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991.
Urszula?KotowskaEmail author Katarzyna?Bieńczyk 《Central European Journal of Chemistry》2013,11(10):1634-1643
Direct immersion solid-phase microextraction has been optimized and applied to the simultaneous determination of the neutral and basic pharmaceuticals: caffeine, carbamazepine, clomipramine, chlorprothixene and clotrimazole at low concentrations in municipal wastewater. Two absorption type stationary phases: polydimethylsiloxane (PDMS) and polyacrylate (PA) have been found to be most effective for extraction of target analytes. The separation and detection were carried out by gas chromatograph coupled with mass spectrometer working in the selected ion monitoring mode. The method was validated for linearity, detection and quantitation limits, selectivity and precision. The average correlation coefficient of the calibration curves was 0.9933. The LOD values in influent and effluent wastewater were in the range of 10–145 ng L?1 and 4–111 ng L?1, respectively, which were a bit higher than those in the deionized water due to matrix effect. The high values of distribution coefficient (K fs ) in PDMS/water and PA/water systems (log K fs between 3.05 and 4.23) indicates the very high applicability of these stationary phases for determination of carbamazepine, clomipramine, chlorprothixene and clotrimazole in water samples.
相似文献
992.
Background
BTBD10 binds to Akt and protein phosphatase 2A (PP2A) and inhibits the PP2A-mediated dephosphorylation of Akt, thereby keeping Akt activated. Previous studies have suggested that BTBD10 plays an important role in preventing motor neuronal death and accelerating the growth of pancreatic beta cells. Because levels of BTBD10 expression are much lower in many non-nervous tissues than nervous tissues, there may be a relative of BTBD10 that has BTBD10-like function in non-neuronal cells.Results
A 419-amino-acid BTBD10-like protein, named KCTD20 (potassium channel tetramerization protein domain containing 20), was to found to bind to all Akt isoforms and PP2A. Overexpression of KCTD20 increased Akt phosphorylation at Thr308, as BTBD10 did, which suggests that KCTD20 as well as BTBD10 positively regulates the function of Akt. KCTD20 was ubiquitously expressed in non-nervous as well as nervous tissues.Conclusions
KCTD20 is a positive regulator of Akt and may play an important role in regulating the death and growth of some non-nervous and nervous cells.993.
Monique?SabatyEmail author Sandrine?Grosse Geraldine?Adryanczyk Séverine?Boiry Frédéric?Biaso Pascal?Arnoux David?Pignol 《BMC biochemistry》2013,14(1):28
Background
YedY, a molybdoenzyme belonging to the sulfite oxidase family, is found in most Gram-negative bacteria. It contains a twin-arginine signal sequence that is cleaved after its translocation into the periplasm. Despite a weak reductase activity with substrates such as dimethyl sulfoxide or trimethylamine N-oxide, its natural substrate and its role in the cell remain unknown. Although sequence conservation of the YedY family displays a strictly conserved hydrophobic C-terminal residue, all known studies on Escherichia coli YedY have been performed with an enzyme containing a 6 histidine-tag at the C-terminus which could hamper enzyme activity.Results
In this study, we demonstrate that the tag fused to the C-terminus of Rhodobacter sphaeroides YedY is detrimental to the enzyme’s reductase activity and results in an eight-fold decrease in catalytic efficiency. Nonetheless this C-terminal tag does not influence the properties of the molybdenum active site, as assayed by EPR spectroscopy. When a cleavable His-tag was fused to the N-terminus of the mature enzyme in the absence of the signal sequence, YedY was expressed and folded with its cofactor. However, when the signal sequence was added upstream of the N-ter tag, the amount of enzyme produced was approximately ten-fold higher.Conclusion
Our study thus underscores the risk of using a C-terminus tagged enzyme while studying YedY, and presents an alternative strategy to express signal sequence-containing enzymes with an N-terminal tag. It brings new insights into molybdoenzyme maturation in R. sphaeroides showing that for some enzymes, maturation can occur in the absence of the signal sequence but that its presence is required for high expression of active enzyme.994.
Background
The regulation of lipid biosynthesis is essential in photosynthetic eukaryotic cells. This regulation occurs during the direct synthesis of fatty acids and triacylglycerols (TAGs), as well as during other controlling processes in the main carbon metabolic pathway.Results
In this study, the mRNA levels of Chlamydomonas citrate synthase (CrCIS) were found to decrease under nitrogen-limited conditions, which suggests suppressed gene expression. Gene silencing by RNA interference (RNAi) was conducted to determine whether CrCIS suppression affected the carbon flux in TAG biosynthesis. Results showed that the TAG level increased by 169.5%, whereas the CrCIS activities in the corresponding transgenic algae decreased by 16.7% to 37.7%. Moreover, the decrease in CrCIS expression led to the increased expression of TAG biosynthesis-related genes, such as acyl-CoA:diacylglycerol acyltransferase and phosphatidate phosphatase. Conversely, overexpression of CrCIS gene decreased the TAG level by 45% but increased CrCIS activity by 209% to 266% in transgenic algae.Conclusions
The regulation of CrCIS gene can indirectly control the lipid content of algal cells. Our findings propose that increasing oil by suppressing CrCIS expression in microalgae is feasible.995.
Tahir Altunbulduk Heinz Meier K?cker Wolfgang Frenzel 《Fresenius' Journal of Analytical Chemistry》1995,351(7):593-598
Detailed investigations have been reported on the application of a common procedure using bromate in nitric acid for the removal of the interference of sulfide in the direct potentiometric determination of chloride using silver-based ion selective electrodes in a flow injection system. It is shown that this procedure is not very efficient and carries a high risk of chloride underestimation. With increasing levels of sulfide the oxidation of chloride to elemental chlorine becomes progressively significant and under certain circumstances virtually no chloride is left irrespective of its initial concentration. Hydrogen peroxide in alkaline medium is proposed as a suitable alternative for the efficient removal of sulfide without any adverse effects on the potentiometric method. 相似文献
996.
Lj. Kolar-Ani? Dj. Misljenovi? S. Ani? G. Nicolis 《Reaction Kinetics and Catalysis Letters》1995,54(1):35-41
The reduction of iodate ion by hydrogen peroxide, originally postulated by Liebhafsky, is considered as a possible step in the kinetic model proposed by Kolar-Ani and G. Schmitz for the overall Bray-Liebhafsky oscillatory process. 相似文献
997.
?. ?upi? S. Anic A. Terlecki-Bari?evi? Lj. Kolar-Ani? 《Reaction Kinetics and Catalysis Letters》1995,54(1):43-49
Behavior of the Bray-Liebhafsky oscillatory reaction in the presence of acid-base polymers with and without ferric ions is analyzed. The influence of hydrogen ions on the overall reaction is shown. 相似文献
998.
Pedro Ca?ada Rudner José Manuel Cano Pavón Amparo García Torres Fuensanta Sánchez Rojas 《Fresenius' Journal of Analytical Chemistry》1995,352(6):615-617
An FI-ICP-AES method for the determination of trace levels of mercury in biological samples has been described, which is based on the extraction of the mercury complex with 1,5-bis (di-2-pyridyl)methylene thiocarbonohydrazide (DPTH) on-line into isobuthyl-methyl ketone (IBMK). The organic phase (containing the complex) has been mixed on-line with SnCl2 in N,N-dimethylformamide. Thus, mercury vapour can be generated directly from the organic phase and separated in a gas-liquid separation device. The detection limit for mercury is 4 ng/ml and the calibration curve is linear at least from 10 to 2500 ng/ml. The relative standard deviation for 10 replicate measurements is ±1% for 100 ng/ml of Hg(II). Results from the analysis of some certified biological reference materials are given. 相似文献
999.
M. Elena Mart��n M. Luz S��nchez Jos�� C. Corchado Aurora Mu?oz-Losa Ignacio Fdez. Galv��n Francisco J. Olivares del Valle Manuel A. Aguilar 《Theoretical chemistry accounts》2011,128(4-6):783-793
The possible influence of the solvent Stark effect (SSE) on the solvatochromic shift in electron transitions has been analyzed by using the ASEP/MD (averaged solvent electrostatic potential from molecular dynamics) method. With this purpose, four molecules, two polar (acrolein and formaldehyde) and two non-polar (p-difluorobenzene and trans-difluoroethene) have been studied in solvents of diverse polarity. Independently of the nature of the system we found that the contribution of SSE on the average value of the solvent shift or on the multipole moment values is negligible. In the case of centro-symmetric molecules, our results permit to discard the SSE as cause of the solvent shift found, which must be assigned to the electrostatic interaction of the solute quadrupole and higher multipoles with the solvent. As the SSE values provide also a measure of the errors introduced by the mean field approximation (MFA), these results indicate that MFA permits a very accurate determination of the solvent shift at the same time that it reduces drastically the computational cost. Finally, a new procedure suited to the ASEP/MD method has been presented that permits to estimate the inhomogeneous broadening of spectral bands, complementing the information provided by mean field theories. This procedure does not need additional quantum calculations and its computational cost is minimal. 相似文献
1000.
Zhi-Hong?Ma Xiao-Huan?Liu Zhan-Gang?Han Xue-Zhong?Zheng Jin?LinEmail author 《Transition Metal Chemistry》2011,36(2):207-210
Three diruthenium carbonyl complexes, namely (η
3:η
5-C5H4C(CH2)2)Ru2(CO)5 (1), (η
3:η
5-C5H4C(CHCH2)(C2H5))Ru2(CO)5 (2), and (η
1:η
5-C5H4C5H8)Ru2(CO)6 (3), were obtained from the reactions of C5H4C(Me)2, C5H4C(Et)2, and C5H4C(CH2)4, respectively, with Ru3(CO)12 in refluxing xylene. The complexes were characterized by elemental analysis, IR and 1H NMR spectra. Single-crystal X-ray diffraction analysis for complexes 1 and 2 revealed that the fulvene ligands bridge two ruthenium atoms in η
3:η
5 fashion. 相似文献