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981.
Gisele A. B. Canuto Emerson A. Castilho-Martins Marina F. M. Tavares Luis Rivas Coral Barbas Ángeles López-Gonzálvez 《Analytical and bioanalytical chemistry》2014,406(14):3459-3476
Miltefosine (MT) (hexadecylphosphocholine) was implemented to cope with resistance against antimonials, the classical treatment in Leishmaniasis. Given the scarcity of anti- Leishmania (L) drugs and the increasing appearance of resistance, there is an obvious need for understanding the mechanism of action and development of such resistance. Metabolomics is an increasingly popular tool in the life sciences due to it being a relatively fast and accurate technique that can be applied either with a particular focus or in a global manner to reveal new knowledge about biological systems. Three analytical platforms, gas chromatography (GC), liquid chromatography (LC) and capillary electrophoresis (CE) have been coupled to mass spectrometry (MS) to obtain a broad picture of metabolic changes in the parasite. Impairment of the polyamine metabolism from arginine (Arg) to trypanothione in susceptible parasites treated with MT was in some way expected, considering the reactive oxygen species (ROS) production described for MT. Importantly, in resistant parasites an increase in the levels of amino acids was the most outstanding feature, probably related to the adaptation of the resistant strain for its survival inside the parasitophorous vacuole. Online Abstract Figure
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982.
Virginia Pérez-Fernández Maria José González Maria Ángeles García Maria Luisa Marina 《Analytica chimica acta》2013
A new CE method has been developed for the simultaneous separation of a group of parent phthalates. Due to the neutral character of these compounds, the addition of several bile salts as surfactants (sodium cholate (SC), sodium deoxycholate (SDC), sodium taurodeoxycholate (STDC), sodium taurocholate (STC)) to the separation buffer was explored showing the high potential of SDC as pseudostationary phase. However, the resolution of all the phthalates was not achieved when employing only this bile salt as additive, being necessary the addition of neutral cyclodextrins (CD) and organic modifiers to the separation media. The optimized cyclodextrin modified micellar electrokinetic chromatography (CD-MEKC) method consisted of the employ of a background electrolyte (BGE) containing 25 mM β-CD-100 mM SDC in a 100 mM borate buffer (pH 8.5) with a 10% (v/v) of acetonitrile, employing a voltage of 30 kV and a temperature of 25 °C. This separation medium enabled the total resolution of eight compounds and the partial resolution of two of the analytes, di-n-octyl phthalate (DNOP) and diethyl hexyl phthalate (DEHP) (Rs ~ 0.8), in only 12 min. The analytical characteristics of the developed method were studied showing their suitability for the determination of these compounds in commercial perfumes. In all the analyzed perfumes the most common phthalate was diethyl phthalate (DEP) that appeared in ten of the fifteen analyzed products. Also dimethyl phthalate (DMP), diallyl phthalate (DAP), dicyclohexyl phthalate (DCP), and di-n-pentyl phthalate (DNPP) were found in some of the analyzed samples. 相似文献
983.
Fábio de Souza Dias Aline Klassen Marina Franco Maggi Tavares Jorge Maurício David 《Chromatographia》2013,76(9-10):559-563
Six phenolic compounds were separated and determined by capillary zone electrophoresis in red wine from Brazil’s region Vale do São Francisco with total analysis time of 12 min. The limit of detections varied from 1.59 to 2.24 mg L?1. The relative standard deviations (for n = 6) varied from 0.28 to 3.50 %. The red wine samples analyzed were bought in the local market and the phenolic compound recoveries were in the range of 98–101 %. The concentrations of gallic acid in the samples of wines varied from 16.0 to 42.0 mg L?1, caffeic acid (3.16–5.18 mg L?1), syringic acid (5.73–13.0 mg L?1), kaempferol (2.32–4.33 mg L?1), quercetin (1.68–4.03 mg L?1), myricetin (7.52–25.1 mg L?1). The concentrations found agree with data reported in the literature. 相似文献
984.
Irina A. Khotina Roberto Consonni Natalia S. Kushakova William Porzio Umberto Giovanella Alexey I. Kovalev Marina A. Babushkina Alexander S. Peregudov Silvia Destri 《European Polymer Journal》2013
Two branched polyphenylenes with 1,3,5-triphenylbenzene as branching centers were synthesized together with a family of phenylene cyclotrimers as model compounds. On the basis of the NMR analysis, specifically 1H NMR, 13C NMR and 2D heteronuclear correlation experiments (HSQC and HMBC) of model compounds, the huge number of overlapping signals in the polymer spectra are attributed to aromatic protons and carbon atoms of the branched phenylene structure. The comparison with absorption spectra of linear model compounds clearly shows that the polymer optical properties depend on the length of the segments between the branching cores. This result strongly supports the proposed NMR assignment proving that the combination of the two techniques is a powerful tool for unveiling complex branched structures. 相似文献
985.
Armando Zarrelli Marina DellaGreca Afef Ladhari Rabiaa Haouala Lucio Previtera 《Helvetica chimica acta》2013,96(6):1036-1045
Phytochemical investigation of the aerial parts of Gymnema sylvestre has led to the isolation of seven new triterpenes, six oleane types ( 5, 7 – 11 ) and a new lupane type ( 12 ), and of the six known analogues 1 – 4, 6 , and 13 . The structures and relative configurations of these compounds were elucidated by spectroscopic analyses, including 1D‐ and 2D‐NMR spectroscopy and mass spectrometry, and by the comparison of their NMR data with those of related compounds. 相似文献
986.
Aequationes mathematicae - We introduce a generalization $$G^{(\alpha )}(X)$$ of the truncated logarithm $$\pounds _1(X)=\sum _{k=1}^{p-1}X^k/k$$ in prime characteristic p, which depends on a... 相似文献
987.
We consider a degenerate abstract wave equation with a time-dependent propagation speed. We investigate the influence of a strong dissipation, namely a friction term that depends on a power of the elastic operator.We discover a threshold effect. If the propagation speed is regular enough, then the damping prevails, and therefore the initial value problem is well-posed in Sobolev spaces. Solutions also exhibit a regularizing effect analogous to parabolic problems. As expected, the stronger is the damping, the lower is the required regularity.On the contrary, if the propagation speed is not regular enough, there are examples where the damping is ineffective, and the dissipative equation behaves as the non-dissipative one. 相似文献
988.
Oleg V. Mikhailov Marina A. Kazymova Tatyana A. Shumilova Svetlana S. Solovieva 《Transition Metal Chemistry》2004,29(7):732-736
Novel complexing processes in the CuII-thiocarbohydrazide-diacetyl triple system proceeding to a copper(II)hexacyanoferrate gelatin-immobilized matrix system in contact with aqueous-alkaline (pH 12) solutions containing thiocarbohydrazide and diacetyl, have been studied. It has been shown that mild template synthesis of copper(II) coordination compounds with (N,S,N,S)- and (N,N,N,N)- tetradentate ligands - 4,5-dimethyl-2,3,6,7-tetraazaoctadien-3,5-dithiohydrazide-1,8 and 3,10-dithio--6,7,13,14-tetramethyl-1,2,4,5,8,9,11,12-octaazacyclotetradecatetraene-1,5,7,12 take place, respectively. At the same time, the complexing process in the system under examination, when it occurs in aqueous-ethanol solution between CuCl2 and the organic compounds indicated, leads to copper(II) coordination compounds with another (N,S,N,S)-tetradentate ligand - 3,9,10,16-tetramethyl-6,13--dimercapto-2,17-dioxo-4,5,7,8,11,12,14,15-tetraazaoctadecahexaene - 3,6,8,10,12,15. In both cases, thiocarbohydrazide and diacetyl are ligand synthons in these complexing processes. 相似文献
989.
V. A. Shalygin H. Diehl Ch. Hoffmann S. N. Danilov T. Herrle S. A. Tarasenko D. Schuh Ch. Gerl W. Wegscheider W. Prettl S. D. Ganichev 《JETP Letters》2007,84(10):570-576
The study of spin photocurrents in (110)-grown quantum well structures is reported. The investigated effects comprise the
circular photogalvanic effect and so far not observed circular photon drag effect. The experimental data can be described
by an analytical expression derived from a phenomenological theory. A microscopic model of the circular photon drag effect
is developed demonstrating that the generated current has a spin dependent origin.
The text was submitted by the authors in English. 相似文献
990.