Improved detectability with a polymer-based trapping device in rapid HPLC analysis for ultra-low levels of bisphenol A (BPA) in environmental samples.

A new high-performance liquid chromatography (HPLC) method has been developed to detect ultra-low concentrations of bisphenol-A (BPA) (below 1 ng/L (ppt)) using column switching electrochemical detection (ECD). The results were superior to those obtained from manual pretreatment procedure with membrane stationary phase. BPA is inherently ubiquitous in the environment, including tools and solvents used for its analysis; to obtain meaningful results, therefore, the concentration of the overall BPA contamination must be below the detection limit for BPA using the analytical system. Therefore, purified water for preparing the standard BPA solution must be filtered with a hydrophobic membrane to suppress BPA background levels of contamination. In addition, we investigated methods for effectively preserving environmental water containing BPA. The addition of a small amount of ethylenediaminetetraacetic acid (EDTA) provided good recovery even after overnight storage. By employing these precautionary measures and procedures to reduce BPA contamination from the analytical procedure, we could accurately determine l(-10) ppt of BPA in environmental water samples using a column switching HPLC system.     

Carbonyl allylations by 3-halopropenes or 2-propenyl mesylate with tin(IV) chloride and tetrabutylammonium iodide

2-Propenyl tin species, prepared from 3-halopropenes or 2-propenyl mesylate with tin(IV) chloride and tetrabutylammonium iodide in dichloromethane, causes nucleophilic addition to aldehydes to produce the corresponding homoallylic alcohols.     

Recursive Fermion System in Cuntz Algebra. I

Embeddings of the CAR (canonical anticommutation relations) algebra of fermions into the Cuntz algebra ?₂ (or ?_{2 d} more generally) are presented by using recursive constructions. As a typical example, an embedding of CAR onto the U(1)-invariant subalgebra of ?₂ is constructed explicitly. Generalizing this construction to the case of ?_{2 p} , an embedding of CAR onto the U(1)-invariant subalgebra of ?_{2 p} is obtained. Restricting a permutation representation of the Cuntz algebra, we obtain the Fock representation of CAR. We apply the results to embed the algebra of parafermions of order p into ?_{2 p} according to Green's ansatz. Received: 3 September 2001 / Accepted: 19 January 2002     

Purification and characterization of gamma-enolase from various mammals.

The gamma subunit of enolase (gamma-enolase) was purified from the brain tissues of cow, dog, goat, pig, rabbit, and rat. The purification was achieved in only three steps: ammonium sulfate-precipitation, DE 53 cellulose ion-exchange chromatography, and polyacrylamide gel electrophoresis (PAGE) in a preparative mode. The purification procedure was comparatively more simple than previously reported methods, and the yield of gamma-enolase was sufficient for subsequent structural and immunological analyses. In all mammals, the purified gamma-enolase migrated in sodium dodecyl sulfate-PAGE (SDS-PAGE) with a molecular mass of 46 kilodaltons (kDa), and the immunological cross-reactivity between those gamma-enolases was very strong. The structural homology of these gamma-enolases was examined by peptide mapping using cyanogen bromide cleavage and subsequent two-dimensional electrophoresis. The resulting peptide patterns were highly similar and in cow, dog, and goat, the patterns were almost identical. These results indicate that structural homology, that is, the species non-specificity of gamma-enolase, appears to be very high.     

Expression of a restricted fragment of staphylococcal tetracycline resistance determinant as a fused product in Escherichia coli

Tetracycline resistance (TcR) plasmid pNS1, a deletion derivative constructed from staphylococcal plasmid pTP5, carries a tet determinant which specifies a TcR protein (TET) with a molecular weight of 50 kilodaltons (kDa). In order to express the pNS1-encoded TET as a fused product, a 0.8 kilobase pairs fragment containing 57.1% of tet determinant was inserted into a chloramphenicol resistance determinant. From the nucleotide sequence, it is deduced that the fusion protein (designated CAT'-TET') is a 53 kDa protein composed of 472 amino acids in which the 199 and 262 amino acids are derived from CAT and TET, respectively. Although the molecular weight of CAT'-TET' obtained from the result of sodium dodecyl sulfate polyacrylamide gel electrophoresis (42 kDa) was not in agreement with its predicted weight (53 kDa), the ratio of TET' segment to the fusion protein (22 kDa/42 kDa) corresponded almost exactly to that deduced from the nucleotide sequence (29 kDa/53 kDa). The expression of CAT'-TET' in Escherichia coli caused a rapid decrease in growth rate and in the number of viable cells. This result is thought to be due to the toxic effect of CAT'-TET' on the cell membrane.     

Improvement of Dispersion and Release Properties of Nifedipine in Suppositories by Complexation with 2-Hydroxypropyl-β-cyclodextrin

Geometries, electronic properties and NMR-shielding of cucurbit[5]uril, decamethylcucurbit[5]uril, cucurbit[6]uril, cucurbit[7]uril, and cucurbit[8]uril are investigated with DFT calculations. All molecules are highly symmetrical with a distinct geometric flexibility. In addition with a characteristic partial charge distribution these findings account for their chemical complex building ability.     

HeII(304Å) photoelectron spectrum of N2O4

The 304 Å HeII photoelectron (PE) spectrum of a mixture of NO₂ and N₂O₄ in the gaseous phase has been measured in the region up to 29 eV. By subtracting the HeII spectrum of NO₂ from the mixed spectrum, the HeII spectrum due to N₂O₄ has been deduced, indicating that there are three new PE bands in the region 20—29 eV. Relative band intensities have also been obtained from the HeII of N₂O₄ below 16 eV, corrected for electron collecting efficiency.     

Regioselective 2 A -2 D -Disulfonylations of Cyclodextrins for Practical Bifunctionalization on the Secondary Hydroxyl Face

A useful technique to bifunctionalize the secondary hydroxyl faces of cyclodextrins is described. Regioselective2^A,2^D-disulfonylations ofcyclodextrins were achieved by reacting cyclodextrins with a combinationof a novel disulfonyl imidazole reagent and molecular sieves inN,N-dimethylformamide. The resulting disulfonates were convertedto 2^A,3^A,2^D,3^D-dimannoepoxy-cyclodextrins and3^A,3^D-diamino-3^A,3^D-dideoxy-(2^AS,3^AS),(2^DS,3^DS)-cyclodextrins, which contain twofunctional groups on the periphery of the molecules.     

Construction of nitrogen-heterocyclic compounds through zirconium mediated intramolecular alkene-carbonyl coupling reaction of N-(o-alkenylaryl)carbamate derivatives

Intramolecular alkene-carbonyl coupling reaction of N-benzyl-N-(o-alkenylaryl)carbamate derivative derived from o-aminostyrene, o-(aminomethyl)styrene and o-aminoallylbenzene smoothly proceeded by treating with zirconocene-butene complex to give the corresponding lactam derivative.     

Ni-catalyzed alkylative dimerization of vinyl grignard reagents using alkyl fluorides

Alkyl halides underwent unique cross-coupling reaction with vinylmagnesium chloride in the presence of Ni catalyst to give 2-alkyl-3-butenyl Grignard reagent (1) in high yields. This reaction proceeded efficiently at 25 degrees C in THF using primary and secondary alkyl fluorides. On the other hand, PhCH=CHMgBr gave double alkylative vinyl coupling product 4 in good yield as the sole coupling product. Alkyl fluorides react as the most suitable alkylating reagent in comparison to the corresponding chlorides, bromides, and iodides.