排序方式: 共有11条查询结果,搜索用时 15 毫秒
1.
Barlow SM Louafi S Le Roux D Williams J Muryn C Haq S Raval R 《Langmuir : the ACS journal of surfaces and colloids》2004,20(17):7171-7176
The bonding and self-assembly of a chirally organized monolayer of alanine on the Cu(110) surface has been investigated using reflection-absorption infrared spectroscopy, low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM). This multitechnique approach has enabled an in-depth understanding of the hierarchy of chirality transfer: from a single adsorbed molecule, to size-defined chiral clusters, and then to an overall chiral assembly. The data have indicated that the alanine is in its anionic form, bound to the copper surface through the oxygens of the ionized carboxylate group and the nitrogen of the neutral amino group. Importantly, the methyl group is held away from the surface, resulting in direct chirality transfer into the footprint of the adsorbed alanine molecules, with the local adsorption motif for S-alanine being the mirror image of that created for R-alanine. STM has shown that S-alanine molecules self-organize to form size-defined chiral clusters of six or eight molecules at the surface, interspersed with chiral channels of bare metal. Together, these clusters and channels further self-assemble into a chiral array with one unique chiral domain sustained across the entire surface. A similar chiral assembly, but with the mirror organization, has been observed for R-alanine. Structural models for the individual clusters are proposed, and in conjunction with LEED data, overall models for these chiral phases of both S- and R-alanine have been constructed. Overall, this adsorption system has been found to be both strongly chemisorbed and capable of extensive intermolecular H-bonding, causing stresses that lead not only to the chiral self-organization of molecules but also to a specific self-organization of the empty chiral channels and spaces that intersperse the structure which, in turn, chirally assemble across macroscopic length scales to give a surface with global organizational chirality. 相似文献
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Souheila Lassoued Régis Gautier Jean-François Halet 《Journal of organometallic chemistry》2010,695(7):987-272
The bonding and structural arrangement in a few representative ring- or chain-containing solid-state metal borides and borocarbides are analyzed with respect to the electron count of the non-metal entities. Similarities (and differences) with molecular analogs are emphasized. 相似文献
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Louaar S Achouri A Lefahal M Laouer H Medjroubi K Duddeck H Akkal S 《Natural product communications》2011,6(11):1603-1604
Six flavonoids, namely 6-methoxykaempferol (1), 6-methoxykaempferol 7-O-glucoside (2), kaempferol 7-O-glucoside (3), 6-methoxyluteolin (4), patuletin 7-O-glucoside (5), and hispidulin 7-O-glucoside (6), were isolated from a n-butanolic fraction of Centaurea microcarpa Coss et Dur. flowers. This work describes for the first time the phytochemical composition of this endemic Algerian plant. 相似文献
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The present study aims to evaluate the chemical composition, metabolites secondary and pharmacology activities of methanolic extract of Marrubium vulgare collected from King Saudi Arabia. Moreover, the primary mode of action of the tested extract was studied here for the first time against E. coli and L. monocytogenes. HPLC analysis shows that the major components in the tested extract are luteolin-7-O-d-glucoside, ferulic acid and premarrubiin. Obtained data demonstrated that the investigated extract was richer in phenol (26.8 ± 0.01 mg/GAE g) than in flavonoids (0.61 ± 0.05 mg EC/mL). In addition, the methanolic extract showed an important antioxidant capacity against the DPPH (IC50 = 35 ± 0.01 µg/mL) and ABTS (IC50 = 25 ± 0.2 µg/mL) radical scavenging and a strong inhibition of acetylcholinesterase enzyme with an IC50 value corresponding to 0.4 mg/mL. The antibacterial activity demonstrated that the evaluated extract had significant activity against both Gram-positive and Gram-negative bacteria. The effect of time on cell integrity on E. coli and L. monocytogenes determined by time–kill and bacteriolysis tests showed that the M. vulgare extract reduced the viability of both strains after 8 and 10 h and had a bacteriolytic effect against two different categories of bacteria, Gram-positive and negative, which are not of the same potency. Based on obtained data, it can be concluded that Saudi M. vulgare has a high pharmacological importance and can be used in preparation of food or drugs. 相似文献
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Chetioui Souheila Zouchoune Bachir Merazig Hocine Bouaoud Salah-Eddine Rouag DjamilAzeddine Djukic Jean-Pierre 《Transition Metal Chemistry》2021,46(2):91-101
Transition Metal Chemistry - The ortho-substituted (E)-1-((2-methoxyphenyl)diazenyl)naphthalen-2-ol and the meta-substituted (E)-1-((3-methoxyphenyl)diazenyl)naphthalen-2-ol were, respectively,... 相似文献
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Souheila Ladraa Abdelmalek Bouraiou Sofiane Bouacida Thierry Roisnel Ali Belfaitah 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(9):o475-o478
In the structures of the two enantiopure diastereoisomers of the title compound, C20H18ClN3O, which crystallize in different space groups, the molecules are very similar as far as bond distances and angles are concerned, but more substantial differences are observed in some torsion angles. The crystal structures of both molecules can be described as zigzag layers along the c axis. The packing is stabilized by hydrogen‐bond interactions of N—H...O, C—H...Cl and C—H...π types for 2‐[(R)‐2‐chloro‐3‐quinolyl]‐2‐[(R)‐1‐(4‐methoxyphenyl)ethylamino]acetonitrile, and of N—H...N, C—H...O and C—H...π types for 2‐[(S)‐2‐chloro‐3‐quinolyl]‐2‐[(R)‐1‐(4‐methoxyphenyl)ethylamino]acetonitrile, resulting in the formation of two‐ and three‐dimensional networks. 相似文献
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Souheila Aloui Ramzi Othman Arnaud Poitou Pierrick Gugan Sami El-Borgi 《Mechanics Research Communications》2008,35(6):392-397
Stress and strain homogeneity, in tested samples, is a crucial assumption during a dynamic test. Whenever this assumption is true, the conventional recovery of the mean strain and stress is valid. However, when the stress and strain fields in the sample are not homogeneous, more sophisticated treatment must be considered. Inverse problem techniques are then proposed. Nevertheless, they may yield a non-physical result. In this paper, a non-parametric solution to the problem of non-homogeneity in dynamic tests is presented. The stress field is deduced from the displacement field measured via a Digital Speckle Photography (DSP) technique and a force boundary condition. 相似文献
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Salah Akkal Souheila Louaar Merzoug Benahmed Hocine Laouer Helmut Duddeck 《Chemistry of Natural Compounds》2010,46(5):719-721
A new isoflavone glycoside, genistein 7-O-xylosyl 8-C-glucoside (1), was isolated from the leaves of Retama sphaerocarpa. Its structure was elucidated by spectroscopic methods. 相似文献