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431.
da Silva R Pedersoli S Lacerda V Donate PM de Albuquerque S Bastos JK de Matos Araújo AL Andrade e Silva ML 《Magnetic resonance in chemistry : MRC》2005,43(11):966-969
The structures of three benzylidenebenzyl butyrolactone lignans (gossypifan, carthamogenin, and savinin) have been established on basis of 1H NMR and 13C NMR spectroscopic data. The 1H NMR and 13C NMR spectra of these lignans have been fully assigned by the use of techniques such as gCOSY, non-edited gHSQC, and gHMBC. Complete assignment and most homonuclear hydrogen coupling constant measurements were performed, also providing enough data for the determination of the relative stereochemistry. 相似文献
432.
Henry Insuasty Martín Estrada Jairo Quiroga Braulio Insuasty Manuel Nogueras 《Tetrahedron letters》2006,47(31):5441-5443
Pyrazolo[1,5-a]-[1,3,5]-triazines 6a-d were obtained by an efficient one-step reaction from S,S-diethyl aroyliminodithiocarbonates 4a-d and 5-amino-3-methylpyrazole 5 or by an alternative two-step reaction from 5 and aroyl isothiocyanates 8a-d to give initially the thiourea derivatives 9a-d, which after S-ethylation and cyclization afforded compounds 6a-d. The intermediate 7a isolated from reaction between 4a and 5 permitted us to establish the orientation. 相似文献
433.
Oscillatory Riemann-Hilbert problems and the corona theorem 总被引:1,自引:0,他引:1
M.A. Bastos 《Journal of Functional Analysis》2003,197(2):347-397
The paper is devoted to the Riemann-Hilbert problem with matrix coefficient having in Hardy spaces [Hp±]2,1<p?∞, on half-planes . Under the assumption of existence of a non-trivial solution of corresponding homogeneous Riemann-Hilbert problem in [H∞±]2 we study the solvability of the non-homogeneous Riemann-Hilbert problem in [Hp±]2,1<p<∞, and get criteria for the existence of a generalized canonical factorization and bounded canonical factorization for G as well as explicit formulas for its factors in terms of solutions of two associated corona problems (in and ). A separation principle for constructing corona solutions from simpler ones is developed and corona solutions for a number of corona problems in H∞+ are obtained. Making use of these results we construct explicitly canonical factorizations for triangular bounded measurable or almost periodic 2×2 matrix functions whose diagonal entries do not possess factorizations. Such matrices arise, e.g., in the theory of convolution type equations on finite intervals. 相似文献
434.
We demonstrate that quantum fluctuations suppress Bose-Einstein condensation of quasi-two-dimensional bosons in a rapidly rotating trap. Our conclusions rest in part on the derivation of an exact expression for the boson action in terms of vortex position coordinates, and in part on a solution of the weakly interacting boson Bogoliubov equations, which simplify in the rapid-rotation limit. We obtain analytic expressions for the collective-excitation dispersion, which is quadratic rather than linear. Our estimates for the boson filling factor at which the vortex lattice melts are consistent with recent exact-diagonalization calculations. 相似文献
435.
Jaime A. Glvez Jairo Quiroga Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(10):o521-o523
Molecules of the title compound, C9H10N4O3, (I), are linked into complex sheets by a combination of one N—H...O hydrogen bond and two C—H...O hydrogen bonds. Comparisons are drawn between (I) and some related compounds in respect of both their molecular conformations and their hydrogen‐bonding arrangements. 相似文献
436.
M. A. Rodrigues M. P. Bemquerer D. B. Tada E. L. Bastos M. S. Baptista M. J. Politi 《Adsorption》2005,11(5-6):595-602
Bioactive materials (having an amino acid, Ac-Tryptophan, A or a peptide, Ac-Trp-Ala-Ala, B) were anchored onto silica particles.
A photoactive linker (N,N′-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (DPN)) was initially attached to the particles and next the amino acids
were bound by using both Zr/P chemistry and 1,3-diisopropylcarbodiimide/1-hydroxybenzotriazole coupling. In A derivative extensive
complexation of Trp with DPN was observed. Photolysis studies showed the presence of excited state reactions on the silica
particles, moreover the radical species (DPN.−, TrpH.+, Trp.) remained alive ∼100 times longer on the particle surface than in solution. These studies show that the formation rate of
these radicals is a function of the supramolecular structures of the peptide and of the amino acid derivative on the silica
particle.
This paper was presented in the 5th Brazilian Meeting on Adsorption, held at Natal, Brazil, 18–21 July, 2004. 相似文献
437.
Plants are known to increase the emission of volatile organic compounds upon the damage of phytophagous insects. However, very little is known about the composition and temporal dynamics of volatiles released by wild plants of the genus Crotalaria (Fabaceae) attacked with the specialist lepidopteran caterpillar Utetheisa ornatrix (Linnaeus) (Erebidae). In this work, the herbivore-induced plant volatiles (HIPV) emitted by Crotalaria nitens Kunth plants were isolated with solid phase micro-extraction and the conventional purge and trap technique, and their identification was carried out by GC/MS. The poly-dimethylsiloxane/divinylbenzene fiber showed higher affinity for the extraction of apolar compounds (e.g., trans-β-caryophyllene) compared to the Porapak™-Q adsorbent from the purge & trap method that extracted more polar compounds (e.g., trans-nerolidol and indole). The compounds emitted by C. nitens were mainly green leaf volatile substances, terpenoids, aromatics, and aldoximes (isobutyraldoxime and 2-methylbutyraldoxime), whose maximum emission was six hours after the attack. The attack by caterpillars significantly increased the volatile compounds emission in the C. nitens leaves compared to those subjected to mechanical damage. This result indicated that the U. ornatrix caterpillar is responsible for generating a specific response in C. nitens plants. It was demonstrated that HIPVs repelled conspecific moths from attacked plants and favored oviposition in those without damage. The results showed the importance of volatiles in plant–insect interactions, as well as the choice of appropriate extraction and analytical methods for their study. 相似文献
438.
Clarke MJ Bailey VM Doan PE Hiller CD LaChance-Galang KJ Daghlian H Mandal S Bastos CM Lang D 《Inorganic chemistry》1996,35(17):4896-4903
Comparisons of the spectroscopic properties of a number of Ru(III) complexes of imidazole ligands provide methods of distinguishing between various types of bonding that can occur in proteins and nucleic acids. In particular, EPR and (1)H NMR parameters arising from the paramagnetism of Ru(III) should aid in determining binding sites of Ru(III) drugs in macromolecules. Electrochemical studies on several imidazole complexes of ruthenium suggest that imidazole may serve as a significant pi-acceptor ligand in the presence of anionic ligands. Crystal structures are reported on two active immunosuppressant complexes. cis-[(Im)(2)(NH(3))(4)Ru(III)]Br(3) crystallizes in the triclinic space group P&onemacr; (No. 2) with the cell parameters a = 8.961(2) ?, b = 12.677(3) ?, c = 7.630(2) ?, alpha = 98.03(2) degrees, beta = 100.68(2) degrees, gamma = 81.59(2) degrees, and Z = 2 (R = 0.044). [(1MeIm)(6)Ru(II)]Cl(2).2H(2)O crystallizes in the monoclinic space group P2(1)/n (No. 14) with the cell parameters a = 7.994(2) ?, b = 13.173(4) ?, c = 14.904(2) ?, beta = 97.89(1) degrees, and Z = 2 (R = 0.052). The average Ru(II)-N bond distance is 2.106(8) ?. 相似文献
439.
Jairo Quiroga Carlos Cisneros Braulio Insuasty Rodrigo Abonía Silvia Cruz Manuel Nogueras Jos Manuel de la Torre Maximiliano Sortino Susana Zacchino 《Journal of heterocyclic chemistry》2006,43(2):299-306
440.
Keyller Bastos Borges Ellen Figueiredo Freire Maria Elisa Pereira Bastos de Siqueira 《Talanta》2009,78(1):233-4556
A method for simultaneous determination of seven benzodiazepines (BZPs) (flunitrazepam, clonazepam, oxazepam, lorazepam, chlordiazepoxide, nordiazepam and diazepam using N-desalkylflurazepam as internal standard) in human plasma using liquid-liquid and solid-phase extractions followed by high-performance liquid chromatography (HPLC) is described. The analytes were separated employing a LC-18 DB column (250 mm × 4.6 mm, 5 μm) at 35 °C under isocratic conditions using 5 mM KH2PO4 buffer solution pH 6.0:methanol:diethyl ether (55:40:5, v/v/v) as mobile phase at a flow rate of 0.8 mL min−1. UV detection was carried out at 245 nm. Employing LLE, the best conditions were achieved with double extraction of 0.5 mL plasma using ethyl acetate and Na2HPO4 pH 9.5 for pH adjusting. Employing SPE, the best conditions were achieved with 0.5 mL plasma plus 3 mL 0.1 M borate buffer pH 9.5, which were then passed through a C18 cartridge previously conditioned, washed for 3 times with these solvents: 3 mL 0.1 M borate buffer pH 9.5, 4 mL Milli-Q water and 1 mL acetonitrile 5%, finally the BZPs elution was carried with diethyl ether:n-hexane:methanol (50:30:20). In both methods the solvent was evaporated at 40 °C under nitrogen flow. The validation parameters obtained in LLE were linearity range of 50-1200 ng mL−1 plasma (r ≥ 0.9927), limits of quantification of 50 ng mL−1 plasma, within-day and between-day CV% and E% for precision and accuracy lower than 15%, and recovery above 65% for all BZPs. In SPE, the parameter obtained were linearity range of 30-1200 ng mL−1 plasma (r ≥ 0.9900), limits of quantification of 30 ng mL−1 plasma, within-day and between-day CV% and E% for precision and accuracy lower than 15% and recovery above 55% for all BZPs. These extracting procedures followed by HPLC analysis showed their suitable applicability in order to examine one or more BZPs in human plasma. Moreover, it could be suggested that these procedures might be employed in various analytical applications, in special for toxicological/forensic analysis. 相似文献