Interaction of isofraxidin with human serum albumin

This study was designed to examine the interaction of isofraxidin with human serum albumin (HSA) under physiological conditions with drug concentrations in the range of 3.3 x 10(-6) mol L(-1)-3.0x10(-5) mol L(-1) and HSA concentration at 1.5 x 10(-6) mol L(-1). Fluorescence quenching methods in combination with Fourier transform infrared (FT-IR) spectroscopy and circular dichroism (CD) spectroscopy were used to determine the drug-binding mode, the binding constant and the protein structure changes in the presence of isofraxidin in aqueous solution. Spectroscopic evidence showed that the interaction results in one type of isofraxidin-HSA complex with binding constants of 4.1266 x 10(5) L mol(-1), 3.8612 x 10(5) L mol(-1), 3.5063 x 10(5) L mol(-1), 3.1241 x 10(5) L mol(-1) at 296 K, 303 K, 310 K, 318 K, respectively. The thermodynamic parameters, enthalpy change (DeltaH) and entropy change (DeltaS) were calculated to be -10.08 kJ mol(-1) and 73.57 J mol(-1) K(-1) according to van't Hoff equation, which indicated that hydrophobic interaction played a main role in the binding of isofraxidin to HSA. The experiment results are nearly in accordance with the calculation results obtained by Silicon Graphics Ocatane2 workstation.     

Study on the interaction of bovine serum albumin with acid cyanine 5R and its application in analysis.

A supramolecular complex of bovine serum albumin (BSA) with acid cyanine 5R (AC 5R, C.I. acid blue 113, C.I.: 26360) has been shown to form in Tris-HCl buffer solution (pH 7.42) by linear sweep voltammetry (LSV), fluorimetry, and spectrophotometry. The binding ratio and binding constant of BSA with AC 5R have been detected by LSV and fluorimetry. The binding mechanism is also preliminarily discussed. In Tris-HCl buffer solution (pH 7.42), AC 5R can easily be reduced on the mercury electrode, and it has a well-defined LSV peak current (Ip) and peak potential (Ep) at -0.65 V (vs. SCE). In the presence of BSA, the Ip of AC 5R decreases, and the peak potential (Ep) shifts to a more positive potential. The decrease of the second-order derivative of reductive peak current (deltaIp') of AC 5R is proportional to the logarithm of BSA concentration in the range of 1.54 x 10(-8) mol x L(-1)-1.54 x 10(-5) mol x L(-1) (r = 0.9931-0.9977). The limit of detection of BSA is 9.0 x 10(-9) mol x L(-1). The relative standard deviation is 1.83% (n = 10), and the standard recovery is 97.5%-104.8%. This method can be used to determine BSA concentration on the basis of the interaction of BSA with AC 5R.     

A combined spectroscopic and molecular docking approach to characterize binding interaction of megestrol acetate with bovine serum albumin

The binding interactions between megestrol acetate (MA) and bovine serum albumin (BSA) under simulated physiological conditions (pH 7.4) were investigated by fluorescence spectroscopy, circular dichroism and molecular modeling. The results revealed that the intrinsic fluorescence of BSA was quenched by MA due to formation of the MA–BSA complex, which was rationalized in terms of a static quenching procedure. The binding constant (K_b) and number of binding sites (n) for MA binding to BSA were 2.8 × 10⁵ L/mol at 310 K and about 1 respectively. However, the binding of MA with BSA was a spontaneous process due to the negative ∆G⁰ in the binding process. The enthalpy change (∆H⁰) and entropy change (∆S⁰) were – 124.0 kJ/mol and –295.6 J/mol per K, respectively, indicating that the major interaction forces in the binding process of MA with BSA were van der Waals forces and hydrogen bonding. Based on the results of spectroscopic and molecular docking experiments, it can be deduced that MA inserts into the hydrophobic pocket located in subdomain IIIA (site II) of BSA. The binding of MA to BSA leads to a slight change in conformation of BSA but the BSA retained its secondary structure, while conformation of the MA has significant change after forming MA–BSA complex, suggesting that flexibility of the MA molecule supports the binding interaction of BSA with MA. Copyright © 2014 John Wiley & Sons, Ltd.     

槐定碱与牛血清白蛋白的相互作用研究

在模拟动物体生理条件下,用荧光猝灭、荧光偏振和紫外-可见吸收光谱法研究了槐定碱与牛血清白蛋白(BSA)结合作用。荧光猝灭数据显示,槐定碱与BSA发生反应生成了新的复合物,属于静态荧光猝灭。求出了不同温度(19、25、31、37℃)下槐定碱与BSA作用的结合常数分别为1.219×106,1.164×106,1.110×106和1.057×106L/mol,由van’tHoff方程式计算槐定碱与BSA反应的热力学参数:焓变ΔH和熵变ΔS值分别为-5.97kJ/mol和96.11J/(mol.K),表明槐定碱与BSA间的作用力以静电引力为主。以华法林和布洛芬(分别为siteI和siteII探针)为标记药物研究槐定碱在BSA上的结合位点,结果表明,槐定碱结合在BSA疏水空腔的siteI位点。     

Molecular characteristics of bovine serum albumin-dextran conjugates

Bovine serum albumin (BSA)-dextran conjugates were prepared by using the Maillard reaction; depending on the ratio of dextran to BSA used, about 0.5-1 mol of dextran could be bound to 1 mol of native BSA. SDS-PAGE patterns revealed that BSA and dextran had been covalently bonded. Structural analyses by fluorescence spectroscopy and circular dichroism indicated that the BSA surface in each conjugate was covered with dextran without any great disruption of the native conformation. The conjugates could be grouped into two fractions on the basis of the weight-average molecular mass measured: the main fraction at 1.95-2.35 x 10(5) g/mol and a less-abundant fraction with aggregates greater than 1.50 x 10(6) g/mol. High-performance size-exclusion chromatography in conjunction with multi-angle laser light scattering detection revealed that the BSA-dextran conjugates prepared by using the Maillard reaction had various molar masses and radii.     

17β-雌二醇对延迟着床期小鼠子宫内膜基质细胞内钙的快速调节效应

本文旨在研究17β-雌二醇(17β-estradiol,E2)对延迟着床期小鼠子宫内膜基质细胞内钙振荡的影响和机制,探讨E2对着床期子宫内膜基质细胞是否存在非基因组快速作用.实验的第一部分,小鼠分为6组,每组4只,即0.1%二甲基亚砜(dimethylsulfoxide,DMSO)对照组、1×10-8mol/L牛血清白蛋白(bovine serum albumin,BSA)对照组、1×10-8mol/L E2组、1×10-8mol/L E2-BSA组、1×10-8mol/L E2 无钙液组、1×10-8mol/L E2 5μg/mL他莫西芬(tamoxifen)组.急性分离延迟着床小鼠孕第7天子宫内膜基质细胞,应用激光共聚焦显微镜技术实时检测各组基质细胞[Ca2 ]I的变化.实验的第二部分,分离7只延迟着床小鼠孕第7天子宫内膜基质细胞,用免疫荧光法检测1×10-8mol/L E2作用前和作用后5 min、15 min、30min细胞内磷酸化磷脂酶C(phospholipase C,PLC)的变化.基质细胞[Ca2 ]I的变化结果显示,在E2,E2-BSA和E2 无钙液组中[Ca2 ];均明显升高,15 min达到高峰,随后下降回到基础值.但DMSO和BSA组中[Ca2 ]I未见明显变化;加入传统雌激素胞浆受体阻断剂tamoxifen不能抑制E2引起的[Ca2 ]I升高.免疫荧光结果显示,加入1×10-8mol/L E2后,PLC的磷酸化水平升高,15 min达高峰(P<0.001),然后逐渐下降回到基础值.结果提示,E2对延迟着床小鼠子宫内膜基质细胞[Ca2 ]I的变化具有快速调节效应,该作用可能是通过非基因组途径实现的,与磷酸化PLC信号途径有关.     

Binding of the bioactive component jatrorrhizine to human serum albumin

The interaction between Jatrorrhizine with human serum albumin (HSA) were studied by fluorescence quenching technique, circular dichroism (CD) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. Fluorescence data revealed the presence of a single class of binding site on HSA and its binding constants (K) are 7.278 x 10(4), 6.526 x 10(4), and 5.965 x 10(4) L.mol(-1) at 296, 303, and 310 K, respectively. The CD spectra and FT-IR spectra have proved that the protein secondary structure changed in the presence of Jatrorrhizine in aqueous solution. The effect of common ions on the binding constants was also investigated. In addition, the thermodynamic functions standard enthalpy (DeltaH(0)) and standard entropy (DeltaS(0)) for the reaction were calculated to be -10.891 kJ.mol(-1) and 56.267 J.mol(-1) K(-1), according to the van't Hoff equation. These data indicated that hydrophobic and electrostatic interactions played a major role in the binding of Jatrorrhizine to HSA. Furthermore, the displacement experiments indicated that Jatrorrhizine could bind to the site I of HSA, which was also in agreement with the result of the molecular modeling study.     

The binding of palmitoyl-CoA to bovine serum albumin

Bovine serum albumin (BSA) is routinely utilized in vitro to prevent the adverse detergent effects of long-chain acyl-CoA esters (i.e., palmitoyl-CoA) in enzyme assays. Determination of substrate saturation kinetics in the presence of albumin would only be valid if the relationship between bound and free substrate concentrations was known. To elucidate the relationship between bound and free palmitoyl-CoA concentrations in the presence of BSA, several different techniques including equilibrium dialysis, equilibrium partitioning, fluorescence polarization and direct fluorescence enhancement were investigated. Direct fluorescence enhancement using a custom synthesized fluorescent probe, 16-(9-anthroyloxy)palmitoyl-CoA (AP-CoA), was the best approach to this question. Measurement of the relationship between mol of palmitoyl-CoA bound per mol of BSA (nu) versus -log[free palmitoyl-CoA] revealed that the binding of palmitoyl-CoA to BSA, like palmitate was nonlinear, suggesting the presence of more than one class of acyl-CoA binding sites. Computer analyses of the binding data gave a best fit to the 2,4 two-class Scatchard model, suggesting the presence of two high-affinity primary binding sites (k1 = (1.55 +/- 0.46) x 10(-6) M-1) and four lower affinity secondary binding sites (k2 = (1.90 +/- 0.09) x 10(-8) M-1). Further analyses using the six parameter stoichiometric (stepwise) ligand binding model supports the existence of six binding sites with the higher affinities associated with the binding of the first mole of palmitoyl-CoA and weaker binding occurring after the first two sites are occupied. The association constants from this model of multiple binding diminish sequentially (i.e., K1 greater than K2 greater than K3 greater than...greater than or equal to K6), suggesting that each mol of long-chain acyl-CoA binds to BSA with decreasing affinities.     

Effect of Chinese medicine alpinetin on the structure of human serum albumin

Alpinetin (7-hydroxy-5-methoxyflavanone), one of the main constituents from the seeds of Alpinia katsumadai Hayata, belongs to flavonoids with its usefulness as antibacterial, anti-inflammatory and other important therapeutic activities of significant potency and low systemic toxicity. In this paper, the interaction of alpinetin to human serum albumin (HSA) has been studied for the first time by spectroscopic method including Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD), and UV-absorption spectroscopy in combination with fluorescence quenching study under physiological conditions with drug concentrations of 3.3 x 10(-6)-2.0 x 10(-5)mol/L. The results of spectroscopic measurements and the thermodynamic parameters obtained (the enthalpy change DeltaH(0) and the entropy change DeltaS(0) were calculated to be -10.20 kJ/mol and 53.97 J/molK(-1) according to the Van't Hoff equation) suggest that hydrophobic interaction is the predominant intermolecular forces stabilizing the complex, which is also good agreement with the results of molecule modeling study. The alterations of protein secondary structure in the presence of alpinetin in aqueous solution were quantitatively estimated by the evidences from FT-IR and CD spectroscopy with reductions of alpha-helices about 24%, decreases of beta-sheet structure about 2%, and increases of beta-turn structure about 21%. The quenching mechanism and the number of binding site (n approximately 1) were obtained by fluorescence titration data. Fluorescent displacement measurements confirmed that alpinetin bind HSA on site III. In addition, the effects of common ions on the constants of alpinetin-HSA complex were also discussed.     

Binding of oxovanadium ions to the major and minor grooves of DNA duplex: stability and structural models.

Vanadate induces DNA strand breaks in cultured human fibroblasts at doses that are relative to the occupational exposure. Oxovanadium compounds also exert preventive effects against chemical carcinogenesis in animals and form complexes with DNA in vivo. This study was designed to examine the interaction of calf-thymus DNA with VO2+ and VO3 ions in aqueous solution at physiological pH, with a constant DNA concentration of 12.5 mmol/L and vanadium-DNA (phosphate) molar ratios (r) of 1:160 to 1:2. Capillary electrophoresis and Fourier transform infrared difference spectroscopy were used to determine the cation binding site, the binding constant, the helix stability, and DNA conformation in the oxovanadium-DNA complexes. Structural analysis showed that VO2+ binds DNA through guanine and adenine N-7 atoms and the backbone PO2 group with apparent binding constants of KG = 8.8 x 10(5) (mol/L)-1 and KA = 3.4 x 10(5) (mol/L)-1. The VO3 shows weaker binding through thymine, adenine, and guanine bases, with K = 1.9 x 10(4) (mol/L)-1 and no interaction with the backbone phosphate group. A partial B-to-A DNA transition occurred upon VO-DNA complexation, while DNA remains in the B-family structure in the VO3 complexes.     

Study of the reaction of proteins with 3-hydroxy-4-(2-hydroxy-4-sulfo-1-naphthalenyl)azo (Cal-Red) by Rayleigh light scattering technique

This is the first report on the determination of proteins with 3-hydroxy-4-(2-hydroxy-4-sulfo-1-naphthalenyl)azo (Cal-Red) by Rayleigh light scattering (RLS). At pH 4.07, the weak RLS of Cal-Red can be enhanced greatly by the addition of proteins. On this basis, the reaction of Cal-Red and proteins was studied. A new quantitative determination method for proteins has been developed. This method is very sensitive (0.45-36.9 microgml(-1) for bovine serum albumen (BSA)), rapid (<2min), simple (one step), and tolerant of most interfering substances. The maximum binding number of Cal-Red to BSA was 143 and the binding constant was 4.1x10(6)mol(-1)L. Four samples of total protein in human serum were determined and the maximum relative error is no more than 3%.     

In vitro study on binding interaction of quinapril with bovine serum albumin (BSA) using multi-spectroscopic and molecular docking methods

The binding interaction between quinapril (QNPL) and bovine serum albumin (BSA) in vitro has been investigated using UV absorption spectroscopy, steady-state fluorescence spectroscopic, synchronous fluorescence spectroscopy, 3D fluorescence spectroscopy, Fourier transform infrared spectroscopy, circular dichroism, and molecular docking methods for obtaining the binding information of QNPL with BSA. The experimental results confirm that the quenching mechanism of the intrinsic fluorescence of BSA induced by QNPL is static quenching based on the decrease in the quenching constants of BSA in the presence of QNPL with the increase in temperature and the quenching rates of BSA larger than 10¹⁰ L mol^?1 s^?1, indicating forming QNPL–BSA complex through the intermolecular binding interaction. The binding constant for the QNPL–BSA complex is in the order of 10⁵ M^?1, indicating there is stronger binding interaction of QNPL with BSA. The analysis of thermodynamic parameters together with molecular docking study reveal that the main binding forces in the binding process of QNPL with BSA are van der Waal’s forces and hydrogen bonding interaction. And, the binding interaction of BSA with QNPL is an enthalpy-driven process. Based on Förster resonance energy transfer, the binding distance between QNPL and BSA is calculated to be 2.76 nm. The results of the competitive binding experiments and molecular docking confirm that QNPL binds to sub-domain IIA (site I) of BSA. It is confirmed there is a slight change in the conformation of BSA after binding QNPL, but BSA still retains its secondary structure α-helicity.     

A study on the interaction between 3‐spiro‐piperidones and bovine serum albumin using spectroscopic approaches

The interaction between 3‐spiro‐2′‐pyrrolidine‐3′‐spiro‐3″‐piperidine‐2,3″‐dione (PPD) and bovine serum albumin (BSA) in aqueous solution was studied using fluorescence and UV–vis spectroscopy. Fluorescence emission data revealed that BSA (1.00 × 10^‐5 mol/L) fluorescence was statically quenched by PPD at various concentrations, which implies that a PPD–BSA complex was formed. The binding constant (K_A), the number of binding sites (n) and the specific binding site of the PPD with BSA were determined. Energy‐transfer efficiency parameters were determined and the mechanism of the interaction discussed. The thermodynamic parameters, ΔG, ΔH and ΔS, were obtained according to van't Hoff's equation, showing the involvement of hydrophobic forces in these interactions. The effect of PPD acting on the BSA conformation was detected by synchronous fluorescence. Copyright © 2012 John Wiley & Sons, Ltd.     

Study on the Interaction Between {\mathrm{Cu}}{\left( {{\mathrm{phen}}} \right)}^{{2 + }}_{3} and Bovine Serum Albumin by Spectroscopic Methods

In this work, the interaction between ${\text{Cu}}\left( {{\text{phen}}} \right)_3^{\,\,2 + } In this work, the interaction between Cu(phen)(2+)(3) and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy combined with UV-vis absorption and circular dichroism (CD) spectroscopic techniques under physiological conditions. The fluorescence data proved that the fluorescence quenching of BSA by Cu(phen)(2+)(3) was the result of the Cu(phen)(2+)(3) -BSA complex formation. The binding constants (K (a)) between Cu(phen)(2+)(3) and BSA at four different temperatures were calculated according to the modified Stern-Volmer equation. The enthalpy change (DeltaH) and entropy change (DeltaS) were calculated to be 10.74 kJ mol(-1) and 54.35 J mol(-1) K(-1), respectively, which indicated that electrostatic interactions played a major role in the formation of Cu(phen)(2+)(3) -BSA complex. The distance r between the donor (BSA) and acceptor[Cu(phen)(2+)(3)] was obtained to be 3.55 nm based on F?rster's energy transfer theory. The synchronous fluorescence and CD spectroscopy results showed that the polarity of the residues increased and the lost of the alpha-helix content of BSA (from 59.84 to 53.70%). These indicated that the microenvironment and conformation of BSA were changed in the presence of Cu(phen)(2+)(3).     

Interactions of some modified mono- and bis-beta-cyclodextrins with bovine serum albumin

Two mono-substituted beta-cyclodextrins and two bridged bis-beta-cyclodextrins, that is, mono(6-(2-aminoethylamino)-6-deoxy)-beta-cyclodextrin (1), mono(6-(2-(2-aminoethylamino)ethylamino)-6-deoxy)-beta-cyclodextrin (2), ethylene-1,2-diamino bis-6-(6-deoxy-beta-cyclodextrin) (3), and iminodiethylene-2,2'-diamino bis-6-(6-deoxy-beta-cyclodextrin) (4), were prepared from beta-cyclodextrin. Their binding ability with bovine serum albumin as a model protein was investigated through proton magnetic resonance (1H NMR), ultraviolet visible spectroscopy (UV-vis), circular dichroism (CD), and fluorescence spectroscopy. In the 1H NMR spectra of the modified cyclodextrins, the resolution of proton signals decreases after the addition of BSA. From the UV and CD spectra, it is found that both the UV absorption and the alpha-helix content of BSA increase with the concentration of the modified cyclodextrins. The protein-ligand interactions cause a fluorescence quenching. The quenching constants are determined using the Stern-Volmer equation to provide an observation of the binding affinity between modified cyclodextrins and BSA. All these results indicate that the modified cyclodextrins can interact with BSA and the bridged bis(beta-cyclodextrin)s (3 and 4) have much stronger interactions than the mono-substituted beta-cyclodextrins (1 and 2). The strong binding stability of bis-cyclodextrins should be attributed to the cooperative effect of two adjacent cyclodextrin moieties. Job's plot shows that the complex stoichiometries of BSA to the modified cyclodextrins were 1:4 for 1 and 2, as well as 1:3 for 3 and 4, respectively.     

Study on the interaction between protein and Eu(III)-chlorotetracycline complex and the determination of protein using the fluorimetric method.

Chlorotetracycline (CTC) can react with europium ions Eu3+, and the complex emits the intrinsic fluorescence of Eu3+. The intensity is greatly enhanced by proteins and this forms the basis of a new fluorimetric method for determination of protein. Further research indicates that under optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of proteins, in the range 2.0 x 10(-7)-1.0 x 10(-5) g/mL for bovine serum albumin (BSA) (linear equation, I(f) = 34.35933 + 11.54467 x 10(6)C)(r = 0.99895) and 8.0 x 10(-7)-1.0 x 10(-5) g/mL for human serum albumin (HSA) (linear equation, I(f) = 76.58881 + 5.3569 x 10(6)C) (r = 0.99283). Detection limits (S/N = 3) were 8.9 x 10(-9) g/mL for BSA and 3.3 x 10(-8) g/mL for HSA. In an assay for BSA in calf serum, this method gave a value close to that determined by the UV spectrophotometric method.     

Study of the interaction of artemisinin with bovine serum albumin

The study on the interaction of artemisinin with bovine serum albumin (BSA) has been undertaken at three temperatures, 289, 296 and 303 K and investigated the effect of common ions and UV C (253.7 nm) irradiation on the binding of artemisinin with BSA. The binding mode, the binding constant and the protein structure changes in the presence of artemisinin in aqueous solution at pH 7.40 have been evaluated using fluorescence, UV–vis and Fourier transform infrared (FT-IR) spectroscopy. The quenching constant K_q, K_sv and the association constant K were calculated according to Stern–Volmer equation based on the quenching of the fluorescence of BSA. The thermodynamic parameters, the enthalpy (ΔH) and the entropy change (ΔS) were estimated to be −3.625 kJ mol⁻¹ and 107.419 J mol⁻¹ K⁻¹ using the van’t Hoff equation. The displacement experiment shows that artemisinin can bind to the subdomain IIA. The distance between the tryptophan residues in BSA and artemisinin bound to site I was estimated to be 2.22 nm using Föster's equation on the basis of fluorescence energy transfer. The decreased binding constant in the presence of enough common ions and UV C exposure, indicates that common ions and UV C irradiation have effect on artemisinin binding to BSA.     

Calcium binding and thermostability of carbohydrate binding module CBM4-2 of Xyn10A from Rhodothermus marinus

Calcium binding to carbohydrate binding module CBM4-2 of xylanase 10A (Xyn10A) from Rhodothermus marinus was explored using calorimetry, NMR, fluorescence, and absorbance spectroscopy. CBM4-2 binds two calcium ions, one with moderate affinity and one with extremely high affinity. The moderate-affinity site has an association constant of (1.3 +/- 0.3) x 10(5) M(-1) and a binding enthalpy DeltaH(a) of -9.3 +/- 0.4 kJ x mol(-1), while the high-affinity site has an association constant of approximately 10(10) M(-1) and a binding enthalpy DeltaH(a) of -40.5 +/- 0.5 kJ x mol(-1). The locations of the binding sites have been identified by NMR and structural homology, and were verified by site-directed mutagenesis. The high-affinity site consists of the side chains of E11 and D160 and backbone carbonyls of E52 and K55, while the moderate-affinity site comprises the side chain of D29 and backbone carbonyls of L21, A22, V25, and W28. The high-affinity site is in a position analogous to the calcium site in CBM4 structures and in a recent CBM22 structure. Binding of calcium increases the unfolding temperature of the protein (T(m)) by approximately 23 degrees C at pH 7.5. No correlation between binding affinity and T(m) change was noted, as each of the two calcium ions contributes almost equally to the increase in unfolding temperature.     

Calf thymus DNA binding studies of the new neodymium-naproxen complex

Fluorescence spectroscopy in combination with UV absorption spectroscopy was carried out to investigate the interaction between the neodymium-naproxen complex (Nd-NAP) and calf thymus DNA (ctDNA). The experimental results showed that Nd-NAP intercalated with the ctDNA base pairs. Analysis of fluorescence quenching data of Nd-NAP by ctDNA at different temperatures using a Stern-Volmer equation revealed that dynamic and static quenching occurred simultaneously. The binding constants and the number of binding sites at 293 and 310 K were obtained as 2.904 × 10(4) L mol(-1), 1.172 and 2.432 × 10(4) L mol(-1), 1.143, respectively. The thermodynamic parameters ΔG, ΔH, and ΔS calculated at different temperatures indicated that hydrogen bonding and van der Waals force were the main binding forces.     

Characterization of the interaction between reserpine and bovine serum albumin: spectroscopic approaches

The characteristics of the interaction between reserpine and bovine serum albumin (BSA) were studied by fluorescence, UV-vis absorption and Fourier transform infrared (FT-IR) spectroscopy. Spectroscopic analysis revealed that fluorescence quenching of BSA by reserpine was through a static quenching procedure. The binding constant K(A) of reserpine with BSA at 293, 301 and 309 K was 1.63, 1.78 and 2.35 x 10(5) moL(-1) L respectively, which indicated degree of binding force between reserpine and BSA. There was one binding site between reserpine and BSA. The entropy and enthalpy changes were positive, indicating that interaction of reserpine and BSA was driven mainly by hydrophobic forces. The average binding distance between the donor (BSA) and the acceptor (reserpine) was about 3.84 nm based on the Forster non-radiation energy transfer theory. Results of synchronous fluorescence and FT-IR spectra indicated that the conformation and microenvironment of BSA were changed by the binding of reserpine. The results may provide important insights into the physiological activity of reserpine.