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排序方式: 共有226条查询结果,搜索用时 281 毫秒
91.
Riaz Ur Rehman Muhammad Zia Bilal Haider Abbasi Gang Lu Muhammad Fayyaz Chaudhary 《Applied biochemistry and biotechnology》2014,173(4):968-979
Plants exposed to salt stress undergo biochemical and morphological changes even at cellular level. Such changes also include activation of antioxidant enzymes to scavenge reactive oxygen species, while morphological changes are determined as deformation of membranes and organelles. Present investigation substantiates this phenomenon for Caralluma tuberculata calli when exposed to NaCl stress at different concentrations. Elevated levels of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) in NaCl-stressed calli dwindled upon application of non-enzymatic antioxidants; ascorbic acid (AA) and salicylic acid (SA). Many fold increased enzymes concentrations trimmed down even below as present in the control calli. Electron microscopic images accentuated several cellular changes upon NaCl stress such as plasmolysed plasma membrane, disruption of nuclear membrane, increased numbers of nucleoli, alteration in shape and lamellar membrane system in plastid, and increased number of plastoglobuli. The cells retrieved their normal structure upon exposure to non-enzymatic antioxidants. The results of the present experiments conclude that NaCl aggravate oxidative molecules that eventually alleviate antioxidant enzymatic system. Furthermore, the salt stress knocked down by applying ascorbic acid and salicylic acid manifested by normal enzyme level and restoration of cellular structure. 相似文献
92.
Stereoselective synthesis of (1S,3R,5R,7S)-(+)-sordidin, the natural male-produced aggregation pheromone of the banana weevil Cosmopolites sordidus (Germar) starting from 5-benzyloxy-(2E)-pentene-1-ol is described. The key transformations employed in the synthesis are Sharpless asymmetric epoxidation, Ueno-Stork cyclization, and Jacobsen kinetic resolution. 相似文献
93.
A chemiluminescence (CL) micro-flow system is presented for rapid determination of chemical oxygen demand (COD) in water at
room temperature. In this system, potassium dichromate is reduced to Cr3+ in 2 mol L−1 H2SO4 during the chemical oxidation of COD substances in the sample, and Cr3+ can be measured with the help of the luminol-H2O2 CL system. The polymethyl methacrylate micro-flow chip with discrete microdroplet sampling was used here. Effects on COD
determination (such as pH, concentrations, the channel length, and interference) were investigated. The linear range for COD
determination was 0.27–10 g L−1, and the detection limit was 100 mg L−1. The method was successfully applied to the determination of COD in wastewater samples. The data obtained with the present
method were in fairly good agreement with those obtained by the titrimetric method.
Correspondence: Zhujun Zhang, Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry
and Materials Science, Shaanxi Normal University, Xi’an 710062, P.R. China; Department of Chemistry, Institute of Analytical
Science, Southwest University, Beibei, Chongqing 400715, P.R. China 相似文献
94.
P. Čolović S. Szilner L. Corradi T. Mijatović G. Pollarolo A. Goasduff D. Montanari R. Chapman E. Fioretto A. Gadea F. Haas D. Jelavić Malenica N. Mărginean D. Mengoni M. Milin G. Montagnoli F. Scarlassara J. F. Smith N. Soić A. M. Stefanini C. A. Ur J. J. Valiente-Dobón 《The European Physical Journal A - Hadrons and Nuclei》2017,53(8):166
95.
Anton Kaufmann Patrick Butcher Kathryn Maden Mirjam Widmer Kevin Giles Diana Uría 《Rapid communications in mass spectrometry : RCM》2009,23(7):985-998
Multiple reaction monitoring (MRM) ratios as provided by tandem mass spectrometers are used to confirm positive residue findings (e.g. veterinary drugs or pesticides). The Commission Decision 2002/657/EEC defines tolerance levels for MRM ratios, which are intended to prevent the reporting of false positives. This paper reports findings where blank sample extracts have been spiked by a drug (difloxacin) and the corresponding measured MRM ratios significantly deviated from MRM ratios observed in matrix‐free solution. The observation was explained by the formation of two different [M+H]+ analyte ions within the electrospray ionization (ESI) interface. These two ions vary only by the site of analyte protonation. Since they are isobaric, they are equally transmitted through the first quadrupole, but are differently fragmented in the collision chamber. The existence of two isobaric ions was deduced by statistical data and the observation of a doubly charged analyte ion. It was hypothesized that the combined presence of [M+H]+ and [M+2H]2+ implies the existence of two different singly charged ion species differing only by the site of protonation. Low‐ and high‐energy interface‐induced fragmentation was performed on the samples. The surviving precursor ion population was mass selected and again fragmented in the collision chamber. Equal product ion spectra would be expected. However, very different product ion spectra were observed for the two interface regimes. This is consistent with the assumption that the two postulated isobaric precursor ions show different stability in the interface. Hence the abundance ratio among the two types of surviving precursor ions will shift and change the resulting product ion spectra. The existence of the postulated singly charged ions with multiple chargeable sites was finally confirmed by successful ion mobility separation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
96.
V. F. Ur’yash I. S. Gorlova N. V. Novoselova N. K. Kon’kova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(7):1257-1259
The energy (enthalpy) of the multiplication of lactobacilli on various nutrient media was measured on a DAK-1-1 differential
microcalorimeter. Cultivation of lactobacilli on the nutrient media studied was accompanied by a release of energy. The time
dependences of heat evolution were similar in shape to the curves of the growth of the microorganism population. The conclusion
was drawn that the quantity of the evolved energy depended on the type of the nutrient medium. 相似文献
97.
98.
99.
The Ammi majus seeds oil constituents of methyl ester derivatives of fatty acids were analyzed using Gas Chromatography coupled to mass spectrometer. The results obtained containing the saturated as well as unsaturated fatty acids of majus seeds oils. A total of 18 different components were identified and quantified. Methyl ester of linoleic acid was found in high concentration 9.00%, among the identified analytes of interest. In addition methyl ester of Oleic acid 5.60%, Palmitic acid 3.98% Linolenic acids 1.42% were found. Concentration of the rest of identified fatty acids analytes were less than 1%. Thus from the results it is apparent that due to the presence of high percentage of valuable analytes concentrations detected in the fatty acid of A. majus, has increased its importance for the consumption in the pharmaceuticals as well as its applications in the new formulations for various skin diseases to prevent and cure from different infections. 相似文献
100.
Osorio-Martínez CA Urías-Benavides A Gómez-Durán CF Bañuelos J Esnal I López Arbeloa I Peña-Cabrera E 《The Journal of organic chemistry》2012,77(12):5434-5438
The role of the amino group twisting ability in the BODIPY photophysics for nonsterically hindered and constrained molecular structures was studied. When a coplanar disposition of the amino and the BODIPY core is feasible, a hemicyanine-like delocalized π-system gives rise to novel blue and efficient BODIPY laser dyes. The key role of such rotamer is confirmed by newly synthesized derivatives where the amino and the BODIPY core are electronically decoupled by steric repulsions. 相似文献