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931.
932.
Christian Folch-Cano Claudio Olea-Azar Eduardo Sobarzo-Sánchez Carmen Alvarez-Lorenzo Angel Concheiro Francisco Otero Carolina Jullian 《Journal of solution chemistry》2011,40(11):1835-1846
The physicochemical properties of 4-hydroxy-7-methoxy-3-phenyl-2H-chromen-2-one (4HC) and β-cyclodextrins (CDs) inclusion
complexes were investigated. The phase solubility profile of 4HC with β-cyclodextrin derivatives was classified as AL-type. Stability constants for complexes with 1:1 molar ratios were calculated from the phase solubility diagrams and indicate
the following trend: DMβCD>HPβCD>βCD. The highest value of the binding constant was for 4HC-DMβCD; the binding association
constant (K
a) for this complex was determined at different temperatures and the thermodynamic data indicate that 4HC-DMβCD association
is mainly an entropically driven process. 1H NMR and ROESY were carried out, revealing that 4HC is embedded in the apolar cavity of DMβCD with the 4OH group buried in
the cyclodextrin cavity with the phenyl group outside, near the primary rim. These results are in agreement with ORACFL values; the decrease in the antioxidant activity of 4HC-DMβCD is explained by the effective protection of the hydroxyl group
due to complexation. 相似文献
933.
The calculation of surface molecular areas through Gibbs adsorption equation has been questioned in some early works on the belief that these areas have been obtained from the apparently constant slope of the surface tension vs. logarithm of concentration curve along the entire region at which surface tension declines rapidly as the concentration increases. This premise leads to consider that Gibbs equation predicts that surface saturation is reached at the beginning of this region. However, through an analysis of the forementioned curve in accordance to Gibbs equation, it can be easily shown that surface saturation is attained at the end of the region. On the other hand, based on a thermodynamic model, it is also shown that the adsorption process, and thus, surface saturation, proceeds before micellization. 相似文献
934.
Pereira AC Magalhães LG Januário AH Pauletti PM Cunha WR Bastos JK Nanayakkara DN Silva ML 《Journal of chromatography. A》2011,1218(39):7051-7054
(±)-Licarin A (1), a neolignan obtained by the oxidative coupling reaction of isoeugenol, had in this study its enantiomers resolved. A novel, quick and efficient enantiomeric resolution of 1 was directly performed by chiral high-performance liquid chromatography (HPLC-PDA) protocol (CHIRALPACK® AD column; 9:1 (v/v) n-hexane:2-propanol; 1.0 mL/min). This method provided a chromatogram profile with a well-resolved peak separation. After isolation of each enantiomer with ee > 99.9%, they were analysed in a polarimeter. Compound 2, which showed a retention time (tr) of 12.13 min, was the (+)-enantiomer and compound 3 (tr = 18.90 min) was the (−)-enantiomer. 相似文献
935.
F. Murilo T. Luna Caio C. B. Araújo Carolina B. Veloso Ivanildo J. SilvaJr. Diana C. S. Azevedo Célio L. CavalcanteJr. 《Adsorption》2011,17(6):937-947
The adsorption of naphthalene and pyrene on two different types of commercial activated carbons was studied by batch and column
experiments. Adsorption equilibrium was measured at three different temperatures. Heats of adsorption were estimated from
the equilibrium results and compared to other previous reports. From the column experiments, using parameters obtained from
the batch experiments and literature correlations, effective surface diffusivities were estimated for naphthalene and pyrene
on both adsorbents in different feed concentrations. The corrected diffusivities, using Darken equation, appear to be almost
constant for naphthalene (ca. 1.3⋅10−8 cm2/min), and for pyrene (ca. 2.3⋅10−10 cm2/min), in both activated carbons. 相似文献
936.
Katz MB Graham GW Duan Y Liu H Adamo C Schlom DG Pan X 《Journal of the American Chemical Society》2011,133(45):18090-18093
Aberration-corrected transmission electron microscopy was used to study atomic-scale processes in Pd-LaFeO(3) catalysts. Clear evidence for diffusion of Pd into LaFeO(3) and out of LaFe(0.95)Pd(0.05)O(3-δ) under high-temperature oxidizing and reducing conditions, respectively, was found, but the extent to which these processes occurred was quite limited. These observations cast doubt that such phenomena play a significant role in a postulated mechanism of self-regeneration of this system as an automotive exhaust-gas catalyst. 相似文献
937.
CdSe/ZnS QDs have demonstrated capacity to act as reducing agent in organic media such as acetonitrile and ethanol. By using fluorescence and Raman spectroscopy, it has been demonstrated that QDs reduce diquat herbicide to its monocation radical. The reaction is characterized to present a high reaction rate making possible to perform the reaction by simple filtration of the solution containing the herbicide through a QDs modified filter. The monocation radical presents a high fluorescence emission spectrum which was selected as the analytical signal to quantify the diquat herbicide. The method described here for the analysis of diquat herbicide in oat grains is simple and fast allowing the analysis of trace level of herbicide in only 6 min. The excellent sensitivity and reproducibility of the methods indicate that the reaction is favoured from both thermodynamic and kinetic point of view. The results presented open up the possibility to use QDs as redox agent. The sensitivity of the method expressed as detection limit was only of 0.01 mg kg(-1).The lineal range was between 0.05 and 0.5 mg kg(-1). The time of analysis per sample, including extraction, reaction and fluorescent measurement was only of 6 min. 相似文献
938.
Salvatore Giovanni De-Simone Guilherme Curty Lechuga Paloma Napoleo-Pêgo Larissa Rodrigues Gomes David William Provance Jr. Vinícius Dias Nirello Ana Carolina Renn Sodero Herbert Leonel de Mattos Guedes 《Molecules (Basel, Switzerland)》2021,26(13)
Introduction: Snakebite envenomation is considered a neglected tropical disease, and SVTLEs critical elements are involved in serious coagulopathies that occur on envenoming. Although some enzymes of this group have been structurally investigated, it is essential to characterize other proteins to better understand their unique properties such as the Lachesis muta rhombeata 47 kDa (Lmr-47) venom serine protease. Methods: The structure of Lmr-47 was studied in solution, using SAXS, DLS, CD, and in silico by homology modeling. Molecular docking experiments simulated 21 competitive inhibitors. Results: At pH 8.0, Lmr-47 has an Rg of 34.5 ± 0.6 Å, Dmax of 130 Å, and SR of 50 Å, according to DLS data. Kratky plot analysis indicates a rigid shape at pH 8.0. Conversely, the pH variation does not change the center of mass’s intrinsic fluorescence, possibly indicating the absence of fluorescent amino acids in the regions affected by pH variation. CD experiments show a substantially random coiled secondary structure not affected by pH. The low-resolution model of Lmr-47 presented a prolate elongated shape at pH 8.0. Using the 3D structure obtained by molecular modeling, docking experiments identified five good and three suitable competitive inhibitors. Conclusion: Together, our work provided insights into the structure of the Lmr-47 and identified inhibitors that may enhance our understanding of thrombin-like family proteins. 相似文献
939.
F. Rahman C.D. Farmer C. Schmidt G. Pfaff C.R. Stanley 《Applied Physics A: Materials Science & Processing》2008,90(2):231-236
The solar cell industry is witnessing an era of unprecedented growth and this trend is set to continue for the foreseeable
future. Here we describe a heat reflection pigment-coated single-junction gallium arsenide solar cell that is capable of reflecting
heat-inducing near-infrared radiation. The cell maintains its performance better than non-coated cells when exposed to infrared-rich
radiant flux. In situations where solar cells get heated mainly from incident infrared radiation, these cells exhibit superior
performance. The heat reflecting pigment, cell structure, coating process and cell performance have been described.
PACS 84.60.Jt; 42.70.Km; 42.79.Wc 相似文献
940.
Fragment-based and classical quantitative structure–activity relationships for a series of hydrazides as antituberculosis agents 总被引:1,自引:1,他引:0
Andrade CH Salum Lde B Castilho MS Pasqualoto KF Ferreira EI Andricopulo AD 《Molecular diversity》2008,12(1):47-59
Worldwide, tuberculosis (TB) is the leading cause of death among curable infectious diseases. Multidrug-resistant Mycobacterium tuberculosis is an emerging problem of great importance to public health, and there is an urgent need for new anti-TB drugs. In the present work, classical 2D quantitative structure-activity relationships (QSAR) and hologram QSAR (HQSAR) studies were performed on a training set of 91 isoniazid derivatives. Significant statistical models (classical QSAR, q (2) = 0.68 and r (2) = 0.72; HQSAR, q (2) = 0.63 and r (2) = 0.86) were obtained, indicating their consistency for untested compounds. The models were then used to evaluate an external test set containing 24 compounds which were not included in the training set, and the predicted values were in good agreement with the experimental results (HQSAR, [Formula: see text] ; classical QSAR, [Formula: see text]). 相似文献