Isolation and structure determination of complexed poly(3-hydroxyalkanoate) from beet (Beta vulgaris L.)

Complexed poly(3-hydroxyalkanoate)s (cPHAs), one of two types of natural PHAs, occur in both prokaryotes and eukaryotes as a complex with biomacromolecules and could be involved in various physiological functions. In this study, a cPHA-component derived from a complex with calcium polyphosphate was isolated from sugar beet (Beta vulgaris L.) and determined to be a homopolymer composed of 3-hydroxybutyrate. MALDI MS provided the number-average molecular weight (Mn = 9,124 Da) and polydispersity index (PDI = 1.01), showing that beet cPHA has a slightly lower molecular mass than the known Escherichia coli cPHA. In addition, the structural analysis of both end groups showed that (i) 100 mol-% of the carboxyl end is free, while about 30 mol-% of the hydroxyl end is free and about 70 mol-% masked and (ii) the end hydroxyl group is masked by at least six identified short-chain alkanoic and alkanedioic acids. Based on such end-group characteristics, the polymerization mechanism of beet cPHA is discussed.     

Rhodium(I)‐Catalyzed Cycloisomerization of Homopropargylallene‐Alkynes through C(sp3)−C(sp) Bond Activation

Upon exposure to a catalytic amount of [RhCl(CO)₂]₂ in 1,4‐dioxane, homopropargylallene‐alkynes underwent a novel cycloisomerization accompanied by the migration of the alkyne moiety of the homopropargyl functional group to produce six/five/five tricyclic compounds in good yields. A plausible mechanism was proposed on the basis of an experiment with ¹³C‐labeled substrate. The resulting tricyclic derivatives were further converted into the corresponding bicyclo[3.3.0] skeletons with vicinal cis dihydroxy groups.     

Sonochemical reactions occurring in organic solvents: reaction kinetics and reaction site of radical trapping with 1,1-diphenyl-2-picrylhydrazyl

The reaction of 1,1-diphenyl-2-picrylhydrazyl (DPPH) with a radical intermediate was investigated in the sonolysis of several organic solvents. The rate of the DPPH consumption in the sonolysis of methanol obeyed first-order kinetics at low concentrations of DPPH, while the rate became zero-order as the concentration of DPPH further increased. The radical trapping reactions of DPPH were found to be considerably slow compared with the formation of hydrogen molecules in the sonolysis of alcohols and hydrocarbons. These results indicate that H atoms formed in the solvent sonolysis quickly react to form stable molecules such as hydrogen in the cavitation bubble and/or at the interface region. The rates of the DPPH consumption were strongly dependent on the vapor pressure and relative evaporation rate of the solvents. It was proposed that the optimum vapor pressure exists for an effective formation of radical species.     

Size-reduction induced ferromagnetism and photo-magnetic effects in azobenzene-thiol-passivated gold nanoparticles

We have observed size-reduction induced ferromagnetism and significant photo-magnetic effects in azobezene-thiol-modified gold nanoparticles. When the particle size was reduced to 1.7 nm, ferromagnetism even at room temperature was observed while diamagnetism was dominating with the particle size of 5.0 nm. Furthermore, reducing the particles size to 1.7 nm also gave rise to photo-magnetic properties because the decrease in particle size provided free volume between each of the azobenzene ligands. This photo-magnetic effect could be attributed to photo-induced changes in the values of d-charge losses due to the photoisomerization of azo-ligands, which were accompanied by the inversion of surface dipole values to the opposite sign.     

ELECTROOPTIC EFFECTS OF THICK FREELY SUSPENDED FERROELECTRIC LIQUID CRYSTAL FILM AND CELL

Abstract

Electrooptic effects of thick freely suspended ferroelectric liquid crystal films and conventional cells that are thicker than helical pitch have been studied. A very slow molecular motion was observed in the case of the thick films that have no solid surface.     

Direct determination of bromine in plastics by electrothermal vaporization/inductively coupled plasma mass spectrometry using a tungsten boat furnace vaporizer and an exchangeable sample cuvette system

A tungsten boat furnace vaporization inductively coupled plasma mass spectrometry (TBF/ICP‐MS) method has been applied to the direct determination of bromine in plastic samples. In the pretreatment, the plastic sample is spread over a small sample cuvette made of tungsten by treating it with a strongly basic organic solution, e.g., octanol or diisobutyl ketone in the presence of potassium hydroxide. The cuvette is placed on a tungsten boat furnace, with which the electrothermal vaporizer is equipped. At the vaporization step, a widely spread thin layer of the sample facilitates its efficient evaporation and introduction into an ICP mass spectrometer. The most remarkable feature is that all the bromine species in plastic samples are decomposed to form a thermally stable inorganic salt during the pretreatment procedure. Therefore, the bromine content in plastic samples can be measured by a calibration curve method constructed with an aqueous standard solution of potassium bromate(V). The detection limit (3σ) was estimated to be 0.77 pg of bromine, which corresponds to a concentration of 0.31 ng g^?1 of bromine in plastic samples when a sample amount taken of 2.5 mg is studied. The relative standard deviation was calculated to be 2.2%. Analytical results of some plastic samples, which contained both inorganic bromide salts and also organic bromine species, are given. Copyright © 2010 John Wiley & Sons, Ltd.     

Photomagnetic K(0.25)Ni(1-x)Co(x)[Fe(CN)6]·nH2O and K(0.25)Co[Fe(CN)6](0.75y)[Cr(CN)6](0.75(1-y))·nH2O Prussian blue analogue solid solutions

Magnetically bistable solid solutions of Prussian blue analogues with chemical formulas of K(α)Ni(1-x)Co(x)[Fe(CN)(6)](β)·nH(2)O (Ni(1-x)Co(x)Fe) and K(α)Co(γ)[Fe(CN)(6)](y)[Cr(CN)(6)](1-y)·nH(2)O (CoFe(y)Cr(1-y)) have been synthesized and studied using mass spectrometry, M?ssbauer spectroscopy, X-ray diffraction, temperature-dependent infrared spectroscopy, and dc magnetometry. These compounds provide insight into interfaces between the photomagnetic Co-Fe Prussian blue analogue and the high-T(C) Ni-Cr Prussian blue analogue that exist in high-T(C) photomagnetic heterostructures. This investigation shows that the bistability of Co-Fe is strongly modified by metal substitution, with Ni(1-x)Co(x)Fe stabilizing high-spin cobalt-iron pairs and CoFe(y)Cr(1-y) stabilizing low-spin cobalt-iron pairs, while both types of substitution cause a dramatic decrease in the bistability of the material.