水溶液中几种芳香族氨基酸π-π自堆叠作用

利用精密的流动混合微量热法测定了298.15 K时D/L-色氨酸、L-色氨酸、L-组氨酸和L-苯丙氨酸四种天然芳香族氨基酸水溶液的稀释焓, 根据所建立的拟等步自堆叠作用的化学模型对实验数据进行了处理, 计算得到模型参数K△Hm. 该化学作用参数与McMillan-Mayer理论模型中的焓对作用系数具有高度一致性, 即hxx=K△Hm. 结合文献报道的结果, 认为芳核π-π自堆叠作用在本质上是一种特殊的疏水-疏水作用, 一般表现为吸热效应; 取代基空间位阻、芳核以外部分的静电、氢键和手性选择性作用等对芳核π-π自堆叠作用有显著影响; 组合参数K△Hm实际上描述了芳核π-π自堆叠作用平衡及焓变的综合效应.     

Decomposition in HTPB bonded HMX followed by heat generation rate and chemiluminescence

The decomposition in HTPB bonded HMX was characterized with two highly sensitive methods: heat flow microcalorimetry (HFMC) and Chemiluminescence (CL). The material is stabilized with a phenolic antioxidant. The heat generation (HFMC) rate was determined from 120 to 150 °C using a TAM™ microcalorimeter and the oxidation of the substance was followed by the CL emission between 100 and 140 °C directly from the solid state sample. The end of antioxidant activity results in both measurements sets in characteristic changes in the curves. Kinetic parameters were calculated applying Arrhenius parameterization for the times to the end of antioxidant activity and by applying modelling with an autocatalytic model extended by a side reaction, which is assigned to the antioxidant consumption. The evaluation with the characteristic times gives good agreement between the two methods; the modelling represents the different but supplementing probing of the two measurement methods. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

野草状纳米氧化锌的制备及标准摩尔生成焓

本文采用反相微乳液法制备了尺寸均匀的野草状ZnO纳米结构. 依据热力学势函数法获得了纳米ZnO与块体ZnO标准摩尔生成焓的关系, 并结合微量热技术求得了所制备产物的标准摩尔生成焓, 为研究其它纳米材料的标准摩尔生成焓提供了一种广泛适用的新方法.     

Comparison of microbial activity in some Brazilian soils by microcalorimetric and respirometric methods

The microbial activity in a Rhodic eutrudox (R), a Typic eutrudox (V) and a Quartzipsamment (Q) was monitored by respirometric and calorimetric methods. CO₂ evolution was monitored for 98 days by titrimetry and conductimetry for control amended samples (A) with 25% of cattle manure (E), municipal refuse compost (L), earthworm casts (H) or 1.25 kg ha⁻¹ of trifluralin (T). Average values of all treatments through respiration at the end of the incubation period were 5.24±0.34, 6.13±0.31 and 6.50±0.33, in mg CO₂ g⁻¹ soil, for R, V and Q, respectively, by titrimetry and 8.89±0.44, 10.41±0.54 and 10.41±0.52, in mg CO₂ g⁻¹ soil, for R, V and Q, respectively, for conductimetry. Excellent correlation (r=1.00) between titrimetry and conductimetry was observed. The decreasing order for respiration was E, H, L and T. After each incubation time, the conductimetric values were higher than those for titrimetry, for all treatments of these Brazilian soils. Average values of the exothermic thermal effect were: 0.58±0.02, 0.60±0.02 and 0.67±0.01 kJ g⁻¹ soil, for R, V and Q, respectively, for 103 days. A significant correlation coefficient of 0.91 and P<0.0001 between calorimetric and respirometric values over 98 days was observed. Based on the obtained calorimetric results, it can be proposed that this technique should be as a useful analytical method for determining the microbial activity in soils.     

Kinetics and thermodynamics of the attack of fluorapatite by a mixture of sulfuric and phosphoric acids at 55 °C

A calorimetric study of kinetics and thermodynamics of the attack of a synthetic fluorapatite by a mixture of sulfuric and phosphoric acids is undertaken at 55 °C. The global enthalpy of the attack equals −409.3 kJ/mol. The recorded thermograms show two peaks leading to calcium sulfate hemihydrate and dihydrate, respectively. The deconvoluted curves were analysed iteratively. A kinetic mechanism based on simultaneous reactions has been proposed for the first peak and confirmed thermochemically by comparing the enthalpies deduced from iteration and that determined from experimental and calculated routes. The second peak of the thermogram was attributed to transformation of calcium sulfate hemihydrate into gypsum according to a dissolution/precipitation scheme. These phenomena are of order one and two, respectively.     

线粒体体外代谢热动力学研究

线粒体是细胞重要的细胞器之一，有细胞的“能源工厂”之称．因为线粒体内有许多酶，是特殊的酶催化氧化反应的场所山；所有动、植物细胞的线粒体都能通过各种营养物的氧化而产生“富能”物质ATP．采用一定的技术可将线粒体从细胞中分离出来，分离出来的线粒体中的酶系统还有一定的活性，而且线粒体内也有一定的营养物质，这样酶系统就能利用这些营养物进行代谢，从而释放出一定的能量．我们用微量热法对两种鱼肝脏线粒体进行了测量，发现线粒体代谢过程分四个阶段：停滞期、活性恢复期、稳定期、活性衰减期．在活性恢复期和活性衰减期，…     

微量热法研究黄嘌呤氧化酶反应

在热导工热量计双参数理论模型的基础上，建立了较快酶仲反应研究的双参数初始速度法的热动力学模型，用微量热法研究了黄嘌呤氧化酶催化氧化黄嘌呤的热动力学，该较快酶促反应遵循Ｍｉｃｈａｅｌｉｓ－Ｍｅｎｔｅｎ这，在２９８．１５Ｋ和ＰＨ＝７．５时，其米氏常数为１．０４×１０＾－３ｍｏｌ．Ｌ＾－１，与文献结果相符。     

Microcalorimetry in the screening of discovery compounds and in the investigation of novel drug delivery systems

Calorimetry has for some time been proposed as a rapid method for determination of bioactivity. This paper describes the background to this application and describes how it has been extended to the study of bioassay techniques via microcalorimetry in the development of structure activity relationships (SARs). That SARs can be developed indicates that it is possible to guide drug synthetic strategy through the results of microcalorimetric investigations, and this approach is explored here. In an extension of this approach it is argued that microcalorimetry is well suited to the examination of novel drug delivery systems, allowing investigation of the capacity of drug delivery molecules to release the drug in the presence of a target organism.     

细菌生长的热动力学性质的研究

前文报导了大肠杆菌在不同培养基中生长的速率及热力学函数.本文在此基础上又测定了不同细菌在相同培养基中生长的规律.细菌生长是一系列非常复杂的过程,为便于研究,使复杂问题简单化,我们采取与过渡状态理论类似的模式进行处理,得出了一些热动力学函数,这些数据为进一步探讨这一复杂过程提供了有用的信息.     

Calorimetric determination of the effect of ammonium-iron(II) phosphate monohydrate on Rhodic Eutrudox Brazilian soil

The fertilizer NH₄FePO₄·H₂O (AIP) was synthesized under mild hydrothermal conditions to be applied on soils to prevent iron deficiencies. The effect of the addition of AIP on soil microbial activity was studied by calorimetry, determining both basal respiration and carbon mineralization by means of the addition of an external carbon source. Thermal analyses (TG and DSC) were also used to provide additional soil properties. The effect of different amounts of AIP on soil microbial activity was quantitatively analyzed by a mass and energy balance performed via the analysis of the power-time curves. These balances allowed determination of the impact of AIP on soil more rapidly than conventional methodologies. The increase in the amount of added AIP leads to a less efficient metabolism, probably due microbial competition for the nitrogen source provided by the AIP and for the carbon source.