Studies on Thermodynamics Features of the Interaction between Imidacloprid and Bovine Serum Albumin

At different temperatures, the interactions between imidacloprid （IMI） and bovine serum albumin （BSA） were investigated with a fluorescence quenching spectrum, a synchronous fluorescence spectrum, a three-dimensional fluorescence spectrum and an ultraviolet-visible spectrum. The average values of bonding constants （KLB： 3.424 × 10^4 L,mol^-1）, thermodynamic parameters （△H： 5.188 kJ,mol^-1, △G^（○—）：-26.36 kJ,mol^-1, △S： 103.9 J,K^-1,mol^-1） and the numbers of bonding sites （n： 1.156） could be obtained through Stern-Volmer, Lineweaver-Burk and ther- modynamic equations. It was shown that the fluorescence of BSA could be quenched for its reactions with IMI to form a certain kind of new compound. The quenching belonged to a static fluorescence quenching, with a non-radiation energy transfer happening within a single molecule. The thermodynamic parameters agree with △H〉 0, △S〉0 and△G^（○-）〈0, suggesting that the binding power between IMI and BSA should be mainly a hydrophobic interaction.     

Study of the Interaction between a Water-soluble Cationic Fluorescent Conjugated Polymer and Bovine Serum Albumin

The interaction between a water-soluble cationic fluorescent conjugated polymer (WCFP) and bovine serum albumin (BSA) was studied using UV?CVis absorption, fluorescence and circular dichroism spectroscopies. The results show that the fluorescence of BSA is strongly quenched by the WCFP under physiological conditions (pH?=?7.4). The quenching mechanism was found to be static, which was confirmed by the quenching rate constant (Kq) and UV?CVis absorption spectra. The thermodynamic parameters (?H ^??, ?S ^?? and ?G ^??) calculated from the complexation constant, determined according to Lineweaver?CBurk equations are 38.6?kJ·mol^?1, 228?J·mol^?1·K^?1 and ?29.4?kJ·mol^?1 at 298?K. The principal interaction was proposed to be electrostatic.     

Interaction between Xanthoxylin and Bovine Serum Albumin

在模拟生理条件下,采用荧光光谱法、圆二色光谱法和红外光谱法研究了花椒油素(XT)与牛血清白蛋白（BSA）的相互作用。结果表明花椒油素与牛血清白蛋白之间发生动态和静态联合猝灭,二者间的的猝灭常数(K)在286, 298和310 K分别为3.31 × 105, 到2.03 × 105 和 0.94 × 105 L∙mol-1. 热力学参数表明, 花椒油素与牛血清白蛋白间以疏水作用力为主。圆二色光谱和红外光谱法表明加入花椒油素后,牛血清白蛋白的二级结构发生了变化,其中α-螺旋减少了3.9%。另外,我们还研究了共存离子对两者结合的影响。     

Spectroscopic Studies on the Interaction of Asiatic Acid with Bovine Serum Albumin

Fluorescence spectroscopy, Fourier transform infrared (FT‐IR) spectroscopy, circular dichroism (CD) and FT‐Raman spectroscopy were employed to analyze the binding of the asiatic acid (AA) to bovine serum albumin (BSA) under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by AA was the result of the formation of BSA‐AA complex. The fluorescence quenching mechanism of BSA by AA was a static quenching procedure. According to the Van′t Hoff equation, the thermodynamic parameters enthalpy change (ΔH⁰) and entropy change (ΔS⁰) for the reaction were evaluated to be ?12.55 kJ·mol^?1 and 67.08 kJ·mol^?1, respectively, indicating that hydrophobic and electrostatic interactions played a major role in stabilizing the complex. The influence of AA on the conformation of BSA has also been analyzed on the basis of FT‐IR, CD and FT‐Raman spectra.     

Kinetic Study on the Exothermic First-stage Decomposition Reaction of 2,4,8,10-Tetranitro-2,4,8,10-tetraaza- spiro[5,5]undecane-3,9-dione

Introduction 2,4,8,10-Tetranitro-2,4,8,10-tetraazaspiro[5,5]udecane- 3,9-dione is a typical cyclourea nitramine (Figure 1). Its crystal density is 1.91 gcm-3. The detonation velocity according to =1.90 gcm-3 is about 8670 ms-1. Its sensitivity to impact is better than that of cyclotrimethy- lenetrinitramine. So it is the potential high explosive. Its preparation,1-3 properties,1-3 hydrolytic behavior4 and electronic structure3 have been reported. In the present work, we report its kinetic pa…     

Spectroscopic Studies on the Binding of Kaempferol‐3,7‐α‐L‐rhamnopyranoside to Bovine Serum Albumin

The binding of kaempferol‐3,7‐α‐L‐rhamnopyranoside (KRR) with bovine serum albumin (BSA) was investigated by different spectroscopic methods under simulative physiological conditions. Analysis of ?uorescence quenching data of BSA by KRR at different temperatures using Stern‐Volmer methods revealed the formation of a ground state KRR‐BSA complex with moderate binding constant of the order 10⁴ L·mol^?1. The existence of some metal ions could weaken the binding of KRR on BSA. The changes in the van't Hoff enthalpy (ΔH⁰) and entropy (ΔS⁰) of the interaction were estimated to be ?26.53 kJ·mol^?1 and 3.33 J·mol^?1·K^?1 and both hydrophobic and electrostatic forces contributed to stabilizing the BSA‐KRR complex. According to the F?ster theory of non‐radiation energy transfer, the distance r between the donor (BSA) and the acceptor (KRR) was obtained (r=2.83 nm). Site marker competitive experiments showed that KRR could bind to Site I of BSA. In addition, synchronous fluorescence, UV‐Vis absorption and circular dichroism (CD) results indicated that the KRR binding could cause conformational changes of BSA.     

Thermal Behavior of N,N＇Bis[N-（2,2,2-trinitroethyl）-N-nitro]ethylenediamine

The thermal behavior and kinetic parameters of the exothermic decomposition reaction of N‐N‐bis[N‐(2,2,2‐tri‐nitroethyl)‐N‐nitro]ethylenediamine in a temperature‐programmed mode have been investigated by means of differential scanning calorimetry (DSC). The results show that kinetic model function in differential form, apparent activation energy E_a and pre‐exponential factor A of this reaction are 3(1 ‐α)^2/3, 203.67 kJ·mol^?1 and 10^20.61s^?1, respectively. The critical temperature of thermal explosion of the compound is 182.2 °C. The values of ΔS^≠ ΔH^≠ and ΔG^≠ of this reaction are 143.3 J·mol^?1·K^?1, 199.5 kJ·mol^?1 and 135.5 kJ·mol^?1, respectively.     

Kinetic Studies on the Reaction of Sodium Hexacyanoferrate（ll） Complex with Peroxydisulfate Anion

The oxidation of Na₄Fe(CN)₆ complex by S₂O anion was found to follow an outer‐sphere electron transfer mechanism. We firstly carried out the reaction at pH=1. The specific rate constants of the reaction, k_ox, are (8.1±0.07)×10^?2 and (4.3±0.1)×10^?2 mol^?1·L·s^?1 at μ=1.0 mol·L^?1 NaClO₄, T=298 K for pH=1 (0.1 mol·L^?1 HCl0₄) and 8, respectively. The activation parameters, obtained by measuring the rate constants of oxidation 283–303 K, were ΔH^≠=(69.0±5.6) kJ·mol^?1, ΔS^≠=(?0.34±0.041)×10² J·mol^?1·K^?1 at pH=l and ΔH^≠=(41.3±5.5) kJ·mol^?1, ΔS^≠=(?1.27±0.33)×10² J·mol^?1·K^?1 at pH=8, respectively. The cyclic voltammetry of Fe(CN) shows that the oxidation is a one‐electron reversible redox process with E_1/2 values of 0.55 and 0.46 V vs. normal hydrogen electrode at μ=1.0 mol·L^?1 LiClO₄, for pH=1 and pH=8 (Tris). respectively. The kinetic results were discussed on the basis of Marcus theory.     

Kinetics and Mechanism of the Exothermic First-stage Decomposition Reaction of Dinitroglycoluril

Introduction Dinitroglycoluril (DINGU) is a typical cyclourea nitramine. Its crystal density is 1.94 gcm-3. The detonation velocity corresponding to =1.94 gcm-3 is about 8450 ms-1. Its sensitivity to impact is better than that of cyclotrimethylenetrinitramine. It has the potential for possible use as high explosive from the point of view of the above-mentioned high performance. Its preparation,1-4 properties1-4 and hydrolytic behavior4 have been reported. In the present paper, we report i…     

Study on the Interaction of Raloxifene and Bovine Serum Albumin by the Tachiya Model

The interaction of bovine serum albumin (BSA) with raloxifene was assessed via fluorescence spectroscopy. The number of binding sites and the apparent binding constants between raloxifene and BSA were analyzed using the Tachiya model and Stern-Volmer equation, respectively. The apparent binding constant and the number of binding sites at 298 K were 2.33×10⁵ L?mol^?1 and 1.0688 as obtained from the Stern-Volmer equation and 2.00×10⁵ L?mol^?1 and 2.6667 from the Tachiya model. The thermodynamic parameters ΔH and ΔS were calculated to be 69.46 kJ?mol^?1 and 121.12 J?K^?1?mol^?1, respectively, suggesting that the force acting between raloxifene and BSA was mainly a hydrophobic interaction. The binding distance between the donor (BSA) and acceptor (raloxifene) was 4.77 nm according to Förster’s nonradiational energy transfer theory. It was also found that common metal ions such as K⁺, Cu²⁺, Zn²⁺, Mg²⁺ and Ca²⁺ decreased the apparent association constant and the number of binding sites between raloxifene and BSA.     

Spectroscopic Study on Interaction of Lomefloxacin with Human Serum Albumin in the Presence of Copper Ion

The interaction of lomefloxacin （LMF） with human serum albumin （HSA） in the presence of copper ions in a physiological medium and its thermodynamic characteristics were investigated by multi-spectroscopy. The experimental results showed that both LMF and LMF-Cu^2＋ could quench the fluorescence of HSA with a static quenching mechanism, indicating that LMF or LMF-Cu^2＋ could react with HSA. The apparent binding constants/numbers of binding sites were estimated as 4.924± 105 Lomol 1/1.473 for LMF-HSA, 8.990± 104 L·mol^-1/1.785 for LMF- Cu^2＋-HSA, 1.10± 105 L·mol^-1/1.21 for LMF-Cu^2＋ and 7.30± 102 L·mol^-1/0.82 for HSA-Cu^2＋, respectively. AH and AS for LMF-HSA system were calculated to be --2.189 kJ·mol^-1 and 61.25 J·mol^-1·K^-1, while those for LMF-Cu^2＋-HSA system were -7.401 kJ·mol^-1 and 47.63 J·mol^-1·K^-1 Although the values of AH and AS in these two systems were different, the treads were similar, which indicated that electrostatic interactions in these two systems played a major role. According to Forster theory, the distances were given as 5.006 nm for HSA-LMF and 4.709 nm for HSA-LMF-Cu^2＋. Synchronous fluorescence and circular dichroism spectra confirmed further that the conformations of human serum albumin before and after interacting with LMF or LMF-Cu^2＋ were different. All the results revealed that copper ions promoted the interaction of lomefloxacin with human serum albumin.     

应用光谱和分子模拟法研究一种聚酰亚胺聚合物与人免疫球蛋白的相互作用

本文利用荧光猝灭法、红外光谱法及计算机模拟技术研究了一种聚酰亚胺聚合物(2,6-Bis(4-amino-2-trifluoromethyl phenoxy-4’- benzoyl)-pyridine,简称BAFP )与人免疫球蛋白（HIgG）的相互作用。同步荧光的结果定性地说明了BAFP影响水溶液中HIgG二级结构的情况。而判定BAFP影响HIgG二级结构的定量依据来自红外光谱,实验数据表明α螺旋结构的含量相比未加入药物时增加了约2.6～10.2%,,β折叠增大了约13.6～27.7%,,而β转角则减小了约23.8～30.3%。分子模拟的结果显示BAFP与HIgG的键合作用很强,并且有四个氢键在BAFP与HIgG分子的色氨酸Trp 170, 缬氨酸Val 105, 甲硫氨酸Met 139 及天冬酰胺Asn 52之间形成;同时也显示出维持药物与蛋白质的相互作用力主要是疏水作用,这与实验所得到的热力学参数判定作用力的结果相一致（依据范德霍夫公式计算得 与 的值分别为-6.70KJ.mol-1 和 71.93 J.mol-1.K-1）。     

Multispectroscopic Studies on the Interaction of a Platinum(II) Complex Containing l-Histidine and 1,10-Phenanthroline Ligands with Bovine Serum Albumin

The mechanism of the interaction between bovine serum albumin (BSA) and [Pt(phen) (histidine)]⁺ complex was studied employing ultraviolet (UV) absorption, circular dichroism (CD), FT-IR, differential pulse voltammetry (DPV), and fluorescence spectral methods. Fluorescence data showed that the intrinsic fluorescence of BSA was strongly quenched by Pt(II) complex in terms of an untypical static quenching process. The corresponding number of binding sites (n) and binding constant (K _b) of BSA and complex at 283, 298, and 310 K were calculated to be 0.61?×?10⁶, 19?×?10⁶, and 42?×?10⁶ M^?1, respectively. The results showed that the increasing temperature improves the stability of the complex–BSA system, which results in a higher binding constant and the number of binding sites of the complex–BSA system. The positive ΔH and positive ΔS indicated that hydrophobic forces might play a major role in the binding between complex and BSA. Based on Forster’s theory of non-radiation energy transfer, the binding distance (r) between the donor (BSA) and acceptor (Pt(II) complex) was evaluated. The results of CD, UV–vis, DPV, and FT-IR spectroscopy showed that the binding of Pt(II) complex to BSA induced conformational changes in BSA     

百草枯与牛血清白蛋白结合作用的荧光光谱

在模拟动物体生理条件下, 用荧光光谱和紫外-可见吸收光谱法研究了在不同温度下, 百草枯(PQ)与牛血清白蛋白(BSA)结合反应的光谱行为. 试验发现, PQ对BSA有较强的荧光猝灭作用. 用Stern-Volmer和Lineweaver-Burk方程分别处理试验数据, 发现BSA与PQ发生反应生成了新的复合物, 属于静态荧光猝灭, 发生分子内的非辐射能量转移. 根据F?rster的偶极-偶极非辐射能量转移理论计算出结合位置距离212位色氨酸残基2.07 nm. 由Lineweaver-Burk方程求出了不同温度下反应时复合物的形成常数K_LB (297 K: 2.035×10⁴ L•mol^－1; 304 K: 3.256×10⁴ L•mo^－1; 311 K: 2.889×10⁴ L•mol^－1)及对应温度下结合反应的热力学参数(⊿H^Ø＝18.50 kJ•mol^－1;⊿S^Ø＝144.7 J•K^－1/145.2 J•K^－1/141.0 J•K^－1; ⊿G^Ø＝－24.50 kJ•mol^－1/－25.66 kJ•mol^－1/－25.36 kJ•mol^－1), 证明二者主要靠疏水作用力结合. 同时用三维荧光光谱及同步荧光光谱法探讨了PQ对BSA构象的影响, 为预防和医治PQ中毒提供了重要依据.     

Spectroscopic Studies on the Interaction of 2,4-Dichlorophenol with Bovine Serum Albumin

The interaction between 2,4-dichlorophenol (DCP) and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy combined with UV-vis absorption and circular dichroism (CD) spectroscopy under simulative physiological conditions. The experiment results show that the fluorescence intensity of BSA is dramatically decreased owing to the formation of a DCP–BSA complex. The corresponding effective quenching constants (K _a) between DCP and BSA at four different temperatures (292, 298, 304 and 310 K) were determined to be 10.08×10⁴, 9.082×10⁴, 8.177×10⁴, and 7.260×10⁴ L?mol^?1, respectively. The thermodynamics parameters enthalpy change (ΔH) and entropy change (ΔS) were calculated to be ?13.64 kJ?mol^?1 and 49.08 J?mol^?1?K^?1, which suggested that hydrophobic interaction was the predominant intermolecular force. Site marker competitive experiments indicated that the binding of DCP to BSA primarily takes place in subdomain IIA. The binding distance (r) between DCP and the tryptophan residue of BSA ias 4.09 nm according to Förster’s theory of non-radioactive energy transfer. The conformational investigation demonstrated that the presence of DCP decreased the α-helical content of BSA and induced a slight unfolding of the polypeptides of protein, which confirmed the occurrence some micro environmental and conformational changes of BSA molecules.     

Thermal studies and spectral characterization of the chelate of bis-(η5-cyclopentadienyl titanium(IV) with salicylidene-4-methylaniline

A new chelate (η⁵-C₅H₅)₂Ti(SB)₂, whereSB=O, N donor Schiff base salicylidene-4-methylaniline, was synthesized. The course of thermal degradation of the chelate was studied by thermogravimetric (TG) and differential thermal analysis (DTA) under dynamic conditions of temperature. The order of the thermal decomposition reaction and energy of activation was calculated from TG curve while from DTA curve the change in enthalpy was calculated. Evaluation of the kinetic parameters was performed by Coats-Redfern as well as Piloyan-Novikova methods which gaven=1, ΔH=1.114 kJ·mol^?1, ΔE=27.01 kJ·mol^?1, ΔS=?340.12 kJ·mol^?1·K^?1 andn=1, ΔH=1.114 kJ·mol^?1, ΔE=20.01 kJ·mol^?1, ΔS=?342.60 kJ·mol^?1·K^?1, respectively. The chelate was also characterized on the basis of different spectral studies viz. conductance, molecular weight, IR, UV-visible and¹H NMR, which enabled to propose an octahedral structure to the chelate.     

4-硝基苯甲醇的低温热容和标准摩尔生成焓

用精密自动绝热量热计测定了4-硝基苯甲醇（4-NBA）在78 ~ 396 K温区的摩尔热容。其熔化温度、摩尔熔化焓及摩尔熔化熵分别为:(336.426 ± 0.088) K, (20.97 ± 0.13) kJ×mol-1 和 (57.24 ± 0.36) J×K-1×mol-1.根据热力学函数关系式,从热容值计算出了该物质在80 ~ 400 K温区的热力学函数值 [HT - H298.15 K] 和[ST - S298.15 K]. 用精密氧弹燃烧量热计测定了该物质在T＝298.15 K的恒容燃烧能和标准摩尔燃烧焓分别为 (C7H7NO3, s)＝- ( 3549.11 ± 1.47 ) kJ×mol-1 和 (C7H7NO3, s)＝- ( 3548.49 ± 1.47 ) kJ×mol-1. 利用标准摩尔燃烧焓和其他辅助热力学数据通过盖斯热化学循环, 计算出了该物质标准摩尔生成焓 (C7H7NO3, s)＝- (206.49 ± 2.52) kJ×mol-1 .     

Study on Dynamic Interfacial Tension of 3‐Dodecyloxy‐2‐hydroxypropyl Trimethyl Ammonium Chloride at n‐Decane/Water Interface

Dynamic interfacial tension (DIT) and interface adsorption kinetics at the n‐decane/water interface of 3‐dodecyloxy‐2‐hydroxypropyl trimethyl ammonium chloride (R₁₂TAC) were measured using spinning drop method. The effects of R_nTAC concentration and temperature on DIT have been investigated, the reason of the change of DIT with time has been discussed. The effective diffusion coefficient, D _a, and the adsorption barrier, ?_a, have been obtained with extended Word‐Tordai equation. The results show that the higher the concentration of surfactants is, and the smaller will be the DIT and the lower will be the curve of the DIT, and the R₁₂TAC solutions follow a mixed diffusion‐activation adsorption mechanism in this investigation. With increase of concentration in bulk solution of R₁₂TAC from 8×10^?4 mol · dm^?3 to 4×10^?3 mol · dm^?3, D _a decreases from 2.02×10^?10 m^?2 · s^?1 to 1.4×10^?11 m^?2 · s^?1 and ? _a increases from 2.60 kJ · mol^?1 to 9.32 kJ · mol^?1, while with increase of temperature from 30°C to 50°C, D _a increases from 2.02×10^?10 m^?2 · s^?1 to 5.86×10^?10 m^?2 · s^?1 and ε_a decreases from 2.60 kJ · mol^?1 to 0.73 kJ · mol^?1. This indicates that the diffusion tendency becomes weak with increase strength of the interaction between surfactant molecules and that the thermo‐motion of molecules favors interface adsorption.     

氢过碘酸）合银（III）配离子氧化L-脯氨酸的反应动力学及机理

L-脯氨酸独有的亚胺基使其在生物医药领域具有许多独特的功能,并广泛用作不对称有机化合物合成的有效催化剂。本文在碱性介质中研究了二（氢过碘酸）合银（III）配离子氧化 L-脯氨酸的反应。经质谱鉴定,脯氨酸氧化后的产物为脯氨酸脱羧生成的 γ-氨基丁酸盐;氧化反应对脯氨酸及Ag(III) 均为一级;二级速率常数 k′ 随 [IO₄^-] 浓度增加而减小,而与 [OHˉ] 的浓度几乎无关;推测反应机理应包括 [Ag(HIO₆)₂]^5-与 [Ag(HIO₆)(H₂O)(OH)]^2-之间的前期平衡,两种Ag（III）配离子均作为反应的活性组分,在速控步被完全去质子化的脯氨酸平行地还原,两速控步对应的活化参数为： k₁ (25 ^oC)＝1.87±0.04（mol·L^-1)^-1s^-1,∆ H₁^≠＝45±4 kJ · mol^-1, ∆ S₁^≠＝-90±13 J· K^-1·mol^-1 and k₂ (25 ^oC) ＝3.2±0.5（mol·L^-1)^-1s^-1, ∆ H₂^≠＝34±2 kJ · mol^-1, ∆ S₂^≠＝-122 ±10 J· K^-1·mol^-1。本文第一次发现 [Ag(HIO₆)₂]^5-配离子也具有氧化反应活性。     

Thermochemistry on the Complex of Erbium Perchlorate with L-α-Glutamic Acid [Er2（L-Glu）2（H2O）6]（ClO4）4·6H2O（s）

A coordination compound of erbium perchlorate with L-α-glutamic acid, [Er2（Glu）2（H2O）6]（ClO4）4·6H2O（s）, was synthesized. By chemical analysis, elemental analysis, FTIR, TG/DTG, and comparison with relevant literatures, its chemical composition and structure were established. The mechanism of thermal decomposition of the complex was deduced on the basis of the TG/DTG analysis. Low-temperature heat capacities were measured by a precision automated adiabatic calorimeter from 78 to 318 K. An endothermic peak in the heat capacity curve was observed over the temperature region of 290-318 K, which was ascribed to a solid-to-solid phase transition. The temperature Ttrans, the enthalpy △transHm and the entropy △transSm of the phase transition for the compound were determined to be： （308.73±0.45） K, （10.49±0.05） kJ·mol^-1 and （33.9±0.2） J·K^-1·mol^-1. Polynomial equation of heat capacities as a function of the temperature in the region of 78-290 K was fitted by the least square method. Standard molar enthalpies of dissolution of the mixture [2ErCl3·6H2O（s）＋2L-Glu（s）＋6NaClO4·H2O（s）] and the mixture {[Er2（Glu）2（H2O）6]（ClO4）4·6H2O（s）＋6NaCl（s）} in 100 mL of 2 mol·dm^-3 HClO4 as calorimetric solvent, and {2HClO4（1）} in the solution A＇ at T=298.15 K were measured to be, △dHm,1=（31.552±0.026） kJ·mol^-1, △dHm,2 = （41.302±0.034） kJ·mol^-1, and △dHm,3 = （ 14.986 ± 0.064） kJ·mol^-1, respectively. In accordance with Hess law, the standard molar enthalpy of formation of the complex was determined as △fHm-=-（7551.0±2.4） kJ·mol^-1 by using an isoperibol solution-reaction calorimeter and designing a thermochemical cycle.