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41.
Hauke Harms Julien Rime Olivier Leupin Stephan J. Hug Jan Roelof van der Meer 《Mikrochimica acta》2005,151(3-4):217-222
A luminescent bacterial biosensor was used to quantify bioavailable arsenic in artificial groundwater. Its light production
above the background emission was proportional to the arsenite concentration in the toxicologically relevant range of 0 to
0.5 μM. Effects of the inorganic solutes phosphate, Fe(II) and silicate on the biosensor signal were studied. Phosphate at
a concentration of 0.25 g L−1 phosphate slightly stimulated the light emission, but much less than toxicologically relevant concentrations of the much
stronger inducer arsenite. No effect of phosphate was oberved in the presence of arsenite. Freshly prepared sodium silicate
solution at a concentration of 10 mg L−1 Si reduced the arsenite-induced light production by roughly 37%, which can be explained by transient polymerization leading
to sequestration of some arsenic. After three days of incubation, silicate did not have this effect anymore, probably because
depolymerization occurred. In the presence of 0.4 mg L−1 Fe(II), the arsenite-induced light emission was reduced by up to 90%, probably due to iron oxidation followed by arsenite
adsorption on the less soluble Fe(III) possibly along with some oxidation to the stronger adsorbing As(V). Addition of 100 μM
EDTA was capable of releasing all arsenic from the precipitate and to transform it into the biologically measurable, dissolved
state. The biosensor also proved valuable for monitoring the effectiveness of an arsenic removal procedure based on water
filtration through a mixture of sand and iron granules. 相似文献
42.
Sénéchal K Maury O Le Bozec H Ledoux I Zyss J 《Journal of the American Chemical Society》2002,124(17):4560-4561
Thermally stable dipolar and octupolar (D2d, D3) NLO-phores are readily accessible by combining one, two, or three 4,4'-bis(dialkylaminostyryl)-[2,2']-bipyridyl ligands with zinc(II) salts. The off-resonant beta0 values point out the superiority of octupoles versus dipoles in terms of nonlinearity/transparency tradeoff. The octahedral tris(bipyridyl)zinc(II) complex exhibits a very large beta0 value (241 x 10-30 esu), which is the largest ever reported for octupolar molecules. 相似文献
43.
An efficient preparation of N-methyl-O-tert-butylhydroxylamine hydrochloride has been settled, which allowed the synthesis of modified Weinreb amides. Nucleophilic addition of organolithium and Grignard reagents on these N-tert-butoxy-N-methylamides afforded efficiently the corresponding ketones and reduction with DIBAL furnished the corresponding aldehydes in good yields up to 97%. 相似文献
44.
Miles S. CongreveCorinne Kay Jan J. ScicinskiSteven V. Ley Geoffrey WilliamsPeter J. Murray Stephen C. McKeownStephen P. Watson 《Tetrahedron letters》2003,44(21):4153-4156
The development of a versatile amine releasing linker based on the modified o-nitrobenzene sulfonamide protective group is described. This new N-Boc-o-nitrobenzenesulfonamide (Boc-ONBS) linker enables the elaboration on resin of primary and secondary amines by sequential substitution of the sulfonamide moiety using the Mitsunobu reaction. A 16-member array of secondary and Boc protected primary amines was then prepared using this linker. 相似文献
45.
Radioimmunoassays were used to investigate the repair of cyclobutane pyrimidine dimers and pyrimidine (6-4)pyrimidone photoproducts ((6-4] photoproducts) in the epidermis of the South American opossum, Monodelphis domestica. In the absence of photoreactivating light, both types of photodamage were excised with similar kinetics, 50% of the damage remaining 8 h after UV irradiation in vivo. Exposure of UV-irradiated skin to photoreactivating light resulted in removal of most of the cyclobutane dimers and an enhanced rate of (6-4) photoproduct repair. Photoenhanced excision repair of non-dimer damage increases the range of biologically effective lesions removed by in vivo photoreactivation. 相似文献
46.
M. Olivier 《Fresenius' Journal of Analytical Chemistry》1969,248(3-4):145-148
Zusammenfassung Die Atom-Absorptionsspektrophotometrie erlaubt die schnelle und genaue Bestimmung von Metallen in Polymeren, und zwar sowohl im ppm- als auch im Prozentbereich. Bei löslichen Polymeren werden vorzugsweise 2%ige Lösungen untersucht. Polymere, die in keinem geeigneten Lösungsmittel löslich sind, werden mit H2SO4/H2O2 aufgeschlossen. für flüchtige Metallverbindungen wird eine Umfällmethode mit anschließender Anreicherung der Metallspuren beschrieben. Untersucht werden Polystyrol, Celluloseester, Polyacrylnitril, ABS-Polymere, Polycarbonat, Polyvinylchlorid und seine Copolymeren, Polyamid, Polyäther, Wolle und Baumwolle. Nachweisgrenzen und günstigste Konzentrationsbereiche für die Elemente Li, Na, K, Mg, Ca, B, Al, Si, Sn, Pb, Sb, Cu, Ag, Au, Zn, Cd, Hg, Ti, Fe und Ni werden angegeben.
Herrn Prof. Dr. K. Hansen zum 60. Geburtstag gewidmet.
An dieser Stelle sei Herrn Dr. A. Reichle, dem Leiter des Wissenschaftlichen Laboratoriums der Farbenfabriken Bayer AG, Werk Dormagen, für seine Unterstützung gedankt.Den Herren K. Schumann und W. Kremer danke ich für ihre sorgfältige experimentelle Mitarbeit. 相似文献
Determination of trace metals in polymers by atomic absorption spectrophotometry
Atomic absorption spectrophotometry allows quick and exact determination of both ppm and percent quantities of metals in polymers. Preferably 2% solutions of soluble polymers are analyzed. Polymers insoluble in a suitable solvent are ashed in H2SO4/H2O2. For volatile metal compounds a double precipitating method followed by enrichment of trace metals is described. The following polymers are studied: polystyrene, cellulose esters, polyacrylonitrile, acrylonitrile-butadiene-styrene-terpolymers, polycarbonate, Polyvinylchloride and its copolymers, polyamide, polyether, wool, and cotton. Detection limits and most favourable concentration ranges are reported for the elements Li, Na, K, Mg, Ca, B, Al, Si, Sn, Pb, Sb, Cu, Ag, Au, Zn, Cd, Hg, Ti, Fe, and Ni.
Herrn Prof. Dr. K. Hansen zum 60. Geburtstag gewidmet.
An dieser Stelle sei Herrn Dr. A. Reichle, dem Leiter des Wissenschaftlichen Laboratoriums der Farbenfabriken Bayer AG, Werk Dormagen, für seine Unterstützung gedankt.Den Herren K. Schumann und W. Kremer danke ich für ihre sorgfältige experimentelle Mitarbeit. 相似文献
47.
Binding and condensation of plasmid DNA onto functionalized carbon nanotubes: toward the construction of nanotube-based gene delivery vectors 总被引:10,自引:0,他引:10
Singh R Pantarotto D McCarthy D Chaloin O Hoebeke J Partidos CD Briand JP Prato M Bianco A Kostarelos K 《Journal of the American Chemical Society》2005,127(12):4388-4396
Carbon nanotubes (CNTs) constitute a class of nanomaterials that possess characteristics suitable for a variety of possible applications. Their compatibility with aqueous environments has been made possible by the chemical functionalization of their surface, allowing for exploration of their interactions with biological components including mammalian cells. Functionalized CNTs (f-CNTs) are being intensively explored in advanced biotechnological applications ranging from molecular biosensors to cellular growth substrates. We have been exploring the potential of f-CNTs as delivery vehicles of biologically active molecules in view of possible biomedical applications, including vaccination and gene delivery. Recently we reported the capability of ammonium-functionalized single-walled CNTs to penetrate human and murine cells and facilitate the delivery of plasmid DNA leading to expression of marker genes. To optimize f-CNTs as gene delivery vehicles, it is essential to characterize their interactions with DNA. In the present report, we study the interactions of three types of f-CNTs, ammonium-functionalized single-walled and multiwalled carbon nanotubes (SWNT-NH3+; MWNT-NH3+), and lysine-functionalized single-walled carbon nanotubes (SWNT-Lys-NH3+), with plasmid DNA. Nanotube-DNA complexes were analyzed by scanning electron microscopy, surface plasmon resonance, PicoGreen dye exclusion, and agarose gel shift assay. The results indicate that all three types of cationic carbon nanotubes are able to condense DNA to varying degrees, indicating that both nanotube surface area and charge density are critical parameters that determine the interaction and electrostatic complex formation between f-CNTs with DNA. All three different f-CNT types in this study exhibited upregulation of marker gene expression over naked DNA using a mammalian (human) cell line. Differences in the levels of gene expression were correlated with the structural and biophysical data obtained for the f-CNT:DNA complexes to suggest that large surface area leading to very efficient DNA condensation is not necessary for effective gene transfer. However, it will require further investigation to determine whether the degree of binding and tight association between DNA and nanotubes is a desirable trait to increase gene expression efficiency in vitro or in vivo. This study constitutes the first thorough investigation into the physicochemical interactions between cationic functionalized carbon nanotubes and DNA toward construction of carbon nanotube-based gene transfer vector systems. 相似文献
48.
Claverie JM Monchois V Audic S Poirot O Abergel C 《Combinatorial chemistry & high throughput screening》2002,5(7):511-522
We outline a joint academic/industrial (CNRS/AVENTIS) functional genomics project aiming at the discovery of new anti-bacterial gene targets. Starting from all publicly available bacterial genomes, a subset of the most evolutionary conserved protein-coding genes has been identified. We retained genes with clear homolog in E. coli and at least one gram-positive bacterium among B.subtilis, M. tuberculosis, L. lactis or S. pyogenes. This subset was further reduced to genes encoding non-membrane proteins of unknown or hypothetical functions. The 221 E. coli Open Reading Frames (ORFs) identified through this comprehensive bioinformatic analysis are now submitted to a systematic 3-D structure determination protocol including cloning, protein expression and purification, crystallisation and X-ray diffraction. Our strategy was designed to focus on promising wide-spectrum targets as well as original biochemical pathways. Bioinformatics is used throughout all phases of project, including the initial large-scale comparative genomics analyses, the purification/expression and crystallisation stages for the detection of helpful sequence-specific features (e.g. cofactor binding motifs, non-structured N- or C- term extremities, etc ), and finally for the interpretation of the structures in conjunction with multiple sequence alignments for the identification of key residues, interaction areas on molecular surfaces, and overall function predictions. 相似文献
49.
Olivier Mentre Anne-Claire Dhaussy Francis Abraham Hugo Steinfink 《Journal of solid state chemistry》1998,140(2):120
The solid solution Sr2−xPbxV3O9, 0≤x≤2, was prepared by solid state reactions and characterized by X-ray diffraction, IR spectroscopy, and magnetic susceptibility measurements. Single crystals of the pure strontium phase and mixed Sr/Pb compounds were prepared by high temperature treatment of the respective powder compositions. Pb2V3O9crystals could only be obtained by the electrochemical reduction of molten PbV2O6. These crystals were always twinned. The previously reported crystal structure of Sr2V3O9was confirmed. It was refined toR=0.050,Rw=0.057, in space group C2/c,a=7.555(1) Å,b=16.275(2) Å,c=6.948(1) Å,β=119.78(1)°. The single crystal structural studies of the Sr1.02Pb0.98V3O9and Sr0.67Pb1.33V3O9members of the series show that the introduction of lead gives rise to a progressively complicated splitting of Sr2+/Pb2+and the tetrahedral vanadium ion crystallographic sites. As a consequence the vanadium framework distorts and beyond the Sr0.5Pb1.5V3O9composition the crystal symmetry becomes triclinic. This distortion is ascribed to the stereochemical effect of the 6s2lone pair of Pb2+. The crystallographic parameters of Pb2V3O9area=7.598(1) Å,b=16.393(3) Å,c=6.972(2) Å,α=91.38(1)°,β=119.35(1)°,γ=90.47(1)°. Pb2V3O9exhibits a more complex IR spectrum than the monoclinic phases. Despite the similarity between the triclinic and monoclinic phases the magnetic susceptibilities indicate differences in the coupling between V4+ions at low temperatures. 相似文献
50.
Clot O Akahori Y Moorlag C Leznoff DB Wolf MO Batchelor RJ Patrick BO Ishii M 《Inorganic chemistry》2003,42(8):2704-2713
The preparations of two new phosphinothiophene ligands, 3,3'-bis(diphenylphosphino)-2,2'-bithiophene (dppbt; 1) and 3,3' "-dihexyl-3',3' '-bis(diphenylphosphino)-2,5':2',2' ':5' ',2' "-quaterthiophene (hdppqt; 2) are reported. Oxidation of 1 gives 3,3'-bis(diphenylphosphine oxide)-2,2'-bithiophene (3), and the crystal structure of this compound was determined. Pd(II) and Au(I) complexes of these ligands have been synthesized and characterized. Crystal structures of [(dppbt)PdCl(2)] (1-Pd), [(hdppqt)PdCl(2)] (2-Pd), [(dppbt)(AuCl)(2)] (1-Au), and [(hdppqt)(AuCl)(2)] (2-Au) were obtained. [(dppbt)(AuCl)(2)] crystallized in two solid-state forms; crystals grown from CH(2)Cl(2)/Et(2)O show a gold-gold interaction of 3.3221(4) A, but from CH(2)Cl(2)/toluene, the molecule crystallizes as a toluene adduct (1-Au-tol) and does not show any gold-gold interaction. All the complexes were characterized via UV-vis spectroscopy and cyclic voltammetry, and the effect of the metal on the energy of the pi-pi transition and oxidation potential was determined. These data are correlated to the interannular torsion angles in the oligothienyl groups from the crystal structure studies. 相似文献