Search results for "ACIDS"
showing 10 items of 3520 documents
Mode of action of herbicidal derivatives of aminomethylenebisphosphonic acid. Part II. Reversal of herbicidal action by aromatic amino acids
1997
The herbicidal action of N-pyridylaminomethylenebisphosphonic acids is accompanied by an impairment of anthocyanin biosynthesis. This suggests that they might act as inhibitors of some steps in aromatic amino acid biosynthesis. Herbicidal effects were reversed by aromatic amino acids using both bacterial and plant models, a finding that strongly supports this hypothesis. Structural features of these compounds suggest the sixth enzyme in the shikimate pathway 5-enol-pyruvoylshikimate-3-phosphate (EPSP) synthase as a possible target, since a strong structural similarity exists between aminomethylenebisphosphonic acid and an inhibitor of EPSP synthase, the herbicide glyphosate. This is, howeve…
Alkyl and diether bridged N,N,N′,N′-tetra(2-hydroxybenzyl)diamines: effects of hydrogen bonding on structure and solubility
2012
A solvent-free one-step method has been used to prepare two N,N,N′,N′-tetra(2-hydroxy-3,5-dimethylbenzyl)diaminoalkanes containing a long n-alkyl bridge (6 and 8 CH2 groups between N-atoms). In addition, three novel N,N,N′,N′-tetra(2-hydroxy-5-alkyl-3-alkylbenzyl)-diaminoalkane-ethers (alkyl = methyl or t-butyl) have been prepared using the same method. The compounds were studied in the solid state using single crystal X-ray diffraction and their solubility was studied using UV/Vis spectroscopy. In the solid state, hydrogen bonding plays a key role in controlling the crystal packing and conformations of the molecules, thus affecting the solubility and properties of the compounds.
Regulation of Farnesyl Diphosphate Synthase Gene Expression by Fatty Acids
2003
Cholesterol biosynthesis depends on the activity of regulatory enzymes, including the peroxisomal Farnesyl Diphosphate Synthase (FPPS ). Cholesterol regulates its own synthesis rate. Hence, as a response to cholesterol depletion, a feed back mechanism is activated, whereby sterol regulatory binding proteins (SREBPla, 1c and 2 ) are subjected to sequential proteolytic activation, which permits their interaction with specific DNA response elements from responsive genes. In turn, the transcriptional activity of cholesterol biosynthesis genes is induced. Conversely, cholesterol accumulation decreases SREBP maturation and transcription of controlled genes. In addition, polyunsaturated fatty acid…
Fatty acid composition of a cultured sturgeon hybrid (×)
2005
Abstract Analyses of fatty acids from the dorsal muscle of Acipenser naccarii × A. baerii sturgeon hybrid were carried out. The data were compared with those reported in the literature for other sturgeons reared for human consumption. This hybrid would seem to be of great nutritional interest, its flesh being more beneficial for human health than those of other cultured sturgeons. In fact, the level of polyunsaturated fatty acids (PUFAs) was very high (34.7 ± 0.67%), being similar to that of monounsaturated fatty acids (37.9 ± 0.83%). Moreover, the PUFAs- n 3/PUFAs- n 6 ratio (6.74) was noticeably higher in this hybrid than in the other cultured sturgeon species. There were also high cont…
The amphipathic peptide mellitin as a tool to study the membrane-dependent activation of tissue transglutaminase
2001
The role of membrane phospholipids on the cross-linking activity of guinea pig liver (tissue) transglutaminase has been investigated using the amphipathic model peptide melittin as glutaminyl substrate and the primary amine monodansylcadaverine as extrinsic amine donor. A marked increase of transglutaminase catalytic activity was observedin vitro assays in the presence of neutral membrane phospholipids. In contrast, activation was abolished in the presence of membranes containing pure anionic lipids. Enzyme activation could be ascribed to a direct binding of the lipid to the protein as demonstrated in enzymatic assays using a non membrane-interacting peptide (Cbz-Gln-Gly). The data obtained…
Dianions of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Juvocimene I
1996
Abstract Juvocimene I is prepared by a non ambiguous synthesis based on the regioselective alkylation of 4-methylhexa-2,4-dienoic acid, and Wittig olefination of the aldehyde corresponding to the alkylated acid.
ChemInform Abstract: Dianions of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Juvocimene I.
2010
Abstract Juvocimene I is prepared by a non ambiguous synthesis based on the regioselective alkylation of 4-methylhexa-2,4-dienoic acid, and Wittig olefination of the aldehyde corresponding to the alkylated acid.
A DFT Study of the Domino Inter [4 + 2]/Intra [3 + 2] Cycloaddition Reactions of Nitroalkenes with Enol Ethers
2000
The molecular mechanism of the domino inter [4 + 2]/intra [3 + 2] cycloaddition reactions of nitroalkenes with enol ethers to give nitroso acetal adducts has been characterized using density functional theory methods with the B3LYP functional and the 6-31G* basis set. The presence of Lewis acid catalyst and solvent effects has been taken into account to model the experimental environment. These domino processes comprise two consecutive cycloaddition reactions: the first one is an intermolecular [4 + 2] cycloaddition of the enol ether to the nitroalkene to give a nitronate intermediate, which then affords the final nitroso acetal adduct through an intramolecular [3 + 2] cycloaddition reacti…
ChemInform Abstract: (S)-Proline Benzyl Ester as Chiral Auxiliary in Lewis Acid-Catalyzed Asymmetric Diels-Alder Reactions.
1989
Asymmetric Diels-Alder reaction of cyclopentadiene (I) with (S)-proline benzyl ester (II) yields a mixture of the diastereomeric cycloadducts (R)-(III) and (S)-(IV).
Separation of amino acid enantiomers using supported liquid membrane extraction with chiral phosphates and phosphonates
1999
A series of dialkyl and monoalkyl phosphates, phosphites and phosphinates based on (−)-menthol and (−)-nopol were synthesized and used as carriers for transport of aromatic amino acids through supported liquid membranes. Although all the compounds were found to be effective carriers (with transport rate dependent on their structure) the enantioselectivity of the process obtained was low or moderate. Aromatic amino acids were enantioselectively transported through supported liquid membranes containing chiral phosphates, phosphites and phosphinates as carriers. Download full-size image