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991.
Susana Chatzipapadopoulos Tobias Zentel Prof. Dr. Ralf Ludwig Matthias Lütgens Prof. Dr. Stefan Lochbrunner Prof. Dr. Oliver Kühn 《Chemphyschem》2015,16(12):2519-2523
Understanding both structure and dynamics is crucial for producing tailor‐made ionic liquids (ILs). We studied the vibrational and structural dynamics of medium versus weakly hydrogen‐bonded C?H groups of the imidazolium ring in ILs of the type [1‐alkyl‐3‐methylimidazolium][bis(trifluoromethanesulfonyl)imide] ([Cnmim][NTf2]), with n=1, 2, and 8, by time‐resolved coherent anti‐Stokes Raman scattering (CARS) and quantum‐classical hybrid (QCH) simulations. From the time series of the CARS spectra, dephasing times were extracted by modeling the full nonlinear response. From the QCH calculations, pure dephasing times were obtained by analyzing the distribution of transition frequencies. Experiments and calculations reveal larger dephasing rates for the vibrational stretching modes of C(2)?H compared with the more weakly hydrogen‐bonded C(4,5)?H. This finding can be understood in terms of different H‐bonding motifs and the fast interconversion between them. Differences in population relaxation rates are attributed to Fermi resonance interactions. 相似文献
992.
993.
Design and Synthesis of High‐Affinity Dimeric Inhibitors Targeting the Interactions between Gephyrin and Inhibitory Neurotransmitter Receptors 下载免费PDF全文
Dr. Hans Michael Maric Vikram Babu Kasaragod Dr. Linda Haugaard‐Kedström Dr. Torben Johann Hausrat Prof. Dr. Matthias Kneussel Prof. Dr. Hermann Schindelin Prof. Dr. Kristian Strømgaard 《Angewandte Chemie (International ed. in English)》2015,54(2):490-494
Gephyrin is the central scaffolding protein for inhibitory neurotransmitter receptors in the brain. Here we describe the development of dimeric peptides that inhibit the interaction between gephyrin and these receptors, a process which is fundamental to numerous synaptic functions and diseases of the brain. We first identified receptor‐derived minimal gephyrin‐binding peptides that displayed exclusive binding towards native gephyrin from brain lysates. We then designed and synthesized a series of dimeric ligands, which led to a remarkable 1220‐fold enhancement of the gephyrin affinity (KD=6.8 nM ). In X‐ray crystal structures we visualized the simultaneous dimer‐to‐dimer binding in atomic detail, revealing compound‐specific binding modes. Thus, we defined the molecular basis of the affinity‐enhancing effect of multivalent gephyrin inhibitors and provide conceptually novel compounds with therapeutic potential, which will allow further elucidation of the gephyrin–receptor interplay. 相似文献
994.
David Gnutt Mimi Gao Oliver Brylski Dr. Matthias Heyden Prof. Dr. Simon Ebbinghaus 《Angewandte Chemie (International ed. in English)》2015,54(8):2548-2551
Biomolecules evolve and function in densely crowded and highly heterogeneous cellular environments. Such conditions are often mimicked in the test tube by the addition of artificial macromolecular crowding agents. Still, it is unclear if such cosolutes indeed reflect the physicochemical properties of the cellular environment as the in‐cell crowding effect has not yet been quantified. We have developed a macromolecular crowding sensor based on a FRET‐labeled polymer to probe the macromolecular crowding effect inside single living cells. Surprisingly, we find that excluded‐volume effects, although observed in the presence of artificial crowding agents, do not lead to a compression of the sensor in the cell. The average conformation of the sensor is similar to that in aqueous buffer solution and cell lysate. However, the in‐cell crowding effect is distributed heterogeneously and changes significantly upon cell stress. We present a tool to systematically study the in‐cell crowding effect as a modulator of biomolecular reactions. 相似文献
995.
Sonja Kracht Dr. Matthias Messerer Dr. Matthieu Lang Dr. Sonja Eckhardt Dr. Miriam Lauz Prof. Bernard Grobéty Prof. Katharina M. Fromm Prof. Bernd Giese 《Angewandte Chemie (International ed. in English)》2015,54(10):2912-2916
Some microorganisms perform anaerobic mineral respiration by reducing metal ions to metal nanoparticles, using peptide aggregates as medium for electron transfer (ET). Such a reaction type is investigated here with model peptides and silver as the metal. Surprisingly, Ag+ ions bound by peptides with histidine as the Ag+‐binding amino acid and tyrosine as photoinducible electron donor cannot be reduced to Ag nanoparticles (AgNPs) under ET conditions because the peptide prevents the aggregation of Ag atoms to form AgNPs. Only in the presence of chloride ions, which generate AgCl microcrystals in the peptide matrix, does the synthesis of AgNPs occur. The reaction starts with the formation of 100 nm Ag@AgCl/peptide nanocomposites which are cleaved into 15 nm AgNPs. This defined transformation from large nanoparticles into small ones is in contrast to the usually observed Ostwald ripening processes and can be followed in detail by studying time‐resolved UV/Vis spectra which exhibit an isosbestic point. 相似文献
996.
Encapsulation of Functional Organic Compounds in Nanoglass for Optically Anisotropic Coatings 下载免费PDF全文
Matthias Stöter Dr. Bernhard Biersack Dr. Sabine Rosenfeldt Markus J. Leitl Dr. Hussein Kalo Prof. Dr. Rainer Schobert Prof. Dr. Hartmut Yersin Prof. Geoffrey A. Ozin Prof. Dr. Stephan Förster Prof. Dr. Josef Breu 《Angewandte Chemie (International ed. in English)》2015,54(16):4963-4967
A novel approach is presented for the encapsulation of organic functional molecules between two sheets of 1 nm thin silicate layers, which like glass are transparent and chemically stable. An ordered heterostructure with organic interlayers strictly alternating with osmotically swelling sodium interlayers can be spontaneously delaminated into double stacks with the organic interlayers sandwiched between two silicate layers. The double stacks show high aspect ratios of >1000 (typical lateral extension 5000 nm, thickness 4.5 nm). This newly developed technique can be used to mask hydrophobic functional molecules and render them completely dispersible in water. The combination of the structural anisotropy of the silicate layers and a preferred orientation of molecules confined in the interlayer space allows polymer nanocomposite films to be cast with a well‐defined orientation of the encapsulated molecules, thus rendering the optical properties of the nanocoatings anisotropic. 相似文献
997.
Dr. Lin He Dr. Kishore Natte Dr. Jabor Rabeah Dr. Christoph Taeschler Dr. Helfried Neumann Prof. Dr. Angelika Brückner Prof. Dr. Matthias Beller 《Angewandte Chemie (International ed. in English)》2015,54(14):4320-4324
Fluorinated organic compounds are gaining increasing interest for life science applications. The replacement of hydrogen in arenes or heteroarenes by a perfluoroalkyl group has a profound influence on the physical and biological properties of such building blocks. Here, an operationally simple protocol for the direct C? H perfluoroalkylation of (hetero)arenes with RfI or RfBr has been developed, using a robust supported platinum catalyst. The ready availability of the starting materials, the excellent substrate tolerance, and the reusability of the catalyst make this method attractive for the synthesis of a variety of perfluoroalkyl‐substituted aromatic compounds. Preliminary mechanistic studies revealed the formation of radicals to be crucial in the reaction system. 相似文献
998.
A Separation‐Integrated Cascade Reaction to Overcome Thermodynamic Limitations in Rare‐Sugar Synthesis 下载免费PDF全文
Nina Wagner Andreas Bosshart Jurek Failmezger Dr. Matthias Bechtold Prof. Sven Panke 《Angewandte Chemie (International ed. in English)》2015,54(14):4182-4186
Enzyme cascades combining epimerization and isomerization steps offer an attractive route for the generic production of rare sugars starting from accessible bulk sugars but suffer from the unfavorable position of the thermodynamic equilibrium, thus reducing the yield and requiring complex work‐up procedures to separate pure product from the reaction mixture. Presented herein is the integration of a multienzyme cascade reaction with continuous chromatography, realized as simulated moving bed chromatography, to overcome the intrinsic yield limitation. Efficient production of D ‐psicose from sucrose in a three‐step cascade reaction using invertase, D ‐xylose isomerase, and D ‐tagatose epimerase, via the intermediates D ‐glucose and D ‐fructose, is described. This set‐up allowed the production of pure psicose (99.9 %) with very high yields (89 %) and high enzyme efficiency (300 g of D ‐psicose per g of enzyme). 相似文献
999.
Inside Cover: Copper and Silver Carbene Complexes without Heteroatom‐Stabilization: Structure,Spectroscopy, and Relativistic Effects (Angew. Chem. Int. Ed. 35/2015) 下载免费PDF全文
1000.
Patrick C. Dolder Matthias E. Liechti Katharina M. Rentsch 《Analytical and bioanalytical chemistry》2015,407(6):1577-1584