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1.
Maria A Girault JP Saatov Z Harmatha J Dinan L Lafont R 《Journal of chromatographic science》2005,43(3):149-157
Ecdysteroid glycosides are found in both animals and plants. The chromatographic behavior of these molecules is characteristic, as they appear much more polar than their corresponding free aglycones when analyzed by normal-phase high-performance liquid chromatography (HPLC), whereas the presence of glycosidic moieties has a very limited (if any) impact on polarity when using reversed-phase HPLC. Biological activity is greatly reduced because the presence of this bulky substituent probably impairs the interaction with ecdysteroid receptor(s). 2-Deoxy-20-hydroxyecdysone 22-O-beta-D-glucopyranoside, which has been isolated from the dried aerial parts of Silene nutans (Caryophyllaceae), is used as a model compound to describe the rationale of ecdysteroid glycoside purification and identification. 相似文献
2.
Controlled polymerization in mesoporous silica toward the design of organic-inorganic composite nanoporous materials 总被引:1,自引:0,他引:1
Choi M Kleitz F Liu D Lee HY Ahn WS Ryoo R 《Journal of the American Chemical Society》2005,127(6):1924-1932
Free-radical polymerization inside mesoporous silica has been investigated in order to open a route to functional polymer-silica composite materials with well-defined mesoporosity. Various vinyl monomers, such as styrene, chloromethyl styrene, 2-hydroxyethyl methacrylate, and methacrylic acid, were polymerized after impregnation into mesoporous silicas with various structures, which were synthesized using polyalkylene oxide-type block copolymers. The location of the polymers was systematically controlled with detailed structures of the silica framework and the polymerization conditions. Particularly noteworthy is the polymer-silica composite structure obtained by in situ polymerization after the selective adsorption of monomers as a uniform film on silica walls. The analysis of XRD data and the N(2) adsorption isotherms indicates the formation of uniform polymer nanocoating. The resultant polymer-silica composite materials can easily be post-functionalized to incorporate diverse functional groups in high density, due to the open porous structure allowing facile access for the chemical reagent. The fundamental characteristics of the composite materials are substantiated by testing the biomolecule's adsorption capacity and catalytic reactivity. Depending on the structure and composition of polymers, the resultant polymer-silica composite materials exhibit notably distinct adsorption properties toward biomolecules, such as proteins. Furthermore, it is demonstrated that the nanocoatings of polymers deposited on the mesopore walls have remarkably enhanced catalytic activity and selectivity, as compared to that of bulk polymer resins. We believe that, due to facile functionalization and attractive textural properties, the mesoporous polymer-silica composite materials are very useful for applications, such as adsorption, separation, host-guest complexes, and catalysis. 相似文献
3.
Frank J. Dinan Willis T. Schwartz Roger A. Wolfe Daniel S. Hojnicki Terry St. Clair J. Richard Pratt 《Journal of polymer science. Part A, Polymer chemistry》1992,30(1):111-118
Solution and solid-state proton decoupled 13C-NMR spectra were determined on two diimides derived from 4, 4′-oxydiphthalic anhydride. Comparison of the individual diimide spectra to that of a mixture of the two diimides indicates that ordering of these materials occurs in the solid state via charge transfer complex formation. A similar study was conducted using two isomeric dianhydrides, 4, 4′-isophthaloyldiphthalic anhydride (IDPA) and 4, 4′-terephthaloyldiphthalic anhydride (TDPA). The solution spectra of these compounds are similar and are those which would be expected for these compounds. However, their solid state spectra differ from each other. The solid-state spectrum of TDPA resembles its solution spectrum, whereas, that of IDPA differs greatly from its solution spectrum and indicates charge transfer complex formation occurs with this molecule. This difference is explained in terms of the stereochemistry of the two isomeric dianhydrides. 相似文献
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5.
N. Z. Mamadalieva N. Sh. Ramazanov L. N. Dinan Z. Saatov 《Chemistry of Natural Compounds》2000,36(5):513-515
The known ecdysteroids 2-dehydroxyecdysone, 2-dehydroxyecdysterone, ecdysterone-22-O-benzoate, ecdysterone, integristerone A, and a new ecdysteroid identified as 2-dehydroxyecdysterone-3-O-benzoate are isolated from roots ofSilene wallichianaKlotzsch 相似文献
6.
The methoxy 1H-NMR assignments in the 2.1–3.7δ region for styrene/methyl methacrylate copolymers have been assessed in terms of pentad sensitivity. Several of the methoxy resonances suggested by this study differ from literature assignments. The evidence in support of these reasignments is based on a comparison of calculated and observed triad distributions and on the good agreement of the value of the reactivity ratio rM calculated from individual triads with that obtained by classical methods. A new procedure for the determination of the tacticity coefficient σ is applied. 相似文献
7.
Gildas Bertho Imed Eddine Oumezziane Cédric Caradeuc Louis Guibout Christine Balducci Laurence Dinan Pierre J. Dilda Serge Camelo René Lafont Nicolas Giraud 《Magnetic resonance in chemistry : MRC》2022,60(5):504-514
We report the analysis of complex samples obtained during the microwave irradiation/heating of norbixin, which has been identified as a potential therapeutic target for age-related macular degeneration (AMD). In this context, identifying the different isomers that are obtained during its degradation is of primary importance. However, this characterization is challenging because, on the one hand, some of these isomers are unstable, and on the other hand, the 1H spectra of these isomeric mixtures are poorly resolved. We could successfully apply 1D pure shift experiments to obtain ultrahigh-resolution 1H nuclear magnetic resonance (NMR) spectra of the norbixin isomer samples and exploit their information content to analyze complementary 2D NMR data and describe accurately their isomeric composition. 相似文献
8.
Jin Guo Tingfeng Wang Dinan Wang Junfeng Shao Anmin Chen Mingxing Jin 《Applied Physics A: Materials Science & Processing》2014,117(3):1367-1374
The thermionic emission of the single-layer gold thin film and the two-layer film was assembled by gold padded with other metals (Ag, Cu, and Ni) and irradiated by the femtosecond laser pulse. Additionally, the emission was simulated by a two-temperature model combined with the Richardson–Dushman equation. It was found that the two-layer metal structure can change the electron temperature of the gold surface and control the thermionic emission compared with the single-layer gold film. With the same laser fluence, the two-layer film structure may shorten the duration of thermionic emission, and the duration of the thermionic emission can be further optimized by changing the proportion of thin film thickness with gold layer in the two-layer structure. The result can be especially beneficial in the context of ultrafast electron emission induced by femtosecond laser. 相似文献
9.
M Ravi A J Hopfinger R E Hormann L Dinan 《Journal of chemical information and computer sciences》2001,41(6):1587-1604
The ecdysteroid-responsive Drosophila melanogaster B(II) cell line is a prototypical homologous inducible gene expression system. A training set of 71 ecdysteroids, for which the -log(EC(50)) potencies in the ecdysteroid-responsive B(II) cell line were measured, was used to construct 4D-QSAR models. Four nearly equivalent optimum 4D-QSAR models, for two modestly different alignments, were identified (Q(2) = 0.76-0.80). These four models, together with two CoMFA models, were used in consensus modeling to arrive at a three-dimensional pharmacophore. The C-2 and C-22 hydroxyls are identified as hydrogen-bond acceptor sites which enhance activity. A hydrophobic site near C-12 is consistent with increasing activity. The side-chain substituents at C-17 are predicted to adopt semiextended "active" conformations which could fit into a cylinder-shaped binding pocket lined largely with nonpolar residues for enhanced activity. A test set of 20 ecdysteroids was used to evaluate the QSAR models. Two 4D-QSAR models for one alignment were identified to be superior to the others based on having the smallest average residuals of prediction for the prediction set (0.69 and 1.13 -log[EC(50)] units). The correlation coefficients of the optimum 4D-QSAR models (R(2) = 0.87 and 0.88) are nearly the same as those of the best CoMFA model (R(2) = 0.92) determined for the same training set. However, the cross-validation correlation coefficient of the CoMFA model is less significant (Q(2) = 0.59) than those of the 4D-QSAR models (Q(2) = 0.80 and 0.80). 相似文献
10.
Copolymers prepared by the bulk copolymerization of p-t-butylstyrene (S) and methyl methacrylate (M) were analyzed by 1H-NMR. The spectra showed fine structure in the δ 2.2–3.6 region similar to that reported for styrene/methyl methacrylate copolymers. Reactivity ratios for S-M copolymers determined by classical composition measurements differed markedly from the same ratios determined by NMR when it was assumed that NMR peak-triad assignments could be made by analogy with published styrene/methyl methacrylate assignments. A new set of peak-triad assignments was proposed that reconciles this difficulty and gives good agreement between triad fractions measured by NMR and those calculated from theory. 相似文献