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991.
Colin J. Burchell Stephen M. Aucott Stuart D. Robertson Alexandra M. Z. Slawin J. Derek Woollins 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4-5):865-868
The psuedohalogens (ECN)2 (E = S, Se) have been prepared by reaction of AgNCS with bromine and AgNCSe with iodine respectively. (SCN)2 spontaneously polymerises to give polythiocyanogen a polymer of unknown structure with empirical formula (SCN)x. A series of late transition metal complexes bearing the ambidentate psuedohalide ligands (ECN) (E = S, Se) have been synthesised. In addition we have prepared a series of late transition metal complexes of the cyanodithioimidocarbonate ion [C2N2S2]2? and the first transition metal complexes of the cyanodiselenocarbonate ion [C2N2Se2]2?. 相似文献
992.
Andrew A. Tolmachew Alexandra A. Chaikovskaya Svetlana D. Kopteva Aleksew O. Pushechnikov Sergei P. Ivonin 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract Convenient methods for introducing dihalogenphosphinogroup at of pyrrole and hran rings have been developed. It was found that dibromphosphinogroup migrated from the second to the third position of the N-methylpyrrole. Convenient methods for phosphorylation of N- alkylcarbazole and iminostilbene have been developed. 相似文献
993.
Agata Dembna Vincenzo Venditto Alexandra R. Albunia Rosa Califano Gaetano Guerra 《先进技术聚合物》2013,24(1):56-61
Fourier Transform Infrared spectroscopy (FTIR) and Wide‐Angle X‐Ray Diffraction (WAXD) measurements have clearly established the occurrence of a dual sorption ability of sulfonated syndiotactic polystyrene samples, which exhibit the nanoporous δ crystalline phase. In fact, large uptake (up to 20–30 wt%) of ionic liquid (IL; e.g. 1‐ethyl‐3‐methylimidazolium dicyanamide) occurs only in the hydrophilic amorphous sulfonated phases and does not disturb the hydrophobic nanoporous crystalline δ phase. On the other hand, a large uptake of organic guests (e.g. naphthalene) occurs prevailingly in the nanoporous hydrophobic crystalline phase, independently of the presence of the IL in the amorphous phase, eventually leading to the formation of syndiotactic polystyrene co‐crystalline phases. The thermal stability of IL can be largely increased by their inclusion in the amorphous phase of sulfonated syndiotactic polystyrene films. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
994.
Dr. Shu‐Ping Luo Dr. Esteban Mejía Aleksej Friedrich Alexandra Pazidis Dr. Henrik Junge Dr. Annette‐Enrica Surkus Dr. Ralf Jackstell Stefania Denurra Prof. Dr. Serafino Gladiali Prof. Dr. Stefan Lochbrunner Prof. Dr. Matthias Beller 《Angewandte Chemie (International ed. in English)》2013,52(1):419-423
995.
Andrey N. Pravdivtsev Prof. Alexandra V. Yurkovskaya Prof. Hans‐Martin Vieth Dr. Konstantin L. Ivanov Prof. Robert Kaptein 《Chemphyschem》2013,14(14):3327-3331
Various hyperpolarization methods are able to enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) by several orders of magnitude. Among these methods are para‐hydrogen‐induced polarization (PHIP) and signal amplification by reversible exchange (SABRE), which exploit the strong nuclear alignment of para‐hydrogen. Several SABRE experiments have been reported but, so far, it has not been possible to account for the experimentally observed sign and magnetic‐field dependence of substrate polarization. Herein, we present an analysis based on level anti‐crossings (LACs), which provides a complete understanding of the SABRE effect. The field‐dependence of both net and anti‐phase polarization is measured for several ligands, which can be reproduced by the theory. The similar SABRE field‐dependence for different ligands is also explained. In general, the LAC concept allows complex spin dynamics to be unraveled, and is crucial for optimizing the performance of novel hyperpolarization methods in NMR and MRI techniques. 相似文献
996.
Carmen Racles Alexandra Nistor Maria Cazacu 《Central European Journal of Chemistry》2013,11(10):1689-1698
Silver nanoparticles (AgNPs) were obtained by a redox reaction, using a glucose-containing cyclosiloxane as a reduction agent and stabilizer. Then the AgNPs aqueous solution was used as the reaction medium for the sol-gel process, starting from tetraethylorthosilicate (TEOS) as silica precursor. The nanocomposite material resulted (SilAg) after solvent removal, aging and calcination and was investigated by infrared spectroscopy (FT-IR), atomic force microscopy (AFM), scanning electron microscopy coupled with energy dispersive X-ray system (SEM/EDX), transmission electron microscopy (TEM), energy-dispersive X-ray fluorescence spectroscopy (EDXRF), X-ray diffraction (XRD) and dynamic vapor sorption (DVS). The results were compared to model silicas obtained without silver. A higher condensation degree in SilAg was obtained due to the basic medium used in the first step and was confirmed by a sorption capacity lower than for the model silicas. The solid surface area calculated with GAB analysis using DVS data for the water vapors is 210 m2 g?1. The nanocomposite showed good catalytic activity for hydrogen peroxide decomposition. 相似文献
997.
Alexandra Gutmann Lars Julian Wesenberg Nadine Peez Prof. Dr. Siegfried R. Waldvogel Prof. Dr. Thorsten Hoffmann 《ChemistryOpen》2020,9(5):568-572
Most of the active pharmaceutical ingredients like Metoprolol are oxidatively metabolized by liver enzymes, such as Cytochrome P450 monooxygenases into oxygenates and therefore hydrophilic products. It is of utmost importance to identify the metabolites and to gain knowledge on their toxic impacts. By using electrochemistry, it is possible to mimic enzymatic transformations and to identify metabolic hot spots. By introducing charged-tags into the intermediate, it is possible to detect and isolate metabolic products. The identification and synthesis of initially oxidized metabolites are important to understand possible toxic activities. The gained knowledge about the metabolism will simplify interpretation and predictions of metabolitic pathways. The oxidized products were analyzed with high performance liquid chromatography-mass spectrometry using electrospray ionization (HPLC-ESI-MS) and nuclear magnetic resonance (NMR) spectroscopy. For proof-of-principle, we present a synthesis of one pyridinated main oxidation product of Metoprolol. 相似文献
998.
Dr. Marco Mende Alexandra Tsouka Jasmin Heidepriem Grigori Paris Dr. Daniela S. Mattes Dr. Stephan Eickelmann Dr. Vittorio Bordoni Dr. Robert Wawrzinek Felix F. Fuchsberger Prof. Dr. Peter H. Seeberger Dr. Christoph Rademacher Dr. Martina Delbianco Dr. Alvaro Mallagaray Dr. Felix F. Loeffler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(44):9954-9963
Single glycan–protein interactions are often weak, such that glycan binding partners commonly utilize multiple, spatially defined binding sites to enhance binding avidity and specificity. Current array technologies usually neglect defined multivalent display. Laser-based array synthesis technology allows for flexible and rapid on-surface synthesis of different peptides. By combining this technique with click chemistry, neo-glycopeptides were produced directly on a functionalized glass slide in the microarray format. Density and spatial distribution of carbohydrates can be tuned, resulting in well-defined glycan structures for multivalent display. The two lectins concanavalin A and langerin were probed with different glycans on multivalent scaffolds, revealing strong spacing-, density-, and ligand-dependent binding. In addition, we could also measure the surface dissociation constant. This approach allows for a rapid generation, screening, and optimization of a multitude of multivalent scaffolds for glycan binding. 相似文献
999.
Alexandra L. Nagelski Majed S. Fataftah Melissa M. Bollmeyer Sean F. McWilliams Samantha N. MacMillan Brandon Q. Mercado Kyle M. Lancaster Patrick L. Holland 《Chemical science》2020,11(47):12710
The active site clusters of nitrogenase enzymes possess the only examples of carbides in biology. These are the only biological FeS clusters that are capable of reducing N2 to NH4+, implicating the central carbon and its interaction with Fe as important in the mechanism of N2 reduction. This biological question motivates study of the influence of carbon donors on the electronic structure and reactivity of unsaturated, high-spin iron centers. Here, we present functional and structural models that test the impacts of carbon donors and sulfide donors in simpler iron compounds. We report the first example of a diiron complex that is bridged by an alkylidene and a sulfide, which serves as a high-fidelity structural and spectroscopic model of a two-iron portion of the active-site cluster (FeMoco) in the resting state of Mo-nitrogenase. The model complexes have antiferromagnetically coupled pairs of high-spin iron centers, and sulfur K-edge X-ray absorption spectroscopy shows comparable covalency of the sulfide for C and S bridged species. The sulfur-bridged compound does not interact with N2 even upon reduction, but upon removal of the sulfide it becomes capable of reducing N2 to NH4+ with the addition of protons and electrons. This provides synthetic support for sulfide extrusion in the activation of nitrogenase cofactors.High-spin diiron alkylidenes give insight into the electronic structure and functional relevance of carbon in the FeMoco active site of nitrogenase. 相似文献
1000.
Antonius R.B. Ola Abdessamad Debbab Amal H. Aly Attila Mandi Ilka Zerfass Alexandra Hamacher Matthias U. Kassack Heike Brötz-Oesterhelt Tibor Kurtan Peter Proksch 《Tetrahedron letters》2014
Neosartorin (1) was isolated from the endophytic fungus Aspergillus fumigatiaffinis. The absolute configuration of 1, including both axial and central chirality elements, was established as (aR,5S,10R,5′S,6′S,10′R) for the first time on the basis of its electronic circular dichroism (ECD) spectra aided with TDDFT–ECD calculations. Neosartorin (1) exhibited substantial antibacterial activity against a broad spectrum of Gram-positive bacterial species including staphylococci, streptococci, enterococci, and Bacillus subtilis with minimal inhibitory concentrations in the range of 4–32 μg/mL. When the toxicity of 1 against eukaryotic cells was measured using a panel of different cancer cell lines such as HELA and BALB/3T3, the average IC50 values exceeded 32 μg/mL. 相似文献