Interaction of cromolyn sodium with human serum albumin: a fluorescence quenching study

The interaction between cromolyn sodium (CS) and human serum albumin (HSA) was investigated using tryptophan fluorescence quenching. In the discussion of the mechanism, it was proved that the fluorescence quenching of HSA by CS is a result of the formation of a CS–HSA complex. Quenching constants were determined using the Sterns–Volmer equation to provide a measure of the binding affinity between CS and HSA. The thermodynamic parameters ΔG, ΔH, and ΔS at different temperatures were calculated. The distance r between donor (Trp²¹⁴) and acceptor (CS) was obtained according to fluorescence resonance energy transfer (FRET). Furthermore, synchronous fluorescence spectroscopy data and UV–vis absorbance spectra have suggested that the association between CS and HSA changed the molecular conformation of HSA and the electrostatic interactions play a major role in CS–HSA association.     

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.     

Studies on the interaction between Oxaprozin-E and bovine serum albumin by spectroscopic methods

The interaction between Oxaprozin-E and bovine serum albumin (BSA) was studied by spectroscopic methods including fluorescence and UV–vis absorption spectroscopy. The quenching mechanism of fluorescence of BSA by Oxaprozin-E was discussed to be a dynamic quenching procedure. The number of binding sites n and apparent binding constant K was measured by fluorescence quenching method. The thermodynamics parameter ΔH, ΔG, ΔS were calculated. The results indicate the binding reaction was mainly entropy-driven and hydrophobic forces played major role in the binding reaction. The distance r between donor (BSA) and acceptor (Oxaprozin-E) was obtained according to Förster theory of non-radioactive energy transfer.     

Synthesis of an octupolar compound and its biological effects on serum albumin

A special rigid planar structural octupolar molecule titled 2,4,6-tris(p-methylstyryl)-s-triazine (TMT) was synthesized and its interaction with bovine serum albumin (BSA) were studied by molecular spectroscopy. The quenching mechanism of fluorescence of BSA by TMT was discussed. The thermodynamic parameters ΔH ^θ, ΔG ^θ, ΔS ^θ at different temperatures were calculated and the results indicate hydrogen bond forces played major role in the reaction and the reaction was mainly enthalpy-driven. The distance r between donor (BSA) and acceptor (TMT) was obtained according to Förster theory of non-radiation energy transfer. Circular dichroism (CD) spectra, synchronous and three-dimensional fluorescence spectra were used to investigate the structural change of BSA molecules with addition of TMT, the result indicates that the α-helical structures of BSA molecules reduced in the presence of TMT. Sketch map of the interaction process was analyzed at molecular level.     

Characterization of intermolecular interaction between cyanidin‐3‐glucoside and bovine serum albumin: Spectroscopic and molecular docking methods

The intermolecular interaction between cyanidin‐3‐glucoside (Cy‐3‐G) and bovine serum albumin (BSA) was investigated using fluorescence, circular dichroism and molecular docking methods. The experimental results revealed that the fluorescence quenching of BSA at 338 nm by Cy‐3‐G resulted from the formation of Cy‐3‐G–BSA complex. The number of binding sites (n) for Cy‐3‐G binding on BSA was approximately equal to 1. The experimental and molecular docking results revealed that after binding Cy‐3‐G to BSA, Cy‐3‐G is closer to the Tyr residue than the Trp residue, the secondary structure of BSA almost not change, the binding process of Cy‐3‐G with BSA is spontaneous, and Cy‐3‐G can be inserted into the hydrophobic cavity of BSA (site II′) in the binding process of Cy‐3‐G with BSA. Moreover, based on the sign and magnitude of the enthalpy and entropy changes (ΔH⁰ = – 29.64 kcal/mol and ΔS⁰ = – 69.51 cal/mol K) and the molecular docking results, it can be suggested that the main interaction forces of Cy‐3‐G with BSA are Van der Waals and hydrogen bonding interactions. Copyright © 2013 John Wiley & Sons, Ltd.     

Combined multispectroscopic and molecular docking investigation on the interaction between strictosamide and human serum albumin

The interaction between strictosamide (STM) and human serum albumin (HSA) was investigated by fluorescence spectroscopy, synchronous fluorescence spectroscopy, three‐dimensional fluorescence spectroscopy, ultraviolet‐visible absorption spectroscopy, circular dichroism spectroscopy and molecular modeling under physiological pH 7.4. STM effectively quenched the intrinsic fluorescence of HSA via static quenching. The binding site number n and apparent binding constant K_a were determined at different temperatures by fluorescence quenching. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) for the reaction were calculated as ?3.01 kJ/mol and 77.75 J/mol per K, respectively, which suggested that the hydrophobic force played major roles in stabilizing the HSA–STM complex. The distance r between donor and acceptor was obtained to be 4.10 nm according to Förster's theory. After the addition of STM, the synchronous fluorescence and three‐dimensional fluorescence spectral results showed that the hydrophobicity of amino acid residues increased and the circular dichroism spectral results showed that the α‐helix content of HSA decreased (from 61.48% to 57.73%). These revealed that the microenvironment and conformation of HSA were changed in the binding reaction. Furthermore, the study of molecular modeling indicated that STM could bind to site I of HSA and the hydrophobic interaction was the major acting force, which was in agreement with the binding mode study. Copyright © 2013 John Wiley & Sons, Ltd.     

Urea‐induced binding between diclofenac sodium and bovine serum albumin: a spectroscopic insight

We investigated the interaction of diclofenac sodium (Dic.Na) with bovine serum albumin (BSA) in the absence and presence of urea using different spectroscopic techniques. A fluorescence quenching study revealed that the Stern–Volmer quenching constant decreases in the presence of urea, decreasing further at higher urea concentrations. The binding constant and number of binding sites were also evaluated for the BSA–Dic.Na interaction system in the absence and presence of urea using a modified Stern–Volmer equation. The binding constant is greater at high urea concentrations, as shown by the fluorescence results. In addition, for the BSA–Dic.Na interaction system, a static quenching mechanism was observed, which was further confirmed using time‐resolved fluorescence spectroscopy. UV–vis spectroscopy provided information about the formation of a complex between BSA and Dic.Na. Circular dichroism was carried out to explain the conformational changes in BSA induced by Dic.Na in the absence and presence of urea. The presence of urea reduced the α‐helical content of BSA as the Dic.Na concentration varied. The distance r between the donor (BSA) and acceptor (Dic.Na) was also obtained in the absence and presence of urea, using fluorescence resonance energy transfer. Copyright © 2015 John Wiley & Sons, Ltd.     

Binding of isofraxidin to bovine serum albumin

The binding of isofraxidin to bovine serum albumin (BSA) was studied under physiological conditions with BSA concentration of 1.5 x 10(-6) mol x L(-1) and drug concentration in the range of 1.67 x 10(-6) mol x L(-1) to 2.0 x 10(-5) mol x L(-1). Fluorescence quenching spectra in combination with uv absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and CD spectroscopy was used to determine the drug-binding mode, binding constant, and the protein structure changes in the presence of isofraxidin in aqueous solution. The linearity of Scatchard plot indicates that isofraxidin binds to a single class of binding sites on BSA and the values given for the binding constants agree very closely with those obtained by the modified Stern-Volmer equation. The thermodynamic parameters, enthalpy change (DeltaH) and entropy change (DeltaS), were calculated to be -17.63 kJ x mol(-1) and 51.38 J x mol(-1) x K(-1) according to the van't Hoff equation, which indicated that hydrophobic interaction played a main role in the binding of isofraxidin to BSA.     

Spectroscopic identification of interactions of formaldehyde with bovine serum albumin

The mechanism of formaldehyde-protein interactions was investigated by determining the effects of formaldehyde on the common protein bovine serum albumin (BSA). The effects at the molecular level were determined by fluorescence, ultraviolet absorption, and circular dichroism (CD) spectrometry. Formaldehyde could decrease the amount of alpha-helix, leading to loosening of the protein skeleton. In the loose structure, internal amino acids are exposed and the characteristic fluorescence of BSA is obviously quenched. The spectroscopic results reveal that formaldehyde exposure induces changes in the microenvironment and conformation of serum albumin, which could lead to toxic effects on the organism.     

Binding of anti-cardiovascular drug to serum albumin: an insight in the light of spectroscopic and computational approaches

Isoprenaline hydrochloride is a potential cardiovascular drug helps in the smooth functioning of the heart muscles. So, we have performed the binding study of ISO with BSA. This study was investigated by UV absorption, fluorescence, synchronous fluorescence, circular dichroism, etc. The analysis of intrinsic fluorescence data showed the low binding affinity of ISO. The binding constant K_b was 2.8 × 103 M-1 and binding stoichiometry (n) was approximately one and the Gibb’s free energy change at 310 K was determined to be -8.69 kcal mol^?1. Negative Gibb’s free energy change shows the spontaneity of the BSA and ISO interaction. We have found ISO-induced alternation in the UV absorption, synchronous fluorescence and CD spectra in the absence and presence of the quencher indicates the complex formation. In synchronous fluorescence, red shift was obtained because of the complex formation of BSA and ISO. The distance (r) between the BSA (donor) and ISO (acceptor) was 2.89 nm, determined by FRET. DLS measurements interpreted complex formation due to the reduction in hydrodynamic radii of the protein in the presence of the drug. The binding site of ISO was found to be nearer to Trp 134 with the help of molecular docking and the ΔG° was found to be –10.2 kcal mol^?1. The esterase activity result suggests that ISO acts as competitive inhibitor. Thus, this study would help to determine the binding capacity of the drug to the protein which may indicate the efficiency of diffusion of ISO into the blood for the treatment of heart diseases.     

The effect of non-enzymatic glycation on the unfolding of human serum albumin

We monitored the unfolding of human serum albumin (HSA) and glycated human serum albumin (gHSA) subjected to guanidine hydrochloride (GndHCl) by using fluorescence and circular dichroism (CD) spectroscopy. A two-state model with sloping baselines best described the Trp-214 fluorescence unfolding measurements, while a three-state model best described the far-UV CD unfolding data. Glycation of HSA increased the [D](50%) point by approximately 0.20M. This corresponded to an increase in the free energy of unfolding of gHSA relative to HSA of 2.6kJ/mol. The intrinsic fluorescence of Trp-214 in gHSA is 0.72 of that of HSA and the far-UV CD spectrum of gHSA is nearly identical to that of HSA. These results showed that glycation altered the local structure around Trp-214 while not significantly impacting the secondary structure, and this alteration translated into an overall change in the stability of gHSA compared to HSA.     

Secondary structural changes of large and small fragments of bovine serum albumin in thermal denaturation and in sodium dodecyl sulfate denaturation

The helicities in various fragments of bovine serum albumin (BSA) were examined in the thermal denaturation and in sodium docecyl sulfate (SDS) denaturation. The thermal denaturation was examined in a temperature range between 2 and 65°C. The helicity decreased with a rise of temperature and it recovered to some degree upon cooling temperature. A rather high reversibility was observed in the BSA fragments, which were located in the N-terminal of the parent protein and then contained the first large loop with no disulfide bridge. The high reversibility was available also for the helicity in the first large loop of the fragment, disulfide bridges of which were reduced. The fragments, which were smaller than one domain, became unstable in the SDS denaturation. The helicities of such fragments decreased in lower SDS concentrations compared with those of the intact BSA and the large fragments, which contained one or more domains. A resistance to the SDS denaturation appeared in the helices of every large loop even after the fragmentation. On the other hand, helicities of the fragments decreased to 20–25% upon the reduction of disulfide bridges. However, the helicities of these fragments increased to 35–40% in the SDS denaturation.     

Spectroscopic analysis of the binding interaction between tinidazole and bovine serum albumin (BSA)

The interaction between bovine serum albumin (BSA) and tinidazole (Tindamax; 1) in aqueous solution was investigated in detail by means of UV/VIS and fluorescence spectroscopy, as well as through resonance light-scattering (RLS) spectroscopy. The apparent binding constant and number of binding sites were determined at three different temperatures, as well as the average binding distances between 1 and the nearest amino acid residue(s) of BSA, as analyzed by means of F?rster's theory of non-radiation energy transfer. Compound 1 was found to quench the inner fluorescence of BSA by forming a tight 1:1 aggregate, based on both static quenching and non-radiation energy transfer. The entropy change upon complexation was positive, and the enthalpy change was negative, indicating that the observed spontaneous binding is mainly driven by electrostatic interactions.     

Binding of amifostine to human serum albumin: A biophysical study

The aim of this present work is to investigate the interaction between amifostine and human serum albumin (HSA) in simulated physiological conditions by spectroscopic methods to reveal potential toxic effects of the drug. The results reflected that amifostine caused fluorescence quenching of HSA through a static quenching process, which was further confirmed by the electrochemical experiments. The binding constants at 290, 297 and 304 K were obtained as 2.53 × 10⁵/M, 8.13 × 10⁴/M and 3.59 × 10⁴/M, respectively. There may be one binding site of amifostine on HSA. The thermodynamic parameters indicated that the interaction between amifostine and HSA was driven mainly by hydrogen bonding and electrostatic forces. Synchronous fluorescence spectra, circular dichroism and Fourier transform infrared spectroscopy results showed amifostine binding slightly changed the conformation of HSA with secondary structural content changes. Förster resonance energy transfer study revealed high possibility of energy transfer with amifostine‐Trp‐214 distance of 3.48 nm. The results of the present study may provide valuable information for studying the distribution, toxicological and pharmacological mechanisms of amifostine in vivo. Copyright © 2014 John Wiley & Sons, Ltd.     

Mesostructure of fibrillar bovine serum albumin gels

The mesostructure of bovine serum albumin (BSA) at low pH was investigated. Rheological measurements were performed to determine the critical percolation concentration (c_p). A decreasing c_p with increasing ionic strength was found. Fibrils with a contour length of about 100–300 nm were found using transmission electron microscopy. The measured conversion of monomers into fibrils was independent of ionic strength (0.20–0.30 M). Dilution of BSA samples showed that the aggregation process is reversible and that there exists a critical concentration for the self-assembly of BSA. We explain the decreasing c_p with increasing ionic strength in terms of an adjusted random contact model.     

Luminescence,circular dichroism and in silico studies of binding interaction of synthesized naphthylchalcone derivatives with bovine serum albumin

Chalcones possess various biological properties, for example, antimicrobial, anti‐inflammatory, analgesic, antimalarial, anticancer, antiprotozoal and antitubercular activity. In this study, naphthylchalcone derivatives were synthesized and characterized using ¹H NMR ¹³C NMR, Fourier transform infrared and mass techniques. Yields for all derivatives were found to be >90%. Protein–drug interactions influence the absorption, distribution, metabolism and excretion (ADME) properties of a drug. Therefore, to establish whether the synthesized naphthylchalcone derivatives can be used as drugs, their binding interaction toward a serum protein (bovine serum albumin) was investigated using fluorescence, circular dichroism and molecular docking techniques under physiological conditions. Fluorescence quenching of the protein in the presence of naphthylchalcone derivatives, and other derived parameters such as association constants, number of binding sites and static quenching involving confirmed non‐covalent binding interactions in the protein–ligand complex were observed. Circular dichroism clearly showed changes in the secondary structure of the protein in the presence of naphthylchalcones, indicating binding between the derivatives and the serum protein. Molecular modelling further confirmed the binding mode of naphthylchalcone derivatives in bovine serum albumin. A site‐specific molecular docking study of naphthylchalcone derivatives with serum albumin showed that binding took place primarily in the aromatic low helix and then in subdomain II. The dominance of hydrophobic, hydrophilic and hydrogen bonding was clearly visible and was responsible for stabilization of the complex.     

Study of the interaction between doxepin hydrochloride and bovine serum albumin by spectroscopic techniques

The binding of doxepin hydrochloride (DH) to bovine serum albumin (BSA) was investigated by spectroscopic (fluorescence, UV–vis absorption and circular dichroism) techniques. The binding parameters have been evaluated by fluorescence quenching method. The thermodynamic parameters, ΔH°, ΔS° and ΔG° calculated at different temperatures indicated that the hydrogen bond and hydrophobic forces played a major role in the interaction of DH with BSA. Based on the Förster's theory of non-radiation energy transfer, the binding average distance, r between the donor (BSA) and acceptor (DH) was evaluated and found to be 2.7 nm. Spectral results observed showed that the binding of DH to BSA induced conformational changes in BSA. The effect of common ions on the binding of DH to BSA was also examined.     

Differential binding of tetracyclines with serum albumin and induced structural alterations in drug-bound protein

Interaction of tetracycline (TC) derivatives viz. oxytetracycline, doxycycline, demeclocycline and chlorotetracycline with bovine serum albumin (BSA) and concomitant changes in protein conformation were studied using fluorescence quenching and circular dichroism measurements. Fluorescence data revealed the presence of one to three binding sites on BSA for different TC derivatives. Binding studies with the marker ligands, warfarin and bilirubin, elucidated site-I as a primary binding site for TCs on albumin. Scatchard analysis revealed the binding affinity (K_a) and capacity (n) for these derivatives vary in the range from 0.8 to 3.2×10⁶ l/mole and 1.3–3.4, respectively. Significant reduction (60–45%) in secondary structure (-helical content) of BSA was noticed upon interaction with different TC derivatives in presence of Cu (II) ions. High affinity binding of TCs with BSA signifies drug stability. However, excessive binding at higher TC concentrations in combination with Cu (II) induces conformational change in protein structure, which may exert detrimental effect on cellular protein.     

Molecular interaction of cationic gemini surfactant with bovine serum albumin: A spectroscopic and molecular docking study

Herein, we report the effect of N,N′-bis(dodecyloxycarbonylmethyl)-N,N,N′,N′-tetramethyl-1,2-ethanediammonium dibromide (dodecyl betainate gemini or DBG) on the structure and function of bovine serum albumin (BSA) by using fluorescence, time resolved fluorescence, circular dichroism and dynamic light scattering techniques. The Stern–Volmer quenching constants K_SV and the corresponding thermodynamic parameters viz ΔH, ΔG and ΔS have been estimated by the fluorescence quenching method. The results indicated that DBG binds spontaneously with BSA through hydrophobic interaction. Time resolved fluorescence data show that the quenching follows the static mechanism pathway. It can be seen from far-UV CD spectra that the α-helical network of BSA is disrupted and its content increases from 71% to 79% at lower concentrations which again decreases to 38% at higher concentration. DLS measurements suggested that hydrodynamic radius (R_h) decreases in the presence of 30 and 40 μM of DBG while it increases when the concentration of DBG was 70 and 100 μM. The molecular docking study indicated that DBG is embedded into subdomain IIA of BSA and binds with the R-914, R-195 and R-217 residues by hydrogen bonding and by hydrophobic interaction.     

Binding characteristics of bovine serum albumin encapsulated in sol-gel glasses: an alternative for protein interaction studies

Silica glasses doped with 500-700 microg of bovine serum albumin were prepared by the sol-gel method; two pH conditions (pH 5 and 7) were assayed for protein encapsulation. Both biomaterials showed a highly porous structure, with pore sizes in the range 5-28 nm. Columns packed with the ground biogels were on-line coupled to a C18 HPLC column for evaluation of the entrapped protein binding properties using propranolol. Binding capacities (at saturation) were approximately 3.7 and 7.1 microg of propranolol (drug-protein molar ratios 1.4 and 2.7) for the biogels prepared at pH 5 and 7, respectively. The significant difference indicates increased albumin denaturation upon encapsulation at pH 5. A frontal analysis study was then performed in cartridges packed with biogel prepared at pH 7 to evaluate the protein interaction with naproxen at low concentrations (相似文献