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排序方式: 共有1041条查询结果,搜索用时 218 毫秒
991.
Junling Guo Dr. Yuan Ping Dr. Hirotaka Ejima Dr. Karen Alt Mirko Meissner Joseph J. Richardson Dr. Yan Yan Prof. Karlheinz Peter Prof. Dominik von Elverfeldt Assoc. Prof. Christoph E. Hagemeyer Prof. Frank Caruso 《Angewandte Chemie (International ed. in English)》2014,53(22):5546-5551
Metal–organic coordination materials are of widespread interest because of the coupled benefits of inorganic and organic building blocks. These materials can be assembled into hollow capsules with a range of properties, which include selective permeability, enhanced mechanical/thermal stability, and stimuli‐responsiveness. Previous studies have primarily focused on the assembly aspects of metal‐coordination capsules; however, the engineering of metal‐specific functionality for capsule design has not been explored. A library of functional metal–phenolic network (MPN) capsules prepared from a phenolic ligand (tannic acid) and a range of metals is reported. The properties of the MPN capsules are determined by the coordinated metals, allowing for control over film thickness, disassembly characteristics, and fluorescence behavior. Furthermore, the functional properties of the MPN capsules were tailored for drug delivery, positron emission tomography (PET), magnetic resonance imaging (MRI), and catalysis. The ability to incorporate multiple metals into MPN capsules demonstrates that a diverse range of functional materials can be generated. 相似文献
992.
Dominik B. Bucher Alexander Schlueter Prof. Dr. Thomas Carell Prof. Dr. Wolfgang Zinth 《Angewandte Chemie (International ed. in English)》2014,53(42):11366-11369
Excited‐state dynamics are essential to understanding the formation of DNA lesions induced by UV light. By using femtosecond IR spectroscopy, it was possible to determine the lifetimes of the excited states of all four bases in the double‐stranded environment of natural DNA. After UV excitation of the DNA duplex, we detected a concerted decay of base pairs connected by Watson–Crick hydrogen bonds. A comparison of single‐ and double‐stranded DNA showed that the reactive charge‐transfer states formed in the single strands are suppressed by base pairing in the duplex. The strong influence of the Watson–Crick hydrogen bonds indicates that proton transfer opens an efficient decay path in the duplex that prohibits the formation or reduces the lifetime of reactive charge‐transfer states. 相似文献
993.
Fingerprinting DNA Oxidation Processes: IR Characterization of the 5‐Methyl‐2′‐Deoxycytidine Radical Cation
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Dominik B. Bucher Bert M. Pilles Toni Pfaffeneder Prof. Dr. Thomas Carell Prof. Wolfgang Zinth 《Chemphyschem》2014,15(3):420-423
Methylated cytidine plays an important role as an epigenetic signal in gene regulation. Its oxidation products are assumed to be involved in active demethylation processes but also in damaging DNA. Here, we report the photochemical production of the 5‐methyl‐2′‐deoxycytidine radical cation via a two‐photon ionization process. The radical cation is detected by time‐resolved IR spectroscopy and identified by band assignment using density functional theory calculations. Two final oxidation products are characterized with liquid chromatography coupled to mass spectrometry. 相似文献
994.
M.Sc. Dominik Brox Dr. Michael Schwering Dr. Johann Engelhardt Dr. Dirk‐Peter Herten 《Chemphyschem》2014,15(11):2331-2336
Recent developments in biology demand an increasing number of simultaneously imaged structures with standard fluorescence microscopy. However, the number of multiplexed channels is limited for most multiplexing modalities, such as spectral multiplexing or fluorescence‐lifetime imaging. We propose extending the number of imaging channels by using chemical reactions, controlling the emissive state of fluorescent dyes. As proof of concept, we reversibly switch a fluorescent copper sensor to enable successive imaging of two different structures in the same spectral channel. We also show that this chemical multiplexing is orthogonal to existing methods. By using two different dyes, we combine chemical with spectral multiplexing for the simultaneous imaging of four different structures with only two spectrally different channels. We characterize and discuss the approach and provide perspectives for extending imaging modalities in stimulated emission depletion microscopy, for which spectral multiplexing is technically demanding. 相似文献
995.
996.
In order to investigate the individual and inhomogenous cellular response, e.g. to external stimuli, single cell analysis is mandatory and may provide new cognitions in proteomics as well as in other fields of systems biology in the future. Here, we report on novel chip architectures for single cell analysis based on full body quartz glass microfluidic chips (QG chips) that extend our previous studies in polydimethylsiloxane (PDMS) chips, and enhance the detection sensitivity of native UV laser-induced fluorescence (UV-LIF) detection. Detection of a 10nM tryptophan solution with an S/N ratio of 11.9, which gives a theoretical limit of detection of 2.5nM (with S/N=3), was possible. With these optimizations the three proteins alpha-chymotrypsinogen A, ovalbumin and catalase each at a concentration of 100mug/mL (equal to 4muM, 0.4muM and 2.2muM) were injected electrokinetically and could be separated with nearly baseline resolution. Furthermore, fluorescence spectra (excitation wavelength, lambda(ex)=266nm) clearly demonstrate the favourable properties like the very high UV transparency and the nearly vanishing background fluorescence of the QG chips as compared to PDMS chips and to PDMS quartz window (PQW) chips. Finally we exploit the improved sensitivity for single cell electropherograms of Spodoptera frugiperda (Sf9) insect cells. 相似文献
997.
Amrit Venkatesh Gilles Casano Yu Rao Federico De Biasi Frédéric A. Perras Dominik J. Kubicki Didier Siri Sébastien Abel Hakim Karoui Maxim Yulikov Olivier Ouari Lyndon Emsley 《Angewandte Chemie (International ed. in English)》2023,62(31):e202304844
The sensitivity of NMR spectroscopy is considerably enhanced by dynamic nuclear polarization (DNP). In DNP polarization is transferred from unpaired electrons of a polarizing agent to nearby proton spins. In solids, this transfer is followed by the transport of hyperpolarization to the bulk via 1H-1H spin diffusion. The efficiency of these steps is critical to obtain high sensitivity gains, but the pathways for polarization transfer in the region near the unpaired electron spins are unclear. Here we report a series of seven deuterated and one fluorinated TEKPol biradicals to probe the effect of deprotonation on MAS DNP at 9.4 T. The experimental results are interpreted with numerical simulations, and our findings support that strong hyperfine couplings to nearby protons determine high transfer rates across the spin diffusion barrier to achieve short build-up times and high enhancements. Specifically, 1H DNP build-up times increase substantially with TEKPol isotopologues that have fewer hydrogen atoms in the phenyl rings, suggesting that these protons play a crucial role transferring the polarization to the bulk. Based on this new understanding, we have designed a new biradical, NaphPol, which yields significantly increased NMR sensitivity, making it the best performing DNP polarizing agent in organic solvents to date. 相似文献
998.
Stephan Dahlke Dominik Lellek Rob Stevenson 《Numerical Functional Analysis & Optimization》2016,37(10):1213-1234
In this article, we are concerned with domain decomposition methods for the stationary incompressible Navier-Stokes equation. We construct an adaptive additive Schwarz method based on discretization by means of a divergence-free wavelet frame. We prove that the method is convergent and asymptotically optimal with respect to the degrees of freedom involved. 相似文献
999.
Calzaferri G Li H Brühwiler D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(25):7442-7449
Artificial photonic antenna systems have been realised by incorporating organic dyes into zeolite L. The size and aspect ratio of the cylindrically shaped zeolite crystals can be tuned over a wide range, adding to the versatility of this host material. A 600 nm sized crystal, for example, consists of about 96 000 one-dimensional channels oriented parallel to the cylinder axis. Geometrical constraints imposed by the host structure lead to supramolecular organisation of the guests, allowing high concentrations of non- or only very weakly interacting dye molecules. A special twist is added to these systems by plugging the channel openings with a second type of fluorescent dye, a so-called stopcock molecule. The two types of molecules are precisely tuned to each other; the stopcocks are able to accept excitation energy from the dyes in the channels, but cannot pass it back. The supramolecular organisation of dyes in the zeolite channels corresponds to a first stage of organisation, allowing light-harvesting within the volume of a cylindrical crystal and radiationless energy transport to either the cylinder ends or centre. The second stage of organisation represents the coupling to an external acceptor or donor stopcock fluorophore at the channel entrances, which can then trap or inject electronic excitation energy. The third stage of organisation is realised by interfacing the material to an external device through a stopcock intermediate. We observed that electronic-excitation-energy transfer in dye-zeolite L materials occurs mainly along the channel axis and we have shown that macroscopically organised materials can be prepared. The new materials offer unique possibilities as building blocks for optical, electro-optical and sensing devices. 相似文献
1000.