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991.
L. A. Srybnaya Z. Tulyabaev A. A. Sadykov D. N. Dalimov 《Chemistry of Natural Compounds》1990,26(3):347-348
A. S. Sadykov Institute of Bioorganic Chemistry, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 413–415,
May–June, 1990. 相似文献
992.
Ayorinde FO Bezabeh DZ Delves IG 《Rapid communications in mass spectrometry : RCM》2003,17(15):1735-1742
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used for the simultaneous detection of sugars, ascorbic acid, citric acid, sodium and/or potassium benzoate in non-alcoholic beverages, with meso-tetrakis(pentafluorophenyl)porphyrin (MW 974) as a matrix. Using potassium hydroxide as dopant, fructose/glucose was detected as the potassiated molecule at m/z 219, whereas potassiated sucrose, [Sucrose. K](+), was detected at m/z 381. Using sodium hydroxide as dopant, the fructose and sucrose ions were detected at m/z 203 and 365, respectively. Citric acid generated multiple ions at m/z 269, 307, and 345, which were assigned to [Citricbond;H+2K](+), [Citricbond;2H+3K](+), and [Citricbond;3H+4K](+), respectively. However, a stored methanolic solution of citric acid produced additional ions at m/z 283, 297, and 321, which were attributed to [Citricbond;2H+CH(3)+2K](+), [Citricbond;3H+2CH(3)+2K](+), and [Citricbond;3H+CH(3)+3K](+), respectively, due to esterification that took place during storage. The limits of detection in water were: ascorbic acid, 0.30 wt%; citric acid, 0.5 wt%; and sodium benzoate, 0.001 wt%. In the beverage formulations, the limits of detection were: ascorbic acid 0.3 wt%, citric acid 0.3 wt%, and sodium benzoate 0.02 wt%. Spiking a water or beverage solution that contained ascorbic and/or citric acid with less than 0.6 wt% of tartaric acid lowered the detection limits of ascorbic and citric acids to 0.2 wt%. This study demonstrates the potential for using MALDI-TOFMS in the quality control analyses of non-alcoholic beverages, particularly with regard to the detection of low molecular weight organic acids in commercial beverage formulations. 相似文献
993.
Liu Y Liu C Zhang Z Wang C 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2001,57(1):35-39
The composite particles of Ag-TiO2 both in a nanocrystal form was prepared by photoreduction of AgNO3 in the rutile colloidal solution. The surface plasmon absorption (SPA) band of the silver clusters supported on the TiO2 nanocrystal was red shift, and a strong surface enhanced Raman scattering (SERS) effect for the composite particles of Ag-nanocrystalline TiO2 was observed. The SERS effect is relating to the red shift phenomenon of SPA band, which could be explained by induced-resonance effect. 相似文献
994.
G F Xie S L Li Z Z Wanc 《Science in China. Series B, Chemistry, life sciences & earth sciences》1992,35(4):429-436
The effects of reduction by DTT, oxidation by DTNB and treatment with NEM on the thiol contents and insulin binding to its receptor in mice liver membranes were studied. Reduction with DTT leads to a parallel increase in the thiol content and the specific binding of insulin to the membrane. Scatchard analysis of the results shows little change in the number of binding sites but a twofold increase of the binding constant. Washing the membrane with bound insulin by a DTT containing buffer results in a more marked increase in the release of bound insulin than washing with buffer alone, suggesting that part of the insulin is bound to its receptor by covalent disulfide linkages through a thiol-disulfide exchange reaction and reduction with DTT leads to a marked increase in this "disulfide-linked" insulin. Treatment with DTNB or NEM of the DTT-reduced membrane seems to reverse the effect of DTT reduction, although the reaction of the untreated membrane with DTNB or NEM had little or no effect on the specific binding of insulin. It is suggested that initially, part of the thiols responsible for the exchange reaction may not be available for reaction with DTNB and reduction with DTT generates further thiols leading to increased specific binding in general and increased insulin binding to the receptor through covalent disulfide linkages in particular. 相似文献
995.
The modification of a Ni-Cr oxide catalyst during reduction was studied by IR spectroscopy of adsorbed CO and NH3 probe molecules. It was determined that in the starting oxidized sample the nickel cations were in the form of oxide clusters distributed over the surface of chromium oxide. As a result of reduction, they were depleted in oxygen, and metal clusters were formed and enlarged. Effective oxidation, by water vapor, of part of the surface of the metallic-nickel clusters that formed during reduction was observed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2718–2725, December, 1991. 相似文献
996.
X-ray diffraction and spectral studies of 1-phenyl-3-methyl-4-(2′,4′-Dimethylphenylazo)-pyrazolone-5
L. G. Kuz'mina L. P. Grigor'eva Yu. T. Struchkov Z. I. Ezhkova B. E. Zaitsev V. A. Zaitseva P. P. Pron'kin 《Chemistry of Heterocyclic Compounds》1985,21(6):680-684
The molecular and crystal structures of 1-phenyl-3-methyl-4-(2,4-dimethyl-phenylazo) pyrazolone-5 were determined. In the crystal the molecule exists as the hydrazone tautomer. The pyrazole ring is planar, and the substituents are practically coplanar with it. The molecule contains an intramolecular NH...O hydrogen bond that closes a practically planar six-membered ring (N...O, 2.77 (I), H...O 2.14 Å, angle at H(N(4)) hydrogen 131 °). The x-ray diffraction data agree with the spectral data and with the CNO calculation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 816–821, June, 1985. 相似文献
997.
A. A. Krauze É. É. Liepin'sh Z. A. Kalme Yu. É. Pelcher G. Ya. Dubur 《Chemistry of Heterocyclic Compounds》1984,20(11):1241-1245
The condensation of benzylideneacetonacetic ester with cyanoacetamide in the presence of triethylamine yielded 3-carbamoyl-3,4-dihydropyridin-2-one, while the condensation of arylidenecyanoacetamides with -aminocrotonic ester in acetic acid yielded 3-cyano-3,4-dihydropyridin-2-ones. It was established by NMR spectroscopy that 3-cyano-4-R-5-ethoxycarbonyl-6-methyl-3,4-dihydropyridin-2-ones exist in solutions in the form of a mixture of cis- and trans-stereoisomers in a 101 ratio.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1504–1508, November, 1984. 相似文献
998.
Intraionic C3 reorientation of the anilinium NH+3 group was evidenced by measurements of the temperature dependence of the proton spin—lattice relaxation time, by rotating frame experiments and cw NMR data. Analysis of the results yielded a rotor hindering potential E = 33.6 kJ/mole and τo = 4 × 10−13 s. 相似文献
999.
General analytic formulas for derivatives of real Slater orbitals with respect to the Cartesian coordinates x and y have been derived. The application of this result to molecular geometry optimization or to the construction of a force constant matrix is briefly discussed. 相似文献
1000.
T. A. Vaganova S. Z. Kusov V. I. Rodionov I. K. Shundrina E. V. Malykhin 《Russian Chemical Bulletin》2007,56(11):2239-2246
Amination of pentafluoropyridine, 2,3,5,6-tetrafluoropyridine, 4-chlorotetrafluoropyridine, 3,5-dichlorotrifluoropyridine,
octafluorotoluene, α,α,α,2,3,5,6-heptafluorotoluene, decafluoro-m-xylene, decafluorobiphenyl, hexafluorobenzene, and pentafluorobenzene with liquid ammonia was investigated. Bis-aminodefluorination
temperatures for the majority of substrates were shown to exceed significantly the corresponding temperatures of monoaminodefluorination.
The optimal conditions for selective preparation of mono-and diaminopolyfluoro(het)arenes were elucidated. An efficient method
for isolation of particular polyfluorophenylenediamines from product mixtures formed in nonselective reactions of pentafluorobenzene
and hexafluorobenzene with aqueous ammonia based on complexation with a crown ether is proposed.
Dedicated to the memory of Academician N. N. Vorozhtsov on the occasion of his 100th anniversary.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2163–2170, November, 2007. 相似文献