Effect of Hydrogenation on Ring C of Flavonols on Their Affinity for Bovine Serum Albumin

In this paper, the effect of hydrogenation on ring C of flavonols on the affinity for bovine serum albumin was investigated. Two differently substituted B-ring hydroxylation flavonols (myricetin and quercetin) and their dihydrides (dihydromyricetin and dihydroquercetin) were used to study their affinities for BSA by quenching the intrinsic BSA fluorescence in solution. From the spectra, the bimolecular quenching constants, the binding constants, the number of binding sites and the binding distances were calculated. The hydroxylation on ring B and hydrogenation on ring C of flavonols significantly affected the binding/quenching process; in general, the hydroxylation increased the affinity and the hydrogenation decreased the affinity. For myricetin and quercetin, the binding constants (K _a) for BSA were 1.84×10⁸ L⋅mol⁻¹ and 3.83×10⁷ L⋅mol⁻¹. For dihydromyricetin, the binding constant was 1.36×10⁴ L⋅mol⁻¹, while dihydroquercetin hardly quenched the BSA intrinsic fluorescence. These results showed that hydrogen bonding and conjugative effects may play an important role in binding of flavonols to BSA. These results also showed that the properties of flavonols are related to their chemical structure.     

Effects of Temperature and Common Ions on Binding of Puerarin to BSA

The effects of temperature and common ions on binding of puerarin to bovine serum albumin (BSA) are investigated. The binding constants (K _a) between puerarin and BSA are 1.13×10⁴ L⋅mol⁻¹ (20 °C) and 1.54×10⁴ L⋅mol⁻¹ (30 °C), and the number of binding sites (n) is (0.95±0.02). However, at a higher temperature (40 °C) the stability of the puerarin–BSA system decreases, which results in a lower binding constant (1.58×10³ L⋅mol⁻¹) and number of binding sites (n=0.73) of the puerarin–BSA system. However, the presence of Cu²⁺ and Fe³⁺ ions increases the binding constants and the number of binding sites in the puerarin–BSA complex.     

Probing the Interaction Between a Surfactant–Cobalt(III) Complex and Bovine Serum Albumin

The mechanism of binding of the surfactant–cobalt(III) complex, cis-[Co(phen)₂(C₁₄H₂₉NH₂)Cl](ClO₄)₂⋅3H₂O (phen = 1,10-phenanthroline, C₁₄H₂₉NH₂ = tetradecylamine) with bovine serum albumin (BSA) was investigated by UV–vis absorption, circular dichroism (CD) and fluorescence spectroscopic techniques. The results of fluorescence titration revealed that the surfactant–cobalt(III) complex quenched the intrinsic fluorescence of BSA through a combination of static and dynamic quenching. The apparent binding constant (K _a) and number of binding sites (n) were calculated below and above the critical micelle concentration (CMC). The thermodynamic parameters determined by the van’t Hoff analysis of the constants (ΔH ^∘=14.87 kJ⋅mol⁻¹; ΔS ^∘=152.88 J⋅mol⁻¹⋅K⁻¹ below the CMC and 25.70 kJ⋅mol⁻¹ and 243.14 J⋅mol⁻¹⋅K⁻¹, respectively, above the CMC) clearly indicate that the binding is entropy-driven and enthalpically disfavored. Based on F?rster’s theory of non-radiation energy transfer, the binding distance, r, between donor (BSA) and the acceptor (surfactant–cobalt(III) complex) was evaluated. UV–vis, CD and synchronous fluorescence spectral results showed that the binding of the surfactant–cobalt(III) complex to BSA induced conformational changes in BSA.     

Binding Interaction of Xanthoxylin with Bovine Serum Albumin

Three independent techniques have been used to investigate the interaction between bovine serum albumin (BSA) and xanthoxylin (XT). UV-Vis absorption spectroscopy measurements showed that there is a XT-BSA complex formed with an overall binding constant of K=1.01×10⁵ L⋅mol⁻¹. Spectroscopic techniques including synchronous fluorescence and Fourier transform infrared (FT-IR) were used to assess the structural effects of XT binding on BSA. The FT-IR experiments showed that there is a decrease of the amount of α-helix from 50.2 to 48.1% and an increase of the β-sheet from 32.9 to 36.9% in the XT-BSA complex. In addition, XT binds to site I of the protein with a distance of 2.07 nm between tryptophan residues and XT.     

Investigation of the Interaction Between Ofloxacin and Bovine Serum Albumin: Spectroscopic Approach

Ofloxacin is an antibacterial compound that belongs to the fluoroquinolone family. In this paper, the interaction between ofloxacin and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy and UV-Vis absorbtion spectroscopy under approximately the human physiological conditions. The thermodynamic parameters were calculated according to the dependence of enthalpy change on the temperature as follows: ΔH has a small negative value (−9.96 kJ⋅mol⁻¹), whereas ΔS has a positive value (54.77 J⋅mol⁻¹⋅K⁻¹). In this work, it was proved that the fluorescence quenching of BSA by ofloxacin is a result of the formation of an ofloxacin–BSA complex. Binding studies concerning the number of binding sites (n=1.14) and apparent binding constant were performed by Scatchard’s procedure. The binding distance r between donor (BSA) and acceptor (ofloxacin) was obtained according to the fluorescence resonance energy transfer (FRET) method.     

苯并咪唑衍生的单核钴(Ⅱ)和单核镍(Ⅱ)配合物与DNA和蛋白质的结合反应性及细胞毒活性研究

利用紫外吸收光谱、荧光光谱、圆二色光谱(CD)等各种光谱手段对比地研究了由苯并咪唑衍生的单核钴配合物[Co(EDTB)]2+(1)和单核镍配合物[Ni(EDTB)]2+(2)(这里EDTB为N,N,N′,N′-四(2′-苯并咪唑甲基)-1,2-乙二胺)与小牛胸腺DNA(CTDNA)和牛血清白蛋白(BSA)的相互作用。结果表明,在生理条件下,配合物1和2均能通过插入方式较强的与CT-DNA结合,诱导DNA构象的改变;且配合物1对DNA的结合能力略强于2,其结合常数分别为Kb(1)=3.23×104L·mol-1和Kb(2)=2.40×104L·mol-1。配合物与BSA相互作用的研究表明,1和2均能与BSA发生较强的相互作用,结合常数均处在104~105 L·mol-1;该结合引起了BSA微环境和构象发生变化,且使BSA内源荧光被淬灭,淬灭机理为静态淬灭。利用MTT法研究了配合物1和2对小鼠白血病细胞株P388和人非小细胞肺癌细胞株A-549的体外细胞毒活性,实验结果表明,配合物1和2对P388不敏感,对A-549在高浓度(10-4~10-5 mol·L-1)下表现出与顺铂相当的细胞毒活性。     

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.     

Studies of the interaction between apigenin and bovine serum albumin by spectroscopic methods

The interaction between apigenin (Ap) and bovine serum albumin (BSA) in physiological buffer (pH = 7.4) is investigated by fluorescence quenching technique and UV-vis absorption spectra. The results reveal that Ap could strongly quench the intrinsic fluorescence of BSA. The quenching mechanism of Ap for BSA varies with the change of Ap concentration. when Ap concentration is lower, it is a static quenching procedure, when Ap concentration is higher, a combined quenching (both static and dynamic) would operate. The apparent binding constants Ka and number of binding sites n of Ap with BSA are obtained by fluorescence quenching method. The thermodynamic parameters, enthalpy change (Δ_r H ^m and entropy change (Δ_r S ^m ), are calculated to be −15.382 kJ mol⁻¹ K⁻¹ < 0 and 104.888 J mol⁻¹ K⁻¹ > 0, respectively, which indicate that the interaction of Ap with BSA is driven mainly by hydrogen bonding and hydrophobic interactions. The distance r between BSA and Ap is calculated to be 1.89 nm based on F?rster’s non-radiative energy transfer theory. The results of synchronous fluorescence spectra show that binding of Ap with BSA cannot induce 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.     

Multi-spectroscopic Study on the Interaction between CdTe Quantum Dots and Bovine Serum Albumin

The interaction between CdTe quantum dots (QDs) and bovine serum albumin (BSA) was systematically investigated by fluorescence, UV‐vis absorption and circular dichroism (CD) spectroscopy under physiological conditions. The experimental results showed that the fluorescence of BSA could be quenched by CdTe QDs with a static quenching mechanism, indicating that CdTe QDs could react with BSA. The quenching constants according to the modified Stern‐Volmer equation were obtained as 1.710×10⁶, 1.291×10⁶ and 1.010×10⁶ L·mol^?1 at 298, 304, and 310 K, respectively. ΔH, ΔS and ΔG for CdTe QDs‐BSA system were calculated to be ?33.68 kJ·mol^?1, 6.254 J·mol^?1·K^?1 and ?35.54 kJ·mol^?1 (298 K), respectively, showing that electrostatic interaction in the system played a major role. According to F?rster theory, the distance between Trp‐214 in BSA and CdTe QDs was given as 2.18 nm. The UV‐vis, synchronous fluorescence and CD spectra confirmed further that the conformations of BSA after addition of CdTe QDs have been changed.     

Investigation on sonocatalytic damage of BSA under ultrasonic irradiation by Fe<Superscript>III</Superscript> complexes with some aminocarboxylic acid

The interaction of BSA and Fe^III complexes ([Fe^III(gly)(H₂O)₄]²⁺, [Fe^III(ida)(H₂O)₃]⁺, and [Fe^III(nta)(H₂O)₂], gly—glyane, ida—iminodiacetic acid, nta—triglycolamic acid) as well as the sonocatalytic damage to BSA was studied by UV-vis and fluorescence spectra. In addition, the influences of ultrasonic irradiation time and Fe^III complex concentration were also examined on the sonocatalytic damage to BSA. The results showed that the fluorescence quenching of BSA solution caused by the Fe^III complexes belonged to the static quenching process. The BSA and Fe^III complexes interacted with each other mainly through weak interaction and coordinate actions. The binding association constants (K) and binding site numbers (n) were calculated. The results were as follows: K ₁ = 0.5353 × 10⁴ l mol⁻¹ and n ₁ = 0.9812 for [Fe^III(gly)(H₂O)₄]²⁺, K ₂ = 1.4285 × 10⁴ l mol⁻¹ and n ₂ = 1.0899 for [Fe^III(ida)(H₂O)₃, and K ₃ = 0.4411 × 10⁴ l mol⁻¹ and n ₃ = 0.9471 for [Fe^III(nta)(H₂O)₂]. Otherwise, under ultrasonic irradiation the BSA were obviously damaged by the Fe^III complexes. The damage degree rose up with the increase of ultrasonic irradiation time and Fe^III complex concentration. And that, [Fe^III(nta)(H₂O)₂] exhibited in a way higher sonocatalytic activity than [Fe^III(gly)(H₂O)₄]²⁺ and [Fe^III(ida)(H₂O)₃]⁺.     

4-氯-2-(1H-咪唑并[4,5-f][1,10]菲咯啉)苯酚铜(Ⅱ)配合物的晶体结构及其与DNA的相互作用

利用菲咯啉酮衍生物4-氯-2-(1H-咪唑并[4,5-f][1,10]菲咯啉)苯酚(HL)设计合成了一种新的单核铜配合物[Cu (L)(5-Cl-sal)(DMF)]ClO₄·DMF (5-Cl-Hsal=5-氯-水杨醛),用元素分析和X射线单晶衍射等手段对配合物进行了表征。该配合物晶体属三斜晶系,P1空间群。用紫外吸收光谱、荧光光谱和凝胶电泳等方法研究了配合物与DNA的相互作用。结果表明,配合物以插入方式与CT-DNA结合,结合常数为1.02×10³ L·mol^-1。同时配合物也能较大程度淬灭EB-DNA复合物的荧光,表观键合常数为4.37×10⁵ L·mol^-1,略小于经典键合常数10⁷ L·mol^-1。淬灭机理为动态淬灭。凝胶电泳实验研究表明配合物在H₂O₂存在下可将pBR322质粒DNA切割为开环缺口型DNA和线型DNA,配合物浓度越大,切割效果越好。机理研究显示,配合物切割DNA的反应是由羟基自由基(·OH)和单线态氧(¹O₂)作为活性物种的氧化切割过程。     

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。     

Conformation and Thermodynamic Properties of the Binding of Vitamin C to Human Serum Albumin

The binding of vitamin C, L-ascorbic acid (AsA), with human serum albumin (HSA) was investigated by various spectroscopic techniques under simulated physiological conditions. The fluorescence quenching constants (K _SV) at four different temperatures (292, 298, 304, and 310 K) were obtained. The thermodynamic parameters ΔH ^∘ and ΔS ^∘ were calculated to be 6.02 kJ⋅mol⁻¹ and 84.55 J⋅mol⁻¹⋅K⁻¹ using the van’t Hoff equation. Additional experiments to determine the stoichiometry (n) were carried out using isothermal titration calorimetry (ITC) and cyclic voltammetry (CV). The distance, r, between AsA and the tryptophan residues of HSA was calculated to be 3.7 nm according to F?rster’s non-radiation energy transfer theory. The effect of AsA on the conformation of HSA was studied by means of three dimensional fluorescence spectra and CD spectra. The results indicate that the presence of AsA resulted in a slight change of the HSA secondary structure. The effect of common ions on the binding of AsA to HSA was also examined.     

金属元素组与血清白蛋白的竞争结合反应性能研究

利用亲和毛细管电泳(Affinity capillary electrophoresis,ACE)法研究金属元素组和血清白蛋白(Bovine serum albumin,BSA)的竞争结合反应性能。基于位点结合模型,构建双金属组[Zn2+,Cu2+]与血清白蛋白结合反应模型,建立多元金属组与生物大分子竞争结合的理论方程,测定结合参数并解析动力学机制。结果表明,金属元素组[Zn2+,Cu2+]与BSA发生竞争结合反应形成配合物Zn2+-BSA和Cu2+-BSA。依据有效淌度变化,通过建立的理论方程非线性拟合竞争结合反应的平均表观结合常数KZn2+-BSA=4.01×104L·mol-1、KCu2+-BSA=7.75×104L·mol-1。结合反应均为快平衡反应,Cu2+对Zn2+离子的结合作用有明显拮抗作用。分析ACE谱显示配合物的峰高与配体结合能力大小、配合物稳定性之间存在量效关系。     

金属元素组与血清白蛋白的竞争结合反应性能研究

利用亲和毛细管电泳（Affinitycapillaryelectrophoresis,ACE）法研究金属元素组和血清白蛋白（Bovineserumalbumin,BSA）的竞争结合反应性能。基于位点结合模型,构建双金属组[Zn²⁺,Cu²⁺]与血清白蛋白结合反应模型,建立多元金属组与生物大分子竞争结合的理论方程,测定结合参数并解析动力学机制。结果表明,金属元素组[Zn²⁺,Cu²⁺]与BSA发生竞争结合反应形成配合物Zn²⁺-BSA和Cu²⁺-BSA。依据有效淌度变化,通过建立的理论方程非线性拟合竞争结合反应的平均表观结合常数K_Zn²⁺-BSA=4.01×10⁴L·mol^-1、K_Cu²⁺-BSA=7.75×10⁴L·mol^-1。结合反应均为快平衡反应,Cu²⁺对Zn²⁺离子的结合作用有明显拮抗作用。分析ACE谱显示配合物的峰高与配体结合能力大小、配合物稳定性之间存在量效关系。     

荧光法研究3-氨基苯硼酸与牛血清白蛋白间的相互作用

为了了解分子印迹反应的机理和最适宜的反应条件, 应用荧光猝灭法研究了3-氨基苯硼酸(APBA)与牛血清白蛋白(BSA)的相互作用, 二者的反应受到体系pH值、离子强度等关键因素的影响. 实验结果表明: 适宜的离子强度和pH值为6.25时, APBA与BSA的色氨酸残基的荧光猝灭反应的物质的量比为2∶1, 表观结合常数K_A＝1.0×10¹¹ L²• mol^－2, 说明二者间形成了较强的化学键. 通过上述研究, 明晰了3-氨基苯硼酸与牛血清白蛋白之间的作用机理, 有助于分离或富集蛋白质中BSA组分, 从而能够改进印迹和洗脱的效率.     

A Study of Haloperidol Inclusion Complexes with <Emphasis Type="Italic">β</Emphasis>-Cyclodextrin Using Phase Solubility,NMR Spectroscopy and Molecular Modeling Techniques

Guest-host interactions of haloperidol (Halo) with β-cyclodextrin (β-CD) have been investigated using several techniques including phase solubility diagrams (PSD), proton nuclear magnetic resonance (¹H-NMR), X-ray powder diffractometry (XRPD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and molecular mechanical modeling (MM⁺). From an analysis of the PSDs, both protonated and neutral Halo (pK _a=8.5) form soluble 1:1 and 1:2 Halo/β-CD complexes, while the insoluble complex has 1:2 (Halo:β-CD) stoichiometry (B_S-type PSD). Ionization of Halo reduces its tendency to complex with β-CD, where the protonated species at pH=4.6 and 6.0 have K ₁₁ values of 100 L⋅mol⁻¹ and 298 L⋅mol⁻¹, respectively, compared with 2000 L⋅mol⁻¹ for neutral species at pH=10.6. The hydrophobic character of Halo was found to provide 32% of the driving force for complex stability, whereas other factors including specific interactions contribute −15 kJ⋅mol⁻¹. ¹H-NMR and MM⁺ studies indicate the formation of isomeric 1:1 and 1:2 complexes, where the chlorophenyl, flurophenyl, piperidine and butanone moieties become included into separate β-CD cavities. The dominant driving force for complexation is evidently van der Waals with very little electrostatic contribution. PSD, ¹H-NMR, XRPD, DSC and SEM studies indicate the formation of inclusion complexes in solution and in the solid state.     

邻菲咯啉乳酸镍配合物的合成与表征及其与牛血清白蛋白相互作用的荧光分析

利用溶液法合成了配合物[Ni(Hlact)₂(phen)]·2H₂O(1),并对该配合物进行了元素分析、红外光谱和X-射线单晶衍射表征。通过荧光光谱法研究了不同温度下配合物1与牛血清白蛋白相互作用的荧光强度的变化,计算在不同温度下,配合物1与牛血清白蛋白(BSA)的结合常数、结合位点数以及热力学函数,进一步讨论了配合物1与BSA相互作用的作用力类型和两者之间的距离。结果表明,配合物1对牛血清白蛋白的荧光猝灭为静态猝灭过程,它与牛血清白蛋白的相互作用有一个位点,结合常数的平均值5.06×10⁵ L·mol^-1,作用距离为2.35 nm,相互作用力表现为氢键和范德华相互作用。     

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.