Photocatalytic oxidation of ethylene to CO2 and H2O on ultrafine powdered TiO2 photocatalysts: Effect of the presence of O2 and H2O and the addition of Pt

The complete photocatalytic oxidation of C₂H₄ with O₂ into CO₂ and H₂O has been achieved on ultrafine powdered TiO₂ photocatalysts and the addition of H₂O was found to enhance the reaction. The photocatalytic reaction has been studied by IR, ESR, and analysis of the reaction products. UV irradiation of the photocatalysts at 275 K led to the photocatalytic oxidation of C₂H₄ with O₂ into CO₂, CO, and H₂O. The large surface area of the photocatalyst is one of the most important factors in achieving a high efficiency in the photocatalytic oxidation of C₂H₄. The photoformed OH species as well as O ₂ ⁻ and O ₃ ⁻ anion radicals play a significant role as a key active species in the complete photocatalytic oxidation of C₂H₄ with O₂ into CO₂ and H₂O. Interestingly, small amount of Pt addition to the TiO₂ photocatalyst increased the amount of selective formation of CO₂ which was the oxidation product of C₂H₄ and O₂.     

Hemopexin as biomarkers for analyzing the biological responses associated with exposure to silica nanoparticles

Practical uses of nanomaterials are rapidly spreading to a wide variety of fields. However, potential harmful effects of nanomaterials are raising concerns about their safety. Therefore, it is important that a risk assessment system is developed so that the safety of nanomaterials can be evaluated or predicted. Here, we attempted to identify novel biomarkers of nanomaterial-induced health effects by a comprehensive screen of plasma proteins using two-dimensional differential in gel electrophoresis (2D-DIGE) analysis. Initially, we used 2D-DIGE to analyze changes in the level of plasma proteins in mice after intravenous injection via tail veins of 0.8 mg/mouse silica nanoparticles with diameters of 70 nm (nSP70) or saline as controls. By quantitative image analysis, protein spots representing >2.0-fold alteration in expression were found and identified by mass spectrometry. Among these proteins, we focused on hemopexin as a potential biomarker. The levels of hemopexin in the plasma increased as the silica particle size decreased. In addition, the production of hemopexin depended on the characteristics of the nanomaterials. These results suggested that hemopexin could be an additional biomarker for analyzing the biological responses associated with exposure to silica nanoparticles. We believe that this study will contribute to the development of biomarkers to ensure the safety of silica nanoparticles.     

Molecular species of triacylglycerols in the hulls of sunflower seeds (Helianthus annuus L.) following microwave treatment

Whole sunflower seeds (Helianthus annuus L.) were exposed to microwaves for 6, 12, 20 or 30 min at a frequency of 2450 MHz. The hulls were then stripped from the seeds. Molecular species and fatty acid distributions of triacylglycerols (TAGs), isolated from total lipids in the hulls, were analyzed by a combination of argentation thin‐layer chromatography (TLC) and gas chromatography. A modified argentation TLC procedure, developed to optimize the separation of the TAGs, provided 10 different groups of TAGs, based on both the degree of unsaturation and the total fatty acid chain‐length. Dilinoleolein (29.5—30.2 wt‐%), trilinolein (18.2—24.2 wt‐%), dilinoleopalmitin and dilinoleostearin (17.0—18.1 wt‐%), palmitoleolinolein and stearoleolinolein (11.4—14.0 wt‐%) and dioleolinolein (7.5—8.6 wt‐%) were the main TAGs detected after microwave roasting. However, roasting caused a significant decrease (p < 0.05), not only in TAG molecular species containing more than four double bonds, but also in the amounts of diene species present in TAGs. These results suggest that microwaves should affect TAGs in the hulls more significantly (p < 0.05) than those in the sunflower kernels.     

Analysis of membrane stereochemistry with homology modeling of sn-glycerol-1-phosphate dehydrogenase

Different enantiomeric isomers, sn-glycerol-1-phosphate andsn-glycerol-3-phosphate, are used as the glycerophosphate backbonesof phospholipids in the cellular membranes of Archaea and theremaining two kingdoms, respectively. In Archaea, sn-glycerol-1-phosphatedehydrogenase is involved in the generation of sn-glycerol-1-phosphate,while sn-glycerol-3-phosphate dehydrogenase synthesizes theenantiomer in Eukarya and Bacteria. The coordinates of sn-glycerol-3-phosphatedehydrogenase are available, although neither the tertiary structurenor the reaction mechanism of sn-glycerol-1-phosphate dehydrogenaseis known. Database searching revealed that the archaeal enzymeshows sequence similarity to glycerol dehydrogenase, dehydroquinatesynthase and alcohol dehydrogenase IV. The glycerol dehydrogenase,with coordinates that are available today, is closely relatedto the archaeal enzyme. Using the structure of glycerol dehydrogenaseas the template, we built a model structure of the Methanothermobacterthermautotrophicus sn-glycerol-1-phosphate dehydrogenase, whichcould explain the chirality of the product. Based on the modelstructure, we determined the following: (1) the enzyme requiresa Zn²⁺ ion for its activity; (2) the enzyme selectively usesthe pro-R hydrogen of the NAD(P)H; (3) the putative active siteand the reaction mechanism were predicted; and (4) the archaealenzyme does not share its evolutionary origin with sn-glycerol-3-phosphatedehydrogenase.     

Photocatalytic decomposition of NO on Ti-HMS mesoporous zeolite catalysts

Titanium oxide species were loaded within the framework of mesoporous materials (Ti-HMS) by hydrothermal synthesis. These Ti-HMS exhibited high and unique photocatalytic reactivity for the decomposition of NO into N₂ and O₂ at 275 K. In situ diffuse reflectance absorption and XRD investigations indicated that the titanium oxide species were dispersed well within the zeolite framework and isolated in tetrahedral coordination with low Ti content. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photocatalytic decomposition of NO on titanium oxide thin film photocatalysts prepared by an ionized cluster beam technique

Transparent TiO₂ thin film photocatalysts were prepared on transparent porous Vycor glass (PVG) by an ionized cluster beam (ICB) method. The UV‐VIS absorption spectra of these films show specific interference fringes, indicating that uniform and transparent TiO₂ thin films are formed. The results of XRD measurements indicate that these TiO₂ thin films consist of both anatase and rutile structures. UV light (λ > 270 nm) irradiation of these TiO₂ thin films in the presence of NO led to the photocatalytic decomposition of NO into N₂, O₂ and N₂O. The reactivity of these TiO₂ thin films for the photocatalytic decomposition of NO is strongly dependent on the film thickness, i.e., the thinner the TiO₂ thin films, the higher the reactivity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigations on the photoluminescence properties of Mo-MCM-41 and the photocatalytic decomposition of NO in the presence of CO

The photocatalytic decomposition of NO into N₂ and CO₂ on Mo-MCM-41 was found to proceed efficiently in the presence of CO. In situ photoluminescence measurements demonstrated that this reaction proceeds in a redox cycle between alternating Mo⁶⁺ and Mo⁴⁺ ions. The yields of N₂ formation in the photocatalytic reaction correspond with the yields of the photoluminescence of the tetrahedrally coordinated Mo oxide species, indicating that the charge transfer excited triplet state of the tetrahedral Mo oxide species plays a significant role in this reaction, leading to the formation of N₂ and CO₂ with a good stoichiometry. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of thermally stable mesoporous TiO2 and investigation of its photocatalytic activity

The effects of heat treatment, dopant type and thickness of sol layer, on the formation and stability of ordered TiO₂ mesostructure were investigated. Higher ageing temperature facilitates the separation of organic phase and inorganic phase, while thinner sol layer facilitates the formation of homogeneous system and improves the mesostructural order of TiO₂. Lanthanum dopant, which is more electropositive than Ti, can improve the thermal stability of mesostructure by enhancing the strength of Ti–O bond. On the contrary, Fe and Pd dopants, which are more electronegative than Ti, decrease the thermal stability of mesostructure. Furthermore, La doped mesoporous TiO₂ shows high activity in the photocatalytic degradation of Rhodamine B under the irradiation of visible light.     

Positional distribution of fatty acids in triacylglycerols and phospholipids from adzuki beans (Vigna angularis)

The fatty acid distributions of triacylglycerols (TAG) and major phospholipids (PL) obtained from adzuki beans (Vigna angularis) were investigated. The total lipids extracted from the beans were separated by thin‐layer chromatography (TLC) into eight fractions. The major lipid components were PL (63.5 wt‐%), TAG (21.2 wt‐%), steryl esters (7.5 wt‐%) and hydrocarbons (5.1 wt‐%), while free fatty acids, diacylglycerols (1,3‐DAG and 1,2‐DAG) and monoacylglycerols were also present in minor proportions (0.2–1.1 wt‐%). The major PL components isolated from the beans were phosphatidylcholine (45.3 wt‐%), phosphatidylethanolamine (25.8 wt‐%) and phosphatidylinositol (21.5 wt‐%). Phosphatidylinositol was unique in that it had the highest saturated fatty acid content among the three PL. With a few exceptions, however, the principal characteristics of the fatty acid distribution in the TAG and three PL were evident in the beans: Unsaturated fatty acids were predominantly concentrated in the sn‐2 position while saturated fatty acids primary occupied the sn‐1 or sn‐3 position in the oils of the adzuki beans. In general, these results could be useful to both consumers and producers for the manufacture of traditional adzuki foods in Japan.     

Preparation of highly dispersed TiO2 in hydrophobic mesopores by simultaneous grafting and fluorinating

TiO₂ photocatalysts highly dispersed in the MCM-41 mesoporous silica material were synthesized using two different TiO₂ precursors of TiF₄ and (NH₄)₂TiO(C₂O₄)₂. The catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption–desorption, transmission electron microscopy (TEM), UV–vis absorption, X-ray photoelectron spectroscopy (XPS), and Ti K-edge X-ray absorption fine structure (XAFS). The hydrophobic properties and catalytic activities of photocatalysts with different TiO₂ precursors and loading amount were examined by adsorption and degradation of iso-butanol diluted in water. The results showed that the TiO₂ loaded MCM-41 prepared from TiF₄ exhibited higher photocatalytic activity than from (NH₄)₂TiO(C₂O₄)₂. The fluorine-modified hydrophobic pore walls formed in the impregnation process using TiF₄ as well as highly dispersed TiO₂ nanoparticles play a crucial role for the high photocatalytic efficiency.