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991.
Bailey DM Hennig A Uzunova VD Nau WM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(20):6069-6077
The coupling of an enzymatic transformation with dynamic host-guest exchange allows the unselective binding of macrocycles to be used for highly selective analyte sensing. The resulting supramolecular tandem enzyme assays require the enzymatic substrate and its corresponding product to differ significantly in their affinity for macrocycles, for example, cation receptors, and to show a differential propensity to displace a fluorescent dye from its host-guest complex. The enzymatic transformation results in a concomitant dye displacement that can be accurately followed by optical spectroscopy, specifically fluorescence. By exploiting this label-free continuous enzyme assay principle with the fluorescent dye Dapoxyl and the macrocyclic host cucurbit[7]uril, a multiparameter sensor array has been designed, which is capable of detecting the presence of amino acids (e.g. histidine, arginine, lysine, and tyrosine) and their decarboxylases. Only in the presence of both, the particular amino acid and the corresponding decarboxylase, is the amine or diamine product formed. These products are more highly positively charged than the substrate, have a higher affinity for the macrocycle and, therefore, displace the dye from the complex. The extension of the high selectivity and muM sensitivity of the tandem assay principle has also allowed for the accurate measurement of D-lysine enantiomeric excesses of up to 99.98 %, as only the L-enantiomer is accepted by the enzyme as a substrate and is converted to the product that is responsible for the observed fluorescence signal. 相似文献
992.
Hebden TJ Denney MC Pons V Piccoli PM Koetzle TF Schultz AJ Kaminsky W Goldberg KI Heinekey DM 《Journal of the American Chemical Society》2008,130(32):10812-10820
Reaction of NaBH4 with (tBuPOCOP)IrHCl affords the previously reported complex (tBuPOCOP)IrH2(BH3) (1) (tBuPOCOP = kappa(3)-C6H3-1,3-[OP(tBu)2]2). The structure of 1 determined from neutron diffraction data contains a B-H sigma-bond to iridium with an elongated B-H bond distance of 1.45(5) A. Compound 1 crystallizes in the space group P1 (Z = 2) with a = 8.262 (5) A, b = 12.264 (5) A, c = 13.394 (4) A, and V = 1256.2 (1) A(3) (30 K). Complex 1 can also be prepared by reaction of BH3 x THF with (tBuPOCOP)IrH2. Reaction of (tBuPOCOP)IrH2 with pinacol borane gave initially complex 2, which is assigned a structure analogous to that of 1 based on spectroscopic measurements. Complex 2 evolves H2 at room temperature leading to the borane complex 3, which is formed cleanly when 2 is subjected to dynamic vacuum. The structure of 3 has been determined by X-ray diffraction and consists of the (tBuPOCOP)Ir core with a sigma-bound pinacol borane ligand in an approximately square planar complex. Compound 3 crystallizes in the space group C2/c (Z = 4) with a = 41.2238 (2) A, b = 11.1233 (2) A, c = 14.6122 (3) A, and V = 6700.21 (19) A(3) (130 K). Reaction of (tBuPOCOP)IrH2 with 9-borobicyclononane (9-BBN) affords complex 4. Complex 4 displays (1)H NMR resonances analogous to 1 and exists in equilibrium with (tBuPOCOP)IrH2 in THF solutions. 相似文献
993.
The mono- and bis-iodo-substituted NHC-stabilized alanes (NHC) ⋅ AlH2I and (NHC) ⋅ AlHI2 offer a convenient entry for further substitution reactions at aluminum. Reactions of (NHC) ⋅ AlH2I 1 – 4 with one equivalent of NaCp afforded the adducts (NHC) ⋅ AlH2Cp 9 – 12 (NHC=Me2ImMe ( 9 ), iPr2ImMe ( 10 ), iPr2Im ( 11 ), Dipp2Im ( 12 )). Alane adducts with two Cp substituents (NHC) ⋅ AlHCp2 13 – 16 (NHC=Me2ImMe ( 13 ), iPr2ImMe ( 14 ), iPr2Im ( 15 ), Dipp2Im ( 16 )) were prepared by the analogous reaction of (NHC) ⋅ AlHI2 5 – 8 using two equivalents of NaCp. The unusual dimeric adducts ((NHC) ⋅ AlH2Cp ⋅ CpMgI)2 17 – 19 (NHC=Me2ImMe ( 17 ), iPr2ImMe ( 18 ), iPr2Im ( 19 )) were obtained from the reaction of 1 – 3 with MgCp2. 相似文献
994.
Lars Holländer Wilhelm Kossack Matthias Kollosche Werner Wirges Friedrich Kremer Reimund Gerhard 《Liquid crystals》2016,43(10):1514-1521
Polymer-dispersed liquid crystals (PDLCs) of ferroelectric poly(vinylidene fluoride-trifluoroethylene) and nematic 4-cyano-4?-n-hexylbiphenyl (6CB) or 4-cyano-4?-n-pentylbiphenyl (5CB) were prepared to study the effect of the remanent polarisation of the polymer on the liquid crystal alignment. We measured the macroscopic alignment of the liquid crystal molecules in the thickness direction by means of Infrared Transition-Moment Orientational Analysis. Electrical poling at 100 V/µm caused an increased order parameter up to 0.15. After subsequent annealing above the nematic-to-isotropic phase-transition temperature, the order parameter was reduced to 0.02. Nevertheless, the order parameter was still higher than for non-poled film indicating a slight orientation in thickness direction. Both values are lower than those expected from model calculations. In agreement with dielectric measurements, we attribute this result to the shielding effect of mobile charge carriers within the liquid crystal inclusions. 相似文献
995.
Regina J. Patinvoh Elisabeth Feuk-Lagerstedt Magnus Lundin Ilona Sárvári Horváth Mohammad J. Taherzadeh 《Applied biochemistry and biotechnology》2016,180(7):1401-1415
Chicken feathers are available in large quantities around the world causing environmental challenges. The feathers are composed of keratin that is a recalcitrant protein and is hard to degrade. In this work, chicken feathers were aerobically pretreated for 2–8 days at total solid concentrations of 5, 10, and 20 % by Bacillus sp. C4, a bacterium that produces both α- and β-keratinases. Then, the liquid fraction (feather hydrolysate) as well as the total broth (liquid and solid fraction of pretreated feathers) was used as substrates for biogas production using anaerobic sludge or bacteria granules as inoculum. The biological pretreatment of feather waste was productive; about 75 % of feather was converted to soluble crude protein after 8 days of degradation at initial feather concentration of 5 %. Bacteria granules performed better during anaerobic digestion of untreated feathers, resulting in approximately two times more methane yield (i.e., 199 mlCH4/gVS compared to 105 mlCH4/gVS when sludge was used). Pretreatment improved methane yield by 292 and 105 % when sludge and granules were used on the hydrolysate. Bacteria granules worked effectively on the total broth, yielded 445 mlCH4/gVS methane, which is 124 % more than that obtained with the same type of inoculum from untreated feather. 相似文献
996.
Dr. Bo Li Dr. Yongji Gong Dr. Zhili Hu Dr. Gustavo Brunetto Dr. Yingchao Yang Gonglan Ye Dr. Zhuhua Zhang Dr. Sidong Lei Zehua Jin Elisabeth Bianco Xiang Zhang Dr. Weipeng Wang Prof. Jun Lou Prof. Douglas S. Galvão Prof. Ming Tang Prof. Boris I. Yakobson Dr. Robert Vajtai Prof. Pulickel M. Ajayan 《Angewandte Chemie (International ed. in English)》2016,55(36):10656-10661
Two‐dimensional (2D) layered semiconducting transition‐metal dichalcogenides (TMDCs) are promising candidates for next‐generation ultrathin, flexible, and transparent electronics. Chemical vapor deposition (CVD) is a promising method for their controllable, scalable synthesis but the growth mechanism is poorly understood. Herein, we present systematic studies to understand the CVD growth mechanism of monolayer MoSe2, showing reaction pathways for growth from solid and vapor precursors. Examination of metastable nanoparticles deposited on the substrate during growth shows intermediate growth stages and conversion of non‐stoichiometric nanoparticles into stoichiometric 2D MoSe2 monolayers. The growth steps involve the evaporation and reduction of MoO3 solid precursors to sub‐oxides and stepwise reactions with Se vapor to finally form MoSe2. The experimental results and proposed model were corroborated by ab initio Car–Parrinello molecular dynamics studies. 相似文献
997.
A detailed investigation is made of the continuity, the compactness and the spectrum of the Cesàro operator \(\mathsf {C}\) acting on the weighted Banach sequence space \(c_0(w)\) for a bounded, strictly positive weight w. New features arise in the weighted setting (e.g. existence of eigenvalues, compactness, mean ergodicity) which are not present in the classical setting of \(c_0\). 相似文献
998.
Reference spectra of important adsorbed organic and inorganic phosphate binding forms for soil P speciation using synchrotron‐based K‐edge XANES spectroscopy 下载免费PDF全文
Jörg Prietzel Gertraud Harrington Werner Häusler Katja Heister Florian Werner Wantana Klysubun 《Journal of synchrotron radiation》2016,23(2):532-544
Direct speciation of soil phosphorus (P) by linear combination fitting (LCF) of P K‐edge XANES spectra requires a standard set of spectra representing all major P species supposed to be present in the investigated soil. Here, available spectra of free‐ and cation‐bound inositol hexakisphosphate (IHP), representing organic P, and of Fe, Al and Ca phosphate minerals are supplemented with spectra of adsorbed P binding forms. First, various soil constituents assumed to be potentially relevant for P sorption were compared with respect to their retention efficiency for orthophosphate and IHP at P levels typical for soils. Then, P K‐edge XANES spectra for orthophosphate and IHP retained by the most relevant constituents were acquired. The spectra were compared with each other as well as with spectra of Ca, Al or Fe orthophosphate and IHP precipitates. Orthophosphate and IHP were retained particularly efficiently by ferrihydrite, boehmite, Al‐saturated montmorillonite and Al‐saturated soil organic matter (SOM), but far less efficiently by hematite, Ca‐saturated montmorillonite and Ca‐saturated SOM. P retention by dolomite was negligible. Calcite retained a large portion of the applied IHP, but no orthophosphate. The respective P K‐edge XANES spectra of orthophosphate and IHP adsorbed to ferrihydrite, boehmite, Al‐saturated montmorillonite and Al‐saturated SOM differ from each other. They also are different from the spectra of amorphous FePO4, amorphous or crystalline AlPO4, Ca phosphates and free IHP. Inclusion of reference spectra of orthophosphate as well as IHP adsorbed to P‐retaining soil minerals in addition to spectra of free or cation‐bound IHP, AlPO4, FePO4 and Ca phosphate minerals in linear combination fitting exercises results in improved fit quality and a more realistic soil P speciation. A standard set of P K‐edge XANES spectra of the most relevant adsorbed P binding forms in soils is presented. 相似文献
999.
Angela A. Albanese José Bonet Werner J. Ricker 《Integral Equations and Operator Theory》2016,86(1):97-112
The Cesàro operator C, when acting in the classical growth Banach spaces \({A^{-\gamma}}\) and \({A_0^{-\gamma}}\), for \({\gamma} > 0\), of analytic functions on \({\mathbb{D}}\), is investigated. Based on a detailed knowledge of their spectra (due to A. Aleman and A.-M. Persson) we are able to determine the norms of these operators precisely. It is then possible to characterize the mean ergodic and related properties of C acting in these spaces. In addition, we determine the largest Banach space of analytic functions on \({\mathbb{D}}\) which C maps into \({A^{-\gamma}}\) (resp. into \({A_0^{-\gamma}}\)); this optimal domain space always contains \({A^{-\gamma}}\) (resp. \({A_0^{-\gamma}}\)) as a proper subspace. 相似文献
1000.
Dr. Roland Frach Patrick Kibies Saraphina Böttcher Tim Pongratz Steven Strohfeldt Simon Kurrmann Dr. Joerg Koehler Martin Hofmann Prof. Dr. Werner Kremer Prof. Dr. Hans Robert Kalbitzer Prof. Dr. Oliver Reiser Prof. Dr. Dominik Horinek Prof. Dr. Stefan M. Kast 《Angewandte Chemie (International ed. in English)》2016,55(39):11713-11713