Alternative pathways for phosphonate metabolism in thermophilic cyanobacteria from microbial mats. (57/125)

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Identification of novel methane-, ethane-, and propane-oxidizing bacteria at marine hydrocarbon seeps by stable isotope probing. (58/125)

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Vanadium nitrogenase reduces CO. (59/125)

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Characterization of isolated nitrogenase FeVco. (60/125)

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Determination of thiamphenicol in honey by dispersive liquid-liquid microextraction with high-performance liquid chromatography. (61/125)

Dispersive liquid-liquid microextraction (DLLME) coupled with high-performance liquid chromatography-variable wavelength detector (HPLC-VWD) was developed for extraction and determination of thiamphenicol (THA) in honey. A mixture of extraction solvent (30 microL 1,1,2,2-tetrachloroethane) and dispersive solvent (1.0 mL of acetonitrile) was rapidly injected into 5.00 mL sample solution for the formation of cloudy solution. The analyte in the sample was extracted into the fine droplets of C(2)H(2)Cl(4). After extraction, phase separation was performed by centrifugation, and the enriched analyte in the sedimented phase was determined by HPLC-VWD. Some important parameters, such as the kind and volume of extraction solvent and dispersive solvent, extraction time, sample solution pH, sample volume, and salt effect, were investigated and optimized. Under the optimum extraction condition, the method yielded a linear calibration curve in the concentration range from 3 to 2000 microg/kg for target analyte. The enrichment factors for THA was 87.9, and the limit of detection (S/N = 3) was 0.1 microg/kg. The relative standard deviation for the extraction of 10 microg/kg of THA was 6.2% (n = 6). The main advantages of DLLME-HPLC method are simplicity of operation, rapidity, low cost, high enrichment factor, high recovery, good repeatability, and extraction solvent volume at the microL level. Honey samples were successfully analyzed using the proposed method.  (+info)

Propane respiration jump-starts microbial response to a deep oil spill. (62/125)

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Isolation of rotational isomers and developments derived therefrom. (63/125)

Isolation of rotational isomer models of ethane-type molecules is described. We could experimentally prove that, if rotational isomers whose molecular shape was chiral, the molecule could be optically active, even though it did not carry an asymmetric carbon atom. As an extension, other types of stereochemically fundamental and optically active molecules were isolated and their absolute stereochemistry was determined. One example is the model of meso-tartaric acid, for which optical inactivity had been attributed to internal compensation but is now explained as follows. On dissolution of meso-tartaric acid in a solvent, the molecule gives two kinds of conformers, one of which is a C(i) molecule and the other is a C(1) molecule. Although the latter is intrinsically optically active, the optical activity is cancelled by its enantiomer. The theory of internal compensation is recommended to be abandoned. As an extension to another area, some reactions of conformers are also discussed.  (+info)

Rapid analysis of dissolved methane, ethylene, acetylene and ethane using partition coefficients and headspace-gas chromatography. (64/125)

Analysis of dissolved methane, ethylene, acetylene, and ethane in water is crucial in evaluating anaerobic activity and investigating the sources of hydrocarbon contamination in aquatic environments. A rapid chromatographic method based on phase equilibrium between water and its headspace is developed for these analytes. The new method requires minimal sample preparation and no special apparatus except those associated with gas chromatography. Instead of Henry's Law used in similar previous studies, partition coefficients are used for the first time to calculate concentrations of dissolved hydrocarbon gases, which considerably simplifies the calculation involved. Partition coefficients are determined to be 128, 27.9, 1.28, and 96.3 at 30 degrees C for methane, ethylene, acetylene, and ethane, respectively. It was discovered that the volume ratio of gas-to-liquid phase is critical to the accuracy of the measurements. The method performance can be readily improved by reducing the volume ratio of the two phases. Method validation shows less than 6% variation in accuracy and precision except at low levels of methane where interferences occur in ambient air. Method detection limits are determined to be in the low ng/L range for all analytes. The performance of the method is further tested using environmental samples collected from various sites in Nova Scotia.  (+info)