نتایج جستجو برای: diethyl phosphate
تعداد نتایج: 109251 فیلتر نتایج به سال:
Chemical modification of amino acid residues with phenylglyoxal, N-ethylmaleimide and diethyl pyrocarbonate indicated that at least one residue each of arginine, cysteine and histidine were essential for the activity of sheep liver serine hydroxymethyltransferase. The second-order rate constants for inactivation were calculated to be 0.016 mM-1 X min-1 for phenylglyoxal, 0.52 mM-1 X min-1 for N...
Copper-catalysed asymmetric allylic alkylation of alkylzirconocenes to racemic 3,6-dihydro-2H-pyrans
Asymmetric allylic alkylation is a powerful reaction that allows the enantioselective formation of C-C bonds. Here we describe the asymmetric alkylation of alkylzirconium species to racemic 3,6-dihydro-2H-pyrans. Two systems were examined: 3-chloro-3,6-dihydro-2H-pyran using linear optimization (45-93% ee, up to 33% yield, 5 examples) and 3,6-dihydro-2H-pyran-3-yl diethyl phosphate with the ass...
The alkynyl phosphate ester, 1-hexynyl diethyl phosphate (I), is a mechanism-based inhibitor of phosphotriesterase. It has been previously determined that a histidine residue in the wild-type phosphotriesterase is covalently modified by this compound. In order to identify which of the seven histidine residues in the native enzyme are required for inactivation, the kinetic properties of phosphot...
Organophosphorus insecticides and nerve agents irreversibly inhibit serine hydrolase superfamily enzymes. One enzyme of this superfamily, the industrially important (for β-lactam antibiotic synthesis) AXE/CAH (acetyl xylan esterase/cephalosporin acetyl hydrolase) from the biotechnologically valuable organism Bacillus pumilus, exhibits low sensitivity to the organophosphate paraoxon (diethyl-p-n...
Mononuclear complexes between Zn(2+) and the following four macrocycles were prepared: 1,4,7,10-tetraazacyclododecane (1), 1-oxa-4,7,10-triazacyclododecane (2), 1,5,9-triazacyclododecane (3) and 1-hydroxyethyl-1,4,7-triazacyclononane (4). The pH rate profiles of values of the observed second-order rate constant log (k(Zn))(app) for Zn(X)(OH(2))-catalyzed cleavage (X = 1, 2, 3 and 4) of 2-hydrox...
BACKGROUND Organophosphorous (OP) pesticides are associated with reduced fetal growth in animals, but human studies are inconsistent. OBJECTIVES We pooled data from four cohorts to examine associations of prenatal OP exposure with birth weight (n = 1,169), length (n = 1,152), and head circumference (n = 1,143). METHODS Data were from the CHAMACOS, HOME, Columbia, and Mount Sinai birth cohor...
The reaction mechanism for the phosphotriesterase from Pseudomonas diminuta has been examined. When paraoxon (diethyl 4-nitrophenyl phosphate) is hydrolyzed by this enzyme in oxygen18-labeled water, the oxygen-18 label is found exclusively in the diethyl phosphate product. The absolute configurations for the (+) and (-) enantiomers of 0-ethyl phenylphosphonothioic acid have been determined by X...
The purification of the enzyme hydrolysing diethyl p-nitrophenyl phosphate (paraoxon) in sheep serum
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