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991.
Gussoni M Greco F Vezzoli A Paleari MA Moretti VM Lanza B Zetta L 《Magnetic resonance imaging》2007,25(1):117-128
By combining NMR relaxation spectroscopy and magnetic resonance imaging techniques, unsalted (us) and salted (s) caviar (Acipenser transmontanus) oocytes were characterized over a storage period of up to 90 days. The aging and the salting effects on the two major cell constituents, water and lipids, were separately assessed. T1 and T2 decays were interpreted by assuming a two-site exchange model. At Day 0, two water compartments that were not in fast exchange were identified by the T1 relaxation measurements on the us oocytes. In the s samples, T1 decay was monoexponential. During the time of storage, an increment of the free water amount was found for the us oocytes, ascribed to an increased metabolism. T1 and T2 of the s oocytes shortened as a consequence of the osmotic stress produced by salting. Selective images showed the presence of water endowed with different regional mobility that severely changed during the storage. Lipid T1 relaxation decays collected on us and s samples were found to be biexponential, and the T1 values lengthened during storage. In us and s oocytes, the increased lipid mobility with the storage was ascribed to lipolysis. Selective images of us samples showed lipids that were confined to the cytoplasm for up to 60 days of storage. 相似文献
992.
Racková L Jancinová V Petríková M Drábiková K Nosál R Stefek M Kostálová D Prónayová N Kovácová M 《Natural product research》2007,21(14):1234-1241
The antiradical activity, protective effect against lipid peroxidation of liposomal membrane, and inhibitory effect on whole blood reactive oxygen species (ROS) liberation of Glycyrrhiza glabra crude extract and glycyrrhizin, its major compound, were assessed. The liquorice extract showed significant activity in all the three assay systems used in a dose dependent manner. It displayed remarkable reactivity with free stable 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radical, inhibitory efficacy in peroxidatively damaged unilamellar dioleoyl phosphatidylcholine (DOPC) liposomes, and inhibition of ROS chemiluminescence, generated by whole blood, induced by both receptor-bypassing stimuli (PMA) and receptor operating stimuli (Opz) in the ranking order of stimuli PMA> Opz. These activities may be attributed to phenolic antioxidants involving isoflavan derivatives, coumarins and chalcones. Nonetheless, triterpene saponin glycyrrhizin exhibited no efficacy in the system of DPPH reaction and peroxidation of liposomal membrane, and negligible inhibition of chemiluminescence generated by inflammatory cells. These results indicate that the mechanism of anti-inflammatory effect of glycyrrhizin most probably does not involve ROS and this major constituent is not responsible for the inhibition effects of liquorice extract on neutrophil functions. 相似文献
993.
[structure: see text]. The first tetramer of the eumelanin precursor 5,6-dihydroxyindole has been obtained, as the acetyl derivative, by peroxidase/H2O2-induced oxidative coupling of 5,5',6,6'-tetrahydroxy-2,4'-biindolyl (2) in the presence of Zn2+ ions. The tetramer, 5,5',5',5',6,6',6',6'-octaacetoxy-2,4':2',3':2',4'-tetraindolyl (acetylated 7), incorporates an unprecedented 2,3'-biindolyl substructure suggestive of a different positional reactivity of the 5,6-dihydroxyindole system when framed into a dimeric scaffold. 相似文献
994.
995.
Gubskaya VP Berezhnaya LSh Gubaidullin AT Faingold II Kotelnikova RA Konovalova NP Morozov VI Litvinov IA Nuretdinov IA 《Organic & biomolecular chemistry》2007,5(6):976-981
Two nitroxide methanofullerenes was synthesized for the first time, and their structures and biological activities studied. It was shown by X-ray single crystal analysis that the methanofullerene with two nitroxide groups forms a 1 : 2 inclusion complex with chloroform and has a nearly tetrahedral (diamond-like) arrangement of fullerene-fullerene interactions in the crystal. For the first time, it has been found that malonate nitroxide methanofullerene in combination with the known anticancer drug cyclophosphamide (CPA) shows high antitumor activity against leukemia P-388. 相似文献
996.
Dizioli Rodrigues de Oliveira C Yonamine M Lucia de Moraes Moreau R 《Journal of separation science》2007,30(1):128-134
A fast method was optimized and validated with the aim to detect cannabinoids (cannabidiol, cannabinol, and delta-9-tetrahydrocannabinol) in human head hair samples. The method was based on an initial procedure of external decontamination of hair samples (10 mg) with petroleum ether, followed by alkaline digestion and further extraction of cannabinoids by means of a headspace solid-phase microextraction technique (HS-SPME). GC-MS was used to identify and quantify the analytes in SIM mode. The LOQs and LODs obtained were 0.07 and 0.12 ng/mg, respectively, for all the studied cannabinoids. The method proved to be simple, rapid, and precise. By using the weighted least squares linear regression (weighting factor 1/x2), the accuracy of the analytical method was improved at the lower end of the calibration curve (from 0.12 to 12 ng/mg; r >0.98). Hair samples collected from eight volunteers (in-patients of a drug abuse rehabilitation clinic) were submitted to the proposed method. Detection of the drugs was observed in samples of the volunteers who reported frequent marijuana use (at least ten times a week). 相似文献
997.
Götz C Fekete A Gebefuegi I Forczek ST Fuksová K Li X Englmann M Gryndler M Hartmann A Matucha M Schmitt-Kopplin P Schröder P 《Analytical and bioanalytical chemistry》2007,389(5):1447-1457
Bacterial intraspecies and interspecies communication in the rhizosphere is mediated by diffusible signal molecules. Many Gram-negative bacteria use N-acyl-homoserine lactones (AHLs) as autoinducers in the quorum sensing response. While bacterial signalling is well described, the fate of AHLs in contact with plants is much less known. Thus, adsorption, uptake and translocation of N-hexanoyl- (C6-HSL), N-octanoyl- (C8-HSL) and N-decanoyl-homoserine lactone (C10-HSL) were studied in axenic systems with barley (Hordeum vulgare L.) and the legume yam bean (Pachyrhizus erosus (L.) Urban) as model plants using ultra-performance liquid chromatography (UPLC), Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and tritium-labelled AHLs. Decreases in AHL concentration due to abiotic adsorption or degradation were tolerable under the experimental conditions. The presence of plants enhanced AHL decline in media depending on the compounds' lipophilicity, whereby the legume caused stronger AHL decrease than barley. All tested AHLs were traceable in root extracts of both plants. While all AHLs except C10-HSL were detectable in barley shoots, only C6-HSL was found in shoots of yam bean. Furthermore, tritium-labelled AHLs were used to determine short-term uptake kinetics. Chiral separation by GC-MS revealed that both plants discriminated D-AHL stereoisomers to different extents. These results indicate substantial differences in uptake and degradation of different AHLs in the plants tested. 相似文献
998.
Sapei L Gierlinger N Hartmann J Nöske R Strauch P Paris O 《Analytical and bioanalytical chemistry》2007,389(4):1249-1257
Horsetail (Equisetum spp.) is known as one of the strongest accumulators of silicon among higher terrestrial plants. We use the combination of
position-resolved analytical techniques, namely microtomography, energy-dispersive X-Ray elemental mapping, Raman microscopy,
as well as small-angle and wide-angle scattering of X-rays, to study the type, distribution and nanostructure of silica in
the internodes of Equisetum hyemale. The predominant silicification pattern is a thin continuous layer on the entire outer epidermis with the highest density
in particular knob regions of the long epidermal cells. The knob tips contain up to 33 wt% silicon in the form of pure hydrated
amorphous silica, while the silica content is lower in the inner part of the knobs and on the continuous layer. In contrast
to the knob tips, the silica in these regions lacks silanol groups and is proposed to be in close association with polysaccharides.
No mentionable amount of crystalline silica is detected by wide-angle X-ray scattering. The small-angle X-ray scattering data
are consistent with the presence of colloidal, sheet-like silica agglomerates with a thickness of about 2 nm. From these results
we conclude that there are at least two distinct forms of silica in E. hyemale which may have different functions. The close association of silica with cell wall polymers suggests that they may act as
a polymeric template that controls the shape and size of the colloidal silica particles similar to many other biominerals
and mineralised tissues. We propose that owing to its specific distribution in E. hyemale, a protective role and possibly also an important biomechanical role are among the most likely functions of silica in these
plants.
Figure 3D rendering of X-ray microtomography data from a dry Equisetum hyemale stalk. The red colour indicates high X-ray absorption values due to local silica accumulations 相似文献
999.
Vanadium dioxide is a prototype material for the discussion of correlation effects in solids. First-principles density-functional theory does not describe the metal-insulator transition, whereas strongly correlated models reproduce the main features. Here we present a parameter-free GW calculation of VO2 and show that the correlation effects in the band structure of both the metallic and the insulating phases are correctly reproduced, provided that quasiparticle energies and wave functions are calculated self-consistently. Our calculations explain the satellite in the photoemission spectrum of the metal as due to a plasmon resonance in the energy-loss function and show that this feature disappears in the insulator. 相似文献
1000.
Zbigniew Kisiel Orest Dorosh Markus Behnke Frank C. De Lucia 《Journal of Molecular Spectroscopy》2007,246(1):39-56
Results are reported of a comprehensive investigation of an almost continuous rotational spectrum of S(CN)2 recorded over the frequency region 110-374 GHz by means of the FASSST spectroscopic technique. The spectrum was analysed in detail and over 22 000 transitions were assigned in total. Precise, octic order spectroscopic constants in the asymmetric rotor Hamiltonian have been determined for the ground state and 12 different vibrationally excited states of the parent isotopologue, including first excited states of five different normal modes. Three states near 370 cm−1 and four states near 490 cm−1 above the ground state were found to be mutually interacting and were successfully analysed in terms of a triad and a tetrad of coupled states, respectively. Rotational transitions in the 34S, 13C, and 15N isotopologues of S(CN)2 have also been assigned and fitted, and newly determined rotational constants were used to derive the geometry of the molecule. The complex multistate analysis of the spectrum was carried out with the newly developed AABS software package for Assignment and Analysis of Broadband Spectra. 相似文献