牛血红蛋白与双十二烷基二甲基溴化铵相互作用的光谱研究

运用荧光光谱、紫外-可见吸收光谱和圆二色谱法研究了双十二烷基二甲基溴化铵(DDAB)与牛血红蛋白(Hb)的相互作用。从紫外-可见吸收光谱观察到,随着DDAB的浓度增大,Hb在406nm处的特征吸收峰强度下降,且峰位蓝移,说明DDAB导致血红素辅基微观环境变化。由荧光光谱研究可以得出随着DDAB的浓度增大,Hb在340nm处的荧光强度逐渐增强,说明导致色氨酸荧光淬灭的血红素辅基与色氨酸的距离增大。由Scatchard方程计算了不同温度下该反应的表观结合常数、结合位点数及结合热力学参数,热力学参数的变化表明DDAB与Hb之间以疏水作用力为主。圆二色谱的研究进一步表明DDAB使Hb产生轻微的二级结构改变,α-螺旋含量增加.     

Characterization and analysis of waxes by differential thermal analysis

The characterization of waxes by differential thermal analysis is described. An endothermic peak at 475-480 degrees is characteristic of microcrystalline and polyethylene waxes, and measurement of its area provides a method for the estimation of these waxes in mixtures.     

Scanning electron microscopic interpretation of the thermal analysis of kaolinite

The morphology of kaolinite thermally processed to 1600° in a thermoanalyzer was studied and related to DTA/TG/DTG data. The results show that DTA/TG/DTG data refined with scanning electron microscopic information offers insight into some of the controversies concerning the kaolinite-mullite transformation. In particular, the study supports the hypothesis that a spinel phase forms in the 950–1000° region. Further, the study shows that during dehyroxylation in the 450–700° region, water escapes by a process opposite to that generally supposed.     

Camphor cryoscopy by differential thermal analysis

The determination of the freezing point depression of organic solutions with camphor as solvent was performed by means of DTA. Amounts of 50–100μg substance and 1–2 mg camphor were weighed on a platinum wire, the camphor being pressed to a pellet by a glass press. The temperature difference between the glass tubes with pure camphor and with solution was recorded versus temperature, while the samples were cooled in a previously heated aluminium block. The difference between the recorded deviations from a straight line was found to be a measure of the freezing point depression. Errors less than 5 % were computed for various samples.     

Purity determinations by differential thermal analysis

Measurement of the melting-point depression of impure samples was compared with a differential method that involved running the impure sample against a pure sample of the same material. Samples of highly purified benzophenone to which had been added known quantities of 4-methylbenzophenone were studied. The area under the curve was proportional to the difference in purity between the sample and reference material over the range studied, 0.3-2.0 mole % with a standard deviation of 0.10 mole %, an uncertainty only half as large as one obtained by the melting-point depression method with the same apparatus.     

Investigation of imidization by differential thermal analysis

The DTA method has been used to show that, in the imidization of polyamido acid in solution in dimethylformamide, there is not only dehydrocyclization but also interaction of the solvent with reactive groups of the polyamido acid.     

高岭石与水分子相互作用的理论研究

为从微观角度深入探讨单个水分子与高岭石最易解理晶面不同暴露末端的作用特点,本工作通过密度泛函理论的计算方法对不同吸附形态的水分子与不同暴露末端的稳定作用构型进行几何结构与电子结构分析.吸附能的计算结果表明水分子在铝氧八面体羟基作为暴露末端的表面上最稳定的吸附方式为水分子的氧原子和氢原子分别与相邻两个羟基的氢原子和氧原子...     

A new method of caesium determination by thermal decomposition of caesium tetrathiocyanatobismuthate(III)

A thermal method of caesium determination is reported. The method is based on precipitation of Cs[Bi(SCN)(4)], thermal decomposition of this compound at 500 degrees , absorption of the evolved SO(2) in Na(2)HgCl(4) solution, and finally titration of the acid formed. The method can be used to determine caesium in the presence of potassium, ammonium and rubidium. When rubidium is present, caesium and rubidium can be determined simultaneously on the basis of the weight of the precipitate and the amount of sulphur dioxide evolved.     

Inhibition of interaction between kaolinite and K2CO3 by pretreatment using calcium additive

The aim of this paper is to investigate an approach for inhibiting the interaction of kaolinite with K₂CO₃ via the pretreatment with calcium additive (Ca(OH)₂ or CaCO₃). The reactions between kaolinite, calcium additive, and K₂CO₃ were, therefore, examined by means of thermogravimetry, differential scanning calorimetry, X-ray diffraction analysis, and inductively coupled plasma atomic emission spectrometry. It was found that Ca(OH)₂ could interact with kaolinite at low temperature, although the bulk reaction indeed required a temperature of higher than 900 °C to afford a crystalline calcium aluminosilicate product. The addition of Ca(OH)₂ to kaolinite even without heat pretreatment was proved to be significantly resistant to the reaction of kaolinite with K₂CO₃, while CaCO₃ showed such a smaller effect. The high-temperature product, calcium aluminosilicate, exhibited an almost complete inactivity for reaction with K₂CO₃ at a typical temperature of catalytic coal gasification (750 °C).     

Investigation of catalytic activities by differential thermal analysis

A calorimetric method is proposed to evaluate the catalytic activity of a solid catalyst with respect to the exothermic oxidation of Volatile Organic Compounds (VOC).This method employs a differential thermal analyzer in which an inert reference and a catalytically active sample are both fluxed at a constant rate with a reactive gaseous mixture composed of an inert gas (N₂ 90% vol.), oxygen and VOC, the last typically 900 to 5000 ppm. While the temperature is varied according to a predefined cycle, the output signal due to the exothermic reaction on the catalyst is continuously recorded. The design of the test chamber, the amount of catalyst, the shape of the holders and finally the flow rate and composition of the gaseous mixture should be carefully selected in order to achieve reproducible results.     

Quantitative estimation of magnesite by differential thermal analysis

A method for quantitative estimation of magnesite in magnesite-rich rocks by differential thermal analysis, using magnesium hydroxide as internal standard, is presented. The effects of variations due to particle size and impurities are discussed.     

Dielectric differential thermal analysis

Dithionates (CaS₂O₆·4H₂O, SrS₂O₆·4H₂O, BaS₂O₆·2H₂O, MnS₂O₆·4H₂O, MgS₂O₆·6H₂O, CoS₂O₆·6H₂O, NiS₂O₆·6H₂O, ZnS₂O₆·6H₂O and CuS₂O₆·4H₂O) were subjected to thermodielectric analysis. The thermoanalytical curves show low temperature effects from 60 to 350°. These are related with the dehydration and decomposition of the dithionates, which could be fully correlated with the knowledge of the thermal behavior of these compouds obtained with other thermal methods.     

Dielectric differential thermal analysis

Thermodielectric analysis has been used to test some very well-characterized kaolins from Cuban deposits. The samples were analysed by thermal analysis, X-ray diffraction, infrared spectrometry, electron microscopy and chemical analysis.The dielectrical thermograms show that the most evident effect for the hydrated versions is the water peak. The second dielectric effect, at high temperatures, is related to the cationic conductions. A relation involving the K content of the sample was observed.

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Zusammenfassung Mittels thermodielektrischer Analyse wurden einige gut charakterisierte Kaoline aus kubanischen Lagerstätten untersucht. Die Proben wurden mittels Thermoanalyse (TA), Röntgendiffraktion (XRD), Infrarotspektroskopie (IR), Elektronenmikroskopie (EM) und Elementaranalyse untersucht. Die Dielektrothermogramme zeigen, daß bei den hydratierten Versionen der augenscheinlichste Effekt der Wasserpeak ist. Der zweite dielektrische Effekt bei höheren Temperaturen wird mit der Kationenleitung in Zusammenhang gebracht, wodurch es möglich wird, Informationen über den K-Gehalt der Proben zu erlangen.

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Dielectrical differential thermal analysis

Sodium faujasites with different Si/Al ratios were studied by means of thermodielectrical method.     

Dielectric differential thermal analysis

The present paper deals with the role of guest molecules in the moleculer sieves systems.     

The relationship between differential thermal analysis data and the detonation characteristics of polynitroaromatic compounds

The thermal stabilities of 37 polynitroaromatic compounds are specified by means of non-isothermal DTA. The initial temperatures of the exotherms T_D, as well as the Piloyan decomposition activation energies, E, of the compounds are determined.A relationship is derived between ET^?1_D and the detonation characteristics of the compounds being measured. It is shown that allocation of the measured compounds to separate forms of the determined relationship is, in addition to thermochemical factors, also determined by the electron configuration and steric conditions in the reaction center of the given molecule.