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71.
Simons R Vincken JP Mol LA The SA Bovee TF Luijendijk TJ Verbruggen MA Gruppen H 《Analytical and bioanalytical chemistry》2011,401(1):305-313
The roots of licorice (Glycyrrhiza glabra) are a rich source of flavonoids, in particular, prenylated flavonoids, such as the isoflavan glabridin and the isoflavene
glabrene. Fractionation of an ethyl acetate extract from licorice root by centrifugal partitioning chromatography yielded
51 fractions, which were characterized by liquid chromatography–mass spectrometry and screened for activity in yeast estrogen
bioassays. One third of the fractions displayed estrogenic activity towards either one or both estrogen receptors (ERs; ERα
and ERβ). Glabrene-rich fractions displayed an estrogenic response, predominantly to the ERα. Surprisingly, glabridin did
not exert agonistic activity to both ER subtypes. Several fractions displayed higher responses than the maximum response obtained
with the reference compound, the natural hormone 17β-estradiol (E2). The estrogenic activities of all fractions, including this so-called superinduction, were clearly ER-mediated, as the estrogenic
response was inhibited by 20–60% by known ER antagonists, and no activity was found in yeast cells that did not express the
ERα or ERβ subtype. Prolonged exposure of the yeast to the estrogenic fractions that showed superinduction did, contrary to
E2, not result in a decrease of the fluorescent response. Therefore, the superinduction was most likely the result of stabilization
of the ER, yeast-enhanced green fluorescent protein, or a combination of both. Most fractions displaying superinduction were
rich in flavonoids with single prenylation. Glabridin displayed ERα-selective antagonism, similar to the ERα-selective antagonist
RU 58668. Whereas glabridin was able to reduce the estrogenic response of E2 by approximately 80% at 6 × 10−6 M, glabrene-rich fractions only exhibited agonistic responses, preferentially on ERα. 相似文献
72.
Durandetti M Hardou L Lhermet R Rouen M Maddaluno J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(45):12773-12783
Carbonickelations of alkynes and functionalization of the resulting vinylnickel moiety have been performed efficiently in a nickel-catalyzed domino cyclization-condensation process. This reaction, which does not require the preparation of any other organometallic reagent, proceeds only by exo-dig cyclization. This convenient and mild method constitutes a one-pot synthesis of substituted dihydrobenzofurans, chromans, isochromans, indoles, or indanes. Theses valuable products are generally obtained in good yields and high stereoselectivity. They are shown to be useful synthons for rapid access to functionalized polycyclic skeletons. 相似文献
73.
Simons R Vincken JP Bohin MC Kuijpers TF Verbruggen MA Gruppen H 《Rapid communications in mass spectrometry : RCM》2011,25(1):55-65
Phytoalexins from soya are mainly characterised as prenylated pterocarpans, the glyceollins. Extracts of non-soaked and soaked soya beans, as well as that of soya seedlings, grown in the presence of Rhizopus microsporus var. oryzae, were screened for the presence of prenylated flavonoids with a liquid chromatography/mass spectrometry (LC/MS)-based screening method. The glyceollins I-III and glyceollidins I-II, belonging to the isoflavonoid subclass of the pterocarpans, were tentatively assigned. The formation of these prenylated pterocarpans was accompanied by that of other prenylated isoflavonoids of the subclasses of the isoflavones and the coumestans. It was estimated that approx. 40% of the total isoflavonoid content in Rhizopus-challenged soya bean seedlings were prenylated pterocarpans, whereas 7% comprised prenylated isoflavones and prenylated coumestans. The site of prenylation (A-ring or B-ring) of the prenylated isoflavones was tentatively annotated using positive-ion mode MS by comparing the (1,3) A(+) retro-Diels-Alder (RDA) fragments of prenylated and non-prenylated isoflavones. Furthermore, the fragmentation pathways of the five pterocarpans in negative-ion (NI) mode were proposed, which involved the cleavage of the C-ring and/or D-ring. The absence of the ring-closed prenyl (pyran or furan) gave exclusively -H(2) O(x,y) RDA fragments, whereas its presence gave predominantly the common RDA fragments. 相似文献
74.
Wierzbinski E de Leon A Davis KL Bezer S Wolak MA Kofke MJ Schlaf R Achim C Waldeck DH 《Langmuir : the ACS journal of surfaces and colloids》2012,28(4):1971-1981
We studied the charge transfer properties of bipyridine-modified peptide nucleic acid (PNA) in the absence and presence of Zn(II). Characterization of the PNA in solution showed that Zn(II) interacts with the bipyridine ligands, but the stability of the duplexes was not affected significantly by the binding of Zn(II). The charge transfer properties of these molecules were examined by electrochemistry for self-assembled monolayers of ferrocene-terminated PNAs and by conductive probe atomic force microscopy for cysteine-terminated PNAs. Both electrochemical and single molecular studies showed that the bipyridine modification and Zn(II) binding do not affect significantly the charge transfer of the PNA duplexes. 相似文献
75.
Wallez G Raison PE Dacheux N Clavier N Bykov D Delevoye L Popa K Bregiroux D Fitch AN Konings RJ 《Inorganic chemistry》2012,51(7):4314-4322
The AnP(2)O(7) diphosphates (An = Th, U, Np, Pu) have been synthesized by various routes depending on the stability of the An(IV) cation and its suitability for the unusual octahedral environment. Synchrotron and X-ray diffraction, thermal analysis, Raman spectroscopy, and (31)P nuclear magnetic resonance reveal them as a new family of diphosphates which probably includes the recently studied CeP(2)O(7). Although they adopt at high temperature the same cubic archetypal cell as the other known MP(2)O(7) diphosphates, they differ by a very faint triclinic distortion at room temperature that results from an ordering of the P(2)O(7) units, as shown using high-resolution synchrotron diffraction for UP(2)O(7). The uncommon triclinic-cubic phase transition is first order, and its temperature is very sensitive to the ionic radius of An(IV). The conflicting effects which control the thermal variations of the P-O-P angle are responsible for a strong expansion of the cell followed by a contraction at higher temperature. This inversion of expansion occurs at a temperature significantly higher than the phase transition, at variance with the parent compounds with smaller M(IV) cations in which the two phenomena coincide. As shown by various approaches, the P-O(b)-P linkage remains bent in the cubic form. 相似文献
76.
Maass JS Zeller M Breault TM Bartlett BM Sakiyama H Luck RL 《Inorganic chemistry》2012,51(9):4903-4905
The syntheses and structural properties of three dinuclear complexes [L(3)Co(μ(2)-O(2)P(Bn)(2))(3)CoL'][L"] [one ionic L(3) = py(3), L' = py, L" = ClO(4)(-) (1) and two molecular L(3) = py(3), L' = Cl (2) and L(3) = py, μ(2)-NO(3)(-), L' = py (3)] are reported. Complexes feature octahedral Co(II) sites bridged by three dibenzylphosphinate ligands to a tetrahedrally ligated Co(II) site, with the remaining coordination sites occupied by py, nitrato, and Cl ligands. The Co-Co distances are 4.248 ? at 291 K and 4.265 ? at 100 K for 1 and 4.278 and 4.0313(7) ? for 2 and 3, respectively at 100 K. A fit of the low-temperature magnetic susceptibility data was derived for complex 1 with g = 2.25, TIP = 700 × 10(-6) cm(3) mol (-1), λ = -173 cm(-1), κ = 0.93, ν = -3.9, Δ = 630 cm(-1), J = 0.15 cm(-1), and θ = -1.8 resulting in R(χ(M)) = 2.5 × 10(-5) and R(χ(M)T) = 5.8 × 10(-5). 相似文献
77.
Abstract
Hydroxymethylphenylphosphinic acid, 1 was synthesized and structurally characterized by single crystal X-ray diffraction. Ligand 1 crystallized in the monoclinic P21 space group with two molecules comprising the unit cell and cell dimensions a = 7.5587(13) ?, b = 5.9019(8) ?, c = 8.808(3) ? and β = 90.90(2)°. Molecules were linked up by hydrogen bonding involving all three oxygen atoms of 1 resulting in 2-dimensional sheets. Reacting 1 with MoO2Cl2 in a mixture of ethanol and dichloromethane afforded the dinuclear molybdenum complex Mo2O4Cl2[(HOCH2)PhPOO]2, 2 where the two molybdenum atoms were bridged by the phosphinate ligand. Complex 2 crystallized in the P21/C space group as a dietherate with a = 9.208(3) ?, b = 14.353(4) ?, c = 12.805(4) ? and β = 98.64(3)° and contained terminal O and Cl atom disorder. The two crystallographically identical molybdenum centers are in distorted octahedral environments. Complexes were analyzed by IR, 31P NMR and X-ray crystallography. 相似文献78.
The objectives are to study and model the aggregate wind power fluctuations dynamics in the multifractal framework. We present here the analysis of aggregate power output sampled at 1 Hz during three years. We decompose the data into several Intrinsic Mode Functions (IMFs) using Empirical Mode Decomposition (EMD). We use a new approach, arbitrary order Hilbert spectral analysis, a combination of the EMD approach with Hilbert spectral analysis (or Hilbert–Huang Transform) and the classical structure-function analysis to extract the scaling exponents or multifractal spectrum ζ(q): this function provides a full characterization of a process at all intensities and all scales. The application of both methods, i.e. structure-function and arbitrary-order Hilbert spectral analyses, gives similar results indicating that the aggregate power output from a wind farm, possesses intermittent and multifractal properties. In order to check this result, we generate stochastic simulations of a Multifractal Random Walk (MRW) using a log-normal stochastic equation. We show that the simulation results are fully compatible with the experimental results. 相似文献
79.
We provide numerical evidence that a p(x)-ip(y) paired Bonderson-Slingerland (BS) non-Abelian hierarchy state is a strong candidate for the observed ν=12/5 quantum Hall plateau. We confirm the existence of a gapped incompressible ν=12/5 quantum Hall state with shift S=2 on the sphere, matching that of the BS state. The exact ground state of the Coulomb interaction at S=2 is shown to have a large overlap with the BS trial wave function. Larger overlaps are obtained with BS-type wave functions that are hierarchical descendants of general p(x)-ip(y) weakly paired states at ν=5/2. We perform a finite-size scaling analysis of the ground-state energies for ν=12/5 states at shifts corresponding to the BS (S=2) and 3-clustered Read-Rezayi (S=-2) universality classes. This analysis reveals very tight competition between these two non-Abelian topological orders. 相似文献
80.
A. S. Hoover M. K. Bacrania N. J. Hoteling P. J. Karpius M. W. Rabin C. R. Rudy D. T. Vo J. A. Beall D. A. Bennett W. B. Doriese G. C. Hilton R. D. Horansky K. D. Irwin J. N. Ullom L. R. Vale 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(1):227-232
Microcalorimeter detectors provide superior energy resolution for the detection of X-rays and gamma-rays. The technology utilizes a cryogenic transition-edge sensor (TES) coupled to a tin bulk absorber. We are working on fabrication methods for the production of arrays with many sensors. In this paper, we present data collected with an array of microcalorimeters using as many as 26 sensor elements simultaneously. Advances in sensor design have extended the useful dynamic range to photon energies up to ~200 keV, while providing resolution performance in the 80–90 eV FWHM range, significantly better than planar high-purity germanium. These sensor arrays have applications in the measurement of nuclear materials. We present data collected from 153Gd, a highly-enriched uranium sample, and a plutonium isotopic standard source. We also demonstrate clean separation of the 235U 185.715 keV peak from the ubiquitous 226Ra 186.211 keV background peak interference. 相似文献