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21.
Lai Hong Wong Asier Unciti-Broceta Michaela Spitzer Rachel White Mike Tyers Lea Harrington 《Chemistry & biology》2013,20(3):333-340
Highlights? Growth arrest induced by human telomerase in yeast is chemically reversible ? Readout is sensitive to telomerase catalytic activity and telomere recruitment ? Three cell-permeable compounds also inhibit purified human telomerase ? Yeast can be successfully used to screen for human telomerase inhibitors 相似文献
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Rich ML Simet IM Coon SR Hanson CD 《Journal of the American Society for Mass Spectrometry》2000,11(12):1118-1124
Although Fourier transform ion cyclotron resonance mass spectrometry is a powerful tool in the qualitative observation of gas phase reactions, ion detection is on the millisecond time scale, orders of magnitude longer than typically found when using a sector instrument. Observations of short-lived species such as chemically activated adduct ions can be accomplished using selective ion excitation as a probe of intermediate lifetime. Whereas ion elimination has been shown to be effective in monitoring ion lifetimes on the microsecond time scale, problems associated with detecting ions produced with high kinetic energies limits the technique. Use of a kinetic energy orifice as an ion skimmer effectively eliminates ions near the center of the ion cell at relatively low kinetic energies. By modifying a single section cell to include a kinetic energy orifice, the lifetimes of chemically activated adduct ions have been investigated. 相似文献
24.
Susanne Schmidt Michaela Zietz Monika Schreiner Sascha Rohn Lothar W. Kroh Angelika Krumbein 《Rapid communications in mass spectrometry : RCM》2010,24(14):2009-2022
Kale is a member of the Brassicaceae family and has a complex profile of flavonoid glycosides. Therefore, kale is a suitable matrix to discuss in a comprehensive study the different fragmentation patterns of flavonoid glycosides. The wide variety of glycosylation and acylation patterns determines the health‐promoting effects of these glycosides. The aim of this study is to investigate the naturally occurring flavonoids in kale. A total of 71 flavonoid glycosides of quercetin, kaempferol and isorhamnetin were identified using a high‐performance liquid chromatography diode‐array detection/electrospray ionization multi‐stage mass spectrometry (HPLC‐DAD/ESI‐MSn) method. Of these 71 flavonol glycosides, 27 were non‐acylated, 30 were monoacylated and 14 were diacylated. Non‐acylated flavonol glycosides were present as mono‐, di‐, tri‐ and tetraglycosides. This is the first time that the occurrence of four different fragmentation patterns of non‐acylated flavonol triglycosides has been reported in one matrix simultaneously. In addition, 44 flavonol glycosides were acylated with p‐coumaric, caffeic, ferulic, hydroxyferulic or sinapic acid. While monoacylated glycosides existed as di‐, tri‐ and tetraglycosides, diacylated glycosides occurred as tetra‐ and pentaglycosides. To the best of our knowledge, 28 compounds in kale are reported here for the first time. These include three acylated isorhamnetin glycosides (isorhamnetin‐3‐O‐sinapoyl‐sophoroside‐7‐O‐D‐glucoside, isorhamnetin‐3‐O‐feruloyl‐sophoroside‐7‐O‐diglucoside and isorhamnetin‐3‐O‐disinapoyl‐triglucoside‐7‐O‐diglucoside) and seven non‐acylated isorhamnetin glycosides. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
25.
Hofmann CC Lindner SM Ruppert M Hirsch A Haque SA Thelakkat M Köhler J 《Physical chemistry chemical physics : PCCP》2010,12(43):14485-14491
A flexible organic triad consisting of two perylene bisimide antennas covalently linked to a [60]fullerene by flexible spacers has been synthesized and studied by electrochemistry, steady-state and time-resolved spectroscopy. We found that π-π-stacking of the two antenna subunits has considerable impact on the photophysics of the system and leads to a reduction of the effective light-harvesting efficiency of the assembly. This finding is important for light harvesting in flexible materials based on the dye antenna-fullerene concept. 相似文献
26.
For many clinical purposes various artificial devices are applied, which contact human tissue and can thus cause adverse reactions between prosthetic surfaces and body components. Of the many materials applied for orthopaedic joint replacements the most common are cobalt-chromium-molybdenum alloys. In these cases considerable amounts of cobalt-chromium-molybdenum wear particles are released from the prostheses which have to be regarded as a cause of long-time problems for the patient.Since these particles are dissolved in body fluids of the surrounding area they are distributed in the whole body via blood. Elevated metal concentrations have been found in blood and urine of persons with endoprostheses. Partly the metals are excreted via urine, but to some extend they accumulate in different organs.Therefore this study dealt with the development of an analytical method for the determination of seven relevant trace elements, namely Al, Co, Cr, Mo, Nb, Ni, and Ti in nine kinds of human tissue (brain, heart, kidney, liver, lung, muscle, lymphatic nodes, spleen, body fat) starting with drawing of the sample, sample work up and finally analysis by means of atomic spectrometry. The optimized method was then applied to determine the metal contents in organs of persons (post mortem) with total hip replacements with metal on metal bearing surfaces. Comparison of the data obtained with those of persons without hip-endoprostheses shows that brain and lung are the main targets for elemental accumulation in persons with hip-endoprostheses. Mo and Nb represent the elements with the highest tendency to be accumulated. 相似文献
27.
Leaching test for calcined kaolinite and kaolinite/TiO<Subscript>2</Subscript> photoactive composite
Michaela Tokarčíková Kateřina Mamulová Kutláková Jana Seidlerová 《Chemical Papers》2016,70(9):1253-1261
Kaolinite is a suitable material for fixing TiO2 nanoparticles in a composite form. The kaolinite/TiO2 composite has promising photoactive properties which are as important as is the possible impact of the composite on the environment. Accordingly, the stability of the kaolinite/TiO2 composite dried at 105°C (KTI1) and calcined at 600 °C (KTI6) and the stability of the original kaolinite treated at various temperatures (105–800 °C) were studied by the leaching test in accordance with European standard BS EN 12457-2:2002 (British Standards Institution, 2002). The stability was evaluated on the basis of elements leached from the materials to extraction agents. Atomic emission spectrometry with inductively coupled plasma was used for determining the concentration of elements. In order to better understand the process of calcination and the structure changes in the kaolinite/TiO2 composite and calcined kaolinite, the materials were evaluated using X-ray powder diffraction and infrared spectroscopy with Fourier transformation. The processes of kaolinite dehydroxylation and metakaolinite formation were observed. Kaolinite is an appropriate carrier for composite preparation due to its stability even after its treatment at high temperatures. The experiments confirmed the TiO2 nanoparticles to be very strongly bound to the kaolinite surface. On the other hand, the experiments demonstrated that the presence of TiO2 on the kaolinite surface caused the release of Al in high concentrations to the final extracts, especially after kaolinite/TiO2 composite calcination. 相似文献
28.
The conformers of the monohalocyclohexasilanes, Si6H11X (X=F, Cl, Br or I) and the haloundecamethylcyclohexasilanes, Si6Me11X (X=F, Cl, Br or I) are investigated by DFT calculations employing the B3LYP density functional and 6‐31+G* basis sets for elements up to the third row, and SDD basis sets for heavier elements. Five minima are found for Si6H11X—the axial and equatorial chair conformers, with the substituent X either in an axial or equatorial position—and another three twisted structures. The equatorial chair conformer is the global minimum for the X=Cl, Br and I, the axial chair for X=F. The barrier for the ring inversion is ~13 kJ mol?1 for all four compounds. Five minima closely related to those of Si6H11X are found for Si6Me11X. Again, the equatorial chair is the global minimum for X=Cl, Br and I, and the axial chair for X=F. Additionally, two symmetrical boat conformers are found as local minima on the potential energy surfaces for X=F, Cl and Br, but not for X=I. The barrier for the ring inversion is ~14–16 kJ mol?1 for all compounds. The conformational equilibria for Si6Me11X in toluene solution are investigated using temperature dependent Raman spectroscopy. The wavenumber range of the stretching vibrations of the heavy atoms X and Si from 270–370 cm?1 is analyzed. Using the van′t Hoff relationship, the enthalpy differences between axial and equatorial chair conformers (Hax?Heq.) are 1.1 kJ mol?1 for X=F, and 1.8 to 2.8 kJ mol?1 for X=Cl, Br and I. Due to rapid interconversion, only a single Raman band originating from the “averaged” twist and boat conformers could be observed. Generally, reasonable agreement between the calculated relative energies and the experimentally determined values is found. 相似文献
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30.
X-Ray Single Crystal and Electron Microscopic Investigations on a New Uranium Niobate: γ-UNbO5 Black cuboid formed crystals of γ-UNbO5 were obtained (at T1) by chemical transport in a temperature gradient (T2 → T1; 1000 °C → 980 °C) using UNb2O7 as starting material (at T2) and a combination of NbCl5 and Cl2 as transport agent. They were examined by X-rays and electron microscopy. The new modification of γ-UNbO5 crystallizes orthorhombically (space group Pmma) with a = 7.492(3) Å, b = 4.124(4) Å and c = 6.434(4) Å. The compound is isostructural to UVO5 and UMoO5. The crystal structure shows parallel layers formed by edge sharing UO7 and NbO6 polyhedra. Polyhedra of neighbouring layers (distance = b) are mutually corner linked. 相似文献