The interaction of dansyl amino acids with bovine serum albumin

The interaction of 5-dimethylaminonaphthalene-1-sulfonyl (DNS or dansyl) amino acids with bovine serum albumin (BSA) was investigated by means of fluorescence measurements. Fluorometric titrations revealed that BSA has one high affinity site (binding constant,K _a=10⁵10⁶ M^–1), and other sites of lower affinity (K _a=10³10⁴ M^–1) for the probes. Static excitation and emission spectra, lifetimes, time resolved emission spectra, and anisotropy data indicated that the binding is stabilized mainly through fixation by the high affinity binding site. The binding constant significantly decreased with the increase of the spacer distance between the dansyl and anionic groups of the probe molecule. This observation was explained by considering the change of the electrostatic interaction between the anionic group of the probe and a cationic residue in the vicinity of the site.     

Fluorescence enhancement of dansylamino acids by bovine serum albumin as mobile phase additive in microcolumn liquid chromatography

Summary The effects of acetonitrile and bovine serum albumin (BSA) concentrations on the signal intensity and retention behavior of dansylamino acids have been examined by using -cyclodextrin-bonded silica gel as the stationary phase in microcolumn liquid chromatography. Fluorescence intensities of dansylamino acids were enhanced by BSA as a mobile phase additive, e.g., detection limits of dansyl derivatives of L-Ala and L-Phe were improved by a factor of 12–18.     

Selectivity of dansyl amino acids in micellar liquid chromatography with an ion-exchange-induced stationary phase

Summary The retention behavior of dansyl amino acids in micellar liquid chromatography has been examined by using ionexchange-induced stationary phases. Several parameters affected the retention of the analytes, including the type and concentration of micellar agent and modifier ion and the concentration of acetonitrile in the mobile phase. The order of elution of dansyl amino acids obtained with the micellar mobile phase was very different from that observed in conventional reversed-phase liquid chromatography. Fluorescence intensities of some dansyl amino acids were enhanced by the micellar mobile phase.     

Probing chiral amino acids at sub-picomolar level based on bovine serum albumin enantioselective films coupled with silver-enhanced gold nanoparticles

A novel electrochemical sensor with capability of probing chiral amino acids with gold nanoparticle (n-Au) labels using bovine serum albumin (BSA) as a chiral selector and subsequent signal amplification step by silver enhancement is introduced. The assay relies on the stereoselectivity of BSA embedded in ultrathin γ-alumina sol–gel film coated on the surface of the glassy carbon electrode (GCE). The recognition to the n-Au-labeled l- or d-amino acids for BSA-GCE could be monitored by the differential pulse voltammetry (DPV), while the DPV signal was greatly amplified by the anchored silver atoms on the n-Au, leading to a new way of quantitatively analysis of chiral amino acids electrochemically at sub-picomolar level. With l-tryptophan as the probe solute, the linear concentration range was from 1.33 × 10⁻¹² to 1 × 10⁻⁹ mol L⁻¹ and detection limit was 5 × 10⁻¹³ mol L⁻¹. For tryptophan enantiomers, the enantioselectivity coefficient 2.3 was obtained.     

Enhanced chemiluminescence detection of some dansyl amino acids in liquid chromatography

Summary The dansylated amino acids alanine, glutamic acid, methionine and norleucine were separated by reversedphase HPLC and detected via chemical excitation using the post-column, TCPO-peroxyoxalate reaction system. Enhancement of the chemiluminescence emission was achieved by including the surfactant Triton X-100 in the eluent.     

Microcolumn ion chromatography of inorganic anions using bovine serum albumin stationary phase with indirect photometric detection

Summary Microcolumn ion chromatography of inorganic anions has been studied using bovine serum albumin immobilized on silica gel as a stationary phase. Several mobile phase solutions were examined, involving sodium iodide, potassium hydrogen phthalate, 2,6-anthraquinone disulfonate (2,6-AQDS) and sodium salicylate. 2,6-AQDS achieved better separation of the analytes tested. Chloride, nitrate, iodide, thiocyanate and sulphate could be separated within 8 min. Detection limits were in the range of 0.9–2.9 M, corresponding to mass detection limits of 0.18–0.59 pmol. The system was applied to the determination of inorganic anions in environmental water and biological samples.     

Signal enhancement by on-column fluorimetric detection in gradient elution of dansyl amino acids in liquid chromatography

Summary Fluorimetric detection in the presence of a stationary phase has been applied to gradient elution of dansyl amino acids in liquid chromatography. A 1.5 mm ID quartz tube packed with the same materials as the separation column was employed for the flow cell. Conventional-size columns were employed. The peak height of analytes increased with increasing retention owing to focusing and environmental effects of the stationary phase, leading to improvements in sensitivity, which was pronounced for analytes eluting late. The lower the gradient, the larger the improvement in sensitivity achieved. Detection limits were improved by a factor of up to 5.1 by fluorimetric detection using the packed flow cell, compared with those achieved using a common empty flow cell.     

Signal enhancement by on-column fluorimetric detection in gradient elution of dansyl amino acids in liquid chromatography

Summary Fluorimetric detection in the presence of a stationary phase has been applied to gradient elution of dansyl amino acids in liquid chromatography. A 1.5 mm ID quartz tube packed with the same materials as the separation column was employed for the flow cell. Conventional-size columns were employed. The peak height of analytes increased with increasing retention owing to focusing and environmental effects of the stationary phase, leading to improvements in sensitivity, which was pronounced for analytes eluting late. The lower the gradient, the larger the improvement in sensitivity achieved. Detection limits were improved by a factor of up to 5.1 by fluorimetric detection using the packed flow cell, compared with those achieved using a common empty flow cell.     

Separation of enantiomers on bovine serum albumin coated zirconia in reversed-phase liquid chromatography

Summary Zirconia is known to be one of the best materials for the chromatographic support due to its excellent chemical, thermal and mechanical stability. In this work we report preparation and use of bovine serum albumin (BSA)-immobilized zirconia as a chiral stationary phase for separation of some enantiomers in reversed-phase liquid chromatography. The BSA-zirconia showed good enantioselectivity for some of the enantiomers studied and could be used for RPLC separations in mobile phases of alkaline pH.     

Interaction of magnolol with bovine serum albumin: a fluorescence-quenching study

The interaction of magnolol with bovine serum albumin(BSA) was studied using fluorescence spectroscopy under physiological conditions. The binding constants, K, and the ratio of quantum yields of protein fluorescence for complex and free protein, f, at 298 K, 304 K, and 310 K were obtained; the values were 6.799×10⁵ L mol^–1, 5.541×10⁵ L mol^–1, and 4.344×10⁵ L mol^–1 and 0.17, 0.30, and 0.34, respectively. The standard enthalpy change (H°) and the standard entropy change (S°) were calculated to be –28.53 kJ mol^–1 and 15.88 J mol^–1 K^–1, which indicated that hydrophobic forces played major role in the interaction of magnolol and BSA. The binding average distance between magnolol and BSA (4.32 nm) was obtained on the basis of the theory of Förster energy transfer.     

溴甲酚绿分光光度法测定牛血清白蛋白

在pH 3.3的Britton-Robinson (B-R)缓冲溶液中, 对溴甲酚绿(BCG)与牛血清白蛋白(BSA)相互作用的吸收光谱进行了初步研究. 结果表明: BCG与BSA作用在室温下能迅速结合成复合物, 并且随着BSA的浓度增大, 在444 nm处的吸收峰降低, 618 nm处吸收峰升高并红移至628 nm. 在此波长下测定其复合物的吸光度, 其吸光度的增加值(ΔA)与BSA的质量浓度在8～260 μg/mL范围内呈良好的线性关系(r=0.9996), 检出限为4 μg/mL. 该方法应用于鲜奶粉和液态纯牛奶样品中总蛋白的测定, 回收率分别为92.7%, 95.5%, 结果与考马斯亮蓝G250法基本一致.     

CE determination of quinolones in the presence of bovine serum albumin

This article describes the influence of bovine serum albumin (BSA) as an additive on the capillary electrophoresis–potential gradient determination of five quinolones, enoxacin, norfloxacin, ofloxacin, fleroxacin, and pazufloxacin. With 10 mg/L of BSA present in the buffer of 30 mM Tris and 3 mM phosphoric acid at pH 9, the detection limits of the five quinolones were in the range of 0.24–0.68 mg/L, i. e. 5.8–16.5‐fold lower than those obtained with the buffer devoid of BSA, and the analysis time was shortened. We suggest that the inner wall‐adsorbed BSA suppresses the adsorption of quinolones and simultaneously enhances the electroosmotic flow rate. Our experiments indicated that adopting the potential gradient detection technique could eliminate the interference of the UV‐active proteins on the detection of quinolones that would occur with conventional optical detection, and therefore offer high detection sensitivity. As a demonstration, the method was applied to the determination of QNs in fortified chicken muscle sample with satisfactory results.     

Electrochemistry of the interaction of furazolidone and bovine serum albumin

The electrochemical behavior of the interaction of furazolidone (Fu) with bovine serum albumin (BSA) was investigated by cyclic voltammetry and differential pulse voltammetry at a glassy carbon electrode. Fu shows an irreversible reduction at − 0.34 V in pH 4.0 Britton–Robinson buffer (B–R) buffer–10% DMF solution. After the addition of BSA into the Fu solution, the reductive peak currents decreased without any significant shift of the peak potential and the appearance of new peaks. The electrochemical parameters of the interaction system were calculated in the absence and presence of BSA. This electrochemical method was further applied to the determination of BSA samples and the results were in good agreement with the traditional cellulose acetate electrophoresis. The linear dynamic range was between 10.0 and 80.0 mg l^− 1. The detection limit was 7.6 mg l^− 1 and the recoveries were obtained from 97.0% to 104.0%.     

金丝桃苷与牛血清白蛋白相互作用的研究

采用荧光共振能量转移法研究了金丝桃苷与牛血清白蛋白的相互作用.金丝桃苷对牛血清白蛋白(BSA)的荧光猝灭类型是静态猝灭,25℃时的结合位点数为0.5451.并依据F(o)ster非辐射能量转移理论,研究了给体(牛血清白蛋白)--受体(金丝桃苷)间的结合距离R.和能量转移效率E分别为2.04nm和0.66.同时,采用同步...     

Chiral discrimination ofN-(dansyl)-dl-amino acids on human serum albumin stationary phase: Effect of a mobile phase modifier

Summary The effect of perchlorate anion as mobile phase modifier on the separation factor, α, forN-(dansyl)-dl-norvaline andN-(dansyl)-dl-tryptophan on a human serum albumin (HSA) column was studied by varying the concentration,c, of the chaotropic agent and the column temperatureT. Gibbs-Helmholtz parameters Δ(ΔH) and Δ(ΔS) between thed andl enantiomers were determined from linear van't Hoff plots of lnα against 1/T. Thermodynamic results indicated that the enhancement of the separation factor observed asc was increased was enthalpically controlled owing to stereoselective H-bonding interactions. Such behavior was used to optimize the chromatographic conditions for separation ofN-(dansyl)-amino acids on HSA.     

Antioxidant activity of bovine serum albumin binding amino acid Schiff-bases metal complexes

Glutamic acid-salicylaldehyde Schiff-base metal complexes are bound into bovine serum albumin (BSA),which afforded BSA binding Schiff-base metal complexes (BSA-SalGluM,M=Cu,Co,Ni,Zn).The BSA binding metal complexes were characterized by UV-vis spectra and Native PAGE.It showed that the protein structures of BSA kept after coordinating amino acid Schiff-bases metal complexes.The effect of the antioxidant activity was investigated.The results indicate that the antioxidant capacity of BSA increased more than 10 times after binding Schiff-base metal complexes.     

A kind of modified bovine serum albumin with great potential for applying in gene delivery

Bovine serum albumin(BSA) was modified through a facile synthesis method to increase its isoelectric point(pI) from 4.8 to 6.0.When pH is higher than 6.0,the protein shows a negative surface charge,on the contrary,the protein is positively charged.In this study,the charge-reversal modified BSA(crBSA) was utilized to assemble with the binary complexes of pDNA/poly(vinylpyrrolidone)-graft-poly(2-dimethylaminoethyl methacrylate)(pDNA/PVP-g-PDMAEMA) to shield the excess positive charges of complexes at physiological pH(pH 7.4).When the complex coated with crBSA located in the environment at endosomal pH(pH 5.0),the charge-reversal of crBSA led to the deviation of crBSA from polyplex by electrostatic repulsion,which would benefit the transfection of the target gene.The crBSA shows great potential for improving the transfection efficiency of pDNA/PVP-g-PDMAEMA.     

Binding of the bioactive component isothipendyl hydrochloride with bovine serum albumin

The binding of isothipendyl hydrochloride (IPH) to bovine serum albumin (BSA) was investigated by fluorescence spectroscopy combined with UV-visible absorption and circular dichroism (CD) techniques under simulative physiological conditions for the first time. The quenching mechanism of fluorescence BSA by IPH was discussed. The binding parameters have been evaluated by fluorescence quenching method. The thermodynamic parameters, ΔH°, ΔS° and ΔG° calculated at different temperatures indicated that the hydrophobic force played a major role in the interaction of IPH to BSA. The distance, r between donor (BSA) and acceptor (IPH) was obtained according to the Förster's theory of non-radiation energy transfer and was found to be 2.21 nm. Experimental results showed that the α-helicity of BSA decreased from 66.4% (in free BSA) to 39.1% (in bound BSA). The effect of common ions on the binding constant was also investigated.     

Synthesis,characterization, and thermodynamic studies of the interaction of some new water-soluble Schiff-base complexes with bovine serum albumin

Some new water-soluble Schiff-base complexes Na₂[M(5-SO₃-2,3-salpyr)(H₂O) _n ]?·?2H₂O (5-SO₃-2,3-salpyr?=?N,N′-bis(5-sulphosalicyliden)-2,3-diaminopyridine and M?=?Zn, Cu, Ni) were synthesized and characterized by elemental analysis, IR, ¹H NMR, magnetic susceptibility measurement, thermal analysis, and UV-Vis spectroscopy. The mechanism of binding of Na₂[M(5-SO₃-2,3-salpyr)(H₂O) _n ]?·?2H₂O with bovine serum albumin (BSA) was investigated by fluorescence spectroscopy. The fluorescence titration revealed that the intrinsic fluorescence of BSA was quenched by Na₂[M(5-SO₃-2,3-salpyr)], which was rationalized in terms of the static quenching mechanism. The values of the Stern–Volmer constants, quenching rate constants, binding constants, binding sites, and average aggregation number of BSA were determined by this method. Thermodynamic parameters were calculated by the van’t Hoff equation. The data clearly indicate that the binding is entropy driven and enthalpically disfavored. Based on the Förster theory of non-radiative energy transfer, the efficiency of energy transfer, and the distance between the donor (Trp residues) and the acceptor (Na₂[M(5-SO₃-2,3-salpyr)]) were evaluated. Also the synchronous fluorescence spectra showed that the microenvironment of the tryptophan residues was not changed. Finally, our results indicate that the complexes can bind to BSA and be efficiently transported in the body, which could be helpful for further drug design.