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941.
In this work we study two types of five-dimensional braneworld models given by sine-Gordon potentials. In both scenarios, the thick brane is generated by a real scalar field coupled to gravity. We focus our investigation on the localization of graviton field and the behaviour of the massive spectrum. In particular, we analyse the localization of massive modes by means of a relative probability method in a Quantum Mechanics context. Initially, considering a scalar field sine-Gordon potential, we find a localized state to the graviton at zero mode. However, when we consider a double sine-Gordon potential, the brane structure is changed allowing the existence of massive resonant states. The new results show how the existence of an internal structure can aid in the emergence of massive resonant modes on the brane. 相似文献
942.
By suitable interpretation of results from the linear analysis of interface dynamics, it is found that the hydrodynamic growth of the size L of domains that follow spinodal decomposition in fluid mixtures scales with time as L approximately t(alpha), with alpha = 4/7 in the inertial regime. The previously proposed exponent alpha = 2/3 is shown to indicate only the scaling of the oscillatory frequency omega(-2/3) approximately L of the largest structures of the system. The viscous dissipation in the system occurs within a layer of thickness L(d) that also follows a power law of the form L(d) approximately L3/4 in the inertial regime. In the viscous regime the growth is linear in time L approximately t and the dissipative region remains constant L(d) approximately L0. 相似文献
943.
944.
Pamela Lemos Cruz Natalja Kulagina Grgory Guirimand Johan-Owen De Craene Sbastien Besseau Arnaud Lanoue Audrey Oudin Nathalie Giglioli-Guivarch Nicolas Papon Marc Clastre Vincent Courdavault 《Molecules (Basel, Switzerland)》2021,26(12)
Plant specialized metabolites are widely used in the pharmaceutical industry, including the monoterpene indole alkaloids (MIAs) vinblastine and vincristine, which both display anticancer activity. Both compounds can be obtained through the chemical condensation of their precursors vindoline and catharanthine extracted from leaves of the Madagascar periwinkle. However, the extensive use of these molecules in chemotherapy increases precursor demand and results in recurrent shortages, explaining why the development of alternative production approaches, such microbial cell factories, is mandatory. In this context, the precursor-directed biosynthesis of vindoline from tabersonine in yeast-expressing heterologous biosynthetic genes is of particular interest but has not reached high production scales to date. To circumvent production bottlenecks, the metabolic flux was channeled towards the MIA of interest by modulating the copy number of the first two genes of the vindoline biosynthetic pathway, namely tabersonine 16-hydroxylase and tabersonine-16-O-methyltransferase. Increasing gene copies resulted in an optimized methoxylation of tabersonine and overcame the competition for tabersonine access with the third enzyme of the pathway, tabersonine 3-oxygenase, which exhibits a high substrate promiscuity. Through this approach, we successfully created a yeast strain that produces the fourth biosynthetic intermediate of vindoline without accumulation of other intermediates or undesired side-products. This optimization will probably pave the way towards the future development of yeast cell factories to produce vindoline at an industrial scale. 相似文献
945.
Cruz Enriquez A Rivero Espejel IA Andrés García E Díaz-García ME 《Analytical and bioanalytical chemistry》2008,391(3):807-815
The interaction of 11-mercaptoundecanoic acid capped gold nanoparticles (MUA-GNPs) with europium ions and aminoacids has been
studied by UV-Vis spectrophotometry, fluorescence, confocal fluorescence microscopy, resonance light scattering and TEM. Results
demonstrated that hyper-Rayleigh scattering emission occurs upon the addition of lysine to the MUA-GNPs–Eu(III) system, thus
providing an inherently sensitive method for lysine determination. The effects of geometrical factors of the gold nanoparticles
(aspect ratio, particle size, cluster formation) and the surrounding medium (pH) on this behavior are discussed. The cooperative
binding interactions of Eu3+ and lysine with gold nanoparticles permitted the discrimination of lysine from other amino acids. The probable mechanism
for the spectral changes and the enhanced resonance light scattering observed is outlined.
Figure Gold nanoparticle resonance light scattering plasmon enhancement through cooperative binding with europium and lysine 相似文献
946.
Pérez L Lenoble J Barberá J de la Cruz P Deschenaux R Langa F 《Chemical communications (Cambridge, England)》2008,(38):4590-4592
Functionalization of [60]fullerene with liquid-crystalline dendrimers and a dibutylaniline-based phenylenevinylene moiety leads to supramolecular materials, the fluorescence of which responds to acid-base stimuli. 相似文献
947.
The ring opening isomerization of [1,2,3]triazolo[1,5-a]pyridines to the corresponding 2-pyridyl derivatives has been studied by means of DFT calculations at the B3LYP/6-31+G(d,p) computational level. The effect of the substitution as well as those of protonation, deprotonation, and lithiation on different positions has been studied. The electronic characteristics of the optimized structures have been analyzed by means of the Atoms In Molecules (AIM), Electron Localization Function (ELF), Molecular Electrostatic Potential (MEP), and Natural Bond Orbital (NBO) methodologies. 相似文献
948.
Filipa P. da Cruz 《Tetrahedron letters》2008,49(48):6812-6815
The versatility of 3,4-O-isopropylidene-2-C-methyl-d-arabinonolactone [from d-erythronolactone] as a chiron for complex piperidines and pyrrolidines is illustrated by the synthesis of (2R,3S,4S)- and (2R,3S,4R)-dihydroxy-2-C-methyl prolines, 1,4-dideoxy-1,4-imino-4-C-methyl-l-ribitol and 1,4-dideoxy-1,4-imino-4-C-methyl-l-arabinitol, and isofagomine derivatives; the enantiomeric series is equally accessible from l-erythronolactone. 相似文献
949.
Fernando Cruz Moraes Murilo F. Cabral Sergio A. S. Machado Lucia H. Mascaro 《Electroanalysis》2008,20(8):851-857
This work describes the development, electrochemical characterization and utilization of a cobalt phthalocyanine modified carbon nanotube electrode for the quantitative determination of dopamine in 0.2 mol L?1 phosphate buffer contaminated with high concentration of ascorbic acid. The electrode surface was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy which showed a modified surface presenting a charge transfer resistance of 500 Ω, against the 16.46 kΩ value found for the bare glassy carbon surface. A pseudo rate constant value of 5.4×10?4 cm s?1 for dopamine oxidation was calculated. Voltammetric experiments showed a shift of the peak potential of DA oxidation to less positive value at 390 mV as compared with that of a bare GC electrode at 570 mV. The electrochemical determination of dopamine, in presence of ascorbic acid in concentrations up to 0.1 mol L?1 by differential pulse voltammetry, yielded a detection limit as low as 2.56×10?7 mol L?1. 相似文献
950.
In this study, gold nanoparticles (AuNP) were synthesized using a novel stabilizer based on dialdehyde starch polymer (DAS) and dimethyl sulfoxide (DMSO) and the nanomaterial was applied to develop a sensor for methyldopa detection. The nanoparticles were characterized by transmission electron microscopy and the proposed sensor was electrochemically characterized by electrochemical impedance spectroscopy, chronocoulometry and square-wave voltammetry. Under optimized conditions (0.1 mol L−1 McIlvaine buffer solution at pH 3.5 and 50 μL AuNP/DAS-DMSO), using square-wave voltammetry, the calibration curve presented a linear range of 0.99 to 19.60 μmol L−1, with a detection limit of 0.50 μmol L−1. The sensor showed good accuracy, with coefficients of variation of 7.8 % (inter-day; n=6) and 5.9 % (intra-day; n=3), and recovery values in the range of 95.3 to 105.2 %. The methyldopa content in a pharmaceutical sample was determined and the results show good correlation with the label value and the method recommended by the Pharmacopoeia, representing a fast and accurate alternative for detecting methyldopa in pharmaceutical products. 相似文献