Spectroscopic studies on the interaction between disperse blue SBL and bovine serum albumin

The interaction of disperse blue SBL (DBSBL) with bovine serum albumin (BSA) was investigated using fluorescence, UV-visible and far-UV circular dichroism (CD) spectroscopy. The results showed that the fluorescence of BSA was quenched by DBSBL through static quenching after correcting for the inner filter effects (IFE). The binding constant K_b of DBSBL with BSA at 288, 298 and 303 K were 0.116×10⁶, 3.18×10⁶ and 12.3×10⁶ L mol⁻¹, respectively. The thermodynamic parameters, standard enthalpy change (ΔH⁰) and standard entropy change (ΔS⁰), for the reaction were evaluated to be 227.2 kJ mol⁻¹ and 886 J mol⁻¹ K⁻¹ according to the van’t Hoff equation. The above data suggested that the forces acting between DBSBL and BSA were predominantly hydrophobic interactions. The results of UV-visible absorption and far-UV CD spectroscopy also revealed that the conformation and microenvironment of BSA molecule were changed after DBSBL binding to BSA. At 288 K one binding site was present but at higher temperatures a second binding site was detected between DBSBL and the BSA molecule. The lower bound for the distance between the bound dye and the Trp residue is 2.35 nm as calculated from Forster energy transfer.     

The investigation of the interaction between edaravone and bovine serum albumin by spectroscopic approaches

The fluorescence and ultraviolet spectroscopies were explored to study the interaction between edaravone (EDA) and bovine serum albumin (BSA) under imitated physiological condition. The experimental results show that the fluorescence quenching mechanism between EDA and BSA is a combined quenching (dynamic and static quenching). The binding constants, binding sites, and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) of the interaction system were calculated at different temperatures. According to Förster non-radiation energy transfer theory, the binding distance between EDA and BSA was calculated to be 3.10 nm. The effect of EDA on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy. In addition, the effects of some common metal ions Mg²⁺, Ca²⁺, Cu²⁺, and Ni²⁺ on the binding constant between EDA and BSA were examined.     

The investigation of the interaction between oxybutynin hydrochloride and bovine serum albumin by spectroscopic methods

The mutual interaction of oxybutynin hydrochloride (OB) with bovine serum albumin (BSA) was investigated by fluorescence, UV–vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopies under simulative physiological conditions. The results of fluorescence titration revealed that OB could quench the intrinsic fluorescence of BSA by static quenching and there was a single class of binding sites on BSA for this drug. The thermodynamic parameters ΔH, ΔS, and ΔG calculated at different temperatures indicated that hydrogen bonds and van der Waals interactions were the dominant intermolecular forces in stabilizing the OB–BSA complexes. According to the theory of Förster’s non-radiation energy transfer, the binding distance r between OB and BSA was evaluated to be 3.27 nm. The displacement experiments confirmed that OB could bind to site I of BSA. The FT-IR and CD spectra showed that the binding of OB to BSA induced conformational changes in BSA.     

Probing the binding of vitexin to human serum albumin by multispectroscopic techniques

The interaction between vitexin and human serum albumin (HSA) has been studied by using different spectroscopic techniques viz., fluorescence, UV-vis absorption, circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy under simulated physiological conditions. Fluorescence results revealed the presence of static type of quenching mechanism in the binding of vitexin to HSA. The binding constants (K_a) between vitexin and HSA were obtained according to the modified Stern-Volmer equation. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) were calculated to be -57.29 kJ mol⁻¹ and -99.01 J mol⁻¹ K⁻¹ via the van't Hoff equation, which indicated that the interaction of vitexin with HSA was driven mainly by hydrogen bond and van der Waals forces. Fluorescence anisotropy data showed that warfarin and vitexin shared a common binding site I corresponding to the subdomain IIA of HSA. The binding distance (r) between the donor (HSA) and the acceptor (vitexin) was 4.16 nm based on the Förster theory of non-radioactive energy transfer. In addition, the results of synchronous fluorescence, CD and FT-IR spectra demonstrated that the microenvironment and the secondary structure of HSA were changed in the presence of vitexin.     

Effect of Cu and Fe for drug delivery: Decreased binding affinity of ilaprazole to bovine serum albumin

The interaction between ilaprazole and bovine serum albumin (BSA) has been investigated in the absence and presence of Cu²⁺ or Fe³⁺ by means of fluorescence spectroscopy. The fluorescence intensity of BSA decreased remarkably with no obvious BSA maximum emission wavelength shift by adding ilaprazole. Similar fluorescence shape with larger quenching extent of BSA was observed with increasing concentrations of ilaprazole in the presence of Cu²⁺ or Fe³⁺. The quenching constants and affinities of ilaprazole with BSA in the presence of Cu²⁺ and Fe³⁺ decreased. The decreased affinity and unchangeable binding distance in the presence of metal ions may result from a competitive binding between ilaprazole and metal ions. The results indicated that the presence of Cu²⁺ or Fe³⁺ could improve ilaprazole′s maximum effects, which may have relevant consequence in rationalizing dosage for patients with gastric and duodenal ulcers.     

Effect of temperature and pH on interaction between bovine serum albumin and cetylpyridinium bromide: Fluorescence spectroscopic approach

The fluorescence spectroscopic technique has been efficiently employed to investigate the interaction between bovine serum albumin (BSA) and cetylpyridinium bromide (CPB) under different pH and temperature conditions. The binding constant, number of binding sites, thermodynamic parameters such as ΔG, ΔH, ΔS, and nature of binding forces between BSA and CPB were obtained by measuring the steady state fluorescence quenching of BSA by CPB. The experimental results showed that the fluorescence quenching of BSA by CPB was a result of the formation of CPB-BSA complex. The static quenching was confirmed from the Stern-Volmer quenching constant at different temperatures. The effect of CPB on the conformation of BSA was analyzed using synchronous and three-dimensional fluorescence spectroscopy. pH dependence complex formation between BSA-CPB is due to the interaction between cationic side chain of CPB and the net charge developed on BSA. The distance ‘r’ between BSA and CPB was obtained according to the fluorescence resonance energy transfer.     

Spectroscopic studies of 7, 8-dihydroxy-4-methylcoumarin and its interaction with bovine serum albumin

The absorption and fluorescence spectra of 7, 8-dihydroxy-4-methylcoumarin (DHMC) in ethanol-water (1:9 v/v) solution at varying pH values were investigated . The interaction between DHMC and bovine serum albumin (BSA) was investigated by fluorescence, FT-IR, and circular dichroism (CD) spectroscopy. The Stern-Volmer quenching constant (K_SV), the quenching rate constant of the bimolecular reaction (K_q), the binding constant, and number of binding sites (n) of DHMC with BSA were evaluated. The results showed that DHMC quenches the fluorescence intensity of BSA through a static quenching process. Positive value of entropy change (ΔS) and negative value of enthalpy change (ΔH) of the BSA-DHMC interaction were obtained according to the van't Hoff equation. The interaction between DHMC and BSA was driven mainly by hydrophobic forces. The binding process was spontaneous and exothermic. The binding distance between the tryptophan residue in BSA and the DHMC was found to be about 2.6 nm based on the Förster theory of non-radiation energy transfer.     

Characterize the interaction between naringenin and bovine serum albumin using spectroscopic approach

Naringenin, a flavanone compound highly enriched in grapefruits, has been identified as a possible inhibitor of cell proliferation; and thus has the potential to act as an antitumorigenic agent. In this study, the binding of naringenin to bovine serum albumin (BSA) was studied at the physiological conditions (pH=7.40) by fluorescence and UV-vis spectroscopy. Naringenin strongly quenches the intrinsic fluorescence of BSA, and a decrease in the fluorescence quenching constant was observed together with an increase in temperature, which indicates that the fluorescence quenching of BSA by naringenin is a result of the formation of naringenin-BSA complex. Binding parameters calculating from Stern-Volmer method and Scatchard method showed that naringenin bind to BSA with the binding affinities of the order 10⁴ L mol⁻¹. Thermodynamic parameters such as ΔG, ΔH and ΔS, were calculated at different temperatures, showing that electrostatic interactions were mostly responsible for the binding of naringenin to BSA. Site marker competitive displacement experiments demonstrating that naringenin bind with high affinity to site I (subdomain IIA) of BSA. Furthermore, the effect of metal ions to naringenin-BSA system was studied, and the specific binding distance r (3.30 nm) between donor (Trp-212) and acceptor (naringenin) was obtained according to fluorescence resonance energy transfer (FRET).     

Study on the interaction between promethazine hydrochloride and bovine serum albumin by fluorescence spectroscopy

The interaction between promethazine hydrochloride (PMT) and bovine serum albumin (BSA) in vitro was investigated by means of fluorescence spectroscopy and absorption spectroscopy. The fluorescence of BSA was quenched remarkably by PMT and the quenching mechanism was considered as static quenching by forming a complex. The association constants K_a and the number of binding sites n were calculated at different temperatures. The BSA-PMT binding distance was determined to be less than 8 nm, suggesting that energy transfer from BSA to PMT may occur. The thermodynamic parameters of the interaction between PMT and BSA were measured according to the van’t Hoff equation. The enthalpy change (ΔH) and entropy change (ΔS) were calculated to be −23.62 kJ mol⁻¹ and −0.10 J mol⁻¹ K⁻¹, respectively, which indicated that the interaction of PMT with BSA was driven mainly by van der Waals forces and hydrogen bonds. The binding process was a spontaneous process in which Gibbs free energy change (ΔG) was negative. In addition, the results of synchronous fluorescence spectra and three-dimensional fluorescence spectra showed that binding of PMT with BSA can induce conformational changes in BSA.     

Spectroscopic and voltammetric characterizations of the interaction of two local anesthetics with bovine serum albumin

The interactions of bovine serum albumin (BSA) with two local anesthetics, procaine hydrochloride (PCH) and tetracaine hydrochloride (TCH) were studied using spectroscopic methods such as fluorescence and ultraviolet visible (UV-vis), and electrochemical techniques including cyclic voltammetry (CV) and differential pulsed stripping voltammetry (DPSV). The results obtained from these techniques turned out that both PCH and TCH could bind to BSA. The binding constants (K_A) and the number of binding sites (n) of the two drugs with BSA at different temperatures were determined, respectively. At 291 K, K_A was found as 2.40×10⁴ and 1.42×10⁴ L mol⁻¹ and n was 1.03 and 0.99 for PCH-BSA and TCH-BSA, respectively. According to van’t Hoff equation, the thermodynamic parameters, ΔG, ΔH and ΔS, were obtained, showing the involvement of hydrophobic and electrostatic force in these interactions. Based on the theory of the Förster energy transference, the distance between the acceptor (PCH or TCH) and the donor (BSA) were determined as 2.32 and 3.62 nm for PCH and TCH, respectively. The effects of Fe³⁺, Cu²⁺, Mg²⁺, Mn²⁺, Zn²⁺ and Ca²⁺ on the binding of PCH or TCH to BSA were also evaluated.     

光谱及电化学方法研究大黄酸与牛血清白蛋白的相互作用

采用荧光光谱、紫外光谱和圆二色光谱法并结合电化学方法,研究了大黄酸与牛血清白蛋白之间的相互作用。结果表明:大黄酸对牛血清白蛋白有较强的荧光猝灭作用且为静态猝灭,并计算得出不同温度下其结合常数(KA)与结合位点数(n)分别为:3.67×105,0.95(298 K);2.60×104,0.83(309 K)。由热力学参数确定它们间的作用力主要是静电引力,并依据F rster能量转移理论求得其结合距离为3.28 nm,同步荧光光谱及圆二色谱表明大黄酸对牛血清白蛋白的构象产生影响。     

油溶性CdSe量子点荧光探针直接检测农药水胺硫磷

基于农药水胺硫磷对油溶性CdSe量子点荧光猝灭的现象,建立了一种简单、快速、直接检测农药水胺硫磷的新方法。在最佳实验条件下,油溶性CdSe量子点的荧光猝灭程度与水胺硫磷浓度在2.30×10-7～1.09×10-5 mol·L-1范围内呈较好的线性关系,相关系数为0.999 9,对水胺硫磷的检出限为1.1×10-7 mol·L-1。本法已成功用于大米和小麦面粉样品中水胺硫磷农药残留的检测,加入回收率在93.3%～105.0%之间,结果满意。结合紫外-可见吸收光谱及时间分辨荧光光谱,探讨了水胺硫磷对油溶性CdSe量子点荧光猝灭的机理。研究结果表明,水胺硫磷能有效改变油溶性CdSe量子点的表面状态,增大了表面缺陷和非辐射重组的发生,从而使油溶性CdSe量子点的荧光猝灭。     

Spectroscopic studies on the interaction and sonodynamic damage of neutral red (NR) to bovine serum albumin (BSA)

In this paper, the interaction of neutral red (NR) with bovine serum albumin (BSA) and the sonodynamic damage to BSA under ultrasonic irradiation was studied by means of ultraviolet-visible (UV-vis) and fluorescence spectra. The quenching constant (K_SV=5.749×10⁴ L/mol), binding constant (K_A=3.19×10⁴ L/mol) and binding site number (n=0.9462) were measured. The binding distance (r=2.47 nm) between NR and BSA was obtained according to Föster’s non-radiative energy transfer theory. The damage process of BSA molecules was detected by the hyperchromic effect of UV-vis spectra and quenching of intrinsic fluorescence spectra. In addition, the influencing factors such as ultrasonic irradiation time and NR concentration on the damage to BSA molecules were also considered. The results showed that the damage degree is enhanced with the increase of ultrasonic irradiation time and NR concentration. The possible mechanism of sonodynamic damage to BSA molecules was mainly mediated by singlet oxygen (¹O₂). Otherwise, the binding and damaging sites to BSA molecules were also estimated by synchronous fluorescence. The results indicated that the NR is more vicinal to tryptophan (Trp) residue than to tyrosine (Tyr) residue and the damage site is also mainly at Trp residues. The research result will bring a certain significance to use sonosensitive drugs in the fields of tumor treatment.     

荧光光谱法研究共存碳纳米管对牛血清白蛋白与加替沙星相互作用的影响

在模拟生理条件下,用荧光光谱法研究了碳纳米管对牛血清白蛋白和加替沙星荧光光谱特性的影响以及有无碳纳米管共存时加替沙星对牛血清白蛋白荧光光谱特性的影响.实验结果表明,加替沙星和碳纳米管都可以使牛血清白蛋白的荧光强度发生静态猝灭.在碳纳米管的存在下,加替沙星与牛血清白蛋白的结合作用有所减弱.Stern-Volmer荧光猝灭...     

Study on the interaction between theasinesin and human serum albumin by fluorescence spectroscopy

The binding properties on theasinesin to human serum albumin (HSA) have been studied for the first time using fluorescence spectroscopy in combination with UV–vis absorbance spectroscopy. The results showed that theasinesin strongly quenched the intrinsic fluorescence of HSA through a static quenching procedure, and non-radiation energy transfer happened within molecules. The number of binding site was 1, and the efficiency of Förster energy transfer provided a distance of 4.64 nm between tryptophan and theasinesin binding site. At 298, 310 and 323 K, the quenching constants of HSA–theasinesin system were 2.55×10³, 2.16×10³ and 1.75×10³ mol L⁻¹. ΔH^θ, ΔS^θ and ΔG^θ were obtained based on the quenching constants and thermodynamic theory (ΔH^θ<0, ΔS^θ>0 and ΔG^θ<0). These results indicated that hydrophobic and electrostatic interactions are the mainly binding forces in the theasinesin–HSA system. In addition, the results obtained from synchronous fluorescence spectra showed that the binding of theasinesin with HSA could induce conformational changes in HSA.     

Study on the interaction of La with bovine serum albumin at molecular level

The interaction of La³⁺ to bovine serum albumin (BSA) has been investigated mainly by fluorescence spectra, UV-vis absorption spectra, and circular dichroism (CD) under simulative physiological conditions. Fluorescence data revealed that the quenching mechanism of BSA by La³⁺ was a static quenching process and the binding constant is 1.75×10⁴ L mol⁻¹ and the number of binding sites is 1 at 289 K. The thermodynamic parameters (ΔH=−20.055 kJ mol⁻¹, ΔG=−23.474 kJ mol⁻¹, and ΔS=11.831 J mol⁻¹ K⁻¹) indicate that electrostatic effect between the protein and the La³⁺ is the main binding force. In addition, UV-vis, CD, and synchronous fluorescence results showed that the addition of La³⁺ changed the conformation of BSA.     

Spectroscopic analyses on interaction of bovine serum albumin (BSA) with toluidine blue (TB) and its sonodynamic damage under ultrasonic irradiation

In this paper, the toluidine blue (TB) with tricyclic quinone imide plane structure is used as sonosensitizer to study the interaction and sonodynamic damage to bovine serum albumin (BSA) by UV-vis and fluorescence spectroscopy. The results show that the TB can bind to BSA molecules, obviously, and the synergetic effects of TB and ultrasonic irradiation can efficiently damage the BSA molecules. Otherwise, some influencing factors such as ultrasonic irradiation time, TB concentration, pH value and ionic strength on the damage of BSA molecules were also considered by the numbers. Synchronous fluorescence spectroscopy indicates that the tyrosine (Tyr) residues of BSA molecules are damaged more seriously than the tryptophan (Trp) residues under ultrasonic irradiation.     

Investigation on the pH-dependent binding of Eosin Y and bovine serum albumin by spectral methods

In this paper, the pH-dependent binding of Eosin Y and bovine serum albumin (BSA) was investigated by spectral methods, including resonance light scattering (RLS), absorption and fluorescence spectrometry. Due to the pH-dependent structure of Eosin Y and BSA, the interaction of BSA and Eosin Y depended on the solution pH value. Especially at pH 2.6 and 9.2, the RLS intensity of BSA was obviously enhanced in the presence of Eosin Y. However, the fluorescence intensity of BSA was quenched in the presence of Eosin Y. To fully understand the pH-dependent binding of BSA and Eosin Y, fluorescence quenching technique was introduced. Based on the fluorescence data obtained, the style of binding, the binding constant, the binding site number and the thermodynamic parameters for the interaction of BSA and Eosin Y were studied. Based on Förster non-radiation energy transfer theory, the distance between donor BSA and acceptor Eosin Y was obtained.     

Interaction of the docetaxel with human serum albumin using optical spectroscopy methods

Docetaxel is a semi-synthetic product derived from the needles of the European yew. It is an antineoplastic agent belonging to the taxoid family. The interaction between docetaxel and human serum albumin (HSA) has been investigated systematically by the fluorescence quenching technique, synchronous fluorescence spectroscopy, ultraviolet (UV)-vis absorption spectroscopy, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) under physiological conditions. Our fluorescence data showed that HSA had only one docetaxel binding site and the binding process was a static quenching procedure. According to the Van’t Hoff equation, the thermodynamic parameters standard enthalpy (ΔH⁰) and standard entropy (ΔS⁰) were calculated to be −41.07 KJ mol⁻¹ and −49.72 J mol⁻¹ K⁻¹. These results suggested that hydrogen bond was the predominant intermolecular force stabling the docetaxel-HSA complex. The data from the CD, FT-IR and UV-vis spectroscopy supported the change in the secondary structure of protein caused by the interaction of docetaxel with HSA.     

Spectroscopic studies on the binding of barbital to bovine serum albumin

In this paper, the interaction between barbital and bovine serum albumin (BSA) was investigated by the method of fluorescence spectroscopy under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by barbital was the result of the formation of BSA-barbital complex, and the effective quenching constants (K_a) were 1.468×10⁴, 1.445×10⁴ and 1.403×10⁴ M⁻¹ at 297, 303 and 310 K, respectively. The thermodynamic parameters enthalpy change (ΔH) and entropy change (ΔS) for the reaction were calculated to be −2.679 kJ mol⁻¹ and 70.76 J mol⁻¹ K⁻¹, respectively, according to the van’t Hoff equation. The results indicated that hydrophobic and electrostatic interactions were the dominant intermolecular force in stabilizing the complex. The results of synchronous fluorescence spectra showed that binding of barbital with BSA can induce conformational changes in BSA. In addition, the effects of Cu²⁺ and Zn²⁺ on the constants of BSA-barbital complex were also discussed.