排序方式: 共有28条查询结果,搜索用时 15 毫秒
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A. V. Kurzin A. N. Evdokimov O. S. Pavlova V. B. Antipina 《Russian Journal of Applied Chemistry》2007,80(5):842-845
Synthesis of esters from tall oil fatty acids and lower aliphatic alcohols is studied, and characteristics of the products as substitutes or components of diesel fuel are determined. 相似文献
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Ruoyu Hong * Jianmin Ding Guoliang Zheng College of Chemistry Chemical Engineering Soochow University Suzhou P. R. China Institute of Process Engineering Chinese Academy of Sciences Beijing P. R. China IBM HYDA/- C Highway North Rochester MN USA *Author to whom correspondence should be addressed. E-mail: rhong@suda.edu.cn 《中国颗粒学报》2004,2(5):207-214
1. Introduction1.1 Silica nanoparticles and synthesis methods Silica (SiO2) nanoparticles are widely used in industry asan active filler for polymer reinforcement, a rheologicaladditive in fluids, a free flow agent in powders, and anagent for chemical mechanical polishing during IC (inte-grated circuit) fabrication (Sniegowski & de Boer, 2000).Silica powder is also used for producing silicon carbide(Koc & Cattamanchi, 1998) or opaque silica aerosols (Leeet al., 1995). Many methods can … 相似文献
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L. Yu. Antipina F. N. Tomilin E. S. Vysotskii S. G. Ovchinnikov 《Journal of Structural Chemistry》2011,52(5):870-875
The Ca2+-regulated photoprotein obelin determines the luminescence of the marine hydroid Obelia longissima. Bioluminescence is initiated by calcium and appears as a result of the oxidative decarboxylation related to the coelenterazine
substrate. The luciferase of the luminescent marine coral Renilla muelleri (RM) also uses coelenterazine as a substrate. However, three proteins are involved in the in vivo bioluminescence of these animals: luciferase, green fluorescent protein, and Ca2+-regulated coelenterazine-binding protein (CBP). In fact, CBP that contains one strongly bound coelenterazine molecule is
the RM luciferase substrate in the in vivo bioluminescent reaction. Coelenterazine becomes available for oxygen and the reaction with luciferase only after binding
CBP with calcium ions. Unlike Ca2+-regulated photoproteins, the coelenterazine molecule is not activated by oxygen in the CBP molecule. In this work, by means
of quantum chemical methods the behavior of substrates in these proteins is analyzed. It is shown that coelenterazine can
form different tautomers: CLZ(2H) and CLZ(7H). The formation of 2-hydroperoxy-coelenterazine is studied. According to the
obtained data, these proteins use different forms of the substrates for the reaction. In obelin, the substrate is in the CLZ(2H)
form that affords hydrogen peroxide. In RM, coelenterazine is in the CLZ(7H) form, and therefore, CBP is not activated by
oxygen. 相似文献
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Antipina MN Dobner B Konovalov OV Shapovalov VL Brezesinski G 《The journal of physical chemistry. B》2007,111(49):13845-13850
In order to be used in versatile DNA delivery systems, novel cationic lipids were synthesized. The head groups of the new compounds represented by monoamines or oligoamines can be charged or uncharged depending on the environmental pH. Since their pK values are unknown, the protonation properties of these lipids have been studied in a wide pH range. In our experiments, the amphiphilic molecules were organized as a Langmuir monolayer at the air-water interface. Total reflection X-ray fluorescence (TRXF) was used to determine the 2D concentration of bromide counterions bound to a positively charged (protonated) Langmuir monolayer. The protonation rate of the novel cationic lipids was estimated by comparing the fluorescence intensity with that of dioctadecyldimethylammonium bromide monolayers as a reference. TRXF investigations were supplemented with results of film-balance measurements, grazing incidence X-ray diffraction, and X-ray reflectivity data. The results obtained display that the monolayers of all studied compounds are completely uncharged at pH values above 10. In the investigated pH region, the highest protonation rate of the monolayers is observed at pH 3. The influence of the monolayer packing density on the protonation properties is clearly shown. 相似文献
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Antipina MN Schulze I Dobner B Langner A Brezesinski G 《Langmuir : the ACS journal of surfaces and colloids》2007,23(7):3919-3926
Cationic liposomes/DNA complexes can be used as nonviral vectors for direct delivery of DNA-based biopharmaceuticals to damaged cells and tissues. In order to obtain more effective and safer liposome-based gene transfection systems, the new cationic lipid 2-amino-3-hexadecyloxy-2-(hexadecyloxymethyl)propan-1-ol (AHHP) was synthesized. In this paper we report on the synthesis of AHHP and investigations of its physical-chemical properties. Langmuir monolayers of AHHP were studied at the air/buffer interface by film balance measurements, grazing incidence X-ray diffraction (GIXD), and infrared reflection absorption spectroscopy (IRRAS). Structure and thermotropic phase behavior of AHHP in aqueous dispersion were examined by small-angle and wide-angle X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC). The results show clear differences in structure and phase behavior of AHHP, both in the monolayer system and in aqueous dispersions, in dependence on the subphase pH due to protonation or deprotonation of the primary amine in the lipid head group. Thermodynamic data derived from pi-A isotherms provide information about the critical temperature (Tc), which is in rough agreement with the temperature of the lipid phase transition from gel to fluid state (Tm) found by X-ray and calorimetry studies of AHHP aqueous dispersions. The packing properties of the molecules in mono- and bilayer systems are very similar. DNA couples to the monolayer of the new lipid at low as well as at high pH but in different amounts. The DNA coupling leads to an alignment of adsorbed DNA strands indicated by the appearance of a Bragg peak. The distance between aligned DNA strands does not change much with increasing monolayer pressure. 相似文献
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In this paper, we consider nonlinear Schrödinger (NLS) equations, both in the anomalous and normal dispersive regimes, which govern the propagation of a single field in a fiber medium with phase modulation and fibre gain (or loss). The integrability conditions are arrived from linear eigen value problem. The variable transformations which connect the integrable form of modified NLS equations are presented. We succeed in Hirota bilinearzing the equations and on solving, exact bright and dark soliton solutions are obtained. From the results, we show that the soliton is alive, i.e. pulse area can be conserved by the inclusion of gain (or loss) and phase modulation effects. 相似文献