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排序方式: 共有120条查询结果,搜索用时 15 毫秒
41.
42.
Cherrier MV Martin L Cavazza C Jacquamet L Lemaire D Gaillard J Fontecilla-Camps JC 《Journal of the American Chemical Society》2005,127(28):10075-10082
Because nickel is both essential and toxic to a great variety of organisms, its detection and transport is highly regulated. In Escherichia coli and other related Gram-negative bacteria, high affinity nickel transport depends on proteins expressed by the nik operon. A central actor of this process is the periplasmic NikA transport protein. A previous structural report has proposed that nickel binds to NikA as a pentahydrate species. However, both stereochemical considerations and X-ray absorption spectroscopic results are incompatible with that interpretation. Here, we report the 1.8 A resolution structure of NikA and show that it binds FeEDTA(H2O)- with very high affinity. In addition, we provide crystallographic evidence that a metal-EDTA complex was also bound to the previously reported NikA structure. Our observations strongly suggest that nickel transport in E. coli requires the binding of this metal ion to a metallophore that bears significant resemblance to EDTA. They also provide a basis for the potential use of NikA in the bioremediation of toxic transition metals and the design of artificial metalloenzymes. 相似文献
43.
Mickaël Kourganoff 《Communications in Mathematical Physics》2016,344(3):831-856
Any smooth surface in \({{\mathbb R}^{3}}\) may be flattened along the z-axis, and the flattened surface becomes close to a billiard table in \({{\mathbb R}^{2}}\). We show that, under some hypotheses, the geodesic flow of this surface converges locally uniformly to the billiard flow. Moreover, if the billiard is dispersive and has finite horizon, then the geodesic flow of the corresponding surface is Anosov. We apply this result to the theory of mechanical linkages and their dynamics: we provide a new example of a simple linkage whose physical behavior is Anosov. For the first time, the edge lengths of the mechanism are given explicitly. 相似文献
44.
Royer S Sécordel X Brandhorst M Dumeignil F Cristol S Dujardin C Capron M Payen E Dubois JL 《Chemical communications (Cambridge, England)》2008,(7):865-867
We report for the first time the use of an amorphous oxide catalyst for the selective oxidation of methanol in the gas phase, leading at 553 K to the production of dimethoxymethane with a selectivity as high as 90% at high methanol conversion (68%). 相似文献
45.
Gicquel M Heully JL Lepetit C Chauvin R 《Physical chemistry chemical physics : PCCP》2008,10(24):3578-3589
Various isomers of carbo-[3]oxocarbon C9O3 have been characterized on the singlet and triplet spin state potential energy surfaces. Despite its localized structure, the ring carbo-mer of [3]oxocarbon is thermodynamically protected from subsequent isomerization and stable versus dissociation into C3O. It therefore appears as a reasonable synthetic target. In contrast, the less stable tetracyclic isomer exhibits electron delocalization both in the central six-membered ring and in the external three-membered rings, as evidenced from structural, magnetic and electron localization function (ELF) analysis. Another monocyclic isomer may be considered as a planar C6(CO)3 "carbon-complex", a carbon version of the related iron carbonyl complex Fe(PH3)2(CO)3. C6 and Fe(PH3)2 are indeed isolobal on the basis of frontier orbital analysis. 相似文献
46.
47.
Amy-Klein A Goncharov A Guinet M Daussy C Lopez O Shelkovnikov A Chardonnet C 《Optics letters》2005,30(24):3320-3322
We demonstrate a new, simple technique for measuring IR frequencies near 30 THz by using a femtosecond (fs) laser optical comb and sum-frequency generation. The optical frequency is directly compared with the distance between two modes of the fs laser, and the resultant beat note is used to control this distance, which depends only on the repetition rate of the fs laser. The absolute frequency of a CO2 laser stabilized onto a SF6 two-photon line has been measured for the first time to the authors' knowledge. This line is an attractive alternative to the usual saturated absorption OsO4 resonances used for the stabilization of CO2 lasers. First results demonstrate a fractional Allan deviation of 3 x 10(-14) at 1 s. 相似文献
48.
Bridging β‐Cyclodextrin Prevents Self‐Inclusion,Promotes Supramolecular Polymerization,and Promotes Cooperative Interaction with Nucleic Acids
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Dr. Pierre Evenou Dr. Julien Rossignol Dr. Gaëlle Pembouong Adélie Gothland Dr. Dmitri Colesnic Dr. Renaud Barbeyron Dr. Sergii Rudiuk Prof. Anne‐Geneviève Marcelin Dr. Mickaël Ménand Prof. Damien Baigl Prof. Vincent Calvez Dr. Laurent Bouteiller Prof. Matthieu Sollogoub 《Angewandte Chemie (International ed. in English)》2018,57(26):7753-7758
49.
Francesco Aquilante Jochen Autschbach Rebecca K. Carlson Liviu F. Chibotaru Mickaël G. Delcey Luca De Vico Ignacio Fdez. Galván Nicolas Ferré Luis Manuel Frutos Laura Gagliardi Marco Garavelli Angelo Giussani Chad E. Hoyer Giovanni Li Manni Hans Lischka Dongxia Ma Per Åke Malmqvist Thomas Müller Artur Nenov Massimo Olivucci Thomas Bondo Pedersen Daoling Peng Felix Plasser Ben Pritchard Markus Reiher Ivan Rivalta Igor Schapiro Javier Segarra‐Martí Michael Stenrup Donald G. Truhlar Liviu Ungur Alessio Valentini Steven Vancoillie Valera Veryazov Victor P. Vysotskiy Oliver Weingart Felipe Zapata Roland Lindh 《Journal of computational chemistry》2016,37(5):506-541
50.
Thi Ngoc Ha Le Mickaël Roffat Quoc Nghi Pham Stéphanie Kodjikian Odile Bohnke Claude Bohnke 《Journal of Sol-Gel Science and Technology》2008,46(2):137-145
The synthesis of the perovskite Li3xLa2/3–x□1/3–2xTiO3 by a chemical solution route, using a triblock copolymer surfactant, PEOn–PPOm–PEOn, is described. This titanate is a non-hygroscopic fast lithium conductor and therefore is a good candidate for electrochemical
applications. It is generally prepared by a conventional solid-state reaction (SSR) method. However this synthesis method
does not allow the preparation of nanopowders or the formation of thin films. For these special purposes, synthesis by a chemical
solution route, with the formation of a polymeric precursor during synthesis, has been investigated. By using the above-mentioned
non-ionic surfactant, the preparation of nanopowders of complex oxides can be done. Furthermore, this way of synthesis leads
to the formation of an intermediate polymeric precursor which can be easily spread on substrates to obtain films. We show
that the formation of a pure phase of the perovskite Li3xLa2/3–x□1/3–2xTiO3 is highly dependent on the synthesis conditions, namely the presence of water in the solvent, the EO/metal ratio, the Li+ content in the precursor and the calcination temperature. The influence of these parameters on the microstructure of the
oxide is studied by X-ray diffraction, scanning electron microscopy and granulometry. A powder of Li3xLa2/3–x□1/3–2xTiO3 (x = 0.10), with an average particles size of 200 nm, has been obtained. The ionic conductivity of this oxide is the same
as the one obtained with oxide prepared by SSR (a bulk conductivity of 1.4 × 10−3 S/cm at 37 °C). The ceramic obtained from this powder after sintering at 1,150 °C shows a good pH response. This material
can then be used as a sensitive membrane in a potentiometric pH sensor. The presence of hydrophobic PPO groups in the polymer
precursor allowed preparing films of Li3xLa2/3–x□1/3–2xTiO3 with a good adherence on Pt substrate. This kind of synthesis is then very promising to prepare micro pH sensors. 相似文献