β-环糊精和十二烷基硫酸钠包合作用的微量热法研究

环糊精（ＣＤ）和客体分子的选择性包合作用是现代化学研究中的一个重要课题，化学和药剂学应用中的分离分析、稳定作用、增溶作用及利用分子识别释放活性物质等都和它有着密切的关系．β－ＣＤ和十二烷基硫酸钠（ＳＤＳ）在毛细管电泳中有着广泛的应用［１］，β－ＣＤ＋...     

正常及肿瘤染色质的荧光寿命法、精确量热法和荧光能量转换

量热法;荧光寿命;正常及肿瘤染色质的荧光寿命法、精确量热法和荧光能量转换     

基于等温滴定量热法表征的红细胞凝集反应热动力学特性研究

采用等温滴定量热法研究植物凝集素(PHA)作用于20%家兔血红细胞(RBC)的凝集反应过程, 以生物热动力学参数表达凝集反应动力学特征. 结果表明, PHA与家兔血红细胞凝集反应的平衡常数K为3.24×10⁵ L•mol^－1, 反应焓变( )为－238.548 kJ•mol^－1, 反应自由能( )为－32.722 kJ•mol^－1, 反应熵变( )为－0.664 kJ•mol^－1•K^－1. 反应为放热反应(Q＞0), 可自发进行(ΔG＜0), 反应为焓驱动、熵减过程(ΔH＜0, ΔS＜0, |ΔH|＞|TΔS|), 由化学键合作用、氢键和范德华力推动, 反应体系最终处于稳定有序状态. 所建立的微量量热法可以客观表征凝集反应的热动力学过程, 也为其他抗原抗体类型反应的过程评价方法提供新的技术参考.     

热动力学的滴定量热法研究2: 单底物酶促反应的热动力学

用滴定量热法分别建立了滴定期和停滴反应期单底物酶促反应热动力学的数学模型。根据这两种模型,可由一次实验的滴定量热曲线同时解析出单底物酶促反应的热力学参数(Δ~rH~m)和动力学参数(K~m和k~2)。用滴定量热法研究了一个经典的单底物酶促反应---过氧化氢酶催化分解过氧化氢反应的热动力学,由滴定期和停滴反应期热动力学模型解析出在298.15K和pH=7.0时该反应的米氏常数K~m分别为(5.41±0.24)×10^-^3和(5.43±0.21)×10^-^3mol.L^-^1,酶转换数k~2分别为(3.58±0.33)×10^3和(3.60±0.41)×10^3s^-^1,摩尔反应焓为(-86.75±0.88)kJ.mol^-^1,实验结果验证了上述热动力学模型的正确性。     

滴定量热法研究氨基酸羧基质子化反应

氨基酸是典型的两性物质,其羧基质子化常数已有报道,文献结果大都由pH电位法得到,而对氨基酸光学异构体(D、L、DL)的对比研究甚少,为检验光学活性起源理论中提出的D与L分子间的能量差异,我们曾用微量量热技术观察了苯丙氨酸、亮氨酸,蛋氨酸和色氨酸4     

热动力学的滴定量热法研究2: 单底物酶促反应的热动力学

用滴定量热法分别建立了滴定期和停滴反应期单底物酶促反应热动力学的数学模型。根据这两种模型,可由一次实验的滴定量热曲线同时解析出单底物酶促反应的热力学参数(Δ~rH~m)和动力学参数(K~m和k~2)。用滴定量热法研究了一个经典的单底物酶促反应---过氧化氢酶催化分解过氧化氢反应的热动力学,由滴定期和停滴反应期热动力学模型解析出在298.15K和pH=7.0时该反应的米氏常数K~m分别为(5.41±0.24)×10^-^3和(5.43±0.21)×10^-^3mol.L^-^1,酶转换数k~2分别为(3.58±0.33)×10^3和(3.60±0.41)×10^3s^-^1,摩尔反应焓为(-86.75±0.88)kJ.mol^-^1,实验结果验证了上述热动力学模型的正确性。     

滴定量热法研究连串一级反应热动力学

本文用滴定量热法分别建立了滴定期和停滴反应期1-1级连串反应热动力学的数学模型。根据这两种模型,由非线性最小二乘法原理直接拟合单次实验结果可同时求得1-1级连串反应的速率常数（ k ₁和 k ₂）和摩尔反应焓。并用滴定量热法研究了丁二酸二乙酯皂化反应的热动力学,实验结果验证了两种数学模型的正确性。     

热动力学的滴定量热法研究2: 考虑热滞后的一级 反应精确热动力学

建立了滴定热量计滴定期一级反应热动力学的精确数学模型,并在此基础上探讨了热滞后对此模型的影响。经过改进的模型大大提高了利用滴定热量计获取动力学数据的准确度,且扩大了滴定热量计研究的一级反应体系的范围,使其适用反应的半衰期可以小至十几秒。本文采用此模型,研究了去离子水溶剂中乙酸乙酯皂化反应的热动力学,实验结果验证了该模型研究一级反应热动力学的适用性。     

热动力学的滴定量热法研究2: 考虑热滞后的一级 反应精确热动力学

建立了滴定热量计滴定期一级反应热动力学的精确数学模型,并在此基础上探讨了热滞后对此模型的影响。经过改进的模型大大提高了利用滴定热量计获取动力学数据的准确度,且扩大了滴定热量计研究的一级反应体系的范围,使其适用反应的半衰期可以小至十几秒。本文采用此模型,研究了去离子水溶剂中乙酸乙酯皂化反应的热动力学,实验结果验证了该模型研究一级反应热动力学的适用性。     

热动力学的滴定量热法研究 Ⅰ.一级反应的热动力学

用滴定量热法分别建立了满定期和停满反应期一级反应热动力学的数学模型．根据这两种模型，均可由一次实验的滴定量热曲线同时解析出一级反应的速率常数（k1）和摩尔反应治（△rHm）．用液定量热法研究了去离子水溶剂中乙酸乙酯皂化反应的热动力学，实验结果验证了本文用滴定量热法研究一级反应热动力学的运用性．     

New Measuring Method in Isothermal Titration Calorimetry Based on a Proportional-Integral Controlled System

This paper introduces a new measuring method in Isothermal Titration Calorimetry (ITC). This method, based on a proportional-integral control system, offers many important advantages when compared to the frequently used proportional control: higher signal-to-noise ratio, improved stability of baseline, increased static and dynamic sensitivity, similar or smaller time constants and calibration constant independent of the control parameters. Here an experimental proof of this method is detailed and full theoretical foundation will be discussed in a next paper. This revised version was published online in July 2006 with corrections to the Cover Date.     

十二烷基磺酸钠对大豆过氧化物酶活性和构象的影响

在不同的pH值体系中, 利用酶活测量、圆二色谱、荧光谱和电子吸收谱研究了十二烷基磺酸钠(SDS)对大豆过氧化物酶(SBP)活性与构象的影响情况. 在pH 2.6和4.2 的体系中, 少量的SDS分子可通过静电作用与SBP结合, 进而与SBP分子中的His169残基结合, 降低其与铁卟啉的配位能力, 使其Soret吸收带蓝移, 二级结构发生轻微的变动, 活性永久丧失. 在pH 5.2体系中, SDS和SBP分子都带负电, 由于静电排斥作用, SDS无法进入SBP的分子内部, 失去与SBP分子中His169残基结合的能力, 对SBP分子的二级结构没有影响, 仅对SBP分子的三级结构有所影响. 当SDS的浓度大于临界胶束浓度时, 由于胶束与SBP的静电排斥作用增强, 限制了铁卟啉中乙烯基的运动, 乙烯基与卟啉环的共轭程度增大, Soret 吸收带红移. 由于SBP活性可完全恢复, 此变化是可逆的.     

Precipitating Sodium Dodecyl Sulfate to Create Ultrastable and Stimulable Foams

Ultrastable foams are made very simply by adding salt (NaCl or KCl) to sodium dodecyl sulfate. The addition of high concentrations of salt leads to the precipitation of the surfactant on the bubble surfaces and as crystals in the interstices between the bubbles. As a consequence, the ageing of the foams is stopped to make them stable indefinitely, or until they are heated above the melting temperature of the crystals. The use of KCl is shown to be much more effective than that of NaCl because potassium dodecyl sulfate has a higher melting temperature and faster rates of crystallization. The crystalline structures have been investigated inside the foam using small angle neutron scattering. The larger lattice spacing of the crystals formed with NaCl in comparison with KCl has been evidenced. These simple temperature stimulable foams could have many potential applications.     

Use of Isothermal Titration Calorimetry in the Development of Molecularly Defined Vaccines

An uptake or a release of heat accompanies practically all molecular binding interactions. Therefore isothermal titration microcalorimetry is universally applicable for the characterisation of such binding processes. Calorimetric analyses do not require marker molecules or intrinsic spectroscopic reporter groups, which can modify the analysed interactions. Furthermore, measurements are carried out in solution and the adsorption of reactants to a solid phase is thus avoided. At variance with most other analytical approaches, titration calorimetry determines simultaneously enthalpy and entropy contributions of the binding interactions, as well as the binding constant and stoichiometry. In our analyses of the interactions between monoclonal antibodies and candidate antigens for vaccines vs. malaria and malignant melanoma, isothermal titration calorimetry has turned out to be a very valuable technique. The obtained quantitative data on biomolecular interactions can substantially support the rational design of epitope-focused vaccines.This revised version was published online in November 2005 with corrections to the Cover Date.     

Isothermal Titration Calorimetry Study of a Bistable Supramolecular System: Reversible Complexation of Cryptand[2.2.2] with Potassium Ions

Isothermal titration calorimetry (ITC) is used to investigate the thermodynamics of the complexation of potassium ions by 1,10‐diaza‐4,7,13,16,21,24‐hexaoxabicyclo[8.8.8]hexacosane (cryptand[2.2.2]) in aqueous solution. By changing the pH of the solution it was possible to trigger the reversible complexation/decomplexation of the cryptand in consecutive in situ experiments and to assess for the first time the use of ITC to monitor the thermodynamics of a bistable system.     

Study of the Enzymatic Activity of Arthrobacter ureafaciens Neuraminidase by Isothermal Titration Calorimetry

Isothermal titration calorimetry was used to determine the enzymatic activity and thermodynamic activation parameters of Arthrobacter ureafaciens sialidase with the sialyl substrates α‐2,3‐, α‐2,6‐sialyllactoses and α‐2,8‐sialic acid dimer. By monitoring the heat released during hydrolysis, the Michaelis constant (K_m), catalytic rate constant (k_cat), activation energy, activation Gibbs energy, enthalpy, and entropy for different monovalent sialyl conjugates were calculated and found to be consistent with those derived by chromatographic or colorimetric assays. The observed decreases in the activation energy and transition entropy of sialyllactoses were larger than the Michaelis activation parameters of lactose‐free di‐sialic acid because of the specific enzyme activity of A. ureafaciens sialidase.     

Complexation of Phenol and Thiophenol by Amine N‐Oxides: Isothermal Titration Calorimetry and ab Initio Calculations

To develop a new solvent‐impregnated resin (SIR) system for removal of phenols from water, the complex formation of dimethyldodecylamine N‐oxide (DMDAO), trioctylamine N‐oxide (TOAO), and tris(2‐ethylhexyl)amine N‐oxide (TEHAO) with phenol (PhOH) and thiophenol (PhSH) is studied. To this end we use isothermal titration calorimetry (ITC) and quantum chemical modeling (on B3LYP/6‐311G(d,p)‐optimized geometries: B3LYP/6‐311+G(d,p), B3LYP/6‐311++G(2d,2p), MP2/6‐311+G(d,p), and spin component scaled (SCS) MP2/6‐311+G(d,p); M06‐2X/6‐311+G(d,p)//M06‐2X/6‐311G(d,p), MP2 with an extrapolation to the complete basis set limit (MP2/CBS), as well as CBS‐Q). The complexes are analyzed in terms of structural (e.g., bond lengths) and electronic elements (e.g., charges). Furthermore, complexation and solvent effects (in benzene, toluene, and mesitylene) are investigated by ITC measurements, yielding binding constants K, enthalpies ΔH⁰, Gibbs fre energies ΔG⁰, and entropies ΔS⁰ of complex formation, and stoichiometry N. The ITC measurements revealed strong 1:1 complex formation between both DMDAO–PhOH and TOAO–PhOH. The binding constant (K=1.7–5.7×10⁴ M ^?1) drops markedly when water‐saturated toluene was used (K=5.8×10³ M ^?1), and π–π interaction with the solvent is shown to be relevant. Quantum mechanical modeling confirms formation of stable 1:1 complexes with linear hydrogen bonds that weaken on attachment of electron‐withdrawing groups to the amine N‐oxide moiety. Modeling also showed that complexes with PhSH are much weaker than those with PhOH, and in fact too weak for ITC determination. CBS‐Q incorrectly predicts equal or even higher binding enthalpies for PhSH than for PhOH, which invalidates it as a benchmark for other calculations. Data from the straightforward SCS‐MP2 method without counterpoise correction show very good agreement with the MP2/CBS values.     

Micellization of Sodium Dodecyl Sulfate in Glycerol Aqueous Mixtures

The effect of glycerol on both micellar formation and the structural evolution of the sodium dodecyl sulfate (SDS) aggregates in the context of the action mechanism of the cosolvent has been studied. The critical micelle concentration and the degree of counterion dissociation of the surfactant over a temperature range from 20°C to 40°C were obtained by the conductance method. The thermodynamic parameters of micellization were estimated by using the equilibrium model of micelle formation. The analysis of these parameters indicated that the lower aggregation of the surfactant is mainly due to a minor cohesive energy of the mixed solvent system in relation to the pure water. The effect of glycerol on the mean aggregation number of the micelles of SDS was analyzed by the static quenching method. It was found that the aggregation number decreased with the glycerol content. This reduction in the micellar size seems to be controlled by an increase in the surface area per headgroup, which was ascribed to a participation of glycerol in the micellar solvation layer. Studies on the micropolarity of the aggregates, as sensed by the probe pyrene, indicated that this microenvironmental parameter is almost unaffected by the presence of glycerol in the mixture. However, an increase in the micellar microviscosity at the surface region was observed from the photophysical behavior of two different probes, rhodamine B and auramine O. These results suggest a certain interaction of the cosolvent in the micellar solvation of SDS micelles.     

脲和盐酸胍诱导过氧化氢酶去折叠的研究

用荧光相图法分别研究了脲和盐酸胍诱导牛肝过氧化氢酶去折叠的过程。当脲 浓度从0依次增大至0.50,4.5和8.0 mol/L时,过氧化氢酶从天然四聚体依次转变 为蓬松的四聚体、部分折叠的无活性二聚体和去折叠态,而当盐酸胍浓度从0依次 变化至0.65,2.5和6.0 mol/L时,过氧化氢酶则从天然四聚体集资转变为部分折叠 的激活二聚体、部分折叠的单体和去折叠态,这表明无论是用脲还是用盐酸胍作为 变性剂,该蛋白的变性过程都符合“四态模型”,但这两种变性剂诱导该蛋白去折 叠的途径和机制有较大差异。实验结果表明荧光相图法可以检测蛋白质去折叠的中 间态。用等温滴定量去热法研究了盐酸胍诱导过氧化氢酶去折叠过程的热力学, 25.0 ℃时低浓度盐酸胍诱导该蛋白从天然四聚体转变为部分折叠的激活二聚体的 本征摩尔构象变化焓、Gibbs自由能和熵分别为-69.2 kJ·mol~(-1),6.43 kJ· mol~(-1)和-254 J·K~(-1)·mol~(-1),据此推断盐酸胍通过熵效应和静电效应来 稳定和激活该二聚体。