A hydrophobic CO
2
physisorbent
Most materials for carbon dioxide (CO
2
) capture of fossil fuel combustion, such as amines, rely on strong chemisorption interactions that are highly selective but can incur a large energy penalty to release CO
2
. Lin
et al
. show that a zinc-based metal organic framework material can physisorb CO
2
and incurs a lower regeneration penalty. Its binding site at the center of the pores precludes the formation of hydrogen-bonding networks between water molecules. This durable material can preferentially adsorb CO2 at 40% relative humidity and maintains its performance under flue gas conditions of 150°C. —PDS
Bi-and monometallic nanoparticles of Au and Pd with a rather narrow size distribution were deposited on polyaniline (PANI) and their structural properties as well as catalytic behavior in the aerobic oxidation of benzyl alcohol were investigated. The size of the mono-and bimetallic particles was controlled in a narrow range (2.4-3.7 nm) using a colloidal preparation route. Admixing Pd to Au resulted in a strong enhancement of selectivity to benzaldehyde reaching a maximum of 98% at full conversion at 100 °C with bimetallic particles containing Au/Pd in a ratio of 1:9. Pure Au particles were significantly more active than pure palladium particles of the same size. Chemical, structural, and electronic properties of the bimetallic catalysts were characterized using high angle annular dark field scanning transmission electron microscopy, atomic absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy. The PANI-supported nanoparticles showed a core shell structure with an Au enriched core and a Pd rich shell. The electronic changes occurring upon admixing Pd to Au were examined with X-ray absorption near-edge specroscopy and XPS. The binding energy of core level electrons and the valence d-band occupation in the bimetallic particles were significantly altered in comparison to the monometallic particles, which together with the core shell structure is supposed to be the main reason for the observed changes in the catalytic behavior.
a b s t r a c tMixed-linker metal-organic frameworks based on the Cu-BTC structure have been synthesized in which the benzene-1,3,5-tricarboxylate (BTC) linkers have been partially replaced by pyridine-3,5-dicarboxylate (PyDC). X-ray-based techniques (powder XRD and XAS), thermal analysis, and infrared spectroscopy proved that a desired amount of PyDC (up to 50%) can be incorporated without changing significantly the crystal structure. The pyridine unit can be seen as a defect site in the local coordination environment of the dimeric copper units, which is significantly altering their electronic structure and the catalytic properties. Both Cu-BTC and the mixed Cu-BTC-PyDCs catalyze the demanding direct hydroxylation of toluene both in acetonitrile and in neat substrate. Different selectivity toward the desired ortho-and para-cresol and other oxidation products (benzaldehyde, benzyl alcohol, methylbenzoquinone) was observed for Cu-BTC and the Cu-BTC-PyDCs, respectively. Leaching tests and comparison with homogeneously dissolved Cu catalysts indicate mainly a heterogeneous reaction pathway.
The MIXMOF concept has been applied to the metal-organic framework compound MIL-53(Al). The random incorporation of two different linker molecules (benzene-1,4-dicarboxylate and 2-aminobenzene-1,4-dicarboxylate) in the framework structure and its influence on thermal stability were proven using several complementary techniques (XRD, ATR-IR, MAS-NMR and TG).
SUMMARYThe fructan-y?-fructosidase activity (1-FEH; EC 3.2.1.80) that degrades inulin in tubers oi Helianthus tuberosus L. appears to be developmentally regulated; it was low in growing tubers but increased during dormancy and sprouting. In spite of relatively high 1-FEH activity in vitro, fructose concentration was very low in developing and dormant tubers and increased markedly only during sprouting. A fructan-/S-fructosidase from such sprouting tubers was purified 41-fold to a single protein band on one-dimensional sodium dodecylsulphate-polyacrylamide gels. The purification procedure included ammonium sulphate precipitation, lectin-affinity chromatography on concanavalin A, anion-exchange and cation-exchange chromatography. The enzyme had an apparent molecular mass of 75000 measured by size-exclusion chromatography, and 79000 measured by one-dimensional sodium dodecylsulphate-polyacrylamide gel electrophoresis. It exhibited a high substrate specificity, hydrolysing terminal /?-(2-l)-fructosyl-fructose-linkages in linear and branched fructan oligomers; y^-(2-6)-linkages were hardly hydrolysed. Hydrolysis of inulin oligomers followed normal saturation kinetics: K^ values for 1,1-kestotetraose and 1,1,1-kestopentaose were 8-3 mM and 12 mM, respectively. Fructosyl residues were hydrolysed from inulin oligomers by a multi-chain mechanism. The fructan-y?-fructosidase showed optimal enzyme activity at pH 5-2, and it retained its full activity after pre-incubation for 1 h at up to 40 °C. The release of fructose from 5 mM 1,1-kestotetraose was reduced by 25 % when 1-FEH was assayed in the presence of 10 mM sucrose. It is proposed that the inhibition of 1-FEH activity by sucrose is a mechanism for controlling fructan degradation in planta.
I NTRODUCTIQNPkytochrome is one of the most fasrinsring; proteins in plants. A great many striking photomorphoyenctie proccssex arc mediated by it (see [l]). Phytechromc is well charactcrizcd by biochemical and immunological techniques and by methods OF molecular biology, Dcspirc this fact, the mechanism of action of phytochrome, the molecular links between its conformational alterations and the ensuing biochemical and morphogenetic phenomena are still unknown, Many sophisticated experiments have not been able to unveil the secret of light-induced signal-transduction by phytochromc. Here we report on findings which we assume could be evidence of the mode of action and the phylogeny of this light-sensing protein.
MATERIALS AND METHODS I. Prepurct~ion of clones uttd scqrrctlcitrgLibraries of cDNA were constructed in the Xgti 1 expression vector.
Phages giving a positive response with a mo~wA~nal antibody (Z-3Bl
As chemists and materials scientists, it is our duty to synthesize and utilize materials for a multitude of applications that promote the development of society and the well-being of its...
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