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1.
Helmut Sprdizer Andrea Pichler Wolfgang Holzer Irene Toth Bettina Zuchart 《Helvetica chimica acta》1997,80(1):139-145
Khusimone (1), one of the main odor-donating compounds of vetiver oil is subject of the following study on structure/odor relationship. The omittance of the ethano bridge of the tricyclic khusimone leads to a bicyclic system. The stereoselective approach to this degraded structure is described, and the olfactory properties are studied. The key step of the synthesis of the hydrindane nucleus is based on a highly diastereoselective conjugate addition to a chiral oxo-cyclopentene-2-carboxylate. 相似文献
2.
Investigations on Metal Catalysts. XXXII. On Alloying and Dispersion of Nickel-Rhenium Catalysts Unsupported Ni? Re catalysts were prepared by reduction of mixtures from NiO and NH4ReO4 at 400°C with hydrogen (1st series), followed by a heat treatment at 650°C in flowing hydrogen (2nd series). The bimetallic powders were characterized by DTA investigations, X-ray measurements, N2 adsorption, and CO chemisorption. The degree of alloying and the changes in dispersion as a result of adding a second metal to a basic one is discussed. 相似文献
3.
Anion excess colorless fluorite-type strontium-yttrium chloride has been prepared. Single crystals of the SrY compound exhibit a primitive cubic lattice with a = 6.967(1)Å. Two mutually exclusive structural models for solutions, neither of which is exact, are discussed. The first is a vacancy model in which the extra charge which results from substitution of Y3+ for Sr2+ is balanced by the simultaneous removal of a Sr2+Cl? ion pair. This model requires individual ion sites to be partially occupied and nonequivalent and is strongly suggestive of vacancy ordering. Refinement in space group P1, with sites refined independenty, led to R = 0.1096. The second model describes the structure in terms of a Willis cluster of defects and includes both anion vacancies and interstitial anions. Full-matrix least squares refinement in space group Fm3m, with positions analogous to those in UO2.12 and (Ca,Y)F2.10, converged at R = 0.0633 for the 114 face-centered parent structure reflections whose |F|;2 > σ(F2). This second model is discussed in relation to a probable true solution which involves longrange order. 相似文献
4.
Zwickl H Traxler E Staettner S Parzefall W Grasl-Kraupp B Karner J Schulte-Hermann R Gerner C 《Electrophoresis》2005,26(14):2779-2785
The secretome of cells and tissues may reflect a broad variety of pathological conditions and thus represents a rich source of biomarkers. The identity of secreted proteins, usually isolated from cell supernatants or body fluids, is hardly accessible by direct proteome analysis, because these proteins are often masked by high amounts of proteins actually not secreted by the investigated cells. Here, we present a novel method for the specific detection of proteins secreted by human tissue specimen as well as cultured cells and chose liver as a model. The method is based on the metabolic labelling of proteins synthesized during a limited incubation period. Then, the cell supernatant is filtered, precipitated, and subjected to two-dimensional gel electrophoresis. Whereas fluorography detected a large number of proteins derived from residual plasma and dead cells, the autoradiographs selectively displayed genuinely secreted proteins. We demonstrate the feasibility of this approach by means of the secretomes of the hepatocellular carcinoma-derived cell line HepG2 and human liver slices. The selective identification of cell- and tissue-specific protein secretion profiles may help to identify novel sets of biomarkers for wide clinical applications. 相似文献
5.
Beate Hager Bettina Schwarzinger Heinz Falk 《Monatshefte für Chemie / Chemical Monthly》2006,137(2):163-168
Summary. Two model compounds for the green fluorescent protein chromophore were prepared. One of them incorporates the natural 4-hydroxybenzylidene
group of the natural tyrosin derived chromophore, the other one bears a methyl group instead of the hydroxy group. Whereas
the photochemically prepared (E)-diastereomer of the first compound very effectively reverted thermally (room temperature) to the thermodynamically stable
(Z)-diastereomer, the (E)-diastereomer of the second derivative proved to be stable even at elevated temperatures for more than a day. This finding
can be rationalized by constructing the appropriate resonance structures showing that only in the first case an effective
delocalization enables partial single bond character of the benzylidene double bond. From the standpoint of chemical etiology,
only Nature’s choice of the tyrosin derived chromophore of the green fluorescent protein provides an efficient radiationless
thermal relaxation channel for the unwanted photo-diastereomerization product formed after excitation besides the dominating
fluorescence channel of its chromophore. 相似文献
6.
Strontium bromide-chloride phases (SrBrxCl2?x) in the composition region 2.00 > x > 0 were prepared and examined by the Guinier powder X-ray diffraction technique. Observed and calculated powder intensities for the compositions x = 1.60, 1.40, and 0.30 are presented. The anions assume an ordered arrangement at the first two compositions and a random arrangement at the third. Two previously unreported intermediate phases at the composition about x = 1.50 and x = 0.60, both of unknown structure, were identified and their d values are reported. SrBr2 is found to be insoluble in SrCl2. 相似文献
7.
8.
New Ternary Clathrate Compounds in the Systems Barium–Indium/Zinc/Cadmium–Germanium: Zintl Compounds with Phase Width? By systematic investigations in the systems barium–indium/zinc/cadmium–germanium we found a couple of new electrovalent ternary compounds with A8X46 clathrate (I) type structures. They crystallize cubically in space-group Pm3n. For Ba8In16Ge30 (a = 1 075.8 pm), Ba8Zn8Ge38 (a = 1 082.0 pm) and Ba8Cd8Ge38 (a = 1 096.0 pm) the structures were verified by X-ray single crystal diffraction data. According to valence and bounding distances the new clathrates should be Zintl compounds. Measurements of the temperature dependence of the electrical resistivity proved, that they are indeed semiconductors. A part of the 2B/3B metal atoms can be substituted by germanium. Charge balance will be retained by creation of vacancies in the A8X46 type structures. By phase analysis the limits of the composition range were determined as Ba8In4Ge9[]3Ge30 (a = 1 084.9 pm), Ba8Zn4Ge10[]2Ge30 (a = 1 073.6 pm) and Ba8Cd4Ge10[]2Ge30 (a = 1 082.0 pm). 相似文献
9.
Adams LA Aggarwal VK Bonnert RV Bressel B Cox RJ Shepherd J de Vicente J Walter M Whittingham WG Winn CL 《The Journal of organic chemistry》2003,68(24):9433-9440
A simple and high-yielding method for the preparation of cyclopropane amino acids is described. The novel method involves the one-pot cyclopropanation of readily available dehydroamino acids using aryl and unsaturated diazo compounds generated in situ from the corresponding tosylhydrazone salts. It was found that thermal 1,3-dipolar cycloaddition followed by nitrogen extrusion gave the cyclopropane amino acid derivatives with good E selectivity, while reactions in the presence of meso-tetraphenylporphyrin iron chloride gave predominantly the corresponding Z isomers. The synthetic utility of this process was demonstrated in the synthesis of (+/-)-(Z)-2,3-methanophenylalanine [(+/-)-(Z)-1], the anti-Parkinson (+/-)-(E)-2,3-methano-m-tyrosine [(+/-)-(E)-2], and the natural product (+/-)-coronamic acid [(+/-)-3]. 相似文献
10.
A gas chromatographic method was developed to determine the purity of synthesized isocyanate monomers, specifically isocyanatoacrylates, and to determine the isocyanate content of synthesized polymers and prepolymers. The method is a modification of an ASTM procedure in which an isocyanate is allowed to react with excess di-n-butylamine. In the ASTM method, the amount of isocyanate present is calculated indirectly from the amount of unreacted di-n-butylamine, determined by back titration with standard hydrochloric acid. Determination of the excess di-n-butylamine by the gas chromatographic method developed has the advantages of providing better precision and requiring less sample than the titrimetric method. The two methods were compared using phenyl isocyanate as a model test compound. A synthesized monomer, methyl alpha-isocyanatoacrylate, was also analyzed, for comparison by both methods. 相似文献