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431.
432.
Ludwig Moser und Maximilian Behr 《Fresenius' Journal of Analytical Chemistry》1924,65(5):186-188
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433.
434.
Optimized sample preparation strategy for the analysis of low molecular mass adducts of a fluorescent cisplatin analogue in cancer cell lines by CE‐dual‐LIF
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Robert Zabel Maximilian Kullmann Ganna V. Kalayda Ulrich Jaehde Günther Weber 《Electrophoresis》2015,36(4):509-517
Pt‐based anticancer drugs, such as cisplatin, are known to undergo several (bio‐)chemical transformation steps after administration. Hydrolysis and adduct formation with small nucleophiles and larger proteins are their most relevant reactions on the way to the final reaction site (DNA), but there are still many open questions regarding the identity and pharmacological relevance of various proposed adducts and intermediates. Furthermore, the role of buffer components or additives, which are inevitably added to samples during any type of analytical measurement, has been frequently neglected in previous studies. Here, we report on adduct formation reactions of the fluorescent cisplatin analogue carboxyfluorescein diacetate platinum (CFDA‐Pt) in commonly used buffers and cell culture medium. Our results indicate that chelation reactions with noninnocent buffers (e.g., Tris) and components of the cell culture/cell lysis medium must be taken into account when interpreting results. Adduct formation kinetics was followed up to 60 h at nanomolar concentrations of CFDA‐Pt by using CE‐LIF. CE‐MS enabled the online identification of such unexpected adducts down to the nanomolar concentration range. By using an optimized sample preparation strategy, unwanted adducts can be avoided and several fluorescent adducts of CFDA‐Pt are detectable in sensitive and cisplatin‐resistant cancer cell lines. By processing samples rapidly after incubation, we could even identify the initial, but transient, Pt species in the cells as deacetylated CFDA‐Pt with unaltered complexing environment at Pt. Overall, the proposed procedure enables a very sensitive and accurate analysis of low molecular mass Pt species in cancer cells, involving a fast CE‐LIF detection within 5 min. 相似文献
435.
Regioselective Catalytic and Stepwise Routes to Bulky,Functional‐Group‐Appended,and Luminescent 1,2‐Azaborinines
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Marius Schäfer Julian Schäfer Dr. Rian D. Dewhurst Dr. William C. Ewing Mirjam Krahfuß Maximilian W. Kuntze‐Fechner Marius Wehner Prof. Dr. Christoph Lambert Prof. Dr. Holger Braunschweig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8603-8609
The regioselective syntheses of 1,2‐azaborinines is achieved using an unsymmetrical iminoborane through both catalytic and stepwise modular routes. The 1,2‐azaborinine ring can be selectively functionalized in the 4‐ and/or 6‐position through control of the stepwise reaction sequence, allowing access to vinyl‐functionalized and redox‐active, luminescent, donor‐functionalized 1,2‐azaborinines. The electrochemistry and photochemistry of a tetraarylamine‐substituted 1,2‐azaborinine are studied. Cyclic voltammetry of this compound, relative to a non‐B,N‐substituted reference molecule, showed an additional oxidation wave assigned to the oxidation of the azaborinine ring, while emission spectroscopy indicated that the azaborinine was significantly more fluorescent than the reference. 相似文献
436.
Vanessa Kristina Seiler Wilhelm Maximilian Hützler Michael Bolte 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(5):379-388
In order to examine the preferred hydrogen‐bonding pattern of various uracil derivatives, namely 5‐(hydroxymethyl)uracil, 5‐carboxyuracil and 5‐carboxy‐2‐thiouracil, and for a conformational study, crystallization experiments yielded eight different structures: 5‐(hydroxymethyl)uracil, C5H6N2O3, (I), 5‐carboxyuracil–N,N‐dimethylformamide (1/1), C5H4N2O4·C3H7NO, (II), 5‐carboxyuracil–dimethyl sulfoxide (1/1), C5H4N2O4·C2H6OS, (III), 5‐carboxyuracil–N,N‐dimethylacetamide (1/1), C5H4N2O4·C4H9NO, (IV), 5‐carboxy‐2‐thiouracil–N,N‐dimethylformamide (1/1), C5H4N2O3S·C3H7NO, (V), 5‐carboxy‐2‐thiouracil–dimethyl sulfoxide (1/1), C5H4N2O3S·C2H6OS, (VI), 5‐carboxy‐2‐thiouracil–1,4‐dioxane (2/3), 2C5H4N2O3S·3C6H12O3, (VII), and 5‐carboxy‐2‐thiouracil, C10H8N4O6S2, (VIII). While the six solvated structures, i.e. (II)–(VII), contain intramolecular S(6) O—H…O hydrogen‐bond motifs between the carboxy and carbonyl groups, the usually favoured R22(8) pattern between two carboxy groups is formed in the solvent‐free structure, i.e. (VIII). Further R22(8) hydrogen‐bond motifs involving either two N—H…O or two N—H…S hydrogen bonds were observed in three crystal structures, namely (I), (IV) and (VIII). In all eight structures, the residue at the ring 5‐position shows a coplanar arrangement with respect to the pyrimidine ring which is in agreement with a search of the Cambridge Structural Database for six‐membered cyclic compounds containing a carboxy group. The search confirmed that coplanarity between the carboxy group and the cyclic residue is strongly favoured. 相似文献
437.
Wilhelm Maximilian Hützler Ernst Egert Michael Bolte 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(8):634-646
The understanding of intermolecular interactions is a key objective of crystal engineering in order to exploit the derived knowledge for the rational design of new molecular solids with tailored physical and chemical properties. The tools and theories of crystal engineering are indispensable for the rational design of (pharmaceutical) cocrystals. The results of cocrystallization experiments of the antithyroid drug 6‐propyl‐2‐thiouracil (PTU) with 2,4‐diaminopyrimidine (DAPY), and of 6‐methoxymethyl‐2‐thiouracil (MOMTU) with DAPY and 2,4,6‐triaminopyrimidine (TAPY), respectively, are reported. PTU and MOMTU show a high structural similarity and differ only in the replacement of a methylene group (–CH2–) with an O atom in the side chain, thus introducing an additional hydrogen‐bond acceptor in MOMTU. Both molecules contain an ADA hydrogen‐bonding site (A = acceptor and D = donor), while the coformers DAPY and TAPY both show complementary DAD sites and therefore should be capable of forming a mixed ADA/DAD synthon with each other, i.e. N—H…O, N—H…N and N—H…S hydrogen bonds. The experiments yielded one solvated cocrystal salt of PTU with DAPY, four different solvates of MOMTU, one ionic cocrystal of MOMTU with DAPY and one cocrystal salt of MOMTU with TAPY, namely 2,4‐diaminopyrimidinium 6‐propyl‐2‐thiouracilate–2,4‐diaminopyrimidine–N,N‐dimethylacetamide–water (1/1/1/1) (the systematic name for 6‐propyl‐2‐thiouracilate is 6‐oxo‐4‐propyl‐2‐sulfanylidene‐1,2,3,6‐tetrahydropyrimidin‐1‐ide), C4H7N4+·C7H9N2OS−·C4H6N4·C4H9NO·H2O, (I), 6‐methoxymethyl‐2‐thiouracil–N,N‐dimethylformamide (1/1), C6H8N2O2S·C3H7NO, (II), 6‐methoxymethyl‐2‐thiouracil–N,N‐dimethylacetamide (1/1), C6H8N2O2S·C4H9NO, (III), 6‐methoxymethyl‐2‐thiouracil–dimethyl sulfoxide (1/1), C6H8N2O2S·C2H6OS, (IV), 6‐methoxymethyl‐2‐thiouracil–1‐methylpyrrolidin‐2‐one (1/1), C6H8N2O2S·C5H9NO, (V), 2,4‐diaminopyrimidinium 6‐methoxymethyl‐2‐thiouracilate (the systematic name for 6‐methoxymethyl‐2‐thiouracilate is 4‐methoxymethyl‐6‐oxo‐2‐sulfanylidene‐1,2,3,6‐tetrahydropyrimidin‐1‐ide), C4H7N4+·C6H7N2O2S−, (VI), and 2,4,6‐triaminopyrimidinium 6‐methoxymethyl‐2‐thiouracilate–6‐methoxymethyl‐2‐thiouracil (1/1), C4H8N5+·C6H7N2O2S−·C6H8N2O2S, (VII). Whereas in (I) only an AA/DD hydrogen‐bonding interaction was formed, the structures of (VI) and (VII) both display the desired ADA/DAD synthon. Conformational studies on the side chains of PTU and MOMTU also revealed a significant deviation for cocrystals (VI) and (VII), leading to the desired enhancement of the hydrogen‐bond pattern within the crystal. 相似文献
438.
Paola Breda Maximilian Hansinger Michael Pfitzner 《Proceedings of the Combustion Institute》2021,38(2):2655-2663
The use of the Eulerian Stochastic Fields (ESF) method to model the sub-grid turbulence-chemistry interaction (TCI) in the LES context can be computationally expensive if detailed chemistry mechanisms are involved. This work aims to assess whether it is possible to neglect the modelling of the TCI on sufficiently refined meshes while using finite rate chemistry, provided that at least 80 % of the turbulent kinetic energy scales are resolved. Turbulent non-premixed methane-air flames showing a moderate degree of local extinction are selected as benchmark. Results obtained for the Sandia flame E with and without transporting the ESF on three different meshes are discussed. Sensible deviations are visible on the fuel-rich side from section x/D = 30, by reducing the grid refinement. The influence of three finite rate chemistry solvers is further investigated on flame D, without the sub-grid scale chemistry model. All simulations are in good agreement with the experimental data and show a weak dependence on the chemistry involved. A trade-off assessment between computational time and accuracy is provided, in order to extend the validation to a more severe extinction regime. 相似文献
439.
Metal casting and polymer molding are widely used for the economical shape processing of complex geometries. In these manufacturing processes, a liquid melt (metal, mineral or synthetic) is filled into a mold with a cavity of the desired shape. Cooling and solidification of the melt results in a product with almost the same shape as the cavity. Numerical simulations can be employed to increase the accuracy of the process. To this end, boundary element method for Stokes flow and a finite element formulation for liquid membranes are investigated in this work. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
440.
Dr. Stephan Hagspiel Dr. Felipe Fantuzzi Dr. Merle Arrowsmith Annalena Gärtner Maximilian Fest Jonas Weiser Prof. Dr. Bernd Engels Prof. Dr. Holger Helten Prof. Dr. Holger Braunschweig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(49):e202201398
The reaction of a cyclic alkyl(amino)carbene (CAAC)-stabilized thiazaborolo[5,4-d]thiazaborole (TzbTzb) with strong Brønsted acids, such as HCl, HOTf (Tf=O2SCF3) and [H(OEt2)2][BArF4] (ArF=3,5-(CF3)2C6H3), results in the protonation of both TzbTzb nitrogen atoms. In each case X-ray crystallographic data show coordination of the counteranions (Cl−, OTf−, BArF4−) or solvent molecules (OEt2) to the doubly protonated fused heterocycle via hydrogen-bonding interactions, the strength of which strongly influences the 1H NMR shift of the NH protons, enabling tuning of both the visible (yellow to red) and fluorescence (green to red) colors of these salts. DFT calculations reveal that the hydrogen bonding of the counteranion or solvent to the protonated nitrogen centers affects the intramolecular TzbTzb-to-CAAC charge transfer character involved in the S0→S1 transition, ultimately enabling fine-tuning of their absorption and emission spectral features. 相似文献