HFIP was evaporated from a PK/HFIP solution, a porous cast‐film with a microparticle structure was formed because the isotactic PKs adopted a helical conformation, and convection during evaporation of the high polarity and low‐boiling‐point HFIP caused aggregation and rolling of the polymer molecules. The addition of plasticizer suppressed particle formation, improving the surface structure and mechanical properties of the film. In particular, the dielectric properties of the film improved significantly. This will enable PKs, which are rigid insulating materials, to be used as dielectric materials, broadening their range of applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 887–892