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981.
Guy PaillotinNicholas E. Geacintov†Jacques Breton 《Photochemistry and photobiology》1983,37(4):475-478
The spatial non-uniformity of a light beam must be taken into account in interpreting phenomena which depend on the light intensity in a non-linear manner. Omission of this effect may lead to incorrect values of parameters obtained from a fitting of theoretical curves, which describe the dependence of a given phenomenon on light intensity, to the experimental data. The effect of spatial non-uniformity of excitation light beams is illustrated utilizing non-linear intensity-dependent fluorescence phenomena in photosvnthetic svstems and a Gaussian light beam profile. 相似文献
982.
Willemsen P Scippo ML Kausel G Figueroa J Maghuin-Rogister G Martial JA Muller M 《Analytical and bioanalytical chemistry》2004,378(3):655-663
We have studied stable transformed human mammary cell lines with highly inducible steroid receptor-mediated luciferase reporter gene expression. Cells responding specifically to glucocorticoids, progestagens, androgens, or estrogens are described and characterized. The use of this high-throughput, cell-based assay for analysis of steroid (ant)agonists is reported. Systematic characterization of endocrine-disrupting activity on human receptors and in a human-cell system is interpreted for a selection of xenobiotics. We show that the phytoestrogens apigenin and genistin have progestagenic and androgenic activity, respectively. Finally, application of cell-based assays to the analysis of environmental samples is discussed. 相似文献
983.
A re-investigation of resveratrol synthesis by Perkins reaction. Application to the synthesis of aryl cinnamic acids 总被引:1,自引:0,他引:1
A re-investigation of resveratrol synthesis by Perkins reaction allowed to improve this method and to determine the configuration of the intermediates. The results were applied to the synthesis of several aryl cinnamic acids for biological evaluation. 相似文献
984.
Alcock NW Clarkson G Glover PB Lawrance GA Moore P Napitupulu M 《Dalton transactions (Cambridge, England : 2003)》2005,(3):518-527
The potentially pentadentate ligand 2,6-bis[N-(2'-pyridylmethyl)carbamyl]pyridine (H2L1), readily prepared from reaction of a diester of pyridine-2,6-dicarboxylic acid (H2dipic) and 2-aminomethylpyridine (ampy), shows limited tendency to form 1:1 M:L complexes with labile metal ions, although [CuL1] and [NiL1] were observed as minor species, the latter characterized by a crystal structure analysis. A mononuclear complex formed with inert Co(III) was characterized by a crystal structure as the neutral 1:2 complex [Co(L1)(HL1)] with two ligands acting as tridentate ligands, one coordinated by the central pyridine and its two flanking deprotonated amido groups, and the other by the central pyridine, one amido and one terminal pyridine group, with the remaining poorly coordinating protonated amide remaining unbound along with other terminal pyridine groups. Fe(III) is known to form a symmetrical 1:2 complex, but that complex is anionic due to binding of all four deprotonated amido groups; the unsymmetrical neutral Co(III) complex converts into a symmetrical anionic species only on heating for hours in aqueous base in the presence of activated carbon. The most remarkable tendency of H2L1, however, is towards the formation of robust double helical complexes: a dinuclear Cu(II) complex [Cu2L1(2)] forms, as well as a trinuclear Ni(II) complex [Ni(3)(L1)2(OAc)2(MeOH)2]. Moreover, in the presence of added H2dipic, the tetranuclear complex [Cu4(L1)2(dipic)2(OH2)2] is obtained. All helical complexes have been characterized by X-ray crystal structure analyses, and all crystals feature a racemic mixture of left- and right-handed double helices stabilized by inter-ligand pi-stacking (inter-ring distances of 3.2-3.8 A) of ligands which each span several metal ions. Using the chelating ligand pentane-2,4-dione (acac), each of the two pairs of adjacent monodentate ligands in [Ni3(L1)2(OAc)2(OH2)2] have been shown to be available for substitution without destroying the helical structure, to form [Ni3(L1)2(acac)2], also characterized by a crystal structure. 相似文献
985.
Peter Von Matt Guy C. Lloyd-Jones Alexander B. E. Minidis Andreas Pfaltz Ludwig Macko Markus Neuburger Margareta Zehnder Heinz Rüegger Paul S. Pregosin 《Helvetica chimica acta》1995,78(2):265-284
Allylpalladium complexes with chiral bis(dihydrooxazole) ligands were studied as catalysts for the enantioselective allylic substitution reaction of rac-1,3-diphenylprop-2-enyl acetate (rac- 5 ) with the anion of dimethyl malonate (Scheme 1). Using enantiomerically pure (S,E)-1-(4-tolyl)-3-phenylprop-2-enyl acatete ((S)- 25 ) as substrate, the reaction was shown to proceed by a clean ‘syn’ displacement of acetate by dimethyl malonate (Scheme 6). The [Pd11(η3-allyl)] complex 18 and the analogous [Pd(η3-1,3-diphenylallyl)] complex 20 , both containing the same bis(dihydrooxazole) ligand, were characterized by X-ray structure analysis and by NMR spectroscopy in solution. The structural data reveal that steric interactions of the allyl system with the chiral ligand result in selective electronic activation of one of the allylic termini. The higher reactivity of one allylic terminus toward nucleophilic attack is reflected in a significantly longer Pd? C bond and a shift of the corresponding 13C-NMR resonance to higher frequency. 相似文献
986.
Guy Samson Jean Claude Morisette Radovan Popovic 《Photochemistry and photobiology》1988,48(3):329-332
Abstract— The copper quenching effect on fluorescence in Dunaliella tertiolecta was studied. 30% of variable fluorescence was quenched in the presence of 70 μ,M CuS04 . We confirmed that the copper inhibitory effect on photosystem II (PSII) activity is located on its oxidizing side. Further, we indicate that the complementary area is decreased by copper. Since the quantum yield of PSII photochemistry was lowered and the rate of PSII primary electron acceptor QA remained unaffected, we can conclude that some PSII reaction centers were inactivated by copper. 相似文献
987.
The angular distribution function P(θ) for intensity of light scattered by a dilute solution of comblike branched molecules has been determined for three situations of some interest for evaluation of experimental data: (1) the molecules are identical with branches of equal length attached equidistantly along linear backbone chains; (2) the molecules are homogeneous in mass, with the same number of branches on each molecule, but the branches are distributed at random along the chain; (3) branches and main chains are still uniform, but the molecules are heterogeneous in mass with the number of branches per molecule distributed according to the binomial distribution and the branches in any molecule spaced randomly along the backbone. Examination of numerical results shows that the scattering functions for models (1) and (2) are not very different. The function for case (3) is somewhat different from the others when the mean number of branches per molecule is small but they contain a large fraction of the mass of the molecule. Over a limited range of the pertinent variables (corresponding roughly to observations on typical vinyl polymers of molecular weights up to 106) all three functions agree quite well with P(θ) for homogeneous linear chains with the same mean-square radius of gyration. 相似文献
988.
Novel illustrations of the specific reactivity of 1,1-diamino-2,2-dinitroethene (DADNE) leading to new unexpected compounds 总被引:2,自引:0,他引:2
1,1-Diamino-2,2-dinitroethene (DADNE) was further investigated and evaluated in oxidation and azidation reactions. DADNE gave new unexpected products as a result of its specific reactivity as previously observed. The X-ray structure determination was the key of success in this work enabling us to perfectly characterise the new products and argue about the reaction mechanisms as well. Once again, the nucleophilic gem-dinitrocarbon of DADNE seemed to be directly involved in these transformations. Attempts to change the regioselectivity were performed by modifying the experimental conditions. 相似文献
989.
The reaction products in the SF6-N2 mixture rf plasma during reactive ion etching of Si and W have been measured by a mass spectrometric method. Two kinds of cathode materials were used in this work; they were stainless steel for the Si etching, and SiO2 for the W etching. The main products detected in the etching experiments of Si and W included SF4, SF2, SO2, SOF2, SOF4, SO2F2, NSF, NF3, N2F4, NxSy, NO2, and SiF4. In the W etching with the SiO2 cathode, additional S2F2, N2O, and WF6 molecules were also obtained. The formation reactions about the novel NSF compound and the sulfur oxyfuorides were discussed. 相似文献
990.