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排序方式: 共有201条查询结果,搜索用时 187 毫秒
1.
Leon N. Schneider Dr. Eva-Maria Tanzer Krauel Dr. Carl Deutsch Dr. Klaus Urbahns Tobias Bischof Kristina A. M. Maibom Dr. Johannes Landmann Dr. Fabian Keppner Dr. Christoph Kerpen Dr. Michael Hailmann Ludwig Zapf Tanja Knuplez Dr. Rüdiger Bertermann Dr. Nikolai V. Ignat'ev Prof. Dr. Maik Finze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(42):10973-10978
Fluorinated groups are essential for drug design, agrochemicals, and materials science. The bis(trifluoromethyl)amino group is an example of a stable group that has a high potential. While the number of molecules containing perfluoroalkyl, perfluoroalkoxy, and other fluorinated groups is steadily increasing, examples with the N(CF3)2 group are rare. One reason is that transfer reagents are scarce and metal-based storable reagents are unknown. Herein, a set of CuI and AgI bis(trifluoromethyl)amido complexes stabilized by N- and P-donor ligands with unprecedented stability are presented. The complexes are stable solids that can even be manipulated in air for a short time. They are bis(trifluoromethyl)amination reagents as shown by nucleophilic substitution and Sandmeyer reactions. In addition to a series of benzylbis(trifluoromethyl)amines, 2-bis(trifluoromethyl)amino acetate was obtained, which, upon hydrolysis, gives the fluorinated amino acid N,N-bis(trifluoromethyl)glycine. 相似文献
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Sofia Quinodoz Michael A. Thomas Jörn Dunkel Eva-Maria Schötz 《Journal of statistical physics》2011,142(6):1324-1336
The trade-off between traits in life-history strategies has been widely studied for sexual and parthenogenetic organisms,
but relatively little is known about the reproduction strategies of asexual animals. Here, we investigate clonal reproduction
in the freshwater planarian Schmidtea mediterranea, an important model organism for regeneration and stem cell research. We find that these flatworms adopt a randomized reproduction
strategy that comprises both asymmetric binary fission and fragmentation (generation of multiple offspring during a reproduction
cycle). Fragmentation in planarians has primarily been regarded as an abnormal behavior in the past; using a large-scale experimental
approach, we now show that about one third of the reproduction events in S. mediterranea are fragmentations, implying that fragmentation is part of their normal reproductive behavior. Our analysis further suggests
that certain characteristic aspects of the reproduction statistics can be explained in terms of a maximum relative entropy
principle. 相似文献
4.
Nils Helge Schebb David Falck Helene Faber Eva-Maria Hein Uwe Karst Heiko Hayen 《Journal of chromatography. A》2009,1216(27):5249-5255
A new liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS) method for the fast determination of phospholipase A2 (PLA2) activity has been developed. For the first time, the method allows the parallel detection of glycerophosphatidylcholine (GroPCho) as PLA2 substrate as well as of its products fatty acid (FA) and lyso-GroPCho. ESI-MS was carried out in negative ion mode, detecting the FA as [M − H]− ions and the lyso-GroPCho and GroPCho as acetate adducts [M + Ac]−. Utilizing a fast gradient on a short C5-modified silica gel column with 3 μm particles, five GroPChos, five FAs and six lyso-GroPChos could be separated according to their chain length in less than 3 min. A very high average chromatographic efficiency of 41,200 theoretical plates (plate height 0.5 μm) was achieved for the separation of the GroPChos. The method was applied for monitoring the release of arachidonic acid (20:4 FA) and 1-stearoyl-lyso-sn-GroPCho (18:0 GroPCho) from unilamellar vesicles of 1-stearoyl-2-arachidonoyl-sn-GroPCho (18:0/20:4 GroPCho). With a limit of detection of 0.5 pmol (total amount injected on column) for the FAs and lyso-GroPChos and 1.5 pmol for the GroPChos as well as a linear range of 1.5 decades, the method has proven to be suitable for the monitoring of different secretory PLA2 (sPLA2) conversions. Furthermore, it was applied to screen a small library of PLA2 inhibitors for their activity towards sPLA2 type V and snake venom of Bothrops moojeni. In both cases, active samples could be directly identified. With its short analysis time, its high chromatographic efficiency and the parallel detection of substrate and all products, the developed LC–ESI-MS method is well suited for the analysis of PLA2 activity. 相似文献
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Mareike Prüfer Christian Wenger Frank F. Bier Eva-Maria Laux Ralph Hölzel 《Electrophoresis》2022,43(18-19):1920-1933
Dielectrophoresis (DEP) is an AC electrokinetic effect mainly used to manipulate cells. Smaller particles, like virions, antibodies, enzymes, and even dye molecules can be immobilized by DEP as well. In principle, it was shown that enzymes are active after immobilization by DEP, but no quantification of the retained activity was reported so far. In this study, the activity of the enzyme horseradish peroxidase (HRP) is quantified after immobilization by DEP. For this, HRP is immobilized on regular arrays of titanium nitride ring electrodes of 500 nm diameter and 20 nm widths. The activity of HRP on the electrode chip is measured with a limit of detection of 60 fg HRP by observing the enzymatic turnover of Amplex Red and H2O2 to fluorescent resorufin by fluorescence microscopy. The initial activity of the permanently immobilized HRP equals up to 45% of the activity that can be expected for an ideal monolayer of HRP molecules on all electrodes of the array. Localization of the immobilizate on the electrodes is accomplished by staining with the fluorescent product of the enzyme reaction. The high residual activity of enzymes after AC field induced immobilization shows the method's suitability for biosensing and research applications. 相似文献
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Laux S Lureau F Radier C Chalus O Caradec F Casagrande O Pourtal E Simon-Boisson C Soyer F Lebarny P 《Optics letters》2012,37(11):1913-1915
Transverse parasitic lasing is well known for limiting the signal gain and the pulse energy that can be extracted from Ti:sapphire petawatt amplifiers. We have developed a technique for suppressing these parasitic lasing modes based on perfect refractive index-matching liquid doped with a broad-bandwidth absorber to suppress the transverse lasing while ensuring proper heat removal from the Ti:sapphire crystal. The 800 nm laser output with a bandwidth of 41 nm (FWHM) and peak energy of 22.7 J at a repetition rate of 1 Hz is demonstrated. 相似文献
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