Enhancing the enantioselectivity of lipase in transesterification by substrate matching: an enzyme memory based approach

The substrate matching strategy is described as a new approach for effectively enhancing the lipase enantioselectivity in organic solvent. In the lipase-catalyzed transesterifications of 3a-c, higher enantioselectivities have been achieved using 1a-c, respectively, as the structurally matched acyl donors.     

Microchip-based one step DNA extraction and real-time PCR in one chamber for rapid pathogen identification

Optimal detection of a pathogen present in biological samples depends on the ability to extract DNA molecules rapidly and efficiently. In this paper, we report a novel method for efficient DNA extraction and subsequent real-time detection in a single microchip by combining laser irradiation and magnetic beads. By using a 808 nm laser and carboxyl-terminated magnetic beads, we demonstrate that a single pulse of 40 seconds lysed pathogens including E. coli and Gram-positive bacterial cells as well as the hepatitis B virus mixed with human serum. We further demonstrate that the real-time pathogen detection was performed with pre-mixed PCR reagents in a real-time PCR machine using the same microchip, after laser irradiation in a hand-held device equipped with a small laser diode. These results suggest that the new sample preparation method is well suited to be integrated into lab-on-a-chip application of the pathogen detection system.     

Analysis of an ancient bronze statue by external beam pixe

A quantitative analysis of an ancient Buddha statue was performed by external beam Proton Induced X-ray Emission for the purpose of identifying its originality. It is shown how the PIXE method can be applied for archeological study. The elemental composition of the statue is compared with that of several samples with definite ages. The experiment was performed by extracting 2.4 MeV proton beam through a 2 mm diameter collimator and 7.6 m kapton foil to the He atmosphere. X-rays were measured by a Si(Li) detector. The analysed elements were Fe, Cu, Ag, Au and Hg for gold coating and Fe, Ni, Cu, Zn, As, Ag, Sn, Au, Pb and Bi for bronze body.     

Two new phenolic amides from the seeds of Pharbitis nil

Two new phenolic amides, pharnilatins A (1) and B (2), were isolated from the seeds of Pharbitis nil. These new compounds possess a p-coumaroyl unit with a structurally unique side chain, (2S,3S)-2,3-dihydroxyputrescine. The chemical structures and absolute stereochemistries of the new compounds were determined on the basis of spectroscopic analyses including 1D- and 2D-NMR experiments and chemical reactions. Compounds 1 and 2 exhibited cytotoxicity against A549, SK-OV-3, SK-MEL-2, and HCT-15 human tumor cells. However, none of the compounds inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-activated microglia cells.     

Effect of the residual silanol group protection on the liquid chromatographic resolution of racemic primary amino compounds on a chiral stationary phase based on optically active (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6

A liquid chromatographic chiral stationary phase (CSP) based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6, which has been utilized in the resolution of alpha-amino acids, amines and amino alcohols, was treated with excess of n-octyltriethoxysilane to prepare a new improved CSP. The residual silanol groups of the original CSP were protected by n-octyl groups in the new CSP. The chiral recognition ability of the new CSP was superior to that of the original CSP in the resolution of alpha-amino acids, amines and amino alcohols. Retention factors (k1) for the resolution of alpha-amino acids were lower on the new CSP than on the original CSP while those for the resolution of amines and amino alcohols were higher on the new CSP than on the original CSP. The improved chiral recognition ability of the new CSP and the retention behaviors of the two enantiomers on the new CSP have been rationalized to stem from the removal of the non-enantioselective interactions between the analytes and the residual silanol groups of the original CSP and the improved lipophilicity of the CSP.     

Post-harvest HPLC determination of chlorfluazuron residues in pears treated with different programs

The present study was conducted to monitor the level of chlorfluazuron residues in pear samples in order to assess the risk posed by the presence of such residues to the consumer. Chlorfluazuron was sprayed onto pear trees at the recommended dose rate at two different times at 30 and 21 days prior to harvesting in one treatment, at 21 and 14 days prior to harvesting in another treatment, and three times at 30, 21 and 14 days prior to harvesting in a third treatment. Chlorfluazuron residues were extracted with acetonitrile and partitioned into ethyl acetate. The residue determination was performed on an Apollo C(18) column using HPLC with a UV detection of 254 nm following the clean-up of the extract by open column chromatography with Florisil. The versatility of this method was evidenced by its good linearity (>0.995) in the concentration range between 0.2 and 10 microg/mL. The majority of the mean recoveries at two different fortification levels, 0.05 and 0.25 ppm, ranged from 84.9 +/- 3.2 to 94.3 +/- 10.6, and the repeatability (as the relative standard deviation) from three repetitive determinations of recovery was between 3.8 and 11%. The calculated limit of detection (LOD) was 0.008 ppm and the limit of quantitation was 0.03 ppm. Trace amounts of chlorfluazuron were detectable when it was applied onto the pear trees at two or three times prior to harvesting; however, the levels of chlorfluazuron were not quantified. The excellent sensitivity and selectivity of this method allowed for quantitation and identification at low levels with a run time of less than 12 min. Chlorfluazuron can be used safely to protect pears when sprayed two or three times at 14 days prior to harvesting.