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41.
Gutierrez-Lugo MT Woldemichael GM Singh MP Suarez PA Maiese WM Montenegro G Timmermann BN 《Natural product research》2005,19(7):645-652
Bioassay guided isolation of an antibacterial extract prepared from the fermentation broth of a Micromonospora sp. P1068 led to the isolation of eight compounds identified as (3R) 3,4',7-trihydroxy-isoflavanone (1), 3-hydroxydehydrodaidzein, daidzein (2), 3-methyl-1H-indole-2-carboxylic acid (3), 1H-indole-3-carboxaldehyde (4), 3-(p-hydroxyphenyl)-N-methylpropionamide, N-methylphloretamide (5), phenyl acetic acid (6), 2-hydroxy phenyl acetic acid (7) and 4-hydroxy-5-methoxy-benzoic acid (8). Compounds 1 and 5 were found to be novel chemical entities while 3 was isolated from a natural source for the first time. All compounds were evaluated for their antimicrobial activities against a panel of clinically significant microorganisms. Compound 4 was active against Staphylococcus aureus (MIC, 32 microg/ml), Enterococcus faecium (MIC, 32 microg/ml) and Escherichia coli (MIC, 64 microg/ml). 相似文献
42.
Julio-César Aguilar Sylvain Bernès Paola Gómez-Tagle Richard A. Bartsch Josefina de Gyves 《Journal of chemical crystallography》2006,36(8):473-479
A new lariat ether, N,N′-di(methylenecarboxyethoxy)-4,10-diaza-2,3,11,12-dibenzo-18-crown-6, C28H38N2O8, has been characterized and tested for Pb2+ extraction in a picrate medium. The isolated complex, [(picrato-O,O′)-(N,N′-di-methylenecarboxyethoxy-4,10-diaza-2,3,11,12-dibenzo-18-crown-6)]-lead(II) picrate, [C34H40N5O15Pb]+[C6H2N3O7]−, includes a 7-coordinated Pb2+ cation complex where sidearms of the macrocycle are involved in complexation, with Pb‐O bond lengths of 2.587(4) and 2.617(4) ?. Picrate ions serve both as co-ligand and as anion for charge balance. Both free ligand and Pb2+ complex have been X-ray characterized: a = 18.4723(16), b = 24.0057(19), c = 14.4309(14) ?, β = 112.962(7)°, P21/c, for the ligand; a = 12.7591(15), b = 21.951(2), c = 16.4389(15) ?, β = 97.144(8)°, P21/n, for the complex. 相似文献
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Dr. Massimiliano Magro Dr. Stefania Domeneghetti Davide Baratella Dr. Petr Jakubec Prof. Dr. Gabriella Salviulo Dr. Emanuela Bonaiuto Dr. Paola Venier Ondřej Malina Dr. Jiří Tuček Dr. Václav Ranc Dr. Giorgio Zoppellaro Prof.Dr. Radek Zbořil Prof. Dr. Fabio Vianello 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14219-14226
The present study is aimed at the exploration of achievable improvements for CrVI ex situ and in situ water remediation by using novel naked colloidal maghemite (γ‐Fe2O3) nanoparticles (surface active maghemite nanoparticles, SAMNs). The reliability of SAMNs for CrVI binding and removal was demonstrated, and SAMN@CrVI complex was characterized, as well as the covalent nature of the absorption was unequivocally proved. SAMNs were structurally and magnetically well conserved after CrVI binding. Thus, in consideration of their affinity for CrVI, SAMNs were exploited in a biological model system, mimicking a real in situ application. The assay evidenced a progressive reduction of revertant colonies of Salmonella typhimurium TA100 strain, as maghemite nanoparticles concentration increased, till the complete suppression of CrVI mutagen effect. Finally, an automatic modular pilot system for continuous magnetic removal and recovery of CrVI from water is proposed. SAMNs, thanks to their colloidal, binding, and catalytic properties, represent a promising tool as a reliable nanomaterial for water remediation by CrVI. 相似文献
45.
Jazmín Alarcón‐Espósito Prof. Dr. Renato Contreras Prof. Dr. Ricardo A. Tapia Dr. Paola R. Campodónico 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(37):13347-13351
We report an experimental study on the effect of solvents on the model SNAr reaction between 1‐chloro‐2,4‐dinitrobenzene and morpholine in a series of pure ionic liquids (IL). A significant catalytic effect is observed with reference to the same reaction run in water, acetonitrile, and other conventional solvents. The series of IL considered include the anions, NTf2?, DCN?, SCN?, CF3SO3?, PF6?, and FAP? with the series of cations 1‐butyl‐3‐methyl‐imidazolium ([BMIM]+), 1‐ethyl‐3‐methyl‐imidazolium ([EMIM]+), 1‐butyl‐2,3‐dimethyl‐imidazolium ([BM2IM]+), and 1‐butyl‐1‐methyl‐pyrrolidinium ([BMPyr]+). The observed solvent effects can be attributed to an “anion effect”. The anion effect appears related to the anion size (polarizability) and their hydrogen‐bonding (HB) abilities to the substrate. These results have been confirmed by performing a comparison of the rate constants with Gutmann's donicity numbers (DNs). The good correlation between rate constants and DN emphasizes the major role of charge transfer from the anion to the substrate. 相似文献
46.
Dr. Caterina Bernacchioni Dr. Cecilia Pozzi Flavio Di Pisa Prof. Stefano Mangani Prof. Paola Turano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16213-16219
Ferritins are iron‐storage nanocage proteins that catalyze the oxidation of Fe2+ to Fe3+ at ferroxidase sites. By a combination of structural and spectroscopic techniques, Asp140, together with previously identified Glu57 and Glu136, is demonstrated to be an essential residue to promote the iron oxidation at the ferroxidase site. However, the presence of these three carboxylate moieties in close proximity to the catalytic centers is not essential to achieve binding of the Fe2+ substrate to the diferric ferroxidase sites with the same coordination geometries as in the wild‐type cages. 相似文献
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49.
Gentilini C Evangelista F Rudolf P Franchi P Lucarini M Pasquato L 《Journal of the American Chemical Society》2008,130(46):15678-15682
The preparation and the properties of gold nanoparticles (Au NPs) protected by perfluorinated amphiphiles are described. The thiols were devised to form a perfluorinated region close to the gold surface and to have a hydrophilic portion in contact with the bulk solvent to impart solubility in water. The monolayer protected clusters were prepared, in an homogeneous phase using sodium thiolates because of the low nucleophilicity of the alpha-perfluorinated thiols, and fully characterized with (1)H, (19)F NMR spectrometry, IR and UV-vis absorption spectroscopies, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Au NPs with core diameters ranging from 1.6 to 2.9 nm, depending on the reaction conditions, were obtained. Water-soluble NPs (MPC-F8-PEGs) were obtained with the thiol HS-F8-PEG ending with a short poly(ethylene glycol) unit (PEG-OMe 550), whereas thiols with shorter PEG chains give rise to NPs insoluble in water. MPC-F8-PEGs undergo an exchange reaction with amphiphilic alkyl thiols. ESR investigations, using a hydrophobic radical probe, indicate that the MPC-F8-PEG monolayer shows a greater hydrophobicity compared to the analogous hydrogenated monolayer. 相似文献
50.
Marine derived polysaccharides for biomedical applications: chemical modification approaches 总被引:1,自引:0,他引:1
Polysaccharide-based biomaterials are an emerging class in several biomedical fields such as tissue regeneration, particularly for cartilage, drug delivery devices and gelentrapment systems for the immobilization of cells. Important properties of the polysaccharides include controllable biological activity, biodegradability, and their ability to form hydrogels. Most of the polysaccharides used derive from natural sources; particularly, alginate and chitin, two polysaccharides which have an extensive history of use in medicine, pharmacy and basic sciences, and can be easily extracted from marine plants (algae kelp) and crab shells, respectively. The recent rediscovery of poly-saccharidebased materials is also attributable to new synthetic routes for their chemical modification, with the aim of promoting new biological activities and/or to modify the final properties of the biomaterials for specific purposes. These synthetic strategies also involve the combination of polysaccharides with other polymers. A review of the more recent research in the field of chemical modification of alginate, chitin and its derivative chitosan is presented. Moreover, we report as case studies the results of our recent work concerning various different approaches and applications of polysaccharide-based biomaterials, such as the realization of novel composites based on calcium sulphate blended with alginate and with a chemically modified chitosan, the synthesis of novel alginate-poly(ethylene glycol) copolymers and the development of a family of materials based on alginate and acrylic polymers of potential interest as drug delivery systems. 相似文献