Spectroscopic studies on in vitro binding of cefixime and tolcapone drugs with serum albumin

The interaction between cefixime (antibacterial) and tolcapone (Parkinson’s disease) drugs with bovine serum albumin (BSA) was investigated using several spectroscopic techniques viz. UV–Vis, fluorescence and circular dichroism. The thermodynamic parameters of the interactions were calculated, which indicated that the binding processes are spontaneous and H-bonding and van der Waals forces play a major role in BSA–cefixime interaction and hydrophobic interactions dominate BSA–tolcapone complexation. Cefixime quenches the intrinsic fluorescence of BSA by dynamic process while tolcapone through static process. The binding constant of the BSA–tolcapone complex (10⁷ L mol^?1) is found to be relatively higher than that of BSA–cefixime complex (10⁴ L mol^?1). The binding distance between BSA and cefixime and tolcapone is calculated to be 3.3 and 4.2 nm, respectively. Both fluorescence and circular dichrosim spectral studies confirmed conformational changes in BSA upon binding with these drugs. Molecular docking studies suggest the possible binding sites in the protein molecule.'     

BCBP与牛血清白蛋白相互作用热力学

塞来昔布衍生物是一类应用非常广泛的治疗急慢性炎症的新型非甾体抗炎药。本文综合利用荧光光谱、紫外吸收光谱、圆二色谱和分子模拟等方法,研究了塞来昔布衍生物1-苯磺酰胺-3-羧基-5-苯基吡唑(BCBP)与牛血清白蛋白(BSA)相互作用的热力学行为。荧光光谱和紫外吸收光谱的分析表明：BCBP能有效猝灭BSA的内源荧光,猝灭机制为静态猝灭。通过所获取的相互作用热力学参数,可知两者之间的相互作用是一个吉布斯自由能降低的自发过程,且二者之间的主要作用力为氢键和范德华力。圆二色谱的分析发现BCBP引起BSA的构象发生改变,其α-螺旋含量降低,无规卷曲含量升高。分子对接的结果与实验结果相符。     

光谱法研究硫鸟嘌呤与七元瓜环及牛血清白蛋白的超分子相互作用

利用紫外-可见吸收光谱法和荧光光谱法研究了抗癌药物硫鸟嘌呤(6-TG)与七元瓜环(Q[7])及牛血清白蛋白(BSA)的相互作用. 结果表明, 6-TG与Q[7]及BSA可形成三元复合物, 且6-TG与Q[7]及BSA均可形成1:1的超分子配合物, 6-TG能引起BSA的荧光猝灭, 猝灭机制为静态猝灭. 此外, 还用同步荧光法和三维荧光法考察了6-TG对BSA构象的影响, 结果表明6-TG的加入使BSA的构象发生了变化, 而同步荧光光谱结果表明结合位点更接近于色氨酸.     

咪唑型离子液体与牛血清蛋白的缔合特性

通过紫外-可见光谱、荧光光谱、同步荧光光谱、圆二色谱、衰减全反射红外光谱、负染-透射电镜、等温滴定微量热等实验方法系统地探讨了咪唑型离子液体与牛血清蛋白(BSA)的缔合特性.结果发现,离子液体[Bmim]Cl的加入使得BSA的紫外吸收强度增加,同时也会导致其荧光猝灭,并且这种猝灭是静态猝灭.同步荧光的研究结果表明,[Bmim]Cl分子可与蛋白质中接近色氨酸残基的区域发生相互作用,使蛋白质的构象和内部的疏水结构发生改变;负染色法透射电镜直观地显示了加入离子液体后形成的蛋白质-离子液体复合物结构逐渐变大;圆二色谱和衰减全反射红外光谱表明:在离子液体与BSA缔合过程中,离子液体的加入使得BSA二级结构中的α-螺旋和β-折叠的含量降低,从而引起蛋白质二级结构的变化;表面张力法和等温滴定微量热法进一步证实上述缔合作用为静电作用和疏水作用共同作用的结果,但离子液体的烷基链与BSA疏水内腔之间的疏水作用是离子液体与BSA缔合的主要驱动力.     

Biophysical Studies on the Site-Selective Binding of a Synthesized Selenium–Quercetin Complex on a Protein

A selenium?Cquercetin complex (SEQC) was synthesized and its structure was identified by IR, LC-MS and ¹H-NMR. Its biochemical effects on bovine serum albumin (BSA) were studied by measuring its molecular spectra including three-dimensional fluorescence, ultraviolet and circular dichroism (CD) spectra. The interaction of SEQC and BSA is discussed in terns of fluorescence quenching and F?rster??s non-radiation energy transfer theory. The thermodynamic parameters $\Delta H^{\uptheta}$ , $\Delta G^{\uptheta}$ , and $\Delta S^{\uptheta}$ were calculated at different temperatures and the results indicate that the interaction is an endothermic as well as an entropy generating process. The binding site was explored by the fluorescence probe technique using warfarin and ibuprofen as markers. It was found that around body temperature hydrophobic forces maintained the average distance from the tryptophan residue in domain?II of BSA (donor) to SEQC (acceptor) at 3.76 nm. The conformational changes of BSA were investigated by three-dimensional fluorescence and circular dichroism spectra.     

具有抗癌活性的新型硒杂环化合物的合成及其与牛血清蛋白的相互作用

合成了一种新的硒二唑衍生物4-(苯并[c][1,2,5]硒二唑-6-yl)苯-1,2-二氨基(BSBD).研究了其抗肿瘤活性,结果发现BSBD具有很好的抗癌活性,特别对Neuro-2a小鼠脑神经瘤细胞表现出很好的选择性.关于作用机制的研究发现,BSBD可呈剂量效应的诱导肿瘤细胞中Sub-G1凋亡峰的累积、染色质固缩及凋亡小体的形成,说明诱导细胞凋亡是BSBD发挥抗肿瘤活性的主要机制.进而应用紫外-可见吸收光谱、荧光光谱法、傅里叶红外光谱、圆二色光谱法研究了其与牛血清白蛋白(BSA)的相互作用.采用位点结合模型公式和热力学公式计算了结合常数、结合位点数及结合力类型,并用紫外-可见吸收光谱、红外光谱和圆二色光谱技术探讨了硒杂环化合物对牛血清白蛋白构象的影响.结果表明:BSBD能有效淬灭牛血清白蛋白的荧光强度,其猝灭机理为静态猝灭,主要作用力类型是氢键和范德华力.而同步荧光、紫外-吸收示差光谱、红外光谱和圆二色光谱都进一步证明了BSBD与BSA结合后,改变了BSA的内部结构.     

Characterization of Phenosafranine–Hemoglobin Interactions in Aqueous Solution

Binding of the drug phenosafranine to hemoglobin (Hb) in aqueous solutions was investigated by fluorescence, UV/vis and circular dichroism (CD) spectral methods at pH=7.4. The fluorescence data showed that fluorescence quenching of Hb by phenosafranine is the result of formation of a phenosafranine–Hb complex with a 1:1 molar ratio. Thermodynamic analysis implied that hydrophobic, electrostatic and hydrogen bond interactions are all involved in stabilizing the complex. The molecular distance (r=4.29 nm) between the donor (Hb) and acceptor (phenosafranine) was calculated according to Förster’s theory. The features of phenosafranine-induced secondary structure changes of Hb have been studied by synchronous fluorescence, CD and three-dimensional fluorescence spectroscopy. This study improves our knowledge of the interaction dynamics of phenazinium drugs to the physiologically important protein Hb.     

吡虫啉与人血清白蛋白相互作用热力学行为

在模拟人体生理条件下,综合利用荧光光谱、紫外吸收光谱、圆二色谱和分子模拟等方法,研究了吡虫啉(IMI)和人血清白蛋白(HSA)相互作用的热力学行为。荧光光谱和紫外吸收光谱的分析表明：吡虫啉能有效猝灭HSA的内源荧光,猝灭机制为静态猝灭;通过所获取的相互作用热力学参数,可知两者之间的相互作用是一个吉布斯自由能降低的自发过程,且二者之间的主要作用力为氢键和范德华力。位点竞争实验和分子模拟的结果表明：吡虫啉在HSA的主要结合位置为位点?。圆二色谱、同步荧光光谱和三维荧光的分析发现：吡虫啉引起HSA的构象发生改变,其α-螺旋含量降低,无规卷曲含量升高,肽链结构在吡虫啉的作用下有所伸展。     

The Interaction Between Crystal Violet and Bovine Serum Albumin: Spectroscopic and Molecular Docking Investigations

The present work reported the investigations on the interaction between a triphenylmethane industrial dye—crystal violet (CV)—and bovine serum albumin (BSA) by spectroscopic methods and molecular docking calculation. The static quenching mechanism of the intrinsic fluorescence of BSA by CV was deduced by the fluorescence measurements and the ground-state complex formation was confirmed from the UV-vis spectra. The site maker competition binding experiments together with the molecular docking showed that the CV molecule specifically bound on the subdomain IIA of BSA. The obtained values of thermodynamic properties of binding suggested that the hydrophobic interaction was dominated as suggested by molecular docking results that the CV molecule was surrounded by hydrophobic amino acid residues. The conformation change of BSA in the binding process was detected by circular dichroism spectra and Fourier-transform infrared (FTIR) spectra and also reflected by the size change of BSA from the measurements by dynamic light scattering (DLS).     

光谱法研究核壳量子点CdTe/CdS与牛血清白蛋白的相互作用

应用荧光光谱、圆二色光谱和紫外吸收光谱等技术研究核壳量子点CdTe/CdS与牛血清白蛋白(BSA)相互作用的结果表明,CdTe/CdS对BSA的荧光猝灭机理为静态猝灭。根据不同温度下量子点对BSA的荧光猝灭作用计算了结合常数、热力学参数,证明了量子点与BSA相互作用力主要是范德华力或氢键作用力。探讨了量子点对BSA构象的影响。     

Analysis of binding interaction between pegylated puerarin and bovine serum albumin by spectroscopic methods and dynamic light scattering

The interaction between bovine serum albumin (BSA) and pegylated puerarin (Pur) in aqueous solution was investigated by UV-Vis spectroscopy, fluorescence spectroscopy and circular dichroism spectra (CD), as well as dynamic light scattering (DLS). The fluorescence of BSA was strongly quenched by the binding of pegylated Pur to BSA. The binding constants and the number of binding sites of mPEG(5000)-Pur with BSA were 2.67±0.12 and 1.37±0.05 folds larger after pegylating, which were calculated from the data obtained from fluorescence quenching experiments. The enthalpy change (ΔH) and entropy change (ΔS) were calculated to be 4.09 kJ mol(-1) and 20.01 J mol(-1) K(-1), respectively, according to Van't Hoff equation, indicating that the hydrophobic force plays a main role in the binding interaction between pegylated Pur and BSA. In addition, the negative sign for Gibbs free energy change (ΔG) implies that the interaction process is spontaneous. Moreover, the results of synchronous fluorescence and CD spectra demonstrated that the microenvironment and the secondary conformation of BSA were changed. Comparing with Pur, all our data collected indicated that pegylated Pur interacted with BSA in the same way as that of Pur, but docked into the hydrophobic pocket of BSA with more accessibility and stronger binding force. DLS measurements showed monomethoxy polyethylene glycol (mPEG) have an effect on BSA conformation, and revealed that changes in BSA size might be due to increases in binding constant and the absolute values of ΔG after Pur pegylation.     

Interaction of Mixed Porphyrin-polypyridyl Ru(II) Complex with Bovine Serum Albumin

The interactions of mixed porphyrin-polypyridyl Ru(II) complexes [m(Py-3′)TPP-Ru(phen) 2 Cl] + (1) and its derivatives [Nim(Py-3′)TPP-Ru(phen) 2 Cl] + (2) and [Cum(Py-3′)TPP-Ru(phen) 2 Cl] + (3)(phen=1,10-phenanthroline; m(Py-3′)TPP=5-(3′-pyridyl)-10,15,20-triphenylporphyrin) with bovine serum albumin(BSA) were investigated by fluorescence, UV-Vis and circular dichroism(CD) spectroscopies. The UV-Vis and CD spectral experiments indicated that the secondary structures of the protein were perturbed in the presence of the porphyrin Ru(II) complex and the perturbation was enhanced under the irradiation with ultra-violet light. The fluorescence quenching mechanism of BSA by the three complexes was determined to be a static process, and the apparent binding constant K values for complexes 1, 2 and 3 measured by fluorescence quenching method were (3.86±0.03)×10 3 L/mol(n=0.94±0.04), (5.69±0.04)×10 3 L/mol(n=1.03±0.06), and (6.54±0.02)×10 3 L/mol(n=1.03±0.05), respectively.     

天麻光谱性质及其与牛血清白蛋白作用的研究

用荧光光谱法和紫外吸收光谱法研究了中药天麻(GE)的光谱性质,以及GE与牛血清白蛋白(BSA)的相互作用。考察了溶剂、煮沸时间和pH值等影响因素对GE荧光性质的影响。实验确定用水提取液煮沸10min配成储备液,在中性条件下进行测定。发现了BSA的荧光被猝灭和GE的荧光被敏化,从而说明二者之间存在能量转移和结合作用。在BSA与GE的作用过程中,BSA中酪氨酸的构象发生了改变。     

1,4-二甲基-6,8-二甲氧基-9,10-蒽醌的合成及其与牛血清白蛋白和DNA的相互作用

合成了大黄素类蒽醌衍生物1,4-二甲基-6,8-二甲氧基-9,10-蒽醌(1)并应用紫外光谱、荧光光谱、圆二色谱等方法研究了其与牛血清白蛋白(BSA)和小牛胸腺DNA(ct-DNA)的相互作用.荧光光谱结果表明,化合物1与BSA的相互作用主要以静态猝灭方式使BSA的内源性荧光发生猝灭;圆二色谱表明,化合物1通过疏水作用及形成氢键破坏了α-螺旋结构,导致BSA分子中的α-螺旋含量下降.在pH 7.4时固定DNA的浓度,加入化合物1后,紫外光谱的最大吸收峰发生红移且吸光度加大.荧光光谱表明,化合物1与DNA-4S green NC的结合为竞争性抑制,并可使溶液体系荧光猝灭;圆二色谱表明,随着化合物1的加入,DNA碱基间作用能迅速减弱,表明化合物1与DNA之间为嵌插作用.此外,MTT方法的结果表明,化合物1对结肠癌细胞株HCT116增殖有明显的抑制作用.     

Spectroscopic Investigation on the Binding of the Antitumoral Pd(II) Complex to Human Serum Albumin

The interaction of human serum albumin (HSA) with 1,10‐phenanthroline‐ethyldithiocarbamatopalladium(II) nitrate complex, [Pd(phen)(Et‐dtc)]NO₃, has been studied by using absorption, fluorescence and circular dichroism spectroscopic measurements. UV‐Vis studies imply that The peptide strands of protein molecules extended more (denatured) upon the addition of Pd(II) complex. This process is spontaneous and exothermic. A fluorescence quenching reaction of Pd(II) complex and HSA was observed and quenching mechanism was suggested as static quenching according to Stern‐Volmer equation. The number of binding sites (n) and apparent association constant (K_A) were calculated using fluorescence quenching data. The circular dichroism results revealed the conformational changes in secondary structure of protein upon its interaction with Pd(II) complex. In these interaction studies, several thermodynamic and binding parameters are also determined which may provide deeper insights into structural changes induced by an antitumor Pd(II) complex on the protein as the metal complex side effects.     

Characterization of Interaction Between Raltitrexed and Bovine Serum Albumin by Optical Spectroscopic Techniques

The interaction of raltitrexed(RTX) with bovine serum albumin(BSA) was investigated by steady state/lifetime fluorescence spectroscopy and circular dichroism(CD) spectroscopy under the simulative physiological conditions. The results of fluorescence titration reveal that RTX could strongly quench the intrinsic fluorescence of BSA via a static quenching procedure. The obtained binding constant K_A of RTX with BSA was 478630 and 44259 L/mol at 298 and 310 K, respectively. According to van’t Hoff equation, the thermodynamic parameters ΔH, ΔG and ΔS were calculated, indicating that hydrophobic forces were the predominant intermolecular forces in stabilizing the complex. The binding process was a spontaneous process, in which Gibbs free energy change was negative. According to Förster’s non-radioactive energy transfer theory, the distance r between donor(BSA) and acceptor(RTX) was 3.82 nm, suggesting that the energy transfer from BSA to RTX occurred with high probability. Displacement experiment and the number of binding sites calculation confirmed that RTX could bind to the site-I of BSA. Furthermore, the effects of pH and some metal ions on the interaction of RTX with BSA were also investigated. The results of synchronous fluorescence and CD spectra show that the RTX-BSA binding induced conformational changes in BSA.     

Biophysical studies of the interaction between a triazole derivative and bovine serum albumin by multi-spectroscopic and molecular modeling methods

The interaction between 3-thiol-4-(2,4-dichlorobenzylideneamino)-5-methyl-4H-1,2,4-triazole (CBTZ) and bovine serum albumin (BSA) under physiological conditions was investigated by fluorescence,UV-vis absorption and circular dichroism (CD) spectroscopy as well as molecular modeling methods. The result of fluorescence experiment indicates the static quenching as a result of the formation of the CBTZ-BSA complex. The binding constants (Ka) at different temperatures were calculated according to the modified St...     

大黄酸铜(Ⅱ)配合物与血清白蛋白的相互作用

采用荧光光谱法和紫外光谱法研究了大黄酸铜配合物与牛血清白蛋白之间的相互作用.大黄酸铜配合物能显著猝灭牛血清白蛋白的内源荧光并以静态猝灭为主;计算了298 K和309 K温度下结合常数、结合位点,根据热力学参数判断大黄酸铜配合物与牛血清白蛋白之间具有较强的疏水作用力;依据F?rster的偶极-偶极非辐射能量转移理论,计算出大黄酸铜在蛋白质中结合位置与色氨酸残基间的距离为3.21 nm, 表明大黄酸铜的部分片段能够插入蛋白质分子内部;用同步荧光光谱和圆二色光谱技术探讨了大黄酸铜对牛血清白蛋白构象的影响.     

Interactions between a surface active imidazolium ionic liquid and BSA

The interactions between a surface active imidazolium ionic liquid (IL), 1-tetradecyl-3-methylimidazolium bromide (C₁₄mimBr) and bovine serum albumin (BSA) were studied. To investigate the structure changes of BSA induced by addition of C₁₄mimBr, this system was studied by surface tension, isothermal titration microcalorimetry, far-UV circular dichroism (CD) and fluorescence spectra. The surface tension measurement shows the formation of C₁₄mimBr/BSA complex and the effect of the complex on surface tension. Furthermore, it reveals the interaction type. The enthalpy change in the whole interaction process between C₁₄mimBr and BSA was obtained by isothermal titration microcalorimetry, and the results prove the alteration of the BSA structure. To realize the structure alteration position more definitely, far-UV CD was used to obtain the contents of α-helix and random coil. Changes of these contents reveal that the secondary structure of BSA changes with addition of C₁₄mimBr. Fluorescence spectra are used to prove that the alteration of the secondary structure is due to the interactions of C₁₄mimBr molecules and amino acid residues. They show that tryptophan (Trp) residues, one of the intrinsic fluorophores in BSA, are exposed to a hydrophobic microenvironment with the addition of C₁₄mimBr.     

Interaction of water-soluble amino acid Schiff base complexes with bovine serum albumin: fluorescence and circular dichroism studies

Fluorescence spectroscopy in combination with circular dichroism (CD) spectroscopy were used to investigate the interaction of water-soluble amino acid Schiff base complexes, [Zn(L1,2)(phen)] where phen is 1,10-phenanthroline and H2L1,2 is amino acid Schiff base ligands, with bovine serum albumin (BSA) under the physiological conditions in phosphate buffer solution adjusted to pH 7.0. The quenching mechanism of fluorescence was suggested as static quenching according to the Stern-Volmer equation. Quenching constants were determined using the Stern-Volmer equation to provide a measure of the binding affinity between amino acid Schiff base complexes and BSA. The thermodynamic parameters DeltaG, DeltaH and DeltaS at different temperatures (298, 310 and 318K) were calculated. The results indicate that the hydrophobic and hydrogen bonding interactions play a major role in [Zn(L1)(phen)]-BSA association, whereas hydrophobic and electrostatic interactions participate a main role in [Zn(L2)(phen)]-BSA binding process. Binding studies concerning the number of binding sites and apparent binding constant Kb were performed by fluorescence quenching method. The distance R between the donor (BSA) and acceptor (amino acid Schiff base complexes) has been obtained utilizing fluorescence resonant energy transfer (FRET). Furthermore, CD spectra were used to investigate the structural changes of the BSA molecule with the addition of amino acid Schiff base complexes. The results indicate that the interaction of amino acid Schiff base complexes with BSA leads to changes in the secondary structure of the protein. Fractional contents of the secondary structure of BSA (f(alpha), f(beta), f(turn) and f(random)) were calculated with and without amino acid Schiff base complexes utilizing circular dichroism spectroscopy. Our results clarified that amino acid Schiff base complexes could bind to BSA and be effectively transported and eliminated in the body, which could be a useful guideline for further drug design.