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181.
Razavet M Artero V Cavazza C Oudart Y Lebrun C Fontecilla-Camps JC Fontecave M 《Chemical communications (Cambridge, England)》2007,(27):2805-2807
The reaction of the new and structurally characterized covalent {Mn(CO)(3)(H(2)O)(2)}(+)-lysozyme adduct with NiS(4) and NiN(2)S(2) complexes generates binuclear Ni-Mn complexes; relevance to the reactivity of the protein-bound {Fe(CO)(CN)(2)} intermediate during maturation of [NiFe] hydrogenases is discussed. 相似文献
182.
Wind M Gebhardt K Grunwald H Spickermann J Donzelli M Kellenberger L Muller M Fullhardt P Schmitt-Hoffmann A Schleimer M 《Rapid communications in mass spectrometry : RCM》2007,21(7):1093-1099
The in vitro metabolic pattern of BAL19403, a novel macrolide antibiotic, was investigated by capillary liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/QTOF-MS) in incubations with human microsomes. For the elucidation of the metabolic pathway, BAL19403 labeled with four deuterium atoms (D4) was used, and detection of metabolites performed using mixtures of the unlabeled (H4) BAL19403 and its D4 analogue (1:1) as substrate. All metabolites appeared with similar chromatographic behavior. MS/MS spectra of BAL19403 and its metabolites are dominated by non-informative fragment ions. Therefore, the structure of the metabolites was elucidated mainly by accurate mass measurements with subsequent proposals of elemental compositions. Main biotransformations were N-demethylation, lactone ring hydrolysis, and oxidation. Additionally, N-dealkylation of the aromatic moiety was identified. This dealkylation results not only in formation of an aldehyde, according to the classical pathway, but also in formation of the corresponding alcohol and carboxylic acid. Final elucidation of their structures was possible, since this dealkylation takes place vicinal to the deuterium-labeled part of BAL19403 and interferes with D/H exchange. The degree of D/H exchange, determined by analysis of the metabolite isotopic pattern, was used to elucidate the adjacent functional group. 相似文献
183.
Jacquin M Muller P Talingting-Pabalan R Cottet H Berret JF Futterer T Théodoly O 《Journal of colloid and interface science》2007,316(2):897-911
We have linked the structural and dynamic properties in aqueous solution of amphiphilic charged diblock copolymers poly(butyl acrylate)-b-poly(acrylic acid), PBA-b-PAA, synthesized by controlled radical polymerization, with the physico-chemical characteristics of the samples. Despite product imperfections, the samples self-assemble in melt and aqueous solutions as predicted by monodisperse microphase separation theory. However, the PBA core are abnormally large; the swelling of PBA cores is not due to AA (the Flory parameter chi(PBA/PAA), determined at 0.25, means strong segregation), but to h-PBA homopolymers (content determined by liquid chromatography at the point of exclusion and adsorption transition, LC-PEAT). Beside the dominant population of micelles detected by scattering experiments, capillary electrophoresis CE analysis permitted detection of two other populations, one of h-PAA, and the other of free PBA-b-PAA chains, that have very short PBA blocks and never self-assemble. Despite the presence of these free unimers, the self-assembly in solution was found out of equilibrium: the aggregation state is history dependant and no unimer exchange between micelles occurs over months (time-evolution SANS). The high PBA/water interfacial tension, measured at 20 mN/m, prohibits unimer exchange between micelles. PBA-b-PAA solution systems are neither at thermal equilibrium nor completely frozen systems: internal fractionation of individual aggregates can occur. 相似文献
184.
Fernández F Cordero B Durand J Muller G Malbosc F Kihn Y Teuma E Gómez M 《Dalton transactions (Cambridge, England : 2003)》2007,(47):5572-5581
A new family of functionalized ligands derived from norborn-5-ene-2,3-dicarboxylic anhydride has been used in Suzuki C-C cross-couplings between aryl boronic acids and aryl bromide derivatives in [BMI][PF(6)] (BMI=1-n-butyl-3-methyl-imidazolium), using palladium acetate as catalytic precursor. High conversions and yields are obtained when amine ligands containing hydroxy groups are involved. TEM analyses after catalysis show the formation of small nanoparticles, in contrast to the agglomerates observed when nanoparticles are intentionally preformed, with a consequent decrease in the catalytic activity in the latter case. Some tests, including the correlation effect between solvent and ligand, are carried out to try to identify the true nature of the catalyst. All the results obtained suggest that formation of nanoparticles is required to lead to a catalytically active system. 相似文献
185.
Alcalde E Ceder RM López C Mesquida N Muller G Rodríguez S 《Dalton transactions (Cambridge, England : 2003)》2007,(25):2696-2706
The synthesis of simple imidazolium-based ligand precursors containing a 1,3-alkylidene-2,4,6-trimethylbenzene spacer was examined and different synthetic protocols were applied depending on the nature of the alkylidene arm. For a methylene arm, simple dications 5a,b.2CI were obtained directly. The higher homologue counterparts were conveniently prepared by general multistep routes following a five-step sequence for ethylene dications 6a,b.2Br or a six-step sequence for propylene dications 7a,b.2Br in > or = 52% overall yield. Imidazolium salts based on the shorter methylene spacer were used to prepare palladium complexes (17-20) with N-heterocyclic carbenes via transmetallation from well-defined silver compounds or directly in basic conditions. In order to facilitate spectroscopic characterisation of the palladium species two [Pd(allyl)(bis-oxazoline)]+ (25-26) complexes with the same ligand bridge were synthesized. [PdX2bisL] complexes appeared in solution as mixtures of species, mononuclear with cis- or trans-geometry or oligomeric compounds. The reaction of [PdCl(allyl)]2 and micro-bis(carbene)(AgX)2 complexes in 1 : 1 or in 0.5 : 1 ratio leads to binuclear compounds [Pd2Cl2(allyl)2(micro-bis-carbene)] (19a,19b) and to very labile monomeric [Pd(allyl)(bis-carbene)]+ (20a,20b) compounds, respectively. The preparation of analogous [Pd(allyl)(bis-oxazoline)]+ complexes showed the formation of one of the four possible isomers. [Pd(allyl)(bis-oxazoline)]PF6 complexes were inactive as catalytic precursors in the allylic substitution reaction. 相似文献
186.
Uwe Muller Christian Schubert Anton E. M. van de Ven 《General Relativity and Gravitation》1999,31(11):1759-1768
We derive an integral representation whichencodes all coefficients of the Riemann normalcoordinate expansion and also a closed formula for thosecoefficients. 相似文献
187.
188.
Sophie Laurent Luce VanderElst Sylvain Houz Nathalie Gurit RobertN. Muller 《Helvetica chimica acta》2000,83(2):394-406
Four derivatives of diethylenetriaminepentaacetic acid (=3,6,9‐tris(carboxymethyl)‐3,6,9‐triazaundecanedioic acid (H5dtpa)), potential contrast agents for magnetic resonance imaging (MRI), carrying benzyl groups at various positions of the parent structure were synthesized and characterized by a thorough multinuclear NMR study, i.e., the (S)‐ and (R)‐stereoisomers 1a and 1b of 4‐benzyl‐3,6,9‐tris(carboxymethyl)‐3,6,9‐triazaundecanedioic acid (H5[(S)‐(4‐Bz)dtpa] and H5[(R)‐(4‐Bz)dtpa], the diamide derivative N,N″‐bis[(benzylcarbamoyl)methyl]diethylenetriamine‐N,N′,N″‐triacetic acid (=3,9‐bis[2‐(benzylamino)‐2‐oxoethyl]‐6‐(carboxymethyl)‐3,6,9‐triazaundecanedioic acid; H3[dtpa(BzA)2]; 2 ), and the diester derivative N,N″‐bis{[(benzyloxy)carbonyl]methyl}diethylenetriamine‐N,N′,N″‐triacetic acid (=3,9‐bis[2‐(benzyloxy)‐2‐oxoethyl]‐6‐(carboxymethyl)‐3,6,9‐triazaundecanedioic acid; H3[dtpa(BzE)2]; 3 ). From the 17O‐NMR chemical shift of H2O induced by their dysprosium complexes with ligands 1 – 3 , it was concluded that only one H2O molecule is contained in the first coordination sphere of these lanthanide complexes. The rotational correlation times (τR) of the complexes were estimated from the 2H‐NMR longitudinal relaxation rate of the deuterated diamagnetic lanthanum complexes. The exchange time of the coordinated H2O molecule (τM) was studied through the temperature dependence of the 17O‐NMR transverse relaxation rate. As compared to [Gd(dtpa)]2−, the H2O‐exchange rate is faster for [Gd{(S)‐(4‐Bz)dtpa}]2− and [Gd{(R)‐(4‐Bz)dtpa}]2−‐, slower for [Gd{dtpa(BzA)2}], and almost identical for [Gd{dtpa(BzE)2}]. The analysis of the 1H‐relaxivity of the gadolinium complexes recorded from 0.02 to 300 MHz established that i) the relaxivity of [Gd{dtpa(BzE)2}] is similar to that of [Gd(dtpa)]2−, ii) the slightly slower molecular rotation of [Gd{dtpa(BzA)2}] induces a mild enhancement of its relaxivity, and iii) the marked increase of relaxivity of [Gd{(S)‐(4‐Bz)dtpa}]2− and [Gd{(R)‐(4‐Bz)dtpa}]2− mainly results from an apparently shorter distance between the gadolinium ion and the H2O protons of the coordinated H2O molecule. 相似文献
189.