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排序方式: 共有528条查询结果,搜索用时 15 毫秒
21.
Elisenda Colàs Mireia Grivé Isabel Rojo Lara Duro 《Journal of solution chemistry》2013,42(8):1680-1690
α-Hydroxy carboxylate ligands like gluconate or polyaminocarboxylate ligands such as ethylenediaminetetraacetate (EDTA) are frequently used in decontamination procedures at nuclear power plants. The presence of these organic substances among nuclear wastes could enhance the solubility of actinides by forming soluble complexes. Thermodynamic data on the stability of gluconate and EDTA with actinides are essential to predict their increase in mobility, especially in high pH systems characteristic of cement environments of a nuclear waste repository. In this work, the solubility of thorium oxyhydroxide in the presence of gluconate and EDTA has been studied. The results highlight the key role of these organics in increasing the solubility of thorium at pHc = 12. The presence of calcium at concentrations below 10?2 mol·dm?3 (characteristic of cement porewaters corresponding to cement compositions at the second degradation stage) does not seem to affect significantly the thorium solubility under the studied conditions. 相似文献
22.
Dr. David E. Herbert Nadia C. Lara Prof. Theodor Agapie 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(48):16453-16460
The meta‐terphenyl diphosphine, m‐P2, 1 , was utilized to support Ni centers in the oxidation states 0, I, and II. A series of complexes bearing different substituents or ligands at Ni was prepared to investigate the dependence of metal–arene interactions on oxidation state and substitution at the metal center. Complex (m‐P2)Ni ( 2 ) shows strong Ni0–arene interactions involving the central arene ring of the terphenyl ligand both in solution and the solid state. These interactions are significantly less pronounced in Ni0 complexes bearing L‐type ligands ( 2‐L : L=CH3CN, CO, Ph2CN2), NiIX complexes ( 3‐X : X=Cl, BF4, N3, N3B(C6F5)3), and [(m‐P2)NiIICl2] ( 4 ). Complex 2 reacts with substrates, such as diphenyldiazoalkane, sulfur ylides (Ph2S?CH2), organoazides (RN3: R=para‐C6H4OMe, para‐C6H4CF3, 1‐adamantyl), and N2O with the locus of observed reactivity dependent on the nature of the substrate. These reactions led to isolation of an η1‐diphenyldiazoalkane adduct ( 2‐Ph2CN2 ), methylidene insertion into a Ni? P bond followed by rearrangement of a nickel‐bound phosphorus ylide ( 5 ) to a benzylphosphine ( 6) , Staudinger oxidation of the phosphine arms, and metal‐mediated nitrene insertion into an arene C? H bond of 1 , all derived from the same compound ( 2 ). Hydrogen‐atom abstraction from a NiI–amide ( 9 ) and the resulting nitrene transfer supports the viability of Ni–imide intermediates in the reaction of 1 with 1‐azido‐arenes. 相似文献
23.
Marta Costas-Rodríguez Lara Lobo Frank Vanhaecke 《Analytical and bioanalytical chemistry》2014,406(18):4393-4399
In this work, a novel approach to measure isotope ratios via multi-collector—inductively coupled plasma—mass spectrometry (MC-ICP-MS) for low amounts of target element is proposed. The methodology is based on mixing of the sample (target element isolate) with a non-enriched in-house standard, previously characterized for its isotopic composition. This methodology has been applied to isotopic analysis of Cu and of Fe in whole blood samples. For this purpose, different mixtures of sample + in-house standard were prepared and adjusted to a final concentration of 500 μg/L of the target elements for isotopic analysis. δ65Cu, δ56Fe, and δ57Fe varied linearly as a function of the amount of in-house standard (or of sample) present in the mixture. The isotopic composition of the sample was calculated considering the isotope ratios measured for (i) the mixture and (ii) the in-house standard and (iii) the relative concentrations of target element contributed by the sample and the standard to the mixture, respectively. For validation purposes, the isotopic analysis of whole blood Cu was carried out using both the conventional (using 2 mL of whole blood) and the newly developed approach (using 500 μL of whole blood). The δ65Cu values obtained using mixtures containing 40 % (200 μg/L) of Cu from the blood samples and 60 % (300 μg/L) of Cu from the in-house standard were in good agreement with the δ65Cu value obtained using the conventional approach (bias ≤0.15?‰). 相似文献
24.
do Nascimento Ticiano Gomes Borges Arthur Luy Tavares Ferreira de Almeida Lara Mendes Ribeiro Êurica Adélia Nogueira Silva Fernanda Geny Calheiros da Costa Silva Valdemir do Nascimento Prata Ana Paula Basílio-Júnior Irinaldo Diniz Goulart Marília Oliveira Fonseca Morilla Demetrius Peireira de Freitas Johnnatan Duarte Aragão Cícero Flávio Soares 《Journal of Thermal Analysis and Calorimetry》2022,147(21):11949-11963
Journal of Thermal Analysis and Calorimetry - This work prepared and characterized microcapsule of Uncaria tomentosa (UT) in order to standardize a spray-dryer Uncaria tomentosa extract. The UT... 相似文献
25.
Leonardo Dalseno Antonino Júlia Rocha Gouveia Rogrio Ramos de Sousa Júnior Guilherme Elias Saltarelli Garcia Luara Carneiro Gobbo Lara Basílio Tavares Demetrio Jackson dos Santos 《Molecules (Basel, Switzerland)》2021,26(8)
Several efforts have been dedicated to the development of lignin-based polyurethanes (PU) in recent years. The low and heterogeneous reactivity of lignin hydroxyl groups towards diisocyanates, arising from their highly complex chemical structure, limits the application of this biopolymer in PU synthesis. Besides the well-known differences in the reactivity of aliphatic and aromatic hydroxyl groups, experimental work in which the reactivity of both types of hydroxyl, especially the aromatic ones present in syringyl (S-unit), guaiacyl (G-unit), and p-hydroxyphenyl (H-unit) building units are considered and compared, is still lacking in the literature. In this work, the hydroxyl reactivity of two kraft lignin grades towards 4,4′-diphenylmethane diisocyanate (MDI) was investigated. 31P NMR allowed the monitoring of the reactivity of each hydroxyl group in the lignin structure. FTIR spectra revealed the evolution of peaks related to hydroxyl consumption and urethane formation. These results might support new PU developments, including the use of unmodified lignin and the synthesis of MDI-functionalized biopolymers or prepolymers. 相似文献
26.
Lara R. S. Fonseca Gonalo R. Silva ngelo Luís Henrique J. Cardoso Sara Correia Ctia V. Vaz Ana P. Duarte Sílvia Socorro 《Molecules (Basel, Switzerland)》2021,26(10)
Sweet cherries (Prunus avium L.) are among the most appreciated fruits worldwide because of their organoleptic properties and nutritional value. The accurate phytochemical composition and nutritional value of sweet cherries depends on the climatic region, cultivar, and bioaccessibility and bioavailability of specific compounds. Nevertheless, sweet cherry extracts are highly enriched in several phenolic compounds with relevant bioactivity. Over the years, technological advances in chemical analysis and fields as varied as proteomics, genomics and bioinformatics, have allowed the detailed characterization of the sweet cherry bioactive phytonutrients and their biological function. In this context, the effect of sweet cherries on suppressing important events in the carcinogenic process, such as oxidative stress and inflammation, was widely documented. Interestingly, results from our research group and others have widened the action of sweet cherries to many hallmarks of cancer, namely metabolic reprogramming. The present review discusses the anticarcinogenic potential of sweet cherries by addressing their phytochemical composition, the bioaccessibility and bioavailability of specific bioactive compounds, and the existing knowledge concerning the effects against oxidative stress, chronic inflammation, deregulated cell proliferation and apoptosis, invasion and metastization, and metabolic alterations. Globally, this review highlights the prospective use of sweet cherries as a dietary supplement or in cancer treatment. 相似文献
27.
Avinash Chettri Jan-Hendrik Kruse Keshav Kumar Jha Lara Dröge Dr. Iuliia Romanenko Dr. Christof Neumann Dr. Stephan Kupfer Prof. Dr. Andrey Turchanin Prof. Dr. Sven Rau Prof. Dr. Felix H. Schacher Prof. Dr. Benjamin Dietzek 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):17049-17058
Recently, porous photocatalytically active block copolymer membranes were introduced, based on heterogenized molecular catalysts. Here, we report the integration of the photosensitizer, i. e., the light absorbing unit in an intermolecular photocatalytic system into block copolymer membranes in a covalent manner. We study the resulting structure and evaluate the orientational mobility of the photosensitizer as integral part of the photocatalytic system in such membranes. To this end we utilize transient absorption anisotropy, highlighting the temporal reorientation of the transition dipole moment probed in a femtosecond pump-probe experiment. Our findings indicate that the photosensitizer is rigidly bound to the polymer membrane and shows a large heterogeneity of absolute anisotropy values as a function of location probed within the matrix. This reflects the sample inhomogeneity arising from different protonation states of the photosensitizer and different intermolecular interactions of the photosensitizers within the block copolymer membrane scaffold. 相似文献
28.
M. Mar Aparicio-Muriana Ivona Lhotská Ana M. García-Campaña Francisco J. Lara 《Electrophoresis》2020,41(3-4):202-208
Fipronil is an insecticide that is not approved in the European Union in food. In 2017, fipronil was involved in a European health alert due to its presence in fresh hen eggs because of an illicit use in poultry farms, so reliable methods are needed to determine fipronil and its main metabolites in these matrixes. In this work, we report the first approach to the study of fipronil and two metabolites, fipronil-sulfone and fipronil-sulfide by CE. MEKC mode was employed using a solution of 50 mM ammonium perfluorooctanoate pH 9.0 with 10% (v/v) methanol as background electrolyte. The proposed method was combined with a simple sample treatment based on salting-out assisted LLE (SALLE) using acetonitrile as extraction solvent and ammonium sulfate as salt. The SALLE–MEKC–UV method allowed the simultaneous quantification of fipronil and fipronil-sulfone. Validation parameters yielded satisfactory results, with precision, expressed as relative SD, below 14% and recoveries higher than 83%. Limits of detection were 90 µg/kg for fipronil and 150 µg/kg for fipronil-sulfone, so in terms of sensitivity further studies of sample treatments allowing extra preconcentration or the use of more sensitive detection, such as MS, would be needed. 相似文献
29.
Jae Won Chang Mohammed Bhuiyan Hsiu‐Ming Tsai Hannah J. Zhang Gang Li Shaghayegh Fathi David C. McCutcheon Lara Leoni Richard Freifelder Chin‐Tu Chen Raymond E. Moellering 《Angewandte Chemie (International ed. in English)》2020,59(35):15161-15165
Herein, we report the development of an 18F‐labeled, activity‐based small‐molecule probe targeting the cancer‐associated serine hydrolase NCEH1. We undertook a focused medicinal chemistry campaign to simultaneously preserve potent and specific NCEH1 labeling in live cells and animals, while permitting facile 18F radionuclide incorporation required for PET imaging. The resulting molecule, [18F]JW199, labels active NCEH1 in live cells at nanomolar concentrations and greater than 1000‐fold selectivity relative to other serine hydrolases. [18F]JW199 displays rapid, NCEH1‐dependent accumulation in mouse tissues. Finally, we demonstrate that [18F]JW199 labels aggressive cancer tumor cells in vivo, which uncovered localized NCEH1 activity at the leading edge of triple‐negative breast cancer tumors, suggesting roles for NCEH1 in tumor aggressiveness and metastasis. 相似文献
30.