Ubiquity of arsenobetaine in marine animals and degradation of arsenobetaine by sedimentary micro-organisms

Arsenic compounds were extracted with chloroform/methanol/water from tissues of marine animals (four carnivores, five herbivores, five plankton feeders). The extracts were purified by cation and anion exchange chromatography. Arsenobetaine [(CH₃)₃As⁺CH₂COO^?], dimethylarsinic acid [(CH₃)₂AsOOH], trimethylarsine oxide [(CH₃)₃AsO] and arsenite, arsenate, and methylarsonic acid [(CH₃)AsO(OH)₂] as a group with the same retention time were identified by high-pressure liquid chromatography. Arsenic was determined in the collected fractions by graphite furnace atomic absorption spectrometry. Arsenobetaine found in all the animals was almost always the most abundant arsenic compound in the extracts. These results show that arsenobetaine is present in marine animals independently of their feeding habits and trophic levels. Arsenobetaine-containing growth media (ZoBell 2216E; solution of inorganic salts) were mixed with coastal marine sediments as the source of microorganisms. Arsenobetaine was converted in both media to trimethylarsine oxide and trimethylarsine oxide was converted to arsenite, arsenate or methylarsonic acid but not to dimethylarsinic acid. The conversion rates in the inorganic medium were faster than in the ZoBell medium. Two dominant bacterial strains isolated from the inorganic medium and identified as members of the Vibro–Aeromonas group were incapable of degrading arsenobetaine.     

Positive steady states for a prey-predator model with some nonlinear diffusion terms

This paper discusses a prey-predator system with strongly coupled nonlinear diffusion terms. We give a sufficient condition for the existence of positive steady state solutions. Our proof is based on the bifurcation theory. Some a priori estimates for steady state solutions will play an important role in the proof.     

Anisotropic susceptibility of (Ti1−xVx)2O3 single crystals

Anisotropy of the susceptibility, which depends on vanadium concentration, was observed for (Ti_1?xV_x)₂O₃(x=0.005, 0.015, 0.02) single crystals. The anisotropy is hard to interpret by localized magnetic states of vanadium ions.     

Reaction of 1-phenyldiazoethane with tetrachloro-p- and o-benzoquinones

Reaction of 1-phenyldiazoethane(1) with tetrachloro-p-benzoquinone(2) gave 1-alkoxy-4-ethenyloxy-tetrachlorobenzene(4). With tetrachloro-o-benzoquinone(5), 1 provided 1-alkoxy-2-ethenyloxy-tetrachlorobenzene(7) and tetrachlorobenzo-1,3-dioxolane(8). The mechanism and the effect of added methanol were discussed.     

Role of Organic Additives in the Sol-Gel Synthesis of Porous CaF2 Anti-Reflective Coatings

Porous CaF₂ anti-reflective coating films were prepared by the sol-gel method. Effects of organic additives on deposition and optical properties of the films were investigated. Amino alcohols (2-aminoethanol, 2-dimethylaminoethanol, and triethanolamine) and alcohols with larger molecular weights (ethyleneglycol, 2-methoxyethanol, cyclohexanol, and 2-(2-n-butoxyethoxy)ethanol) were chosen as the organic additives. Among these additives, cyclohexanol was the most effective to control the surface morphology and the optical properties of the films. By changing the amount of cyclohexanol in the coating solution, it was possible to control the optical thickness of the CaF₂ films. Accordingly, the wavelength giving the maximum transmittance could be changed in the UV region.     

Selective single ring-opening polymerization of spiroorthoesters with aluminium (III) acetylacetonate

A spiroorthoester, 2-methyl-1,4,6-trioxaspiro[4.6]undecane ( 1 ), was polymerized with aluminium (III) acetylacetonate as a catalyst. The resulting polymer structure was analyzed in detail by FT-IR and 270 MHz ¹H NMR, and consisted of poly(orthoester) which was obtained by selective ring-opening of the seven-membered ring. In contrast, 2-methyl-1,4,6-trioxaspiro[4.5]decane ( 2 ) and 2-methyl-1,4,6-trioxaspiro[4.4]nonane ( 3 ) did not afford any polymers. The reactivity difference of these monomers was discussed in terms of their strain energies on the basis of MM2 calculations.     

Structural effects on valence tautomerism : VII. An NMR and molecular mechanics study of the steric effects of t-butyl substituents on the cycloheptatriene-norcaradiene equilibrium of 7-cyano-7-m

7-Cyano-7-methylcycloheptatrienes containing one t-butyl group on the 1-position ($\text{2}$) or two t-butyl groups on the 1- and 3-, 1- and 4-, or 1- and 5-positions ($\text{3}$, $\text{4}$, or $\text{5}$, respectively) were synthesized and their cyclo- heptatriene (CHT)-norcaradiene (NCD) equilibria measured by variable-temperature ¹H NMR for CS₂-CD₂Cl₂ solutions. The ¹H NMR chemical shifts of the 7-methyl group indicate that these compounds are composed of essentially one CHT and one NCD tautomer with an endo geometry of the methyl group. The introduction of a t-butyl group at the 1-position of 7-cyano-7-methylcycloheptatriene ($\text{1}$) markedly shifts the equilibrium to the NCD side and the addition of the second t-butyl group further favors the NCD form, with the NCD populations for $\text{2}$, $\text{3}$, $\text{4}$, and $\text{5}$ at 25 °C 70.9, 96.5, 92.3, and 99.3%, respectively. An application of molecular mechanics (MMPI) calculations to various t-butylated CHT-NCD systems suggests that the t-butyl groups sterically destabilize the CHT form more than the NCD form, bringing about increased NCD populations.     

PHYTOCHROME-MEDIATED PHOTOTROPISM IN Adiantum PROTONEMATA-I. PHOTOTROPISM AS A FUNCTION OF THE LATERAL Pfr GRADIENT*

Abstract— Phytochrome-mediated phototropism of the protonema of the fern Adiantum capillus-veneris was studied in view of the hypothesis that phototropism is controlled by the gradient of Pfr (phytochrome in the far-red-absorbing form) across the short axis of the protonema. Fluence-response relationships were investigated using a microbeam irradiation technique that allowed simultaneous stimulation of the two sides of the subapical portion of the protonema with different fluences of red light. Mathematical models describing the tropic response as a function of fluence were derived from the hypothesis in consideration of the minimal phototransformation kinetics of phytochrome. and the fitness of the functions to the experimental data was examined. The analytical results were then evaluated in view of the photochemical properties of phytochrome known from the literature. It is concluded that the extent of the tropic response is determined by the difference in the Pfr concentrations between the two sides of the protonemal cell. It is further suggested that, even if phytochrome exists as a dimer in vivo, the physiological unit of phytochrome is the monomer.     

Concise synthesis of cyclic ethers via the palladium-catalyzed coupling of ketene acetal triflates and organozinc reagents. Application to the iterative synthesis of polycyclic ethers

The reaction of the ketene acetal triflates 9a-e and a zinc homoenolate 10 in the presence of a catalytic amount of Pd(PPh(3))(4) gave the enol ethers 11a-e in good yields. The products were converted to the corresponding cyclic ethers 14a and 14b by hydroboration and lactonization. The present methodology allowed us to synthesize the DE and GH ring segment of gambierol in a concise manner. Iterative syntheses of the polycyclic ethers 26 and 32 are also described.