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排序方式: 共有72条查询结果,搜索用时 15 毫秒
31.
E. Díaz-Barrientos M. Bejarano L. Madrid 《Analytical and bioanalytical chemistry》1997,357(8):1164-1167
Formation of complexes between Cu and organic polymers present in olive mill wastewater (OMW) is shown to be a cause of metal
solubilization by the residue, using C-18 reverse-phase cartridges (RPC) for separating the complexed metal. Nearly 100% of
the metal released from a polluted river sediment by OMW solutions is retained by the cartridges. The proportion of Cu retained
by the cartridges is somewhat lower (50–80%), if the OMW solution initially contains Cu. About 70–80% of Cu released by OMW
from a soil column previously loaded with high doses of metal is also retained by the cartridges. Incomplete Cu retentions
are not thought to be due to a lack of efficiency of RPC in immobilizing Cu complexes, but to the formation of an equilibrium
between free and complexed forms of the metal.
Received: 3 June 1996/Revised: 29 September 1996/Accepted: 10 October 1996 相似文献
32.
Rodrigo M. Galazzi Katherine Chacn‐Madrid Daniel C. Freitas Luana F. da Costa Marco A.Z. Arruda 《Rapid communications in mass spectrometry : RCM》2020,34(Z3)
The widespread application of nanoparticles (NPs) in recent times has caused concern because of their effects in biological systems. Although NPs can be produced naturally, industrially synthesized NPs affect the metabolism of a given organism because of their high reactivity. The biotransformation of NPs involves different processes, including aggregation/agglomeration, and reactions with biomolecules that will be reflected in their toxicity. Several analytical techniques, including inductively coupled plasma mass spectrometry (ICP‐MS), have been used for characterizing and quantifying NPs in biological samples. In fact, in addition to providing information regarding the morphology and concentration of NPs, ICP‐MS‐based platforms, such as liquid chromatography/ICP‐MS, single‐particle ICP‐MS, field‐flow fractionation (asymmetrical flow field‐flow fractionation)‐ICP‐MS, and laser ablation‐ICP‐MS, yield elemental information about molecules. Furthermore, such information together with speciation analysis enlarges our understanding of the interaction between NPs and biological organisms. This study reports the contribution of ICP‐MS‐based platforms as a tool for evaluating NPs in distinct biological samples by providing an additional understanding of the behavior of NPs and their toxicity in these organisms. 相似文献
33.
Sine-generated curves (i.e.?curves in which the curvature is a sine function of the arc-length parameter) have been used in the past to describe river meanders. Here we show how these curves spontaneously appear during the decay of high-aspect-ratio surfaces mediated by surface diffusion. We obtained analytical results for the kinetic evolution of such processes relevant to a wide class of initial geometries. Our theoretical results were satisfactorily compared with numerical simulations and with results from previous approaches to the same problem, and they can be useful for interpreting and designing experiments related to the technologically important process of high-temperature annealing on nano/micro-structured samples. 相似文献
34.
Mayer M Lang PT Gerber S Madrid PB Pinto IG Guy RK James TL 《Chemistry & biology》2006,13(9):993-1000
We have synthesized a series of phenothiazine derivatives, which were used to test the structure-activity relationship of binding to HIV-1 TAR RNA. Variations from our initial compound, 2-acetylphenothiazine, focused on two moieties: ring substitutions and n-alkyl substitutions. Binding characteristics were ascertained via NMR, principally by saturation transfer difference spectra of the ligand and imino proton resonance shifts of the RNA. Both ring and alkyl substitutions manifested NMR changes upon binding. In general, the active site, while somewhat flexible, has regions that can be capitalized for increased binding through van der Waals interactions and others that can be optimized for solubility in subsequent stages of development. However, binding can be nontrivially enhanced several-fold through optimization of van der Waals and hydrophilic sites of the scaffold. 相似文献
35.
J. C. Rosales P. A. García-Sánchez J. I. García-García J. A. Jiménez Madrid 《Semigroup Forum》2003,67(1):145-158
We study the set of numerical semigroups containing a given numerical semigroup. As an application we prove characterizations of irreducible numerical semigroups that unify some of the existing characterizations for symmetric and pseudo-symmetric numerical semigroups. Finally we describe an algorithm for computing a minimal decomposition of a numerical semigroup in terms of irreducible numerical semigroups. 相似文献
36.
37.
Several gentamicin bulk samples from different origins were investigated using an LC/MS method.LC equipped with ion trap MS with positive ionization was performed on a Capcell Pak C18(AQ) column with the mobile phase containing 50 mM trifluoroacetic(TFA) and methanol.Impurities present in batches of gentamicin bulk samples were elucidated and compared according to their fragmentation behavior.In total seventeen impurities present in samples,five impurities were not elucidated and two compounds were identifi... 相似文献
38.
Due to growing problems with drug resistance, there is an outstanding need for new, cost-effective drugs for the treatment of malaria. The 4-aminoquinolines have provided a number of useful antimalarials, and Plasmodium falciparum, the causative organism for the most deadly form of human malaria, is generally slow to develop resistance to these drugs. Therefore, diverse screening libraries of quinolines continue to be useful for antimalarial drug discovery. We report herein the development of an efficient method for producing libraries of 4-aminoquinolines variant in the side chain portion of the molecule. The effects of these substitutions were evaluated by screening this library for activity against P. falciparum, revealing four potent compounds active against drug-resistant strains. 相似文献
39.
D. Tenorio M. Jiménez‐Reyes A. Cabral‐Prieto M.G. Siles‐Dotor H. Flores‐Ramírez J.L. Galván‐Madrid 《Hyperfine Interactions》2000,128(4):381-396
Neutron activation analysis, Mössbauer spectroscopy and X‐ray diffraction techniques were used to characterize pre‐Hispanic potsherds and modern ceramic pottery, samples of which were collected in Tenexco, San Luis Potosi, Mexico. Elementary and spectroscopic analysis showed differences between ancient and modern ceramics. While the modern ceramics studied were practically new and not used at all, the ancient ones were probably used in domestic or ceremonial activities. Besides, the latter were kept buried for a long time, and it is quite probable that their manufacture was also slightly different from that of the former. These assumptions could provide the clues to understand some of the observed differences between the composition of ancient and modern ceramics whose raw materials may have the same origin. 相似文献
40.
Alejandra Catalina Moller Carol Parra Bastian Said Enrique Werner Susana Flores Joan Villena Alessandra Russo Nelson Caro Ivn Montenegro Alejandro Madrid 《Molecules (Basel, Switzerland)》2021,26(1)
The aim of this study was to determine, first, the chemical composition of Aloysia polystachya (Griseb) Moldenke essential oil, from leaves harvested in central Chile; and second, its antioxidant and cytotoxic activity. Eight compounds were identified via gas chromatography–mass spectrometry (GC–MS) analyses, with the most representative being R-carvone (91.03%), R-limonene (4.10%), and dihydrocarvone (1.07%). For Aloysia polystachya essential oil, antioxidant assays (2,2-diphenyl-1-picrylhydrazyl (DPPH), H2O2, ferric reducing antioxidant power (FRAP), and total reactive antioxidant potential (TRAP)) showed good antioxidant activity compared to commercial antioxidant controls; and anti-proliferative assays against three human cancer cell lines (colon, HT-29; prostate, PC-3; and breast, MCF-7) determined an IC50 of 5.85, 6.74, and 9.53 µg/mL, and selectivity indices of 4.75, 4.12, and 2.92 for HT-29, PC-3, and MCF-7, respectively. We also report on assays with CCD 841 CoN (colon epithelial). Overall, results from this study may represent, in the near future, developments for natural-based cancer treatments. 相似文献