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31.
Stará IG Alexandrová Z Teplý F Sehnal P Starý I Saman D Budesínský M Cvacka J 《Organic letters》2005,7(13):2547-2550
[reaction: see text] A new approach to nonracemic [7]helicene-like molecules has been developed. Stereoselective Co(I)-mediated [2 + 2 + 2] cycloisomerization of aromatic triynes containing an asymmetric carbon atom produces [7]helicene-like scaffolds in diastereomeric ratios up to 100:0. This central-to-helical chirality transfer can be controlled by the absolute configuration at the asymmetric center and by the presence of carbon substituents. 相似文献
32.
Lhiaubet-Vallet V Sarabia Z Boscá F Miranda MA 《Journal of the American Chemical Society》2004,126(31):9538-9539
A remarkable stereodifferentiation has been observed in the interaction between the excited triplet state of carprofen (CP) and human serum albumin (HSA). Time-resolved measurements using laser flash photolysis reveal the presence of two components with different lifetimes in triplet decay. This is explained by complexation of CP to the two possible HSA binding sites. The shorter-lived components are ascribed to the CP/HSA complexes in site I, where stereodifferentiation is more important (tauR/tauS ca. 4). This is correlated with formation of a dehalogenated photoproduct upon steady-state photolysis. 相似文献
33.
The methodology and instrumentation for fast denaturing electrophoresis in short capillaries was developed and exemplified by detection of short tandem repeat polymorphism in the endothelin 1 gene. The resolution of two nucleotides, which is required for the detection of a dinucleotide repeat polymorphism, was achieved in a capillary of an effective length of 2.5 cm at a temperature of 600C and an electric field strength of 600 V/cm in 42 s. Thus, the use of denaturing electrophoresis in short capillaries with laser-induced fluorescence detection resulted in a reduction of analysis time by a factor of 200 when compared to the conventional slab gel electrophoresis. The developed methodology and instrumentation is advantageous for an implementation in clinical diagnostics and genetic population screening where fast analytical instrumentation amenable to automation is of paramount importance. 相似文献
34.
EPR study has shown that the anticancer agent vanadocene dichloride (Cp2VCl2) interacts with carbonate contained in physiological solutions. Chelate complex Cp2VO2CO (|A(iso)(51V)| = 175.1 MHz, g(iso) = 1.9861) is the only paramagnetic species formed in the range about the physiological pH (5.5-11.0). The super-hyperfine coupling (|a(iso)(13C)| = 24.1 MHz) was evidenced at measurements using 13C labelled carbonate. The structure of carbonate complex was validated by comparison of observed and theoretical calculated HFC tensors (at the density functional level of theory). 相似文献
35.
Muchová L Jirsa M Kuroki M Dudková L Benes MJ Marecek Z Smíd F 《Biomedical chromatography : BMC》2001,15(6):418-422
Carcinoembryonic cell adhesion molecule 1 (CEACAM1) is a human membrane glycoprotein belonging to the carcinoembryonic antigen (CEA) family and to the immunoglobulin superfamily. It is expressed in apical membranes of many epithelial cells in gastrointestinal and urogenital tract and also in granulocytes and lymphocytes, and its biological effect in human tissues has recently been discussed in literature. The purpose of this study was to isolate CEACAM1 glycoprotein from bile and characterize its purity and recovery which has not been described before. Affinity chromatography of CEACAM1 on hydrazide-activated cellulose with immobilized monoclonal anti-CEA F34-187 antibody is described. The immunoglobulin carbohydrate moiety was oxidized by periodate and then bound to hydrazide-activated matrix. Crude protein fraction from bile was applied on the affinity column and after extensive washing of non-bound proteins CEACAM1 was eluted with 6 M guanidine-HCl. A single immunopositive 85 kDa band was detected on Western blots with anti-CEA antibody after SDS-PAGE. We found out that CEACAM1 was not stainable with any common method of protein staining and the only non-specific method which could detect the 85 kDa band was a lectin staining. 相似文献
36.
Mineralization procedures for arsenic and selenium analysis are usually limited to wet digestion methods owing to high volatility of these analytes. On the other hand, variable amounts of silicon in some types of samples imply elaborated mineralization procedures to liberate analytes which may be retained in an insoluble residue. Consequently, methods for such material generally include an hydrofluoric step followed by an evaporation to dryness. This type of mineralization is most easily accomplished using a dry ashing procedure. For plant analysis, a well validated and readily applicable dry ashing method is used for a long time in several laboratories but up today one could suppose that As and Se determinations cannot be performed after such a type of mineralization. Surprisingly, it has been observed that for plant samples these analytes are detected even after a calcination at 450 degrees C. The general usefulness of a dry ashing method for analysis of all other analytes (main, minor and trace elements) incitates us to also verify As and Se recoveries. Results obtained in this work indicate clearly that plants of terrestrial origin may be mineralized using dry ashing procedure without As and Se losses. This statement was confirmed by analyses of several reference terrestrial plant samples (RMs) and laboratory control samples. Another confirmation was given by the direct graphite furnace analysis of the same plant samples but in slurried form (SS-ETAAS). As a direct consequence, As and Se analysis in terrestrial plants no more necessitates a separate preparation methodology. On the other hand, significant losses of As and Se were observed for aquatic plants, e.g. algaes. For the analysis of this type of samples, a separate wet digestion procedure remains unavoidable if the determination of As and Se has to be considered. Also some preparation procedures were tested for As and Se-analysis of soil and sediment reference samples. In these cases the wet digestion with a mixture of nitric, perchloric and hydrofluoric acids seems to remain the best alternative. 相似文献
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