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...     

Interaction between varenicline tartrate and bovine serum albumin

This paper mainly investigated the interaction between varenicline tartrate and bovine serum albumin. The Stern–Volmer quenching constant and bimolecular quenching rate constant were determined; furthermore, the fluorescence quenching mechanism between varenicline tartrate and bovine serum albumin was clarified. The binding constants and the number of binding sites were deduced from the double logarithm regression curve. Thermodynamic parameters were calculated, which indicated that the binding process was spontaneous and the acting force were mainly hydrophobic forces. The binding distance was calculated to be 4.80 nm, which means that there was nonradiative energy transfer from varenicline tartrate to bovine serum albumin during the process. And the bovine serum albumin conformation affected by varenicline tartrate was analyzed through ultraviolet–visible and synchronous fluorescence spectroscopy.     

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.     

Studies on interaction between flavonoids and bovine serum albumin by spectral methods

The interaction between three kinds of flavonoids and bovine serum albumin (BSA) was investigated by fluorescence and UV-vis absorption spectrometry. The results indicated that flavonoids have strong ability to quench the intrinsic fluorescence of BSA by forming complexes. The binding constants, number of binding sites, thermodynamic parameters and energy transfer mechanisms were also investigated. Conformation change of BSA was observed from synchronous, three-dimensional fluorescence and circular dichroism spectrum.     

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。     

Spectrofluorimetric study on the interaction between antimicrobial drug sulfamethazine and bovine serum albumin

The interaction between the antimicrobial drug sulfamethazine (STM) and bovine serum albumin (BSA) has been studied using steady state and synchronous fluorescence spectroscopy. Fluorescence emission data revealed that BSA (2×10⁻⁶ M) fluorescence was statically quenched by STM at various concentrations, which implies that STM-BSA complex has been formed. The fluorescence emission data was analyzed via applying the Stern-Volmer analysis in combination with thermodynamic investigation, where obtained results revealed that quenching is static with quenching constants of 2.371, 1.658, and 0.916×10⁵ M⁻¹ at 298, 304, and 310 K, respectively. Binding constants and number of binding sites at different temperatures were also determined by applying the Scatchard method, which in turn were used to construct the van't Hoff plot in order to estimate the enthalpy (ΔH) and entropy changes (ΔS) for the complexation process. An average of 1.00±0.17 was estimated for the number of sites of BSA, which indicated that STM binds to BSA with stoichiometric ratio of 1:1. The values that were estimated from the van't Hoff plot for ΔH and (ΔS) were −36.8 kJ mol⁻¹ and −14.9 J mol⁻¹ K⁻¹, respectively, which indicate that the STM-BSA complex is stabilized with hydrogen bonds and van der Waals interactions. Synchronous fluorescence data was obtained at Δλ of 15 and 60 nm, where obtained results confirmed that STM binds to BSA at the tryptophan residue (Trp. 213). In addition, the distance between STM and the Trp. 213 was estimated via employing the Förster's non-radiative energy-transfer theory, and was found to be 2.73 nm, which in turn indicated that STM can bind to BSA with high probability.     

Studies on the antagonistic action between chloramphenicol and quinolones with presence of bovine serum albumin by fluorescence spectroscopy

Chloramphenicol (CHL) and quinolone drugs like ofloxacin (OFLX), lomefloxacin (LMX) and ciprofloxacin (CPFX) can all quench the fluorescence of bovine serum albumin (BSA) in the aqueous solution of pH=7.40. This quenching effect becomes more significant when CHL and quinolone drugs coexist. Based on this, further studies on the interactions between CHL and quinolone drugs using fluorescence spectrum are established. The results showed that the interaction between the drugs would increase the binding constant and binding stability of the drug and protein, thus reducing the amount of drugs transported to their targets. Therefore, free drug concentration at targets would decrease, reducing the efficacy of the drugs. It indicated that there exists antagonistic action between drugs. The results also showed that the quenching mechanism of BSA by the drugs is a static procedure. The number of binding sites is 1 in various systems. Due to the existence of the antagonistic action between drugs, the binding distance r is reduced. Studies utilizing synchronous spectra showed that the antagonistic action between the drugs would affect the conformation of BSA, making protein molecules extend and hydrophobic decrease. The order of antagonistic action between CHL and quinolone drugs is: CPFX>OFLX>LMX with presence of BSA.     

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.     

Study on the competitive reaction between bovine serum albumin and neomycin with ponceau S as fluorescence probe

A competitive reaction exists between bovine serum albumin (BSA) and neomycin (NM) when ponceau S (PS) is chosen as fluorescent probe. This reaction was studied by fluorescence spectroscopy and UV-vis absorption spectroscopy. The static fluorescence quenching process between BSA and PS was confirmed and the binding constant, the number of binding sites and type of interaction forces between BSA and PS were obtained. It was observed that when NM was added into BSA-PS system, the relative fluorescence intensity of BSA was recovered gradually with increase in concentration of NM, which shows that there existed competitive reaction between BSA and NM. According to competitive reaction mechanism, the equilibrium concentration of PS, the binding constant and the type of interaction forces between PS and NM were obtained.     

Investigation of the interaction between trazodone hydrochloride and bovine serum albumin

In this paper, the binding of trazodone hydrochloride (TZH) to bovine serum albumin (BSA) was investigated by spectroscopic (fluorescence, spectrophotometry and circular dichroism) techniques under simulative physiological conditions. A strong fluorescence quenching reaction of TZH to BSA was observed and the quenching mechanism was suggested as dynamic quenching according to the Stern-Volmer equation. The binding constants of TZH with BSA at 288, 302 and 309 K were calculated as (1.56±0.003)×10⁴, (2.31±0.002)×10⁴ and (5.44±0.004)×10⁴ M⁻¹, respectively. The thermodynamic parameters, ΔH⁰ and ΔS⁰ were obtained to be 39.86±0.008 kJ mol⁻¹ and 217.89±0.011 J mol⁻¹ K⁻¹, respectively, which indicated the presence of hydrophobic forces between TZH and BSA. The spectral results observed showed that the binding of TZH to BSA induced conformational changes in BSA. Based on the Förster's theory of non-radiation energy transfer, the binding average distance, r between donor (BSA) and acceptor (TZH) was found to be 2.4 nm. The effect of common ions on binding of TZH to BSA was also examined.     

Interaction of the flavonoid hesperidin with bovine serum albumin: A fluorescence quenching study

The interaction between the flavonoid hesperidin and bovine serum albumin (BSA) was investigated by fluorescence and UV/Vis absorption spectroscopy. The results revealed that hesperidin caused the fluorescence quenching of BSA through a static quenching procedure. The hydrophobic and electrostatic interactions play a major role in stabilizing the complex. The binding site number n, and apparent binding constant K_A, corresponding thermodynamic parameters ΔG^o, ΔH^o, ΔS^o at different temperatures were calculated. The distance r between donor (BSA) and acceptor (hesperidin) was obtained according to fluorescence resonance energy transfer. The effect of Cu²⁺, Zn²⁺, Ni²⁺, Co²⁺, and Mn²⁺ on the binding constants between hesperidin and BSA were studied. The effect of hesperidin on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy and UV/Vis absorption spectroscopy.     

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 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.     

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.     

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.     

Study on the binding of 2,3-diazabicyclo[2.2.2]oct-2-ene with bovine serum albumin by fluorescence spectroscopy

The interaction of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) with bovine serum albumin (BSA) has been studied using absorption and steady state fluorescence techniques. Fluorescence spectrum of BSA (λ_exi=280 nm) in the presence of DBO clearly shows that DBO acts as a quencher. The number of binding sites ‘n’ and apparent binding constant ‘K’ were measured by Stern-Volmer equation. Synchronous fluorescence and absorption spectra were used to study protein conformation. The interaction between DBO and BSA is consistent with static quenching and the conformational changes of BSA observed.     

Study on the interaction between methyl blue and human serum albumin by fluorescence spectrometry

The interaction of methyl blue (MB) with human serum albumin (HSA) was studied by fluorescence and absorption spectroscopy. The intrinsic fluorescence of HSA was quenched by MB, which was rationalized in terms of the static quenching mechanism. The number of binding sites and the apparent binding constants at different temperatures were obtained from the Stern-Volmer analysis of the fluorescence quenching data. The thermodynamic parameters determined by the van’t Hoff analysis of the binding constants (ΔH°=39.8 kJ mol⁻¹ and ΔS°=239 J mol⁻¹ K⁻¹) clearly indicate that binding is absolutely entropy-driven and enthalpically disfavored The efficiency of energy transfer and the distance between the donor (HSA) and the acceptor (MB) were calculated as 60% and 2.06 nm from the Förster theory of non-radiation energy transfer.     

Mechanistic and conformational studies on the interaction of anti-inflammatory drugs, isoxicam and tenoxicam with bovine serum albumin

The mechanism of interaction of the non-steroidal anti-inflammatory drugs, isoxicam (IXM) and tenoxicam (TXM) with bovine serum albumin (BSA) has been studied using spectroscopic techniques, viz., spectrofluorescence, circular dichroism (CD), UV-visible absorption and FT-IR under simulative physiological conditions. Stern-Volmer analysis of fluorescence quenching data shows the presence of the static quenching mechanism. Thermodynamic parameters (negative ΔH⁰ and positive ΔS⁰ values obtained in the present study) revealed that the hydrophobic interactions played a major role in the interaction of these drugs with BSA. The distance, r between the donor (BSA) and acceptor (IXM/TXM) was calculated based on the Forster’s theory of non-radiation energy transfer and the values were observed to be 3.85 nm and 2.60 nm in IXM-BSA and TXM-BSA system, respectively. CD and FT-IR studies indicated that the binding of IXM/TXM to BSA induced conformational changes in BSA. The effect of common ions on the binding of IXM/TXM to BSA has been investigated.     

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).     

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.