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921.
R. Kh. Dadashev Kh. B. Khokonov D. Z. Elimkhanov Z. I. Bichueva 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(7):1181-1183
A surface tension isotherm equation for ternary systems was derived based on general thermodynamic expressions with consideration for the concentration dependence of the molar surface area. Within the experimental errors, the equation describes the properties of ternary systems with smooth surface tension isotherms. 相似文献
922.
For benzenoid hydrocarbons the distribution of pi-electrons amongst rings is characterized in the context of Randis mode of assignment attending to the different Kekulé structures. In particular the mean and mean deviation from the mean are considered, and the benzenoids which achieve maximum deviation are identified. 相似文献
923.
The thermal stabilities of two series of segmented polyurethane fibres have been compared with their chemical structure. The polyurethanes were synthesized from trimethylene diamine; 4, 4′ diphenylmethane di-isocyanate and two polyether based macrodi-isocyanates. Thermal stability was measured by thermogravimetric analysis and differential thermal analysis. By comparing the changes in weight loss and DTA peaks with chemical structure it has been found possible to separate soft segment from hard segment degradation.In the initial stages stability increases as soft segment concentration increases while the reverse is true in the later stages of degradation. The 100% soft segment polymer (polytetrahydrofuran) and the 100% hard segment polymer appear to behave anomalously. It is suggested that the hard segment has a stabilizing influence on the degradation of the soft segment. The results are discussed in the light of various theories of polyurethane degradation. 相似文献
924.
Lépine F Milot S Déziel E He J Rahme LG 《Journal of the American Society for Mass Spectrometry》2004,15(6):862-869
The opportunistic pathogen Pseudomonas aeruginosa produces a large array of 4-hydroxy-2-alkylquinolines (HAQs). These compounds were analyzed by LC/MS, using positive electrospray ionization, in the culture supernatant of strain PA14. Fifty-six HAQs and related compounds were detected and their [M + H](+) ions were further analyzed by collision induced dissociation (CID). These HAQs were grouped into five different series based on the presence of an hydrogen or hydroxyl group at the 3 position, an N-oxide group in place of the quinoline nitrogen, and an unsaturation on their alkyl side chain. Two new analogs of 3,4-dihydroxy-2 heptylquinoline, the Pseudomonas quinolone signal (PQS), were found with an alkyl chain longer by one and two methylene groups. Moreover, two additional series of compounds were identified in which a saturated or unsaturated alkyl side chain is located at the 3 position along with an hydroxyl group at the 3 position and a ketone at the 2 position. No HAQ N-oxides, nor any compounds from the latter two series, were detected in a pqsL mutant derivative of PA14, indicating that this gene is involved in the biosynthesis of these compounds. This work demonstrates the large repertoire of HAQ and HAQ-related compounds produced by P. aeruginosa, and provides insight into N-oxides biosynthesis and confirm the hypothesis that N-oxides are the precursors of compounds from Series 6 and 7. 相似文献
925.
Bílková Z Stefanescu R Cecal R Korecká L Ouzká S Jezová J Viovy JL Przybylski M 《European journal of mass spectrometry (Chichester, England)》2005,11(5):489-495
Epitope extraction technique is based on the specific digestion of a target protein followed by immunoaffinity isolation of a specific recognition peptide. This technique, in combination with mass spectrometry, has been efficiently used for epitope identification. The major goal of this work was to utilize newly developed enzyme and immunoaffinity magnetic reactors for the epitope extraction procedure and confirm the efficiency of this improved system for epitope screening of proteins. Alginic acid-coated magnetite microparticles with immobilized TPCK-trypsin provided high working efficiency with low non-specific adsorption, digestion time in minutes and low frequency of missed cleavages. The sensitivity and specificity of tryptic fragmentation of the beta-amyloid-peptide Abeta (1-40) as a model polypeptide was confirmed by Fourier-transform ion cyclotron resonance mass spectrometry analysis. The Sepharose reactor or immunoaffinity magnetic reactors, both with anti-amyloid-beta monoclonal antibodies, were used for specific isolation and identification of target peptides. In this way, the epitope extraction technique combined with mass spectrometric analysis is shown to be an excellent base for molecular screening of potential vaccine lead proteins. 相似文献
926.
Xie Z Sielemann S Schmidt H Li F Baumbach JI 《Analytical and bioanalytical chemistry》2002,372(5-6):606-610
A combination of a custom-designed ion mobility spectrometer (IMS) with a UV ionization source and a high speed capillary column (HSCC) has been developed as an analytical device for the sensitive detection of volatile organic compounds (VOCs), e.g. 2-propanone (acetone), 2-butanone and 3-pentanone (diethyl ketone) in the gas phase. A fast separation of the three selected substances and benzene, toluene and m-xylene (BTX) - all of which occur in human breath - has been achieved within less than four minutes at a carrier gas flow rate of 4.5 mL x min(-1). Multi-dimensional correlations presented support the interpretation of the acquired spectra of mixtures. Method detection limits were 2.7 microg x L(-1) for acetone and 2-butanone and 3.0 microg x L(-1) for diethyl ketone in nitrogen, respectively. The assay linear dynamic range is 4-320 microg x L(-1). 相似文献
927.
The conditions of thermal decomposition of thep-aminosalicylates of Y, La and the lanthanides from Ce(III) to Lu have been studied. On heating, the hydrated complexes of La and the light lanthanides decompose to the oxides with the intermediate formation of Ln2[H2N·C6H3(O)COO]3. Only the complex of La decomposes to La2O3 through La2[H2N·C6H3(O)COO]3 and La2O2CO3. The anhydrous complexes of the heavy lanthanides decompose directly to the oxides, whereas the anhydrous complex of Y decomposes to Y2O3 via Y2[H2N·C6H3(O)COO]3 formation. During heating, the hydrated complexes lose crystallization water and decompose simultaneously, and the endothermic effect of dehydration is masked by the strong exothermic effect of burning of the organic ligand.
Zusammenfassung Es wurden die Bedingungen für die thermische Zersetzung derp-Aminosalicylate von Y, La und der Lanthanoide von Ce(III) bis Lu untersucht. Beim Erhitzen zersetzen sich die hydratierten Komplexe von La und der leichteren Lanthanoide unter Bildung des Zwischenproduktes Ln2[H2NC6H3(O)COO]3 in ihre Oxide. Nur der Komplex mit La zersetzt sich zu La2O3 über die Zwischenstufen La2[H2NC6H3(O)COO]3 und La2O2CO3. Die wasserfreien Komplexe der schweren Lanthanoide zersetzen sich direkt in die Oxide, wÄhrend sich der wasserfreie Komplex von Y über die Bildung von y2[H2NC6H3(O)COO]3 in y2O3 zersetzt. Beim Erhitzen verlieren die hydratierten Komplexe ihr Kristallwasser und zersetzen sich gleichzeitig, der endotherme Effekt der Dehydratation wird durch den starken exothermen Effekt der Verbrennung der organischen Liganden überdeckt.相似文献
928.
V. V. Zverev B. M. Musin V. M. Vakar' Z. G. Bazhanova V. B. Ivanov 《Journal of Structural Chemistry》1994,35(2):209-214
The electronic structure of some amino-N-sulfenyl chlorides and related compounds is studied by photoelectron spectroscopy
and ab initio calculations. Similar values of IP(n
S
) and IP(n
N
) and the total energy minimum indicate that in stable conformations the n
S
and n
N
orbitals are orthogonal. These conformers are characterized by an effective nN-σ
S-Cl
*
interaction. The relationship between the intramolecular shift of charge and ionization potential values and the spatial
structure of amino-N-sulfenyl chlorides is analyzed.
A. E. Arbuzov Institute of Organic and Physical Chemistry, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 2, pp. 69–73, March–April, 1994.
Translated by L. Smolina 相似文献
929.
S. D. Fazylov A. M. Gazaliev M. Zh. Zhurinov R. Z. Kasenov A. B. Tateeva M. Z. Kokzhalova 《Chemistry of Natural Compounds》1994,30(3):371-372
The results are given of the synthesis and a comparative study of the toxicities of some phosphorylated derivatives of the
alkaloids l-ephedrine and d-pseudoephedrine. It has been shown that the introduction of phosphorus- and sulfur-containing
fragments considerably lowers the toxicity of the alkaloids.
Institute of Organic Synthesis and Coal Chemistry, National Academy of Sciences of the Republic of Kazakhstan, Karaganda.
Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 406–408, May–June, 1994. 相似文献
930.
O. G. Yarosh Z. G. Ivanova T. D. Burnashova M. G. Voronkov 《Russian Chemical Bulletin》1984,33(11):2394-2396
Conclusions The reaction of magnesium bromide derivatives of di- and triethynylsilanes with dimethylethynylfluorosilane gave 1,2-disubstituted silylacetylenes containing ethynyl and vinyl groups at the silicon atoms.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2614–2616, November, 1984. 相似文献