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41.
The Gauge/Bethe correspondence of Nekrasov and Shatashvili relates the spectrum of integrable spin chains to the ground states
of supersymmetric gauge theories. Up to now, this correspondence has been an observation; the underlying reason for its existence
remaining elusive. We argue here that geometrical representation theory is a mathematical foundation of the Gauge/Bethe correspondence,
and it provides a framework to study families of gauge theories in a unified way. 相似文献
42.
Lana G. Kaiser Ma?gorzata Marjańska Gerald B. Matson Isabelle Iltis Seth D. Bush Brian J. Soher Susanne Mueller Karl Young 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2010,202(2):259-266
Glutathione (GSH) is a powerful antioxidant found inside different kinds of cells, including those of the central nervous system. Detection of GSH in the human brain using 1H MR spectroscopy is hindered by low concentration and spectral overlap with other metabolites. Previous MRS methods focused mainly on the detection of the cysteine residue (GSH-Cys) via editing schemes. This study focuses on the detection of the glycine residue (GSH-Gly), which is overlapped by glutamate and glutamine (Glx) under physiological pH and temperature. The first goal of the study was to obtain the spectral parameters for characterization of the GSH-Gly signal under physiological conditions. The second goal was to investigate a new method of separating GSH-Gly from Glx in vivo. The characterization of the signal was carried out by utilization of numerical simulations as well as experiments over a wide range of magnetic fields (4.0–14 T). The proposed separation scheme utilizes J-difference editing to quantify the Glx contribution to separate it from the GSH-Gly signal. The presented method retains 100% of the GSH-Gly signal. The overall increase in signal to noise ratio of the targeted resonance is calculated to yield a significant SNR improvement compared to previously used methods that target GSH-Cys residue. This allows shorter acquisition times for in vivo human clinical studies. 相似文献
43.
Anna‐Kristina Marel Susanne Rappl Alicia Piera Alberola Joachim Oskar Rädler 《Macromolecular bioscience》2013,13(5):595-602
A robust and effortless procedure is presented, which allows for the microstructuring of standard cell culture dishes. Cell adhesion and proliferation are controlled by three‐dimensional poly(ethylene glycol)‐dimethacrylate (PEG‐DMA) microstructures. The spacing between microwells can be extended to millimeter size in order to enable the combination with robotic workstations. Cell arrays of microcolonies can be studied under boundary‐free growth conditions by lift‐off of the PEG‐DMA layer in which the growth rate is accessible via the evolution of patch areas. Alternatively, PEG‐DMA stencils can be used as templates for plasma‐induced patterning.
44.
45.
Jitka Daďová Susanne Kümmel Christian Feldmeier Jana Cibulková Dr. Richard Pažout Dr. Jaroslav Maixner Prof. Dr. Ruth M. Gschwind Prof. Dr. Burkhard König Dr. Radek Cibulka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(3):1066-1075
A series of 10‐arylflavins (10‐phenyl‐, 10‐(2′,6′‐dimethylphenyl)‐, 10‐(2′,6′‐diethylphenyl)‐, 10‐(2′,6′‐diisopropylphenyl)‐, 10‐(2′‐tert‐butylphenyl)‐, and 10‐(2′,6′‐dimethylphenyl)‐3‐methylisoalloxazine ( 2 a – f )) was prepared as potentially nonaggregating flavin photocatalysts. The investigation of their structures in the crystalline phase combined with 1H‐DOSY NMR spectroscopic experiments in CD3CN, CD3CN/D2O (1:1), and D2O confirm the decreased ability of 10‐arylflavins 2 to form aggregates relative to tetra‐O‐acetyl riboflavin ( 1 ). 10‐Arylflavins 2 a – d do not interact by π–π interactions, which are restricted by the 10‐phenyl ring oriented perpendicularly to the isoalloxazine skeleton. On the other hand, N3? H???O hydrogen bonds were detected in their crystal structures. In the structure of 10‐aryl‐3‐methylflavin ( 2 f ) with a substituted N3 position, weak C? H???O bonds and weak π–π interactions were found. 10‐Arylflavins 2 were tested as photoredox catalysts for the aerial oxidation of 4‐methoxybenzyl alcohol to the corresponding aldehyde (model reaction), thus showing higher efficiency relative to 1 . The quantum yields of 4‐methoxybenzyl alcohol oxidation reactions mediated by arylflavins 2 were higher by almost one order of magnitude relative to values in the presence of 1 . 相似文献
46.
Susanne Kern Hafida Dkhil Prisca Hendarsa Graham Ellis Andreas Natsch 《Analytical and bioanalytical chemistry》2014,406(25):6165-6178
On prolonged exposure to air, linalool can form sensitizing hydroperoxides. Positive hydroperoxide patch tests in dermatitis patients have frequently been reported, but their relevance has not been established. Owing to a lack of analytical methods and data, it is unclear from which sources the public might be exposed to sufficient quantities of hydroperoxides for induction of sensitization to occur. To address this knowledge gap, we developed analytical methods and performed stability studies for fine fragrances and deodorants/antiperspirants. In parallel, products recalled from consumers were analysed to investigate exposure to products used in everyday life. Liquid chromatography–mass spectrometry with high mass resolution was found to be optimal for the selective and sensitive detection of the organic hydroperoxide in the complex product matrix. Linalool hydroperoxide was detected in natural linalool, but the amount was not elevated by storage in a perfume formulation exposed to air. No indication of hydroperoxide formation in fine fragrances was found in stability studies. Aged fine fragrances recalled from consumers contained a geometric mean linalool concentration of 1,888 μg/g and, corrected for matrix effects, linalool hydroperoxide at a concentration of around 14 μg/g. In antiperspirants, we detected no oxidation products. In conclusion, very low levels of linalool hydroperoxide in fragranced products may originate from raw materials, but we found no evidence for oxidation during storage of products. The levels detected are orders of magnitude below the levels inducing sensitization in experimental animals, and these results therefore do not substantiate a causal link between potential hydroperoxide formation in cosmetics and positive results of patch tests. Graphical Abstract
47.
Anna-Lena Leistner Susanne Kirchner Johannes Karcher Tobias Bantle Mariam L. Schulte Peter Gödtel Christian Fengler Dr. Zbigniew L. Pianowski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(31):8094-8099
Molecular photoswitches triggered with red or NIR light are optimal for photomodulation of complex biological systems, including efficient penetration of the human body for therapeutic purposes (“therapeutic window”). Yet, they are rarely reported, and even more rarely functional under aqueous conditions. In this work, fluorinated azobenzenes are shown to exhibit efficient E→Z photoisomerization with red light (PSS660nm >75 % Z) upon conjugation with unsaturated substituents. Initially demonstrated for aldehyde groups, this effect was also observed in a more complex structure by incorporating the chromophore into a cyclic dipeptide with propensity for self-assembly. Under physiological conditions, the latter molecule formed a supramolecular material that reversibly changed its viscosity upon irradiation with red light. Our observation can lead to design of new photopharmacology agents or phototriggered materials for in vivo use. 相似文献
48.
49.
Determination of conditional stability constants for some divalent transition metal ion‐EDTA complexes by electrospray ionization mass spectrometry 下载免费PDF全文
Susanne Boija Ann Almesåker Erik Hedenström Dan Bylund Håkan Edlund Magnus Norgren 《Journal of mass spectrometry : JMS》2014,49(7):550-556
Conditional stability constants of coordination complexes comprising divalent transition metals, Cu2+, Ni2+, Zn2+, Co2+, and ethylenediaminetetraacetic acid (EDTA) were determined utilizing electrospray ionization mass spectrometry. The deviation of signal response of a reference complex was monitored at addition of a second metal ion. The conditional stability constant for the competing metal was then determined through solution equilibria equations. The method showed to be applicable to a system where Co2+ and Zn2+ competed for EDTA at pH 5. When Cu2+ and Ni2+ competed for EDTA, the equilibrium changed over time. This change was shown to be affected in rate and size by the type of organic solvent added. In this work, 30% of either methanol or acetonitrile was used. It was found that if calibration curves are prepared for both metal complexes in solution and the measurements are repeated with sufficient time space, any change in equilibrium of sample solutions will be discovered. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
50.
Susanne Bhr Sabine Brinkmann‐Chen Marc Garcia‐Borrs John M. Roberts Dimitris E. Katsoulis K. N. Houk Frances H. Arnold 《Angewandte Chemie (International ed. in English)》2020,59(36):15507-15511
Compared to the biological world's rich chemistry for functionalizing carbon, enzymatic transformations of the heavier homologue silicon are rare. We report that a wild‐type cytochrome P450 monooxygenase (P450BM3 from Bacillus megaterium, CYP102A1) has promiscuous activity for oxidation of hydrosilanes to give silanols. Directed evolution was applied to enhance this non‐native activity and create a highly efficient catalyst for selective silane oxidation under mild conditions with oxygen as the terminal oxidant. The evolved enzyme leaves C?H bonds present in the silane substrates untouched, and this biotransformation does not lead to disiloxane formation, a common problem in silanol syntheses. Computational studies reveal that catalysis proceeds through hydrogen atom abstraction followed by radical rebound, as observed in the native C?H hydroxylation mechanism of the P450 enzyme. This enzymatic silane oxidation extends nature's impressive catalytic repertoire. 相似文献