排序方式: 共有53条查询结果,搜索用时 171 毫秒
21.
Highly Enantioselective Transfer Hydrogenation of Ketones with Chiral (NH)2P2 Macrocyclic Iron(II) Complexes 下载免费PDF全文
Raphael Bigler Raffael Huber Prof. Dr. Antonio Mezzetti 《Angewandte Chemie (International ed. in English)》2015,54(17):5171-5174
Bis(isonitrile) iron(II) complexes bearing a C2‐symmetric diamino (NH)2P2 macrocyclic ligand efficiently catalyze the hydrogenation of polar bonds of a broad scope of substrates (ketones, enones, and imines) in high yield (up to 99.5 %), excellent enantioselectivity (up to 99 % ee), and with low catalyst loading (generally 0.1 mol %). The catalyst can be easily tuned by modifying the substituents of the isonitrile ligand. 相似文献
22.
S. Abdul Sattar B. Seetharami Reddy V. Koteswara Rao K. Ramnarayana G. J. Naga Raju S. Bhuloka Reddy T. KD. Phanisree P. V. Madhusudhana Rao 《X射线光谱测定》2012,41(2):111-116
A trace elemental analysis was carried out in various parts of 12 anticancer medicinal plants, using the PIXE (particle‐induced X‐ray emission) technique. A 3‐MeV proton beam was used to excite the samples, and spectra were recorded using a Si (Li) detector. Data analysis was done using the GUPIX software. The elements Cl, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, Br and Sr were identified, and their concentrations estimated. The results of the present study provide justification for the usage of these medicinal plants in the development of anticancer drugs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
23.
Michal Roth‐Konforti Ori Green Mario Hupfeld Lars Fieseler Nadine Heinrich Julian Ihssen Raffael Vorberg Lukas Wick Urs Spitz Doron Shabat 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(30):10469-10475
Detection of Salmonella and L. monocytogenes in food samples by current diagnostic methods requires relatively long time to results (2–6 days). Furthermore, the ability to perform environmental monitoring at the factory site for these pathogens is limited due to the need for laboratory facilities. Herein, we report new chemiluminescence probes for the ultrasensitive direct detection of viable pathogenic bacteria. The probes are composed of a bright phenoxy‐dioxetane luminophore masked by triggering group, which is activated by a specific bacterial enzyme, and could detect their corresponding bacteria with an LOD value of about 600‐fold lower than that of fluorescent probes. Moreover, we were able to detect a minimum of 10 Salmonella cells within 6 h incubation. The assay allows for bacterial enrichment and detection in one test tube without further sample preparation. We anticipate that this design strategy will be used to prepare analogous chemiluminescence probes for other enzymes relevant to specific bacteria detection and point‐of‐care diagnostics. 相似文献
24.
Stabilization of Organic–Inorganic Perovskite Layers by Partial Substitution of Iodide by Bromide in Methylammonium Lead Iodide 下载免费PDF全文
Raffael Ruess Felix Benfer Felix Böcher Martina Stumpp Prof. Dr. Derck Schlettwein 《Chemphyschem》2016,17(10):1505-1511
Thin films of the methylammonium lead halides CH3NH3Pb(I1?xBrx)3 are prepared on fluorine‐doped tin oxide substrates and exposed to humid air in the dark and under illumination. To characterize the stability of the materials, UV/Vis spectra are acquired at fixed intervals, accompanied by XRD, energy‐dispersive X‐ray spectroscopy, SEM, and confocal laser scanning microscopy. Different degradation mechanisms are observed depending on the environmental conditions. It is found that bromide can successfully suppress the transformation of the perovskite into the monohydrate, presumably owing to stronger hydrogen‐bonding interactions with the organic cation. However, under illumination in humid air, rather rapid decomposition of the perovskites was still observed, which is due to phase segregation. The use of increased bromide content in methylammonium lead halide absorbers is discussed in terms of their application in perovskite solar cells. 相似文献
25.
M. Sc. Raffael C. Wende B. Sc. Alexander Seitz M. Sc. Dominik Niedek Dipl.‐Chem. Sören M. M. Schuler Dr. Christine Hofmann Dr. Jonathan Becker Prof. Dr. Peter R. Schreiner 《Angewandte Chemie (International ed. in English)》2016,55(8):2719-2723
Here we report the development of the first enantioselective Dakin–West reaction, yielding α‐acetamido methylketones with up to 58 % ee with good yields. Two of the obtained products were recrystallized once to achieve up to 84 % ee. The employed methylimidazole‐containing oligopeptides catalyze both the acetylation of the azlactone intermediate and the terminal enantioselective decarboxylative protonation. We propose a dispersion‐controlled reaction path that determines the asymmetric reprotonation of the intermediate enolate after the decarboxylation. 相似文献
26.
Nils Trapp Michael Wörle Bernd Kuhn Paul Gerber Raffael Vorberg Erick M. Carreira Klaus Müller 《Helvetica chimica acta》2023,106(2):e202200146
The molecular and crystal structures of 19 N-alkyl-substituted pipecolamide derivatives with partial fluorination of N-propyl and N-butyl groups are presented. Fluorination patterns include one F-atom at internal or terminal locations, two F-atoms in geminal or vicinal arrangements at various positions, as well as terminal trifluoromethylation. Due to the presence of the carboxamide side chain in pipecolamide derivatives, enantiomeric fluorination patterns in the N-alkyl group result in diastereomeric compounds, which exhibit dramatically different crystal and molecular structures. An extraordinary conformational diversity is diagnosed for the various N-alkylpiperidine units. Structural comparisons and theoretical assessments based on extensive force field calculations provide insight into consistent conformational patterns that point to intramolecular factors as well as intermolecular modulations due to crystal packing effects. 相似文献
27.
Hrdina R Müller CE Wende RC Wanka L Schreiner PR 《Chemical communications (Cambridge, England)》2012,48(19):2498-2500
Multicatalysts consisting of non-natural oligopeptides with distinctly different catalytic moieties create molecular complexity in a multistep one-pot sequence starting from simple alkenes yielding highly enantiomerically enriched trans-diols. 相似文献
28.
Breast cancer proteomics by laser capture microdissection, sample pooling, 54-cm IPG IEF, and differential iodine radioisotope detection 总被引:7,自引:0,他引:7
Neubauer H Clare SE Kurek R Fehm T Wallwiener D Sotlar K Nordheim A Wozny W Schwall GP Poznanović S Sastri C Hunzinger C Stegmann W Schrattenholz A Cahill MA 《Electrophoresis》2006,27(9):1840-1852
The presence of progesterone receptor (PR) in estrogen receptor (ER)-positive breast cancer is associated with a good prognosis, and indicates that tumors are likely to respond to tamoxifen. However, ER+/PR- tumors respond less well. To reveal the potential molecular mechanism of this phenomenon, we sought to identify differential protein abundances between invasive ductal carcinoma cells from cryopreserved ER+/PR+ and ER+/PR- mammary tumor specimens. Because current proteomics methods are hampered in the examination of most primary human tumor samples by the extreme tissue heterogeneity, we used laser capture microdissection (LCM) to isolate tumor cells and developed a sample pooling strategy to analyze small sample protein lysates. Proteins from LCM-harvested tumors were pooled into four sub-pools from each condition of three tumors/sub-pool, and proteins from respective paired sub-pools were co-electrophoresed by 2-DE using 54-cm IEF over pH 4-9. Abundance ratios were accurately quantified by a differential multiplex radioactive ProteoTope method at low attomole levels ( approximately 3.6 microg protein per labeling reaction, <180 ng per multiplex protein sample per 54-cm gel). Applying this approach, differentially displayed proteins were identified by MS using comigrating non-radioactively labeled tumor proteins. They include decreased cytochrome b5 and transgelin, and more abundant CRABP-II, cyclophilin A, Neudesin, and hemoglobin in ER+/PR+ tumors versus ER+/PR- providing a possible explanation for differential susceptibility against tamoxifen as a result of deregulated cytochrome b5-dependent metabolism. This study demonstrates the potential of ProteoTope and LCM to enable extremely sensitive and precise differential analyses from well-defined primary clinical specimen. 相似文献
29.
30.
Thin films of methylammonium lead halides, CH3NH3PbI3 and CH3NH3PbI3-xClx, were deposited onto symmetrical microstructured electrode arrays of gold or platinum on Si/SiO2 wafers. Polarization studies were carried out on perovskite films under vacuum in the dark. For poling, a constant voltage was applied to the samples while the temperature was cycled between 295 K and 4 K. The measured current densities depending on the temperature showed distinct characteristics relating strongly to the crystal phase and the dielectric properties of the perovskite films. Voltage sweeps were carried out at different scan rates at specific temperature intervals after poling. The polarization of the films due to the migration of iodide vacancies in direction of the blocking perovskite/metal interface was frozen almost up to room temperature. Charge carriers were only able to cross the blocking barrier and contribute to the current where the ions have accumulated during poling. All J-V curves showed hysteresis: inverted and regular hysteresis at room temperature and below, respectively. Inverted hysteresis originates from the slow accumulation of ions at the blocking barrier, while regular hysteresis arises from a distortion in the adjacent crystals which will be discussed. 相似文献