Evidence for albumin -Cu(I1)amino acid ternaxy complex. Can. J.Biochem. 46, 601 (I 968).Commercially obtained pure human serum albumin (HSA) was shown to contain molecular aggregates m d was significantly contaminated with CuOI). A solution of c o m e r d d HSA was fist passed through a Sephadex G-260 c o % u m to obtain pure monomeric HSA. The monomer of HSA was subsequently passed through CheIex-100 resin to free it from Cu(1I). AI1 Cu(I1)-binding studies were conducted with monomeric and copper-fm MSA. The first Cu(I1)-binding site on MSA appears to be stronger than the second and the subsequent binding sites. Sigmifieant mounts of L-histidine and L-themnine were bound to HSA when ChqIf) was added in the form of Cu(I1)amino acid complexes. In the absence of Cu(%I), free hist ti dine or L-threonine do not bind to HSA at pH 7.4. It is concluded that, in the presence of either L-histidine or L-threonine, ternary complex formation is involved both at the first and the subsequent binding sites for Cu(I1) on HSA. In view of this finding, it appears that the equilibrium between HSA-CuOI) and CuQI)a d n o acid complex is mediated through a ternary complex HSA -Cu(H%)amino acid.
A method has been developed for introducing a variety of substituents into the position α to the nitrogen atom of dibenzylamine. Treatment of either the nitroso or the benzoyl derivative of dibenzylamine with lithium diisopropylamide generates a carbanion which reacts with alkyl halides or carbonyl compounds producing α-substitution products in yields of 66–99%. The method also gives good yields of derivatives of N-phenyl-N′-nitroso-piperazine. Attempts to form the carbanion of N-benzoylpiperidine failed.
A supercritical fluid extraction (SFE) procedure is described to isolate fluazifop-P-butyl and its major metabolite, fluazifop-P acid, directly from onions without any further cleanup procedures. A sample of onions is homogenized and freeze-dried. The dry sample is added to a SFE extraction vessel between two layers of silanized glass wool to prevent the clogging of the frits by fine particles in the sample. A modifier solvent (1 mL of methanol) is added with a pipet directly onto the sample, which is then extracted with supercritical fluid (SF) carbon dioxide at 80 eC and 400 atm for 10-min static followed by 60-min dynamic modes. The extract is trapped in three culture tubes connected in series, each containing methanol (3 mL). The methanol solutions are combined, evaporated, and analyzed by high-performance liquid chromatography (HPLC) with an ultraviolet (UV) detector. Alternately, the same extract may also be methylated and analyzed by a gas chromatograph (GC) with a mass selective detector (MSD). Using HPLC/UV, the average recoveries of fluazifop-P acid and the butyl ester at the fortification range 0.6-6.0 ppm are 94.4-78.3 % and 92.8-77.8%, respectively, with a limit of detection (LOD) of 0.2 ppm. When the extract is methylated and determined by GC/MSD, the average recoveries at fortification range 0.06-0.6 ppm are 89.1-101.2% for the methyl ester and 96.9-100.6% for the butyl ester with a LOD of 0.02 ppm for both analytes.
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