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961.
Summary The previously described method yielding apolar, chemically bonded methyl polysiloxane glass capillary columns was extended to the production of capillary systems of controlled polarity. The approach involved prior synthesis of a reactive methyl-phenyl polysiloxane polymer by copolymerisation of a mixture of dimethyl and diphenyl chlorosilanes. The polymer was then chemically bonded to the capillary glass surface to yield remarkably stable, high resolution analytical systems which were shown to be particularly well suited to the separation of biochemical mixtures at the subnanogram level. The principle of copolymerisation of differently substituted silanes confers to the method a considerable flexibility which could be used to devise polar capillary systems tailor made for a given analytical problem. 相似文献
962.
Teh-Ming Kung J. C. M. Li 《Journal of polymer science. Part A, Polymer chemistry》1986,24(10):2433-2445
The DSC thermograms of the shear band material cut out by a diamond saw to include some undeformed material revealed two Tg's clearly separated by about 10°C. The first Tg was at the same temperature as the Tg of the undeformed material. The second Tg, which was at a higher temperature than the first Tg, appeared shortly after the shear strain recovery during the heating of the shear band material in the DSC. When the shear strain in the shear band was partially reversed by mechanical means before taking the DSC thermogram, the ΔT between the two Tg's decreased and when the shear strain was mechanically reversed to almost zero, the second Tg disappeared. The stored energy of shear band material was found to be similar to that of the bulk compressed material for large strains. Dimensional recovery during heating of specimens with thick and fine bands was similar, both taking place above Tg. 相似文献
963.
R Pietruszko C de Zalenski H Theorell 《Acta chemica Scandinavica. Series B: Organic chemistry and biochemistry》1976,(7):595-599
ADH from human liver forms binary complexes with NADH, associated with a blue shift of the peak of the fluorescence emission of NADH. The wavelength shift is the same for all isoenzymes but the accompanying intensification of the fluorescence is different. The fluorescence is further increased by the formation of the very tight ternary enzyme-NADH-isobutyramide complexes. These properties are similar to those for the horse liver ADH, as well as the molecular weight of E=40 000 per active site of the dimer molecule (EE). "Stopped-flow" determined velocity constants (ER in equilibrium E+R) were found to be in good agreement with ethanol activity constants previously determined by activity measurement, confirming the validity of the ordered ternary complex mechanism also for the human ADH. No single isoenzyme activity as high as that reported by Mourad and Woronick or Drum has been found. 相似文献
964.
Single vibronic lifetimes of two-photon excited states are measured in the low pressure limit for naphthalene. The two-photon spectrum, besides yielding new states in S1, is also free of the interference from the neighborhood of the S2, known from one-photon experiments, and hence unperturbed lifetimes can be measured to higher excess energies. The overall pattern of lifetimes with excess energy including both one-photon and two-photon states shows that the vibronic structure is subordinate to an overall monotonic decrease, much as found earlier for β-naphthylamine. This indicates, at least for naphthalene, that radiationless processes into triplets are dominated by Franck—Condon factors and not by vibronic inductions and promoting modes. 相似文献
965.
Kazimiera J. L. Paciorek James H. Nakahara Reinhold H. Rratzer 《Journal of mass spectrometry : JMS》1976,11(11):1217-1219
Electron impact fragmentation patterns were obtained for perfluoroalkylether nitriles, C,F,O[CF(CF3)CFIO]ICF(CF3)CN (x = 1 and 2), perfluoroalkylether acyl halides, CSF,OCF(CF,)-CF2OCF(CF3)COX (X = F and Cl), n-perfluorooctanonitrile and n-perfiuorooctanoyl chloride. The perfluoroalkyl and perfluoroalkylether nitriles afforded ions characteristic of the nitrile function. The major fragment from the acyl chlorides was the [COClJ]+ ion; the presence of chlorine was evidenced also by rearrangement ions of the general form [RfCl] t. The perfluoroalkylether compounds appeared to undergo a typical fragmentation governed by the cleavage of the carbon-oxygen bond. 相似文献
966.
Ammonium hexanitratocerate (in acetonitrile) solution has been used as an oxidimetric reagent for the visual and potentiometric determination of thiourea and its alkyl derivatives in acetonitrile medium. The thioureas are oxidized to their corresponding disulphides. The method is simple, accurate, reliable and widely applicable. 相似文献
967.
On Fluorescent Compounds of Copper(I) Iodide with Aromatic Nitrogenous Bases The easily obtainable compounds of copper(I) iodide with esters of nicotinic acid, with nicotinic acid amide and nitrile, as well as with quinoline, isoquinoline and quinaldine are strongly fluorescent in ultraviolet light. They are remarkably stable against water and air, compared with analogous picoline and lutidine compounds. Only in one case (nicotinic acid hexyl ester-copper(I) iodide) the phenomenon of fluorescence thermochromism has been observed. 相似文献
968.
Zusammenfassung Das Überleben der Hefezellen nach - und -Bestrahlung wurde durch das Koloniebildungsvermögen ermittelt; bei gleicher Dosis und Dosisleistung wurden nur schwach unterschiedliche Effekte festgestellt. Das Nucleotidverteilungsmuster zeigte nach -Bestrahlung mit 300 000 rad größere quantitative Änderungen als nach -Bestrahlung. Die Konzentrationen an Nucleosidtriphosphaten war nach -Bestrahlung stärker herabgesetzt.Mit 5 AbbildungenLeiter: Prof. Dr.K. Kaindl. 相似文献
969.
De Wasch K De Brabander HF Van de Wiele M Vercammen J Courtheyn D Impens S 《Journal of chromatography. A》2001,910(1):79-86
Direct gas chromatographic methods to analyse phenylurea pesticides are discouraged by the thermal instability of these compounds, that in conventional hot splitless inlet systems leads to extensive and irreproducible formation of isocyanates and amines. However a careful control of the operating conditions, like the inlet temperature, the pressure and the presence of suitable chemical additives (as acetic acid, low-molecular-mass amines, organic anhydrides) can either: (i) minimise the thermal decomposition enabling the direct GC-MS analysis of phenylureas, or (ii) lead to reproducible conversion to isocyanates. Experimental design was employed to study the effect of the experimental variables on the thermal transformation of phenylurea pesticides in splitless inlet system. Two strategies were alternatively optimised: (i) the minimisation of degradation reactions to increase the signal of phenylureas; (ii) the maximisation of the degradation to isocyanates that are in turn determined. The maximal yields in isocyanate were obtained with high inlet temperatures, low carrier flows in the injection phase and the presence of acetic anhydride. By contrast, the use of relatively low inlet temperatures, high carrier flows during the injection and the presence of an amine maximise the response of the parent compounds. 相似文献
970.
[structure: see text] We report an initial step toward the development of sulfonamide-based complements for extended peptide strands. A molecule containing one secondary sulfonamide unit and one valine residue linked by a turn-forming segment was found by IR and NMR to exhibit a doubly hydrogen-bonded folding pattern in chloroform. 相似文献