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41.
In this article, we derive the intrinsic equations for a generalized relaxed elastic line on an oriented surface in the Galilean 3-dimensional space G3. These equations will give direct and more geometric approach to questions concerning about generalized relaxed elastic lines on an oriented surface in G3. 相似文献
42.
Luis Simn FranciscoM. Muiz Silvia Sez Csar Raposo Francisca Sanz JoaquínR. Morn 《Helvetica chimica acta》2005,88(7):1682-1701
Different xanthone‐based receptors ( 2 – 10 ) for lactones and lactams have been prepared, and the feasibility of these compounds to mimic the known enzymatic ‘oxyanion‐hole’ structure is discussed. The self‐association of the receptors was found to pose a serious drawback for complex formation. X‐Ray crystal structures of receptor dimers allowed us to understand the reasons for their self‐association and to improve the design of the catalysts. The catalytic activity of the receptors has been tested towards the nucleophilic addition of pyrrolidine to unsaturated lactones. Since the resulting complexes were very weak in organic solvents, new receptors were developed for lactams, which showed better stabilities, and their catalytic activities were studied. 相似文献
43.
Adina Borbély Dr. Eduard Figueras Ana Martins Dr. Lizeth Bodero Dr. André Raposo Moreira Dias Dr. Paula López Rivas Dr. Arianna Pina Dr. Daniela Arosio Dr. Paola Gallinari Dr. Marcel Frese Dr. Christian Steinkühler Prof. Dr. Cesare Gennari Prof. Dr. Umberto Piarulli Prof. Dr. Norbert Sewald 《ChemistryOpen》2019,8(6):737-742
RGD-cryptophycin and isoDGR-cryptophycin conjugates were synthetized by combining peptidomimetic integrin ligands and cryptophycin, a highly potent tubulin-binding antimitotic agent across lysosomally cleavable Val-Ala or uncleavable linkers. The conjugates were able to effectively inhibit binding of biotinylated vitronectin to integrin αvβ3, showing a binding affinity in the same range as that of the free ligands. The antiproliferative activity of the novel conjugates was evaluated on human melanoma cells M21 and M21-L with different expression levels of integrin αvβ3, showing nanomolar potency of all four compounds against both cell lines. Conjugates containing uncleavable linker show reduced activity compared to the corresponding cleavable conjugates, indicating efficient intracellular drug release in the case of cryptophycin-based SMDCs. However, no significant correlation between the in vitro biological activity of the conjugates and the integrin αvβ3 expression level was observed, which is presumably due to a non-integrin-mediated uptake. This reveals the complexity of effective and selective αvβ3 integrin-mediated drug delivery. 相似文献
44.
Lenneke WA van Hooijdonk Muhammad Ichwan Thomas F Dijkmans Theo G Schouten Marijke WA de Backer Roger AH Adan Fons J Verbeek Erno Vreugdenhil Carlos P Fitzsimons 《BMC neuroscience》2009,10(1):2-19
Background
In the adult hippocampus, the granule cell layer of the dentate gyrus is a heterogeneous structure formed by neurons of different ages, morphologies and electrophysiological properties. Retroviral vectors have been extensively used to transduce cells of the granule cell layer and study their inherent properties in an intact brain environment. In addition, lentivirus-based vectors have been used to deliver transgenes to replicative and non-replicative cells as well, such as post mitotic neurons of the CNS. However, only few studies have been dedicated to address the applicability of these widespread used vectors to hippocampal cells in vivo. Therefore, the aim of this study was to extensively characterize the cell types that are effectively transduced in vivo by VSVg-pseudotyped lentivirus-based vectors in the hippocampus dentate gyrus. 相似文献45.
The sucrose derivative 1′,2,3,3′,4,4′-hexa-O-benzylsucrose is a key intermediate for the chemoselective synthesis of various useful materials, such as macrocycles, crown ether analogs, and polymers. Several strategies for the synthesis of this compound were explored by applying microwave-assisted protocols, thus permitting significant reductions of time and energy compared to other routes. The outcomes of the different approaches were compared and the optimal one, in terms of yield and reproducibility, was found to be the initial protection at the positions 6 and 6′, with tert-butyldiphenylsilylchloride (TBDPSCl) in the presence of 4-(dimethylamino)pyridine (4-DMAP) and pyridine as a solvent, then perbenzylation of the remaining hydroxyl groups, followed by selective deprotection of the TBDPS groups to obtain the title compound. 相似文献
46.
47.
The complexation of CH3Hg+ with major ions present in sea and estuary waters (Cl?, SO42? and CO32?) was studied potentiometrically in an NaClO4 medium in the ionic strength range 0.1–3.0 mol dm?3 at 25 °C. The potentiometric data, treated with non‐linear least squares computer programs, led us to establish the formation of the species CH3HgCl in equilibrium with chloride, CH3Hg(SO4)? species with sulfate and no complex with carbonate. The stoichiometric stability constants obtained at the different ionic strengths were correlated by means of the modified Bromley methodology (MBM) to determine the corresponding thermodynamic constants and interaction parameters. This study is the second of a series designed to simulate, using the MBM thermodynamic model, the behaviour of methylmercury in different conditions of sea and estuary waters. In the first study of the series, the hydrolysis equilibria of methylmercury in NaClO4 ionic media were established. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
48.
M. T. Raposo J. D. Ardisson A. I. C. Persiano R. A. Mansur 《Hyperfine Interactions》1994,83(1):235-238
The Fe-Nb system was investigated by means of X-ray diffraction and Mössbauer spectroscopy (at 300 and 77 K), in the range from 1 to 66.7 at%. We have found that the limit of solubility of Fe in Nb at 1100°C is between 3 and 4 at% Fe, and observed the coexistence of the Nb solid solution (Nbss) phase and Fe21Nb19 in the range from 4 to 40 at% Fe. The Mössbauer parameters of all the single phases are reported. The lattice parameters of Nbss phase present no significant variation with the Nb content. The X-ray pattern for the Fe21Nb19 phase could not be solved. The Laves phase Fe2Nb presents Mössbauer and X-ray parameters that agree with the literature. 相似文献
49.
The Fries rearrangement of dibenzofuran-2-yl ethanoate as a route to o-hydroxyacetyldibenzofurans has been investigated, both under thermal Lewis-acid catalysed and non-catalysed photochemical conditions. The reactions were examined theoretically at semi-empirical (PM3 and ZINDO/S) and density functional theory (DFT) levels. The correct selection of reaction conditions provides viable preparative routes to ortho-acylated hydroxydibenzofurans. 相似文献
50.
The complexation of As(V) in aqueous solutions in the presence of iron(III) was investigated spectrophotometrically with both
variable and constant ionic strengths. The determined thermodynamic and stoichiometric formation constants of the FeHAsO4+ species are log10∘β = 9.21± 0.01 and log10Iβ (1.0mol⋅dm−3 NaClO4) = 7.78 ± 0.01, respectively. The numerical treatment of the obtained spectral data was performed with the SPECA program. The analysis required the consideration
of the hydrolysis of Fe(III) and the protonation of As(V) in the pH range studied. No significant hydrolysis was observed
because of the low pH values (pH < 2.5) involved. The stabilities of the solid Fe(III) arsenates was established by solubility
experiments. All of the solubility experiments were performed in aqueous NaClO4 solutions at constant ionic strength (1.0mol⋅dm−3) and at 25∘C. The experimental data were consistent with FeAsO4⋅2H2O being the solid phase (log10 ∘ Kso = −24.30± 0.08). The corresponding thermodynamic constants were computed by means of the Modified Bromley's Methodology (MBM)
that describes the variation of the activity coefficients of all of the ions involved in the complexation and precipitation
equilibria with the medium and ionic strength. Finally, the solid phase obtained in this work was also characterized by FT-IR
and FT-Raman spectroscopies, and the hydration of the solid iron arsenate was confirmed by X-ray diffraction data. 相似文献