Comparison of CO2 Reduction Performance with NH3 and H2O between Cu/TiO2 and Pd/TiO2

The aim of this study is to clarify the effect of doped metal type on CO₂ reduction characteristics of TiO₂ with NH₃ and H₂O. Cu and Pd have been selected as dopants for TiO₂. In addition, the impact of molar ratio of CO₂ to reductants NH₃ and H₂O has been investigated. A TiO₂ photocatalyst was prepared by a sol-gel and dip-coating process, and then doped with Cu or Pd fine particles by using the pulse arc plasma gun method. The prepared Cu/TiO₂ film and Pd/TiO₂ film were characterized by SEM, EPMA, TEM, STEM, EDX, EDS and EELS. This study also has investigated the performance of CO₂ reduction under the illumination condition of Xe lamp with or without ultraviolet (UV) light. As a result, it is revealed that the CO₂ reduction performance with Cu/TiO₂ under the illumination condition of Xe lamp with UV light is the highest when the molar ratio of CO₂/NH₃/H₂O = 1:1:1 while that without UV light is the highest when the molar ratio of CO₂/NH₃/H₂O = 1:0.5:0.5. It is revealed that the CO₂ reduction performance of Pd/TiO₂ is the highest for the molar ratio of CO₂/NH₃/H₂O = 1:1:1 no matter the used Xe lamp was with or without UV light. The molar quantity of CO per unit weight of photocatalyst for Cu/TiO₂ produced under the illumination condition of Xe lamp with UV light was 10.2 μmol/g, while that for Pd/TiO₂ was 5.5 μmol/g. Meanwhile, the molar quantity of CO per unit weight of photocatalyst for Cu/TiO₂ produced under the illumination condition of Xe lamp without UV light was 2.5 μmol/g, while that for Pd/TiO₂ was 3.5 μmol/g. This study has concluded that Cu/TiO₂ is superior to Pd/TiO₂ from the viewpoint of the molar quantity of CO per unit weight of photocatalyst as well as the quantum efficiency.     

Determination of selenium in human serum by liquid chromatography/electron capture atmospheric pressure chemical ionization mass spectrometry after acid digestion and derivatization using 2,3-diaminonaphthalene

Analysis of selenium in biological samples is very important and numerous analytical methods for the element have been developed. One of the most convenient and widely used methods for routine determination of serum selenium is a fluorometric method using 2,3-diaminonaphthalene (DAN); however, this method lacks specificity. We observed that 4,5-benzopiazselenol (BPS), a selenium derivative of DAN, is ionized with electron capture in an atmospheric pressure chemical ionization (APCI) interface, and subsequently established a method for determining total human serum selenium by means of liquid chromatography/atmospheric pressure chemical ionization mass spectrometry. All pretreatment procedures were carried out in a single test tube to minimize selenium loss. The recovery of organic or inorganic selenium spiked to human serum was 97-103%.The detection limit of BPS was equivalent to 0.2 ng of selenium and the lower quantitative limit of serum selenium was 10 ng mL(-1). The coefficient of variation of standard concentrations in control serum samples was 4.5%. The purity of the observed peak obtained from serum samples was confirmed using the ion cluster technique.     

Synthesis of MoVNbTe(Sb)O(x) composite oxide catalysts via reduction of polyoxometalates in an aqueous medium

The synthesis of MoVNbTe(Sb)O(x)() composite oxide catalysts based on the self-organization of polyoxometalates (POMs) was investigated. The catalysts which were synthesized via reduction of POMs by using reducing agents under mild conditions and/followed by calcination in an O(2)-excluded atmosphere which superior performance for propane (amm)oxidation. It was suggested that the metastable phase formed at an elevated temperature with a specific oxidation state corresponds to the catalytic activity.     

Novel method to control release of lipophilic drugs with high potency from silicone

Silicone has been utilized as a carrier material for sustained release system of lipophilic drugs. Extensive studies revealed that drug release rate is influenced by factors such as physicochemical properties of the drug and additives.(1-5)) When a lipophilic drug is highly potent at low concentrations, the drug release rate should be strictly controlled so as to avoid side effects. In this study, using vitamin D(3) (VD(3)) as an example of such drugs, we investigated novel method to suppress initial burst and to modify drug release rate from silicone matrix. As a result, it was found that (a). addition of human serum albumin (HSA) suppressed initial burst and enhanced release rate in the later stage, resulting constant release of VD(3), (b). covering a matrix formulation with a membrane of low diffusivity (core-rod formulation) suppressed initial burst and released drug in a constant rate, and (3) using materials for which the drug has high affinity as dissolution solvent (reservoir formulation), the drug release rate was reduced.     

Total synthesis of leustroducsin B

A convergent total synthesis of leustroducsin B (1), which is known to exhibit a variety of biological activities, was successfully carried out. Notable features of our synthesis include construction of the C8 stereocenter by lipase-mediated desymmetrization of meso-diol 4 (90.2% ee) and preparation of the C9-C11 anti-diol moiety by the addition of alkynylzinc reagent 20 to the aldehyde 19. Furthermore, a new diol protecting group, p-silyloxybenzylidene, was developed for the deprotection from densely functionalized substrates under weakly acidic conditions. The protecting group was easily removed in a two-step procedure ((HF)3.Et3N; AcOH-THF-H2O).     

Diastereoselective imino-aldol condensation of chiral 3-(p-Tolylsulfinyl)-2-furaldimine and ester enolates

(Ss)-3-(p-Tolylsufinyl)-2-furaldimine was synthesized, and condensation of the chiral furaldimine with lithium ester enolates has been examined. The product distribution of the reaction is dependent upon reaction conditions and on the kind of the substituent placed on the esters. Disubstituted ester enolate resulted in the exclusive formation of (4R)-beta-lactam, while unsubstituted, tert-butyl ester enolate preferentially gave (3R)-beta-amino ester. With the monosubstituted ester enolates, the condensation afforded (4R)-beta-lactams and/or (3R)-beta-amino esters as major products. This method has been applied to an efficient route to chiral furyl beta-lactams.     

Quenching of bacteriochlorophyll fluorescence in chlorosomes from Chloroflexus aurantiacus by exogenous quinones

The quenching of bacteriochlorophyll (BChl) c fluorescence in chlorosomes isolated from Chloroflexus aurantiacus was examined by the addition of various benzoquinones, naphthoquinones (NQ), and anthraquinones (AQ). Many quinones showed strong quenching in the micromolar or submicromolar range. The number of quinone molecules bound to the chlorosomes was estimated to be as small as one quinone molecule per 50 BChl c molecules. Quinones which exhibit a high quenching effect have sufficient hydrophobicity and one or more hydroxyl groups in the alpha positions of NQ and AQ. Chlorobiumquinone has been suggested to be essential for the endogenous quenching of chlorosome fluorescence in Chlorobium tepidum under oxic conditions. We suggest that the quenching effect of chlorobiumquinone in chlorosomes from Chl. tepidum is related to the 1'-oxo group neighboring the dicarbonyl group.     

Synthesis and structure of 5,6,7,12-tetrahydrodibenz[c,f][1,5]azabismocines

Hypervalent organobismuth compounds, 6-tert-butyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azabismocines, with 13 different substituents on the bismuth atom including halogens, alkyl, alkenyl, alkynyl, aryl, or phenylthio groups have been synthesized. A key compound, 12-chloro-6-tert-butyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azabismocine, which is a precursor for other azabismocines, has been synthesized by two different procedures; one is based on Akiba’s method using 2-bromobenzylbromide as one of the starting materials and the other is a newly developed one using a cheaper starting material, 2-chlorobenzyl chloride. The structures of 12 new bismuth compounds were determined by X-ray diffraction. The eight-membered tetrahydroazabismocine ring has proved to be highly flexible and the hypervalent Bi-N bond distances vary ranging from 2.568(3) to 2.896(5) Å, depending on the electronic nature of the substituents on the bismuth atom. The Bi-N bond distances have good linear relationship against Hammett’s σ_m constants.     

Improved complementary polymer pair system: switching for enzyme activity by PEGylated polymers

The development of technology for on/off switching of enzyme activity is expected to expand the applications of enzyme in a wide range of research fields. We have previously developed a complementary polymer pair system (CPPS) that enables the activity of several enzymes to be controlled by a pair of oppositely charged polymers. However, it failed to control the activity of large and unstable α-amylase because the aggregation of the complex between anionic α-amylase and cationic poly(allylamine) (PAA) induced irreversible denaturation of the enzyme. To address this issue, we herein designed and synthesized a cationic copolymer with a poly(ethylene glycol) backbone, poly(N,N-diethylaminoethyl methacrylate)-block-poly(ethylene glycol) (PEAMA-b-PEG). In contrast to PAA, α-amylase and β-galactosidase were inactivated by PEAMA-b-PEG with the formation of soluble complexes. The enzyme/PEAMA-b-PEG complexes were then successfully recovered from the complex by the addition of anionic poly(acrylic acid) (PAAc). Thus, dispersion of the complex by PEG segment in PEAMA-b-PEG clearly plays a crucial role for regulating the activities of these enzymes, suggesting that PEGylated charged polymer is a new candidate for CPPS for large and unstable enzymes.