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Phenolic Groups (phenolic + groups)
Selected AbstractsBound amino acids in humic acids from arable cropping systemsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2004Lech Szajdak Abstract We investigated the varying concentrations of bound amino acids in humic acids (HA) extracted from soils under both crop rotation and continuous cropping of rye. The experiment was created in 1957. Since then, winter rye had been grown continuously and also the sequence of the 7 yr rotation had been started: potato, spring barley, alfalfa, alfalfa, oil seed rape, winter rye, and winter rye. Soils were fertilized with NPK and manure. Continuous cropping of rye increased total acidity of soils and the contents of carboxylic and phenolic groups in HA. The total amounts of the bound amino acids in HA from soils under crop rotation were higher than from continuous cropping of rye. Fertilization with NPK increased the contents of bound amino acids more than manure. Neutral amino acids dominated in all samples of HA, and basic amino acids had the lowest concentrations. In both types of cultivation, glutamic acids, glycine, alanine, valine, and lysine dominated. The proline contents in HA from continuous rye cropping were higher than in HA from soils under crop rotation. The concentrations of ,-alanine and lysine were higher in HA from crop rotation indicating a higher microbial biomass since these compounds are typical constituents of bacteria cell walls. In Huminsäuren gebundene Aminosäuren aus Böden unterschiedlicher Anbausysteme In Bodenproben aus Feldern mit Roggen-Monokultur und Fruchtwechsel wurde die Konzentration von Anminosäuren in Huminsäuren untersucht. Der Feldversuch wurde im Jahre 1957 angelegt. Auf einem Teil des Feldes wurde Winterroggen in Monokultur angebaut, auf dem anderen Teil wurde eine Fruchtfolge aus Kartoffeln, Sommergerste, Luzerne, Raps, Winterroggen und Winterrogen angebaut. Die Böden wurden mit NPK und Stallmist gedüngt. Unter der Roggen-Monokultur vergrößerten sich die Gesamtazidität des Bodens und die Anteile von Karboxyl- und phenolischen OH-Gruppen in den Huminsäuren. Die Aminosäuregehalte der Huminsäuren waren bei Fruchtfolge höher als unter Monokultur. Bei Nutzung von Mineraldüngern war die Konzentration der Aminosäuren höher als bei Stallmist. Die neutralen Aminosäuren waren immer in größeren Gehalten vorhanden als die sauren Aminosäuren. Unabhängig von den Pflanzen dominierten immer Glutaminsäure, ß-Alanin, Valin und Lysin. Bei Monokultur war die Menge an Prolin höher als bei der Fruchtfolge. Die Gehalte an ß-Alanin und Lysin verhielten sich umgekehrt, was durch eine höhere mikrobielle Biomasse erklärt wird, da ,-Alanin und Lysin in Zellwände von Bakterien eingebaut sind. [source] Synthesis and characterization of new hyperbranched poly(aryl ether oxadiazole)sJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2001Fang-Iy Wu Abstract A new AB2 monomer was synthesized for use in the preparation of a hyperbranched poly(aryl ether oxadiazole) with terminal phenol functionality. The AB2 monomer contains two phenolic groups and a single aryl fluoride group that is activated toward nucleophilic displacement by the attached oxadiazole ring. The nucleophilic substitution of the fluoride with the phenolate groups led to the formation of an ether linkage. Subsequently, a hyperbranched poly(aryl ether oxadiazole) having approximately a 44% degree of branching, as determined by a combination of model compound studies and 1H NMR, was obtained. The terminal phenolic groups underwent facile functionalization, furnishing hyperbranched polymers with a variety of functional chain ends. The nature of the chain-end groups had a significant influence on the physical properties of the polymers, such as the glass-transition temperature and their solubility. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3851,3860, 2001 [source] Assessment of UV Biological Spectral Weighting Functions for Phenolic Metabolites and Growth Responses in Silver Birch SeedlingsPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2009Titta Kotilainen In research concerning stratospheric ozone depletion, action spectra are used as biological spectral weighting functions (BSWFs) for describing the effects of UV radiation on plant responses. Our aim was to evaluate the appropriateness of six frequently used BSWFs that differ in effectiveness with increasing wavelength. The evaluation of action spectra was based on calculating the effective UV radiation doses according to 1,2) two formulations of the generalized plant action spectrum, 3) a spectrum for ultraviolet induced erythema in human skin, 4) a spectrum for the accumulation of a flavonol in Mesembryanthemum crystallinum, 5) a spectrum for DNA damage in alfalfa seedlings and 6) the plant growth action spectrum. We monitored effects of UV radiation on the concentration of individual UV absorbing metabolites and chlorophyll concentrations in leaves and growth responses of silver birch (Betula pendula) seedlings. Experiments were conducted outdoors using plastic films attenuating different parts of the UV spectrum. Chlorophyll concentrations and growth were not affected by the UV treatments. The response to UV radiation varied between and within groups of phenolics. In general, the observed responses of phenolic groups and individual flavonoids were best predicted by action spectra extending into the UV-A region with moderate effectiveness. [source] The relationship between changes in the cell wall, lipid peroxidation, proliferation, senescence and cell deathPHYSIOLOGIA PLANTARUM, Issue 1 2003Gerhard Spiteller Plants and mammals contain polyunsaturated fatty acids (PUFAs) in their membranes. PUFAs belong to the most oxygen sensitive molecules encountered in nature. It would seem that nature has selected this property of PUFAs for signalling purposes: PUFAs are stored in the surface of cells and organelles not in free form but conjugated to phospho- and galactolipids. Any change in membrane structure apparently activates membrane-bound phospholipases, which cleave the conjugates. The obtained free PUFAs are substrates for lipoxygenases (LOX). These transform PUFAs to lipidhydroperoxides (LOOHs). LOOHs are converted to a great variety of secondary products. These lipid-peroxidation (LPO) products and the resulting generated products thereof represent biological signals, which do not require a preceding activation of genes. They are produced as a non-specific response to a large variety of external or internal impacts, which therefore do not need interaction with specific receptors. When, due to an external impact, e.g. attack of a microorganism, or to a change in temperature, the amount of liberated free PUFAs exceeds a certain threshold, LOX commit suicide. Thus iron ions, located in the active centre of LOX, are liberated. Iron ions react with LOOHs in the close surroundings by generating alkoxy radicals (LO.). These induce a non-enzymatic LPO. A fraction of the LO. radicals generated from linoleic acid (LPO products derived from linoleic acid play a dominant role in signalling which was previously overlooked) is converted to 2,4-dienals which induce the programmed cell death (PCD) and the hypersensitive reaction (HR). While peroxyl radicals (LOO.) generated as intermediates in the course of an enzymatic LPO are transformed within the enzyme complex to corresponding anions (LOO,), and thus lose their reactivity, peroxyl radicals generated in non-enzymatic reactions are not deactivated. They not only react by abstraction of hydrogen atoms from activated X-H bonds of molecules in their close vicinity, but also by epoxidation of double bonds and oxidation of a variety of biological molecules, causing a dramatic change in molecular structure which finally leads to cell death. As long as reducing agents, like glutathione, or compounds with free phenolic groups are available, the amount of LOOHs is kept low. Cell death is induced in a defined way by apoptosis. But when the reducing agents have been consumed, PCD seems to switch to necrotic processes. Thus proliferation is induced by minor changes at the cell membrane, while slow changes at cell membranes are linked with apoptosis (e.g. response to attack of microorganisms or drought) and necrosis (severe wounding), depending only on the amount, but not on the type, of applied stimulus. [source] Surface Modification of Tobacco Mosaic Virus with "Click" ChemistryCHEMBIOCHEM, Issue 4 2008Michael A. Bruckman Click conjugation of tobacco mosaic virus: As a prototype of "click" chemistry, the CuI catalyzed azide-alkyne cycloaddition reaction in combination with diazonium-coupling proved to be an efficient, versatile, and benign method to conjugate a wide range of compounds to phenolic groups of protein tyrosines. In particular, plant virus tobacco mosaic virus was chosen as a multivalent protein scaffold to demonstrate this bioconjugation strategy. [source] Inhibition of Hsp90 with Resorcylic Acid Macrolactones: Synthesis and Binding StudiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2010Dr. James Abstract A series of resorcylic acid macrolactones, analogues of the natural product radicicol has been prepared by chemical synthesis, and evaluated as inhibitors of heat shock protein 90 (Hsp90), an emerging attractive target for novel cancer therapeutic agents. The synthesis involves acylation of an ortho -toluic acid dianion, esterification, followed by a ring-closing metathesis to form the macrocycle. Subsequent manipulation of the protected hydroxymethyl side chain allows access to a range of new analogues following deprotection of the two phenolic groups. Co-crystallization of one of the new macrolactones with the N -terminal domain of yeast Hsp90 confirms that it binds in a similar way to the natural product radicicol and to our previous synthetic analogues, but that the introduction of the additional hydroxymethyl substituent appears to result in an unexpected change in conformation of the macrocyclic ring. As a result of this conformational change, the compounds bound less favorably to Hsp90. [source] Selective Binding of Imidazolium Cations in Building Multi-Component LayersCHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2010Irene Ling Abstract Addition of 1-alkyl-3-methylimidazolium (Cn -mim) cations 3,5 to a mixture of bis-phosphonium cation 2 and sodium p -sulfonatocalix[4]arene (1) in the presence of lanthanide ions results in the selective binding of an imidazolium cation into the cavity of the calixarene. The result is a multi-layered solid material with an inherently flexible interplay of the components. Incorporating ethyl-, n -butyl- or n -hexyl-mim cations into the multi-layers results in significant perturbation of the structure, the most striking effect is the tilting of the plane of the bowl-shaped calixarene relative to the plane of the multi-layer, with tilt angles of 7.2, 28.9 and 65.5°, respectively. The lanthanide ions facilitate complexation, but are not incorporated into the structures and, in all cases, the calixarene takes on a 5, charge, with one of the lower-rim phenolic groups deprotonated. ROESY NMR experiments and other 1H,NMR spectroscopy studies establish the formation of 1:1 supermolecules of Cn -mim and calixarene, regardless of the ratio of the two components, and indicate that the supermolecules undergo rapid exchange on the NMR spectroscopy timescale. [source] Tyrosine Hydrogen Bond Properties for the Two Binding Sites of ApoovotransferrinCHINESE JOURNAL OF CHEMISTRY, Issue 10 2005Ying-Qi Li Abstract The interaction of gallium(III) with the ligands containing phenolic group(s), such as salicylic acid, 8-hydroxyquinoline, N,N' -bis(2-hydroxybenzyl)ethylenediamine- N,N, -diacetic acid (HBED), N,N, -ethylenebis[2-(o -hydroxyphenyl)glycine (EHPG), and ovotransferrin, was studied, respectively, by means of fluorescence in 0.01 mol/L Hepes at pH 7.4 and room temperature. Fluorescence intensity showed an increase when gallium(III) was bound to 8-hydroxyquinoline and HBED. In contrast, it was decreased with the interaction of gallium(III) with salicylic acid and EHPG. At pH 7.4, there was N···HO type intramolecular hydrogen bond in the former, and the latter existed O···HO type intramolecular hydrogen bond. Fluorescence titration of apoovotransferrin with gallium(III) displayed that the fluorescence intensity was decreased at the N-terminal binding site, while enhanced at the C-terminal binding site. It can account for the O···HO type intramolecular hydrogen bonds for the phenolic groups of Tyr92 and Tyr191 residues at the N-terminal binding site. And there are N···HO type intramolecular hydrogen bonds for Tyr431 and Tyr524 residues at the C-terminal binding site. In addition, under the same conditions, the conditional binding constant of gallium(III) with EHPG or HBED determined by fluorescence method is lg KGa-EHPG=19.18 or lg KGa-HBED=19.08. [source] | |||||||||||||