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21.
Annika Pohl Gunnar Westin Kjell Jansson 《Journal of Sol-Gel Science and Technology》2003,26(1-3):257-260
The first purely alkoxide-based sol-gel route to nano-phase powders and thin films of perovskite La0.75Sr0.25MnO3 is described. The phase and microstructure evolution on heat treatment of free gel films to form the target nano-phase oxide were investigated by TGA, IR spectroscopy, powder XRD, SEM and TEM-EDS. The xerogel consisted of a hydrated oxo-carbonate, without remaining alkoxo groups or solvent. Heating at 5°C·min–1 decomposed the carbonate groups and yielded the pure perovskite La0.75Sr0.25MnO3 at 760°C. The cell dimensions were virtually unchanged from the first observation of perovskite at 680°C, to 1000°C, 4 h. The monoclinic cell of La0.75Sr0.25MnO3 obtained at 1000°C, 4 h, had the dimensions a = 5.475(1), b = 5.504(2), c = 7.771(1) Å, = 90.50(2), fitting the literature data quite well. Crack-free, homogenous, 150 nm thick La0.75Sr0.25MnO3 films were prepared by spin-coating Si/SiO2/TiO2/Pt and polycrystalline -Al2O3 substrates with a 0.6 M alkoxide solution, followed by heating at 5°C·min–1 to 800°C, 30 min. 相似文献
22.
Charged Langmuir-Blodgett monolayers deposited at an immobilised liquid-liquid interface have been used as a simple model for a biological membrane to investigate the membrane activity of biotechnological oligopeptide drugs. 相似文献
23.
Analyse von Protease‐Inhibitor‐Interaktionen unter Nutzung evolvierbarer tricyclischer Microviridine
24.
Johannes C. B. Dietschreit Annika Wagner T. Anh Le Philipp Klein Prof. Dr. Hermann Schindelin Prof. Dr. Till Opatz Prof. Dr. Bernd Engels Prof. Dr. Ute A. Hellmich Prof. Dr. Christian Ochsenfeld 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):12769-12773
The absence of fluorine from most biomolecules renders it an excellent probe for NMR spectroscopy to monitor inhibitor–protein interactions. However, predicting the binding mode of a fluorinated ligand from a chemical shift (or vice versa) has been challenging due to the high electron density of the fluorine atom. Nonetheless, reliable 19F chemical-shift predictions to deduce ligand-binding modes hold great potential for in silico drug design. Herein, we present a systematic QM/MM study to predict the 19F NMR chemical shifts of a covalently bound fluorinated inhibitor to the essential oxidoreductase tryparedoxin (Tpx) from African trypanosomes, the causative agent of African sleeping sickness. We include many protein–inhibitor conformations as well as monomeric and dimeric inhibitor–protein complexes, thus rendering it the largest computational study on chemical shifts of 19F nuclei in a biological context to date. Our predicted shifts agree well with those obtained experimentally and pave the way for future work in this area. 相似文献
25.
Leonid I. Goryunov Vitalij D. Shteingarts Joseph Grobe Bernt Krebs Michael U. Triller 《无机化学与普通化学杂志》2002,628(8):1770-1779
Trimethylsilyldimethylarsane Me3SiAsMe2 was used as a reagent for the substitution of fluorine in polyfluoroarenes C6F5X (X = F, H, Cl) and C5NF5 by the Me2As group. The reactions occur between 50 — 180 °C, either in benzene or without solvent, to give as a rule 4‐X‐1‐(dimethylarsano)tetrafluorobenzenes XC6F4AsMe2, ( 1—3 ) and 4‐dimethylarsano‐tetrafluoropyridine C5NF4AsMe2 ( 4 ), respectively, in yields between 43 and 94 %. In the case of C6F6, also double substitution is observed affording 1, 4‐bis(dimethylarsano)tetrafluorobenzene 5 in addition to the monosubstituted derivative. The time and temperature dependencies of the reactions increase in the sequence: C6F6< C6F5H < C6F5Cl < C5NF5. The arsanes 1 and 4 were transformed to the potentially valuable bidentate ligands 1‐(dimethylarsano)‐4‐(dimethylphosphano)tetrafluorobenzene 6 and 4‐(dimethylarsano)‐2‐(dimethylphosphano)trifluoropyridine 8 by reaction with trimethylsilyl‐dimethylphosphane Me3SiPMe2. 6 reacts with oxygen to yield the corresponding phosphane oxide 7 . Trimethylsilyl‐dimethylamine Me3SiNMe2 also was successfully tested as a reagent for the dimethylamination of polyfluoroarenes C6F5X [X = F, H, Cl, CF3, P(S)Me2], 1‐P(S)Me2‐4‐H‐C6F4 and 4‐X‐C5NF4 [X = F, PMe2, P(S)Me2]. Sulfuration of the new Me2P derivatives 8 and 20 leads to the corresponding thiophosphanes 9 and 21 (Schemes 2 and 3). Furthermore, the recently reported very efficient one‐pot synthesis of Me2P substituted polyfluoroarenes (e.g. XC6F4PMe2 with X = F, Me2PC6F4) was extended to the preparation of Me2As and MeS derivatives of pentafluoropyridine using a mixture of Me3SnH, As2Me4 (or S2Me2) and C5NF5 as precursors for the one‐pot reaction. The expected products 4‐(dimethylarsano)tetrafluoropyridine 4 and 4‐(methylthio)tetrafluoropyridine 22 , respectively, were obtained in 84 and 82 % isolated yields. The novel compounds were characterized by spectroscopic (NMR, MS) and analytical data. Compounds 5 , 7 , 9 and 21 could be isolated in form of single crystals and their structures have been studied by X‐ray diffraction. 相似文献
26.
Nicole Reddig Michael U. Triller Daniel Pursche Annette Rompel Bernt Krebs 《无机化学与普通化学杂志》2002,628(11):2458-2462
The tetranuclear manganese(II) complex [Mn4(ppi)6](BPh4)2 ( 2 ) (Hppi = 2‐pyridylmethyl‐2‐hydroxy phenylimine) is prepared by using the precursor complex [Mn(ppi)2]·H2O ( 1 ). Based on UV/Vis‐ and IR‐spectroscopy data in combination with mass spectrometry it has been concluded that 1 is a mononuclear neutral MnII complex, in which two ppi ligands chelate the manganese atom. Compound 2 crystallizes in the triclinic space group P1¯ (no. 2), with a = 17.500(3), b = 17.955(4), c = 19.101(4) Å, α = 113.79(3)°, β = 111.33(3)°, γ = 93.91(3)°, V = 4950(2) Å3 and Z = 2. In the tetranuclear [Mn4(ppi)6]2+ complex cation Mn(1), Mn(2), and Mn(3) are equivalently coordinated by two deprotonated Hppi ligands leading to a N4O2 donor set. The environment of the central Mn(4) is formed by coordination of three [Mn(ppi)2] fragments resulting in a phenoxo bridged star‐shaped Mn4O6 core motif. The average distance of directly adjacent manganese ions is 3.310 Å, whereas the average distance of Mn(1), Mn(2), and Mn(3) among each other is 5.732 Å. 相似文献
27.
Dr. Tobias W. Giessen Florian Altegoer Annika J. Nebel Roman M. Steinbach Dr. Gert Bange Prof. Dr. Mohamed A. Marahiel 《Angewandte Chemie (International ed. in English)》2015,54(8):2492-2496
The incorporation of non‐proteinogenic amino acids represents a major challenge for the creation of functionalized proteins. The ribosomal pathway is limited to the 20–22 proteinogenic amino acids while nonribosomal peptide synthetases (NRPSs) are able to select from hundreds of different monomers. Introduced herein is a fusion‐protein‐based design for synthetic tRNA‐aminoacylation catalysts based on combining NRPS adenylation domains and a small eukaryotic tRNA‐binding domain (Arc1p‐C). Using rational design, guided by structural insights and molecular modeling, the adenylation domain PheA was fused with Arc1p‐C using flexible linkers and achieved tRNA‐aminoacylation with both proteinogenic and non‐proteinogenic amino acids. The resulting aminoacyl‐tRNAs were functionally validated and the catalysts showed broad substrate specificity towards the acceptor tRNA. Our strategy shows how functional tRNA‐aminoacylation catalysts can be created for bridging the ribosomal and nonribosomal worlds. This opens up new avenues for the aminoacylation of tRNAs with functional non‐proteinogenic amino acids. 相似文献
28.
Kimmo Smolander Risto J?rnstr?m Annika Sajalinna 《Fresenius' Journal of Analytical Chemistry》1989,335(4):392-394
Summary The matric effect of boric acid was investigated in the determination of iron in the primary circuit coolant water of nuclear power plants by furnace atomic absorption spectrometry. The effect of boric acid was of particular interest. The method was applied during refuelling and maintenance periods and the results were used to interpret the chemical changes in the water.
Einfluß von Borsäure auf die Bestimmung von Eisen in Reaktorkühlwasser durch GF-AAS相似文献
29.
Red single crystals of Gd2[Pt2(SO4)4(HSO4)2](HSO4)2 (triclinic, , Z = 1, a = 844.02(9), b = 908.50(9), c = 939.49(8) pm, α = 107.73(1)°, β = 112.10(1)°, γ = 103.53(1)°) were obtained by the reaction of [Gd(NO3)(H2O)7][PtCl6]·4H2O with sulfuric acid at 320 °C in a sealed glass ampoule. In the crystal structure, Pt2 dumbbells are coordinated by four chelating sulfate groups and two monodentate hydrogensulfate ions. Two further HSO4? ions are not bonded to the Pt2 dumbbell. The Gd3+ ions are eightfold coordinated by oxygen atoms. The IR data of Gd2[Pt2(SO4)4(HSO4)2](HSO4)2 are typical for these type of compounds. The thermal decomposition of the compound leads to elemental platinum and Gd2O3. 相似文献
30.
Annika Arndt Damir Posavec Stefan Schwarzer Mathias S. Wickleder Prof. Dr. 《无机化学与普通化学杂志》2008,634(3):431-435
The reaction of the nitrates M(NO3)3·6H2O (M = La, Pr) and (H3O)2PtCl6 led to yellow single crystals of [M(NO3)2(H2O)6]2[PtCl6]·2H2O (M = La, Pr) (monoclinic, P21/c, Z = 2, La/Pr: a = 697.4(3)/695.5(1), b = 1654.5(1)/1652.5(2), c = 1317.7(6)/1318.5(3) pm, β = 93.97°(7)/93.93°(2), Rall = 0.0169/0.0659) while the reaction of M(NO3)3·5H2O (M = Gd, Dy) and (H3O)2PtCl6 yielded yellow single crystals of [M(NO3)(H2O)7][PtCl6]·4H2O (monoclinic, P21/n, Z = 4, Gd/Dy: a = 838.72(3)/838.40(2), b = 2131.98(6)/2139.50(7), c = 1142.63(3)/1143.10(3) pm, β = 95.670(4)/95.698(3), Rall = 0.0475/0.0337). The crystal structures consist of octahedral [PtCl6]2? anions and complex [M(NO3)2(H2O)6]2+ and [M(NO3)(H2O)7]2+ cations, respectively. The thermal decomposition of both types of compounds leads via various steps to elemental platinum and the oxide chlorides MOCl (M = La, Pr, Gd, Dy). 相似文献