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861.
Yu. N. Mitrasov E. A. Simakova I. I. Antonova O. V. Kondrat'eva V. G. Skvortsov 《Russian Journal of General Chemistry》2005,75(9):1386-1392
Reaction of derivatives of 1-methyl-2,2-dichlorocyclopropanecarboxylic acid with three- and four-coordinate phosphorus acids was studied. It was established that the nucleophilic substitution on the carbonyl carbon atom proceeds without cleavage of the three-membered ring and leads to new types of phosphorus-containing cyclopropanes. The products were found to enhance the germination energy and laboratory germination of cereal, legume, and vegetable seeds. 相似文献
862.
Cytochrome P-450 isozymes represent a critical component of nature’s spectrum of detoxification catalysts that could be exploited
for bioremediation. The ethanol-inducible human cytochrome P-450 2E1 serves as a model eukaryotic P-450 that complements the
bacterial P-450 cam in dehalogenation and detoxification of environmental pollutants. We explored the construction of novel
chimeric P-450s using cytochrome P-450 camC and 2E1 genes. For construction of chimera 1 (478 amino acids, 55.14 kDa), 145 amino acids from the N-terminus of P-450 2E1 protein
(493 amino acids, 56.84 kDa) were replaced with 130 amino acids from the N-terminus of P-450 camC protein (415 amino acids,
46.66 kDa). In chimera 2 (525 amino acids, 60.24 kDa) the strategy involves replacement of 28 amino acids in the C-terminus
of chimera 1 with 75 amino acids from the C-terminus of P-450 camC gene. Homology models of both the chimeric proteins were
developed using SWISS-MODEL based on the known crystal structure of cytochrome P-450 camC, BM-3, 1DT6A, and 2C17A. The models
indicated that the proposed heme-binding site was intact, which is inevitable for catalytic activity of cytochrome P-450s.
The expression of chimera 1 and 2 genes in Escherichia coli DH5α was evident from light-pink cell pellets, protein band in sodium dodecyl sulfate polyacrylamide gel electrophoresis,
and diagnostic carbon monoxide-difference spectra. Our studies show that strategies can be developed to exploit the natural
diversity of the P-450 superfamily to generate chimeric biocatalysts that would provide new templates amenable to directed
evolution. 相似文献
863.
864.
Bistable ferroelectric liquid crystal photoswitch triggered by a dithienylethene dopant 总被引:1,自引:0,他引:1
The spontaneous polarization (PS) of a ferroelectric liquid crystal is modulated reversibly by photocyclization of the dopant 1,2-bis[5'-(4' '-heptyloxyphenyl)-2'-methylthien-3'-yl]perfluorocyclopentene. The magnitude of PS photomodulation increases with dopant concentration up to 3 mol %, and the resulting photoswitch is fatigue resistant and bistable. To the best of our knowledge, this is the first example of a bistable ferroelectric liquid crystal photoswitch to be reported in the literature. 相似文献
865.
A. Küçükönder B. G. Durdu Ö. Sö?üt E. Büyükkasap 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(1):89-97
L X-ray fluorescence cross sections, and intensity ratios were measured for elements in the 70£Z£92 atomic range at the excitation energy 59.5 keV using a Si(Li) detector. Furthermore, L X-ray fluorescence cross sections
and intensity ratios were calculated for elements in the same range. The average L shell fluorescence yields were derived
using experimental L X-ray fluorescence cross sections and theoretical photoionization cross sections. The obtained results
were compared with other experimental and theoretical values.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
866.
R. A. Cherkasov V. I. Galkin N. G. Khusainova O. A. Mostovaya A. R. Garifzyanov G. Kh. Nuriazdanova N. S. Krasnova E. A. Berdnikov 《Russian Journal of Organic Chemistry》2005,41(10):1481-1484
New and previously known β-aminoethylphosphonates were synthesized by addition of primary and secondary amines to vinylphosphonates, and their IR and NMR spectra were examined. Diethyl 2-diethylaminoethylphosphonate and diethyl 2-morpholinoethylphosphonate were found to be stronger bases than the corresponding aminomethylphosphonates, but all these are weaker bases than their precursors, nonphosphorylated amines. Distribution constants of β-aminophosphonates between water and some organic solvents were determined and compared with those of their α-amino homologs. 相似文献
867.
R. K. Chernova L. M. Kozlova E. M. Spiridonova L. V. Burmistrova 《Journal of Analytical Chemistry》2006,61(8):760-766
The main analytical characteristics of the reaction of hexaoxacycloazochrom with lead were determined. A method for the sorption preconcentration of lead on the Thiopan 14 sorbent was proposed. Procedures were developed for the photometric determination of lead in natural waters, air, and soil at the level of the maximum permissible concentration. A new melange gel technique for preparing silicic acid xerogels modified with hexaoxacycloazochrom was developed for the test determination of lead in environmental samples at the level of the maximum permissible concentration. 相似文献
868.
P. Quevauviller M. Lachica E. Barahona A. Gomez G. Rauret A. Ure H. Muntau 《Fresenius' Journal of Analytical Chemistry》1998,360(5):505-511
Single extraction tests are commonly used to study the eco-toxicity and mobility of metals in soils, e.g. to assess the bioavailable
metal fraction (and thus to estimate the related phyto-toxic and nutritional deficiency effects) and the environmentally accessible
trace metals upon disposal of e.g. sediment on to a soil (e.g. contamination of ground waters). However, the lack of uniformity
in the different procedures does not allow the results to be compared worldwide nor the procedures to be validated. This paper
describes the interlaboratory testing of EDTA- and DTPA-extraction procedures for soil analysis, followed by the preparation
of a calcareous soil reference material (CRM 600), the homogeneity and stability studies and the analytical work performed
for the certification of the EDTA- and DTPA- extractable contents of some trace metals (following the standardized extraction
procedures).
Received: 21 May 1997 / Revised: 4 July 1997 / Accepted: 9 July 1997 相似文献
869.
S. J. Parry B. A. Bennett R. Benzing A. E. Lally 《Journal of Radioanalytical and Nuclear Chemistry》1997,219(2):191-196
Radiochemical techniques play an important role in nuclear waste management studies at the Centre for Analytical Research in the Environment. Current research includes the measurement of atmospheric emissions from a reprocessing plant, modelling of environmental pathways, and evaluation of reactor materials for the prediction of releases from ultimate disposal sites. A radiochemical separation procedure has been developed for129I, which has been applied to a study of emissions from the Sellafield nuclear reprocessing plant. Atmospheric emissions, rainfall, grass, milk and wild food are analysed to model the ultimate fate of129I. A new procedure has been developed for measuring sub-ppm concentrations of chlorine in archive steel samples as part of programme to produce an inventory of arisings of36Cl from nuclear power stations. The method has been extended to other reactor materials and this paper describes the application of the radiochemical method for Magnox alloys, mild steel and cast iron. 相似文献
870.
L. Ya. Zakharova S. B. Fedorov L. A. Kudryavtseva V. A. Bel'skii A. B. Mirgorodskaya B. E. Ivanov 《Russian Chemical Bulletin》1990,39(8):1555-1559
The hydrolysis of bis(chloromethyl)phosphonic acid p-nitroanilide has been studied in the pH range 6.86–13.0 and the effects of ionic surfactant micelles on this process have also been examined. The nature of the micellar effects of cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) on this reaction lead us to conclude that both the neutral and anionic forms of the substrate are reactive, and that in the range of pH > pKa hydrolysis of the ionic form of the anilide predominates, while at pH < pKa the reaction of the neutral form is predominant. The binding constants for both the neutral and anionic forms of bis(chloromethyl)phosphonic acid p-nitroanilide in micellar CTAB and SDS solutions have been determined using a kinetic method, as well as by measuring the changes in the acid-base properties of the substrate resulting from the influence of micelles.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1718–1722, August, 1990. 相似文献