Archive for the ‘researches 4’ Category
Sunday, March 16th, 2008
Sub-lethal Levels of Electric Current Elicit the Biosynthesis of Plant Secondary Metabolites.
Many secondary metabolites that are normally undetectable or in low amounts in healthy plant tissue are synthesized in high amounts in response to microbial infection. Various abiotic and biotic agents have been shown to ...
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Sunday, March 16th, 2008
Optimization of the Media Ingredients for Cutinase Production from Colleotrichum lindemuthianum Using Mixture Design Experiments.
Optimal concentrations of yeast extract, glucose and potassium phosphate in the fermentation medium have been identified for the maximum cutinase production from the fungi Colleotrichum lindemuthianum. A simplex lattice experimental design ...
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Sunday, March 16th, 2008
Asymmetric Synthesis of cis- and trans-2,5-Disubstituted Pyrrolidines from 3-Oxo Pyrrolidine 2-Phosphonates: Synthesis of (+)-Preussin and Analogs.
Pyrrolidine enones, derived from 3-oxo pyrrolidine 2-phosphonates and a HWE reaction with aldehydes, on Luche reduction give pyrrolidine allylic alcohols. The alcohols on hydrogenation (Pd/H2) give cis-2,5-disubstituted pyrrolidines and on ...
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Sunday, March 16th, 2008
One Step Cascade Synthesis of 4,5-Disubstituted-1,2,3-(NH)-Triazoles.
A Lewis base-catalyzed three-component cascade reaction was developed for the synthesis of 4,5-disubstituted-1,2,3-(NH)-triazoles. More than 25 new (NH)-triazoles were prepared in good to excellent yields under mild conditions. The availability of the C-4 vinyl group allows easy conversion into other ...
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Sunday, March 16th, 2008
Realization of Anti-S(N)2\' Selective Allylation of 4-Cyclopentene-1,3-diol Monoester with Aryl- and Alkenyl-Zinc Reagents.
Anti-SN2\' mode of allylation of the monoester of 4-cyclopentene-1,3-diol with aryl and alkenyl anions was achieved, for the first time, with the MeOCH2CO2- group as a leaving group to which R-ZnBr and CuCl ...
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Sunday, March 16th, 2008
Modular Synthesis of Functionalized Benzosiloles by Tin-Mediated Cyclization of (o-Alkynylphenyl)silane.
Trimethylstannyllithium promotes cyclization of (o-alkynylphenyl)silane into a 3-stannylbenzosilole, via addition to the triple bond followed by intramolecular cyclization in a cascade fashion. This intermediate can be functionalized with either electrophiles or nucleophiles to allow modular synthesis ...
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Sunday, March 16th, 2008
Convenient Synthesis of Branched-Chain Glycosamines by Radical Addition of Nitromethane to Glycals.
Radical addition-reduction-acetylation is the simple three-step sequence for the synthesis of branched-chain glycosamines 3 from glycals 1 and nitromethane (2). The intermediary formed 2-C-nitromethyl-pyranosides are valuable precursors for the synthesis of C-2 branched disaccharides.
Elamparuthi ...
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Sunday, March 16th, 2008
A Facile and Patternable Method for the Surface Modification of Carbon Nanotube Forests Using Perfluoroarylazides.
A facile patterning method for the functionalization of vertically aligned carbon nanotubes is described. Modification of the surface of nanotube forests with hydrophilic, hydrophobic, or polymerizable small molecules was achieved via ...
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Sunday, March 16th, 2008
Regioselective Activation of Oxo Ligands in Functionalized Dawson Polyoxotungstates.
The organic side chain of tin-substituted Dawson polyoxotungstates alpha1- and alpha2-[P2W17O61{SnCH2CH2COOH}]7- can be used to direct regioselective acylations of oxo ligands in the inorganic backbone, which was examined both experimentally and computationally. Acylation of the oxo ligand ...
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Sunday, March 16th, 2008
Biosynthesis and Structures of Cyclomarins and Cyclomarazines, Prenylated Cyclic Peptides of Marine Actinobacterial Origin.
Two new diketopiperazine dipeptides, cyclomarazines A and B, were isolated and characterized along with the new cyclic heptapeptide cyclomarin D from the marine bacterium Salinispora arenicola CNS-205. These structurally related cyclic peptides ...
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Sunday, March 16th, 2008
Two-Photon Fluorescent Turn-On Probe for Lipid Rafts in Live Cell and Tissue.
We report a new two-photon fluorescence turn-on probe 6-[(E)-3-oxo-1-dodecenyl]-2-[N-methyl-N-(carboxymethyl)amino]naphthalene (CL2) that is designed specifically for visualizing lipid rafts in living cells and tissues. This probe emits much brighter two-photon excited fluorescence in lipid rafts ...
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Sunday, March 16th, 2008
Pressure Response of Three-Dimensional Cyanide-Bridged Bimetallic Magnets.
Effects of pressure on the structures and magnetic properties of three types of 3-D cyanide-bridged bimetallic coordination polymer magnets, MnIICrIII ferrimagnet [Mn(en)]3[Cr(CN)6]2.4H2O (1; en = ethylenediamine), NiIICrIII ferromagnet [Ni(dipn)]3[Cr(CN)6]2.3H2O (2; dipn = N,N-di(3-aminopropyl)amine), and NiIIFeIII ferromagnet [Ni(dipn)]2[Ni(dipn)(H2O)][Fe(CN)6]2.11H2O (3), were ...
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Sunday, March 16th, 2008
Alkyl Peroxides Reveal the Ring Opening Mechanism of Verdoheme Catalyzed by Heme Oxygenase.
Heme oxygenase (HO) catalyzes heme catabolism through three successive oxygenation steps where the substrate heme itself activates O2. Although a rate-determining step of the HO catalysis is considered as third oxygenation, the verdoheme ...
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Sunday, March 16th, 2008
Spontaneous Self-Assembly of Metal-Organic Cationic Nanocages to Form Monodisperse Hollow Vesicles in Dilute Solutions.
In this communication we report the unprecedented spontaneous self-assembly of cationic nanoporous metal-organic coordination cages (nanocages) into giant hollow vesicle-like structures in polar solvents. Such highly soluble nanocages (macrocations) have separated hydrophobic ...
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Sunday, March 16th, 2008
Azo Supramolecules on Au(111) with Controlled Size and Shape.
Using a subtle balance between weak intermolecular C-H...N hydrogen bonds and molecule-surface interactions, supramolecules of azobenzene-related molecules on Au surfaces were prepared. For analysis, modeling based on first-principles calculations was performed.
Wang Y, Ge X, Schull G, Berndt ...
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Sunday, March 16th, 2008
Construction of a Chiral Quaternary Carbon Center by Indium-Catalyzed Asymmetric alpha-Alkenylation of beta-Ketoesters.
Construction of a nonracemic all-carbon quaternary stereocenter at the alpha-position of beta-ketoesters was achieved by way of an indium(III)-catalyzed diastereoselective alpha-alkenylation reaction of chiral enamines with 1-alkynes. The enamine bearing a chiral auxiliary ...
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Sunday, March 16th, 2008
Half-Metallicity in Edge-Modified Zigzag Graphene Nanoribbons.
Graphene is an important material with potential application in spintronics. Edge-modified zigzag graphene nanoribbons (ZGNR) are investigated with density functional theory. The modifications are realized by saturating the dangling edge bonds by different terminal groups, such as H, NH2, NO2, ...
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Sunday, March 16th, 2008
Linear Assemblies of Magnetic Nanoparticles as MRI Contrast Agents.
Using a one-step procedure we have prepared magnetic fluids comprising of polyelectrolyte stabilized magnetite nanoparticles. These nanocomposites are comprised of linear, chain-like assemblies of magnetic nanoparticles, which can be aligned in parallel arrays by an external magnetic ...
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Sunday, March 16th, 2008
Determination of the Origin of Stereoselectivity in Multiple-Transition-State Reactions Using DFT Calculations: Enantioselective Synthesis of Homoallylic Alcohols from Aliphatic Methyl Ketones via an Auxiliary-Mediated Allylation.
Computational investigations on the highly stereoselective allylation of butanone in the presence of a chiral norpseudoephedrine-derived auxiliary have been performed. They ...
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Sunday, March 16th, 2008
Computational Modeling of the Optical Rotation of Amino Acids: A New Look at an Old Rule for pH Dependence of Optical Rotation.
The molar rotation of a solution of a natural alpha amino acid is changed in the positive direction by addition of a strong acid. ...
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Sunday, March 16th, 2008
Atomic Structure of a Short alpha-Helix Stabilized by a Main Chain Hydrogen-Bond Surrogate.
Herein we report the 1.15 A X-ray crystal structure of a short alpha-helix in which the N-terminal i and i + 4 main chain hydrogen bond is replaced with a carbon-carbon bond. The ...
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Sunday, March 16th, 2008
Iron Complexes of Dendrimer-Appended Carboxylates for Activating Dioxygen and Oxidizing Hydrocarbons.
The active sites of metalloenzymes are often deeply buried inside a hydrophobic protein sheath, which protects them from undesirable hydrolysis and polymerization reactions, allowing them to achieve their normal functions. In order to mimic the ...
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Sunday, March 16th, 2008
pi(*)-pi(*) Bonding Interactions Generated by Halogen Oxidation of Zirconium(IV) Redox-Active Ligand Complexes.
The new complex, [Zr(pda)2]n (1, pda2- = N,N\'-bis(neo-pentyl)-ortho-phenylenediamide, n = 1 or 2), prepared by the reaction of 2 equiv of pdaLi2 with ZrCl4, reacts rapidly with halogen oxidants to afford the new product ...
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Sunday, March 16th, 2008
Topochemical 3D Polymerization of C(60) under High Pressure at Elevated Temperatures.
Fullerene C60 monomer crystals were compressed to a face-centered cubic (fcc) phase with a lattice parameter of a = 11.93(5) A and a micro-Vickers hardness of 4500 kg/mm2 using high-pressure and high-temperature conditions of 15 ...
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Sunday, March 16th, 2008
Aquation of the Ruthenium-Based Anticancer Drug NAMI-A: A Density Functional Study.
We carried out density functional theory (DFT) calculations to investigate the thermodynamics and the kinetics of the double aquation reaction of the anticancer drug NAMI-A. Three explicit water molecules were included in the calculations to ...
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