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排序方式: 共有232条查询结果,搜索用时 15 毫秒
1.
Naringenin is a natural widespread flavanone occurring in different foodstuffs that presents several important biological activities. Although its properties are well documented, its mechanisms of action are still controversial. The present article reports a conformational analysis of naringenin, using the semiempirical AM1 and ab initio methods, at the Hartree–Fock level of theory. The 3-21G, 3-21G*, 6-31G, and 6-31G** basis sets were used. The electron correlation effects were included through the Møller–Plesset second-order perturbation theory. The solvation of naringenin has been investigated through the standard SCRF, the supermolecule (SM), and the combined SM/SCRF models. The results have shown that there are two degenerate forms of naringenin, differing mainly by the orientation of a hydroxyl group (C4—OH). The energy barrier for the interconversion between them is ca. 6 kcal.mol–1, suggesting some conjugation between the -system of the aromatic B ring and the hydroxyl group (C4—OH). 相似文献
2.
Valérie Chevalier-Billosta Jean-Paul Joseleau Alain Cochaux Katia Ruel 《Cellulose (London, England)》2007,14(2):141-152
The composition and ultrastructural arrangement of cell wall polymers in wood fibres have determining influence on the properties
of wood derived materials. It is therefore important to improve our understanding of the relationship between fibres organisation,
the modifications induced by pulping treatments, and the resulting paper sheet mechanical properties. The different treatments
to which fibres are subjected during the manufacturing of pulps and papers induce morphological and micro-structural alterations
due to the removal of wall constituents and of microfibrillar elements. The impact of pulping processes on fibres was investigated
at the ultrastructural scale of transmission electron microscopy. Particular attention was given to the effects of beating
in refiners at various intensities on the ultrastructure of fibres. The most characteristic effects consisted of delaminations,
microfibril disorganisation, and even fractures, of varying importance depending on the intensity of the mechanical refining.
The consequences of internal alterations and surface modifications of the fibres were examined in relation to the paper sheet
mechanical properties. Correlations between the type of alteration observed in the fibres and its possible impact on a given
paper mechanical property are suggested. With similar approaches, the effects of drying and recycling were studied. 相似文献
3.
Katia Wehbe Jacob Filik Mark D. Frogley Gianfelice Cinque 《Analytical and bioanalytical chemistry》2013,405(4):1311-1324
The study of individual cells with infrared (IR) microspectroscopy often requires living cells to be cultured directly onto a suitable substrate. The surface effect of the specific substrates on the cell growth—viability and associated biochemistry—as well as on the IR analysis—spectral interference and optical artifacts—is all too often ignored. Using the IR beamline, MIRIAM (Diamond Light Source, UK), we show the importance of the substrate used for IR absorption spectroscopy by analyzing two different cell lines cultured on a range of seven optical substrates in both transmission and reflection modes. First, cell viability measurements are made to determine the preferable substrates for normal cell growth. Successively, synchrotron radiation IR microspectroscopy is performed on the two cell lines to determine any genuine biochemically induced changes or optical effect in the spectra due to the different substrates. Multivariate analysis of spectral data is applied on each cell line to visualize the spectral changes. The results confirm the advantage of transmission measurements over reflection due to the absence of a strong optical standing wave artifact which amplifies the absorbance spectrum in the high wavenumber regions with respect to low wavenumbers in the mid-IR range. The transmission spectra reveal interference from a more subtle but significant optical artifact related to the reflection losses of the different substrate materials. This means that, for comparative studies of cell biochemistry by IR microspectroscopy, it is crucial that all samples are measured on the same substrate type. Figure
Cell separation by PCA due to the refractive index of the substrate used, revealing transmission artifact. 相似文献
4.
Dr. Alessandro Barge Marina Caporaso Prof. Giancarlo Cravotto Dr. Katia Martina Dr. Paolo Tosco Prof. Silvio Aime Dr. Carla Carrera Dr. Eliana Gianolio Dr. Giorgio Pariani Dr. Davide Corpillo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):12086-12092
We report the synthesis and characterization of a water‐soluble, star‐shaped macromolecular platform consisting of eight β‐cyclodextrin (β‐CD) units anchored to the narrower rim of a γ‐CD core through bis(triazolyl)alkyl spacers. The efficient synthetic protocol is based on the microwave (MW)‐promoted Cu‐catalyzed 1,3‐dipolar cycloaddition of CD monoazides to CD monoacetylenes. The ligand‐hosting capability of the construct has been assessed by relaxometric titration and nuclear magnetic relaxation dispersion (NMRD) profiling, which showed it to be good, and this was supported by molecular dynamics simulations. To demonstrate the feasibility of obtaining supramolecular structures with high hosting ability, we designed a dimeric platform, formed by joining two nonamers through the γ‐CD cores through a bis(lithocholic acid) linker. With a view to the potential biological applications, cytotoxicity and extent of binding to human serum albumin were assessed. The properties of this dendrimeric multicarrier make it suitable for pharmaceutical and diagnostic purposes, ranging from targeted drug delivery to molecular imaging. 相似文献
5.
Tien Song Hiep Pham Shinichi Hasegawa Peter Mahon Katia Guérin Marc Dubois Aimin Yu 《Electroanalysis》2022,34(3):435-444
Three reduced graphene oxide nanocomposites were employed to achieve the simultaneous electrochemical determination of multi-drugs including acetaminophen (ACTM), carbendazim (CB) and ciprofloxacin (CFX). All nanocomposite modified electrodes showed improved current responses for three drugs. Notably cauliflower-like platinum nanoparticles decorated reduced graphene oxide modified electrode (or Pt−RGO/GCE) exhibited the best performance in terms of electrochemical stability. Using Pt−RGO/GCE, the linear detect ranges of 30–120 μM, 25–115 μM and 10–25 μM, and detection limit values of 3.49, 2.96, and 1.53 μM were achieved for ACTM, CB and CFX respectively. The electrode was further used for the successful determination of above drugs in tap and river water using differential pulse voltammetry. From the obtained results, we believe that Pt-RGO/GCE is highly promising for the fabrication of robust electrochemical sensors for simultaneously determining ACTM, CB and CFX or similar types of drugs in the future. 相似文献
6.
de Oliveira Thomas Rafael Tannous Katia de Lima Elisangela Cristina Trevisan 《Journal of Thermal Analysis and Calorimetry》2022,147(13):7431-7448
Journal of Thermal Analysis and Calorimetry - This work aims to investigate the thermal decomposition and reaction kinetics of the hybrid energy cane, as well as its thermochemical properties.... 相似文献
7.
We analyze light self-confinement induced by multiple nonlinear resonances in a two-dimensional chi(2) photonic crystal. With reference to second-harmonic generation in a hexagonal lattice, we show that the system can not only support two-color (1+1)D solitary waves with enhanced confinement and steering capabilities but also enable novel features such as wavelength-dependent soliton routing. 相似文献
8.
Beatriz B. Caravieri Pollyanna F. de Oliveira Ricardo A. Furtado Denise C. Tavares Eduardo J. Nassar Katia J. Ciuffi Eduardo F. Molina 《Journal of Sol-Gel Science and Technology》2014,72(3):627-636
Herein, we used tri-ureasil organic–inorganic hybrid material (tU5000) in order to enhance the solubility of nonsteroidal anti-inflammatory drugs and fine tuning the drug delivery profile. For the first time, we used tU5000 as a film-forming agent in order to provide an alternative vehicle for transdermal drug delivery systems which the cell viability of practically 100 % for the highest and the lowest tested concentrations of pure tU5000 indicated that the material was not cytotoxic. The physicochemical properties of the tU5000 drug carrier and drug-loaded hybrids were systematically studied using powder X-ray diffraction, differential scanning calorimetry, small-angle X-ray scattering, and Fourier-transform infrared spectroscopy. The structural changes of tU5000 as well as the relationships between the drug content and in vitro drug release behaviors were investigated. The results showed that the ibu molecules were homogeneously distributed in the tU5000 xerogels contributing to fine-tuning the drug delivery profile. Considering the ability to incorporated high drug content, simple and mild preparation procedure by one-pot sol–gel route, high stability of the materials, sustained-release property, this class of hybrid based on polymers and inorganic compounds may have potential applications in the design of pharmaceutical formulation as ophthalmic (contact lenses), transdermal (patches) and implantable (soft tissue) drug delivery systems. 相似文献
9.
Anja Müller Katia Sparnacci Wolfgang E.S. Unger Sven Tougaard 《Surface and interface analysis : SIA》2020,52(11):770-777
Most real core-shell nanoparticle (CSNP) samples deviate from an ideal core-shell structure potentially having significant impact on the particle properties. An ideal structure displays a spherical core fully encapsulated by a shell of homogeneous thickness, and all particles in the sample exhibit the same shell thickness. Therefore, analytical techniques are required that can identify and characterize such deviations. This study demonstrates that by analysis of the inelastic background in X-ray photoelectron spectroscopy (XPS) survey spectra, the following types of deviations can be identified and quantified: the nonuniformity of the shell thickness within a nanoparticle sample and the incomplete encapsulation of the cores by the shell material. Furthermore, CSNP shell thicknesses and relative coverages can be obtained. These results allow for a quick and straightforward comparison between several batches of a specific CSNP, different coating approaches, and so forth. The presented XPS methodology requires a submonolayer distribution of CSNPs on a substrate. Poly(tetrafluoroethylene)-poly(methyl methacrylate) and poly(tetrafluoroethylene)-polystyrene polymer CSNPs serve as model systems to demonstrate the applicability of the approach. 相似文献
10.
Rapid and high-performance analysis of thyreostatic drug residues in urine using gas chromatography-mass spectrometry 总被引:1,自引:0,他引:1
Peter Batjoens Hubert F. De Brabander Katia De Wasch 《Journal of chromatography. A》1996,750(1-2):127-132
A more sensitive method was developed using the hyphenated technique of gas chromatography-mass spectrometry (GC-MS) supplementary to the official high-performance thin-layer chromatography (HPTLC) method. Even combined with less efficient extraction and clean-up methods, GC-MS is able to lower the detection limit to less than 50 ppb. The powerful technique of GC-MS-MS is tried out to reduce the detection limit even more, in combination with simplified extraction methods. This time-saving approach combined with the increase in sensitivity is of great importance for a routine technique. 相似文献