Interaction Between Ranitidine Hydrochloride and Bovine Serum Albumin in Aqueous Solution

The interaction between ranitidine hydrochloride (RAN) and bovine serum albumin (BSA) in aqueous solution was investigated by means of fluorescence, synchronous fluorescence, and UV-Vis spectroscopy. The fluorescence of BSA was quenched remarkably by RAN and the quenching mechanism was concluded to be static quenching. The binding constants K and the number of binding sites n were calculated at three different temperatures. The RAN–BSA binding distance was determined to be less than 8 nm, suggesting that energy transfer may occur from BSA to RAN. The interaction process is spontaneous. Based on the obtained thermodynamic parameters, electrostatic forces may play a major role in this process. In addition, the effect of RAN on the conformation of BSA was analyzed using synchronous fluorescence spectra.     

Interaction of Surface-active Fluorescence Probes with Bovine Serum Albumin

The binding between three surface-active substituted 3H-indole fluorescence probes and bovine serum albumin (BSA) in aqueous solution was studied using fluorescence quenching. The binding constants of 3H-indole molecules with BSA were obtained. According to the Foerster resonance energy transfer theory, the distances between 3H-indole molecules and tryptophan of BSA were calculated. The results show that the oligoethyloxyethylene chain of 3H-indole molecules is longer, the binding between them is stronger, the energy transfer efficiency is higher, and the distance between tryptophan and 3H-indole is nearer.     

Conjugation of Chitooligosaccharide-5-fluorouracil with Bovine Serum Albumin

The interaction between chitooligosaccharide-5-fluorouracil (COS-5FU) and bovine serum albumin (BSA) was studied by fluorescence spectroscopy. It was found that an energy transfer between COS-5FU and BSA had been occurred. The binding constants were calculated, k298K=1.175×104 L·mol-1.Based on the mechanism of energy transfer of dipole-dipole interaction between the donor and acceptor, the distance between BSA and COS-5FU was determined.     

Interaction between Glyoxal-bis-(2-hydroxyanil) and Bovine Serum Albumin in Solution

The interaction between glyoxal-bis-(2-hydroxyanil) (GBH) and bovine serum albumin (BSA) was studied by spectroscopic methods including fluorescence spectroscopy, circular dichroism (CD) and UV–visible absorption spectra. The mechanism for quenching the fluorescence of BSA by GBH is discussed. The number of binding sites n and observed binding constant K _b were measured by the fluorescence quenching method. The thermodynamic parameters ΔH ^θ , ΔG ^θ , and ΔS ^θ were calculated at different temperatures and the results indicate that hydrogen bonding and van der Waals forces played major roles in the reaction. The distance r between the donor (BSA) and acceptor (GBH) molecules was obtained according to Förster’s theory of non-radiation energy transfer. Synchronous fluorescence and three-dimensional fluorescence spectra were used to investigate the structural change of BSA molecules that occur upon addition of GBH, and these results indicate that the secondary structure of BSA molecules is changed by the presence of GBH.     

Spectroscopic Study on Interaction of Lomefloxacin with Human Serum Albumin in the Presence of Copper Ion

The interaction of lomefloxacin （LMF） with human serum albumin （HSA） in the presence of copper ions in a physiological medium and its thermodynamic characteristics were investigated by multi-spectroscopy. The experimental results showed that both LMF and LMF-Cu^2＋ could quench the fluorescence of HSA with a static quenching mechanism, indicating that LMF or LMF-Cu^2＋ could react with HSA. The apparent binding constants/numbers of binding sites were estimated as 4.924± 105 Lomol 1/1.473 for LMF-HSA, 8.990± 104 L·mol^-1/1.785 for LMF- Cu^2＋-HSA, 1.10± 105 L·mol^-1/1.21 for LMF-Cu^2＋ and 7.30± 102 L·mol^-1/0.82 for HSA-Cu^2＋, respectively. AH and AS for LMF-HSA system were calculated to be --2.189 kJ·mol^-1 and 61.25 J·mol^-1·K^-1, while those for LMF-Cu^2＋-HSA system were -7.401 kJ·mol^-1 and 47.63 J·mol^-1·K^-1 Although the values of AH and AS in these two systems were different, the treads were similar, which indicated that electrostatic interactions in these two systems played a major role. According to Forster theory, the distances were given as 5.006 nm for HSA-LMF and 4.709 nm for HSA-LMF-Cu^2＋. Synchronous fluorescence and circular dichroism spectra confirmed further that the conformations of human serum albumin before and after interacting with LMF or LMF-Cu^2＋ were different. All the results revealed that copper ions promoted the interaction of lomefloxacin with human serum albumin.     

Studies on Interaction between Gatifloxacin and Bovine Serum Albumin by Spectroscopy

The interaction of gatifloxacin （HGA） with bovine serum albumin （BSA） at 15 and 37 ℃ has been investigated by fluorescence quenching spectroscopy in aqueous solution. The bimolecular quenching rate constant was determined by Stem-Volmer curves and the values were Kq=9.28× 10^12 L·mol^-1·s^-1 （15 ℃） and Kq=8.51 ×10^12 L·mol^-1·s^-1 （37 ~C）. The results showed that the fluorescence quenching mechanism of BSA by HGA was a static quenching procedure. The thermodynamic parameters indicated that electrostatic forces played major role in the interaction of BSA with HGA. Studies on the relationship between the concentration of HGA and the fluorescence intensity of BSA showed that BSA and HGA bound at the molar ratio 1 ： 1 and the equilibrium constant K0 was 6.80 ×10^4 L·mol^-1. The binding distances between BSA and HGA and the energy transfer efficiency were obtained based on the Ftrster＇s theory.     

Protein—Protein Interactions in Aqueous Ammonium Sulfate Solutions. Lysozyme and Bovine Serum Albumin (BSA)

Osmotic pressures have been measured to determine lysozyme—lysozyme,BSA—BSA, and lysosyme—BSA interactions for protein concentrations to 100 g-L^–1in an aqueous solution of ammonium sulfate at ambient temperature, as a functionof ionic strength and pH. Osmotic second virial coefficients for lysozyme, forBSA, and for a mixture of BSA and lysozyme were calculated from theosmotic-pressure data for protein concentrations to 40 g-L^–1. The osmotic second virialcoefficient of lysozyme is slightly negative and becomes more negative withrising ionic strength and pH. The osmotic second virial coefficient for BSA isslightly positive, increasing with ionic strength and pH. The osmotic second virialcross coefficient of the mixture lies between the coefficients for lysozyme andBSA, indicating that the attractive forces for a lysozyme—BSA pair areintermediate between those for the lysozyme—lysozyme and BSA—BSA pairs. For proteinconcentrations less than 100 g-L^–1, experimental osmotic-pressure data comparefavorably with results from an adhesive hard-sphere model, which has previouslybeen shown to fit osmotic compressibilities of lysozyme solutions.     

Spectroscopic Study of the Interactions of Buflomedil to Serum Albumin and β-Cyclodextrin

The effects of buflomedil (BFM), a novel cerebrovascular medicine, on serum albumin and the feasibility of ??-cyclodextrin (??-CD) acting as a controlled releaser for BFM were investigated by molecular spectroscopy methods, including fluorescence emission, UV?Cvisible absorption, Fourier transform infrared (FT-IR), synchronous and three-dimensional fluorescence spectroscopies. The interaction of BFM with bovine serum albumin (BSA) was analyzed by fluorescence quenching and it was found that BFM had reacted with BSA in the ground state and had affected the secondary structure of BSA. The observed binding constant K _b, the number of binding sites n, the distance r between donor (BSA) and acceptor (BFM), the enthalpy change (??H ^?? ), Gibbs energy change (??G ^?? ) and entropy change (??S ^?? ) at different temperatures were calculated. The inclusion reaction between ??-CD and BFM was explored by the Lineweaver?CBurk equation. The inclusion constants and the thermodynamic parameters were determined. The mechanism of the inclusion reaction was discussed and the controlled release characteristics of ??-CD to BFM were considered at the molecule level.     

Spectroscopic Probe–Aluminum(III)–Chrome Azure S Enhanced Determination of Serum Albumin in Microemulsion Medium

Abstract

The sensitizing effect of spectroscopic probe and microemulsion media on the determination of serum albumin by spectrometry was developed. The main factors affecting the determination were investigated in detail. The results showed that serum albumin reacted with spectroscopic probe Al(III)‐CAS to form a blue complex at pH=3.0 in the p‐octyl polyethyleneglycolphenyether microemulsion (Triton X‐100‐M). The λ_max=641 nm, and Beer's law was obeyed in the range of 0.0 and 35.0 µg · ml^?1 for bovine serum albumin (BSA). The sensitizing effect of spectroscopic probe in Triton X‐100-M microemulsion was higher than that in aqueous media. The proposed method has been used to determine protein in serum with satisfactory results.     

A Study on the Reaction Mechanism of Bromocresol Green with Bovine Serum Albumin

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Competitive Adsorption between Bovine Serum Albumin and Collagen Observed by Atomic Force Microscope

Atomic force microscopy (AFM) was used to study the competitive adsorption between bovine serum albumin (BSA) and type I collagen on hydrophilic and hydrophobic silicon wafers. BSA showed a grain shape and the type I collagen displayed fibril-like molecules with relatively homogeneous height and width, characterized with clear twisting (helical formation). These AFM images illustrated that quite a lot of type I collagen appeared in the adsorption layer on hydrophilic surface in a competitive adsorption state, but the adsorption of BSA was more preponderant than that of type I collagen on hydrophobic silicon wafer surface. The experiments showed that the influence of BSA on type I collagen adsorption on hydrophilic surface was less than that on hydrophobic surface.     

Spectroscopic Study on the Interaction between Bovine Serum Albumin and Tween‐20

The interaction between nonionic surfactant Tween-20 and bovine serum albumin (BSA) is studied in Tris‐HCl buffer solution by spectroscopic methods. The intrinsic fluorescence of BSA is quenched by the addition of Tween‐20. The UV‐visible absorption spectra and the synchronous fluorescence spectra show that the addition of Tween‐20 changes the polarity of the environment around tryptophan (trp) residues of BSA. The fraction of trp residues on the surface of BSA with and without Tween- 20 is calculated via I^? quenching experiments.     

Investigation of the Interaction between Isoflavonoids and Bovine Serum Albumin by Fluorescence Spectroscopy

The interactions of bovine serum albumin （BSA） with three structurally related isoflavonoids, genistein, puerarin and daidzein, were studied under physiological conditions by fluorescence spectroscopic technique. The quenching mechanism of these compounds with BSA was suggested as static quenching and the binding constants were determined at different temperatures based on the fluorescence quenching results. The transfer efficiency of energy and distance between the acceptor and BSA were investigated on the basis of the mechanism of the Forster energy transference. According to the thermodynamic parameters it has been suggested that the acting force be mainly hydrophobic force. The comparison of binding potency of the three isoflavonoids to BSA showed that the substitution by 5-OH and 8-Glc could enhance the binding affinity. All these obtained in the work can make us better understand the mode of the action and pharmacological activities of the isoflavonoids.     

Studies on Interactions of Antibiotics with Serum Albumin by Surface Plasmon Resonance Biosensor

Introduction Humanserumalbumin(HSA)isawell known transportproteinforavarietyofmoleculesandions[1].Thebindingofadrugtoserumalbuminhasimportant pharmacokineticconsequencesbecauseitinfluences distribution,excretionandpharmacologicaleffectsof thedruginthebody…     

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.     

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.     

Electric Field-induced Conformational Transition of Bovine Serum Albumin from α-helix to β-sheet

The conformational change of a biomolecule plays an important role in biologicalactivity. Electric field induced conformational transitions of helix-coil have beenreported for the proteins directly exposed to a high electric field, which is the results ofelectric birefringence and the electrooptical Kerr effectsl'2. The adsorbed proteins atelectrode interfaces3,4 also show conformational changes. One of the reasons for this isthat electric double layer near electrode surface offers a very stro…     

Characterization of the Interaction between Bovine Serum Albumin and Lomefloxacin by Capillary Zone Electrophoresis

Three capillary zone electrophoresis (CZE) methods of the frontal analysis (FA), vacancypeak (VP) and simplified Hummel-Dreyer (SHD) were applied to investigate interaction betweenbovine serum albumin (BSA) and lomefloxacin, the experimental condition was established after alarge number of tests. Based on the site-binding model, the binding parameters were measuredaccording to the site model by Scatchard.     

Characterization of Interactions Between Fluoroquinolones and Human Serum Albumin by CE–Frontal Analysis

The binding of fluoroquinolones to the transport protein, human serum albumin (HSA), under simulated physiological conditions has been studied by capillary electrophoresis–frontal analysis (CE–FA). The binding of these drugs to human plasma was evaluated by using ultrafiltration and capillary electrophoresis. The free drug concentration [D]_f at each HSA concentration was determined by the plateau height in the electropherograms and the calibration lines. The binding constants of fluoroquinolones and HSA were estimated using nonlinear regression with origin 7.5 software. The fluoroquinolones were found to show low affinity toward HSA, with binding constants ranging from 1.73 × 10² to 5.40 × 10² M^?1. The percentages of protein binding (PB) for fluoroquinolones to HSA were between 8.6 and 22.2%, while the PB percentages for fluoroquinolones to human plasma were between 10.2 and 33.1%. It can be found that the PB percentages for fluoroquinolones to HSA are mostly lower than those for fluoroquinolones to human plasma. It suggests that HSA is the primary protein responsible for the binding of fluoroquinolones in human plasma. The thermodynamic parameters were obtained by CE–FA. The positive ?H and ?S values obtained by CE–FA showed that the binding reaction was an endothermic process, and the entropy drive the binding and hydrophobic interaction played major roles in the binding of fluoroquinolones to HSA.