Human Serum Albumin Complex Research Articles

Combined molecular docking and multi-spectroscopic investigation on the interaction between Eosin B and human serum albumin

The binding of Eosin B to human serum albumin (HSA) was studied using molecular docking, fluorescence, UV–vis, circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy. The mechanism of interaction between Eosin B and HSA in terms of the binding parameters, the thermodynamic functions and the effect of Eosin B on the conformation of HSA were investigated. Protein-ligand docking study indicated that Eosin B bound to residues located in the subdomain IIA of HSA and Eosin B–HSA complex was stabilized by hydrophobic force and hydrogen bonding. In addition, fluorescence data revealed that Eosin B strongly quenched the intrinsic fluorescence of HSA through a static quenching procedure. Furthermore, alteration of the secondary structure of HSA in the presence of the dye was conformed by UV–vis, FT-IR and CD spectroscopy.

Determination of Energies and Sites of Binding of PFOA and PFOS to Human Serum Albumin

Structure and energies of the binding sites of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) to human serum albumin (HSA) were determined through molecular modeling. The calculations consisted of a compound approach based on docking, followed by molecular dynamics simulations and by the estimation of the free binding energies adopting WHAM-umbrella sampling and semiempirical methodologies. The binding sites so determined are common either to known HSA fatty acids sites or to other HSA sites known to bind to pharmaceutical compounds such as warfarin, thyroxine, indole, and benzodiazepin. Among the PFOA binding sites, five have interaction energies in excess of -6 kcal/mol, which become nine for PFOS. The calculated binding free energy of PFOA to the Trp 214 binding site is the highest among the PFOA complexes, -8.0 kcal/mol, in good agreement with literature experimental data. The PFOS binding site with the highest energy, -8.8 kcal/mol, is located near the Trp 214 binding site, thus partially affecting its activity. The maximum number of ligands that can be bound to HSA is 9 for PFOA and 11 for PFOS. The calculated data were adopted to predict the level of complexation of HSA as a function of the concentration of PFOA and PFOS found in human blood for different levels of exposition. The analysis of the factors contributing to the complex binding energy permitted to outline a set of guidelines for the rational design of alternative fluorinated surfactants with a lower bioaccumulation potential.

Study of interaction of butyl p-hydroxybenzoate with human serum albumin by molecular modeling and multi-spectroscopic method

Abstract Study of the interaction between butyl p -hydroxybenzoate (butoben) and human serum albumin (HSA) has been performed by molecular modeling and multi-spectroscopic method. The interaction mechanism was predicted through molecular modeling first, then the binding parameters were confirmed using a series of spectroscopic methods, including fluorescence spectroscopy, UV–visible absorbance spectroscopy, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. The thermodynamic parameters of the reaction, standard enthalpy Δ H 0 and entropy Δ S 0 , have been calculated to be −29.52 kJ mol −1 and −24.23 J mol −1 K −1 , respectively, according to the Van’t Hoff equation, which suggests the van der Waals force and hydrogen bonds are the predominant intermolecular forces in stabilizing the butoben–HSA complex. Results obtained by spectroscopic methods are consistent with that of the molecular modeling study. In addition, alteration of secondary structure of HSA in the presence of butoben was evaluated using the data obtained from UV–visible absorbance, CD and FT-IR spectroscopies.

Complex of nicosulfuron with human serum albumin: A biophysical study

Nicosulfuron is a sulfonylurea herbicide developed by DuPont that has been used successfully for weed control in maize. The binding mechanism and binding site identified in human serum albumin (HSA) with the use of fluorescence, circular dichroism (CD) and molecular modeling is the subject of this paper. From the CD, synchronous and three-dimensional fluorescence results, it was apparent that the interaction of nicosulfuron with HSA caused secondary structure changes in the protein. Fluorescence data revealed that the nicosulfuron induced the fluorescence quenching of HSA through a static quenching procedure. Thermodynamic analysis results implied the role of hydrophobic and hydrogen bonds interactions in stabilizing the nicosulfuron–HSA complex. Site marker competitive experiments showed the binding of nicosulfuron to HSA primarily took place in subdomain IIA (Sudlow’s site I), this corroborates the guanidine hydrochloride (GuHCl) induced denaturation of HSA, hydrophobic probe ANS displacement and molecular modeling results. In this work, the presented binding research extends our knowledge of the binding properties of sulfonylurea herbicides to the important plasma protein HSA.

Complexes between Fluorescent Cholic Acid Derivatives and Human Serum Albumin. A Photophysical Approach To Investigate the Binding Behavior

Interaction between bile acids and plasma proteins has attracted considerable attention over past decades. In fact, binding of bile acids to human serum albumin (HSA) determines their level in plasma, a value that can be used as a test for liver function. However, very little is known about the role that bile acids-HSA complexes play in hepatic uptake. In the present paper, we report on the utility of the singlet excited state properties of 4-nitrobenzo-2-oxa-1,3-diazole (NBD) fluorescent derivatives of cholic acid (ChA); namely, 3alpha-NBD-ChA, 3beta-NBD-ChA, 3beta-NBD-ChTau, 7alpha-NBD-ChA, and 7beta-NBD-ChA to clarify key aspects of bile acids-HSA interactions that remain poorly understood. On the basis of either absorption or emission measurements, formation of NBD-ChA@HSA complexes with 1:1 stoichiometry has been proven. Enhancement of the fluorescence emission upon addition of HSA has been used for determination of the binding constants, which are in the range of 10(4) M(-1). Energy transfer from tryptophan to NBD-ChA occurs by a FRET mechanism; the donor-acceptor distances have been determined according to Forster's theory. The estimated values (27-30 A) are compatible with both site I and site II occupancy and do not provide sufficient information for a safe assignment; however, fluorescence titration using warfarin (site I probe) and ibuprofen (site II probe) for displacement clearly indicates that the employed cholic acid derivatives bind to HSA at site I.

Interaction of coomassie brilliant blue G250 with human serum albumin: Probing of the binding mechanism and binding site by spectroscopic and molecular modeling methods

Abstract The interaction between coomassie brilliant blue G250 and human serum albumin was investigated by spectroscopic methods such as fluorescence quenching, synchronous fluorescence , 3D fluorescence spectra, circular dichroism spectra and UV–vis absorption as well as molecular modeling. The fluorescence quenching of human serum albumin by coomassie brilliant blue G250 was attributed to static interaction. The binding reaction was mainly enthalpy-driven. Both van der Waals and hydrogen bonding forces played major roles in stabilizing the coomassie brilliant blue G250–human serum albumin complex. The Stern–Volmer quenching constant ( K SV ) and corresponding thermodynamic parameters (Δ H Θ , Δ G Θ and Δ S Θ ) were determined. Site marker competitive experiments indicated that coomassie brilliant blue G250 bound to site I (subdomain IIA) of human serum albumin. Molecular docking study further confirmed the binding mode obtained by experimental study. The conformational investigation demonstrated very minor micro-environmental and conformational changes in human serum albumin molecules.

Binding of caffeine, theophylline, and theobromine with human serum albumin: A spectroscopic study

The interaction between three purine alkaloids (caffeine, theophylline, and theobromine) and human serum albumin (HSA) was investigated using UV/vis absorption, circular dichroism (CD), fluorescence, synchronous fluorescence, and three-dimensional fluorescence spectra techniques. The results revealed that three alkaloids caused the fluorescence quenching of HSA by the formation of alkaloid–HSA complex. The binding site number n and apparent binding constant K A, corresponding thermodynamic parameters the free energy change (Δ G), enthalpy change (Δ H), and entropy change (Δ S) at different temperatures were calculated. The hydrophobic interaction plays a major role in stabilizing the complex. The distance r between donor (HSA) and acceptor (alkaloids) was obtained according to fluorescence resonance energy transfer. The effect of alkaloids on the conformation of HSA was analyzed using circular dichroism (CD), UV/vis absorption, synchronous fluorescence and three-dimensional fluorescence spectra techniques.

Interaction of the docetaxel with human serum albumin using optical spectroscopy methods

Docetaxel is a semi-synthetic product derived from the needles of the European yew. It is an antineoplastic agent belonging to the taxoid family. The interaction between docetaxel and human serum albumin (HSA) has been investigated systematically by the fluorescence quenching technique, synchronous fluorescence spectroscopy, ultraviolet (UV)–vis absorption spectroscopy, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) under physiological conditions. Our fluorescence data showed that HSA had only one docetaxel binding site and the binding process was a static quenching procedure. According to the Van’t Hoff equation, the thermodynamic parameters standard enthalpy (Δ H 0) and standard entropy (Δ S 0) were calculated to be −41.07 KJ mol −1 and −49.72 J mol −1 K −1. These results suggested that hydrogen bond was the predominant intermolecular force stabling the docetaxel–HSA complex. The data from the CD, FT-IR and UV–vis spectroscopy supported the change in the secondary structure of protein caused by the interaction of docetaxel with HSA.

Investigation of the interaction between pentachlorophenol and human serum albumin using spectral methods

The interaction between human serum albumin (HSA) and pentachlorophenol (PCP) was investigated by UV/vis absorption, circular dichroism (CD), fluorescence, synchronous fluorescence, and three-dimensional fluorescence spectra techniques under physiological pH 7.40. PCP effectively quenched the intrinsic fluorescence of HSA via static quenching. The process of binding PCP on HSA was a spontaneous molecular interaction procedure. The hydrophobic interaction played a major role in stabilizing the PCP–HSA complex. The distance r between donor and acceptor was obtained to be 3.35 nm according to Förster’s theory. The binding site of PCP to HSA mainly located within hydrophobic cavity between domain II and domain I. The effect of PCP on the conformation of HSA was analyzed using synchronous fluorescence spectroscopy, CD and three-dimensional fluorescence spectra.

Molecular interaction of human serum albumin with paracetamol: Spectroscopic and molecular modeling studies

The interaction between paracetamol and human serum albumin (HSA) under physiological conditions has been investigated by fluorescence, circular dichroism (CD) and docking. Fluorescence data revealed that the fluorescence quenching of HSA by paracetamol was the result of the formed complex of HSA–paracetamol, and the binding constant ( K a) and binding number obtained is 1.3 × 10 4 at 298 K and 2, respectively for the primary binding site. Circular dichorism spectra showed the induced conformational changes in HSA by the binding of paracetamol. Moreover, protein–ligand docking study indicated that paracetamols (two paracetamols bind to HSA) bind to residues located in the subdomain IIIA.

Proton NMR relaxation in albumin solutions doped with Mn(II)

The aim of this study is to obtain further information about the source of proton relaxation in the Mn(II)-human serum albumin complex. For this purpose, proton relaxation rates in albumin solutions 1/T1 and 1/T2 were measured versus increasing amounts of manganese [Mnt]. The fractions of manganese bound to albumin [Mnb] and free manganese [Mnf] were then determined from proton relaxation rate enhancement data. Paramagnetic contributions of bound manganese to the observed relaxation rates (1/T1p*)b and (1/T2p*)b were also determined. Finally, the (1/T2p*)b/(1/T1p*)b ratio was used in a derived equation to estimate an effective correlation time τ. Mean τ value of the complex was found to be in the order of 3 ns, while the hydration number of bound manganese q was estimated to be about 4. The 1/τ was found to be the sum of the inverse values of rotational correlation time 1/τr, mean residence time of water in hydration spheres of the complex 1/τm, and longitudinal electronic relaxation time of manganese 1/τs in the complex. In conclusion, the relaxation mechanism in albumin solutions containing Mn(II) can be interpreted through dipolar and scalar interactions modulated by τr, τm and τs. This analysis enables one to get reasonable figures for the τr and q of Mn(II) in albumin solution.

Chloramphenicol binding to human serum albumin: Determination of binding constants and binding sites by steady-state fluorescence

The interaction between chloramphenicol and human serum albumin (HSA) was studied by fluorescence, UV/vis, circular dichroism (CD) and three-dimensional fluorescence spectroscopy. Fluorescence data revealed that the fluorescence quenching of HSA by chloramphenicol was the result of the formation of drug–HSA complex, and the effective quenching constants ( K a) were 2.852 × 10 4, 2.765 × 10 4, 2.638 × 10 4 and 2.542 × 10 4 M −1 at 287, 295, 303 and 311 K, respectively. The thermodynamic parameters, enthalpy change (Δ H) and entropy change (Δ S) for the reaction were calculated to be −3.634 kJ mol −1 and 72.66 J mol −1 K −1 according to van’t Hoff equation. The results indicated that the hydrophobic and electrostatic interactions played a major role in the binding of drug to HSA. The distance r between donor and acceptor was obtained to be 3.63 nm according to Förster’s theory. Site marker competitive experiments indicated that the binding of drug to HSA primarily took place in subdomain IIA. The alterations of HSA secondary structure in the presence of chloramphenicol were confirmed by the evidences from synchronous fluorescence, CD and three-dimensional fluorescence spectra. In addition, the effect of common ions on the binding constants of drug–HSA complex was also discussed.

Specific interaction of 4′- O-(a- l-Cladinosyl) daunorubicin with human serum albumin: The binding site II on HSA molecular using spectroscopy and modeling

This study was designed to examine the interaction of 4′- O-(a- l-Cladinosyl) daunorubicin (CDNR), a disaccharide anthracycline with potent antitumor activity against leukemia cell line K562 cells and colon cancer cell line SW620 cells, with human serum albumin (HSA) for the first time by fluorescence spectroscopy in combination with UV-absorption and molecular modeling under simulative physiological conditions. The quenching mechanism was suggested to be static quenching according to the fluorescence measurement. The thermodynamic parameters, enthalpy change (Δ H) and entropy change (Δ S) were calculated to be −19.89 KJ/mol and 26.23 J/mol/K, according to the Van’t Hoff equation. These data suggested that hydrophobic interaction was the predominant intermolecular forces stabilizing the complex, which was in good agreement with the results of molecular modeling study. The effect of CDNR on the conformation of HSA was analyzed using synchronous fluorescence spectroscopy and UV/vis absorption spectroscopy. In addition, the effects of common ions on the binding constant of CDNR–HSA complex were also discussed at room temperature.

Interaction between titanium dioxide nanoparticles and human serum albumin revealed by fluorescence spectroscopy in the absence of photoactivation

Titanium dioxide (TiO 2) nanoparticles (NPs) are widely used as an important kind of biomaterials. The interaction between TiO 2 (P25) at 20 nm in diameter and human serum albumin (HSA) was studied by fluorescence spectroscopy in this work. Under the simulative physiological conditions, fluorescence data revealed the presence of a single class of binding site on HSA and its binding constants ( K a ) were 2.18±0.04×10 4, 0.87±0.05×10 4, 0.68±0.06×10 4 M −1 at 298, 304 and 310 K, respectively. In addition, according to the Van’t Hoff equation, the thermodynamic functions standard enthalpy (Δ H 0) and standard entropy (Δ S 0) for the reaction were calculated to be −75.18±0.15 kJ mol −1 and −170.11±0.38 J mol −1 K −1. These results indicated that TiO 2 NPs bond to HSA mainly by van der Waals force and hydrogen bonding formation in low dielectric media, and the electrostatic interactions cannot be excluded. Furthermore, the effects of common ions on the binding constant of TiO 2 NPs–HSA complex were discussed.

Characterization of the mangiferin–human serum albumin complex by spectroscopic and molecular modeling approaches

The interactions between mangiferin and human serum albumin (HSA) were investigated by spectroscopy and molecular modeling. The results proved the formation of complex between mangiferin and HSA. Hydrophobic interaction dominated in the association reaction. Mangiferin statically quenched the fluorescence of HSA in a concentration dependent manner positively deviating from the linear Scatchard equation. The binding of mangiferin to HSA lead to changes in the conformation of HSA according to synchronous fluorescence spectra, FT-IR, UV–vis and CD data. The presence of amino acids and metal ion affected the binding constant of mangiferin–HSA complex. Computational mapping of the possible binding sites of mangiferin revealed the molecule to be bound in the large hydrophobic cavity of subdomain IIA.

Studies on the interaction between imidacloprid and human serum albumin: Spectroscopic approach

The interaction between imidacloprid (IMI) and human serum albumin (HSA) was investigated using fluorescence and UV/vis absorption spectroscopy. The experimental results showed that the fluorescence quenching of HSA by IMI was a result of the formation of IMI–HSA complex; static quenching was confirmed to result in the fluorescence quenching. The apparent binding constant K A between IMI and HSA at three differences were obtained to be 1.51 × 10 4, 1.58 × 10 4, and 2.19 × 10 4 L mol −1, respectively. The thermodynamic parameters, Δ H° and Δ S° were estimated to be 28.44 kJ mol −1, 174.76 J mol −1 K −1 according to the van’t Hoff equation. Hydrophobic interactions played a major role in stabilizing the complex. The distance r between donor (HSA) and acceptor (IMI) was obtained according to fluorescence resonance energy transfer. The effect of IMI on the conformation of HSA was analyzed using synchronous fluorescence spectroscopy CD and three-dimensional fluorescence spectra, the environment around Trp and Tyr residues were altered.

Dynamical and Structural Changes of an Anesthetic Analogue in Chemical and Biological Nanocavities

We report on photophysical studies of the interaction between an anesthetic analogue, methyl 2-amino-4,5-dimethoxybenzoate (ADMB), with the human serum albumin (HSA) protein and the normal micelle of n-octyl-beta-D-glucopyranoside (OG) in water solutions. We used steady-state and picosecond time-resolved emission spectroscopy to follow the dynamical and structural changes due to their hydrophobicity and confinement on the photophysical behavior of ADMB. The formed 1:1 complex with the protein is robust with an equilibrium constant of 9.6 x 10(4) M(-1) at 293 K. The fluorescence lifetimes of the 1:1 entity become longer (up to approximately 10 ns), and the emission transients show complex behavior due to the heterogeneity of the media. Rotational time (45 ns) from picosecond anisotropy measurements clearly indicates strong confinement in the robust ADMB:HSA complex. For the ADMB:OG one, the anisotropy decays give time constants of 50 and 980 ps, assigned to free and restricted rotors within the micelle, respectively. The process of energy transfer from the excited tryptophan 214 (Trp214) of HSA to the trapped ADMB occurs with an efficiency of 50%, and the calculated distance between both chromophores is 19 A. We believe that these results are important for a better understanding of processes occurring in encapsulated drugs and thus should be relevant to nanopharmacodynamics.

Chemical and Biological Caging Effects on the Relaxation of a Proton-Transfer Dye

We report studies of the interaction between a proton-transfer dye (1'-hydroxy,2'-acetonaphthone, HAN), with the human serum albumin (HSA) protein and a beta-cyclodextrin derivative (DM-beta-CD) in neutral water solutions. We used steady-state and picosecond time-resolved emission spectroscopy to follow the structural changes of HAN due to the hydrophobicity and confinement effect of these nanocavities. Upon encapsulation, the fluorescence intensity of the 1:1 inclusion complex in both cavities increases, and the emission lifetimes become longer. For the DM-beta-CD complexes, we obtained 430 and 920 ps, whereas for the HSA complexes we obtained 630 ps and 2 ns. Picosecond anisotropy measurements show strong confinement due to protein docking. The rotational time for the CD complex is 660 ps, whereas for the protein complex we find 6 ns. The process of energy transfer from the excited triptophan 214 (Trp214) of HSA to the trapped HAN occurs with high efficiency (71%), and the calculated distance between both chromophores is 17 A. We believe that the results are important for a better understanding of the processes occurring in inclusion complexes such as those in nanopharmacodynamics.

Ibuprofen Induces an Allosteric Conformational Transition in the Heme Complex of Human Serum Albumin with Significant Effects on Heme Ligation

Human serum albumin (HSA), the most prominent protein in blood plasma, is able to bind a wide range of endogenous and exogenous compounds. Among the endogenous ligands, HSA is a significant transporter of heme, the heme-HSA complex being present in blood plasma. Drug binding to heme-HSA affects allosterically the heme affinity for HSA and vice versa. Heme-HSA, heme, and their complexes with ibuprofen have been characterized by electronic absorption, resonance Raman, and electron paramagnetic resonance (EPR) spectroscopy. Comparison of the results for the heme and heme-HSA systems has provided insight into the structural consequences on the heme pocket of ibuprofen binding. The pentacoordinate tyrosine-bound heme coordination of heme-HSA, observed in the absence of ibuprofen, becomes hexacoordinate low spin upon ibuprofen binding, and heme dissociates at increasing drug levels. The electronic absorption spectrum and nu(Fe-CO)/nu(CO) vibrational frequencies of the CO-heme-HSA-ibuprofen complex, together with the observation of a Fe-His Raman mode at 218 cm(-1) upon photolysis of the CO complex and the low spin EPR g values indicate that a His residue is one of the low spin axial ligands, the sixth ligand probably being Tyr161. The only His residue in the vicinity of the heme Fe atom is His146, 9 A distant in the absence of the drug. This indicates that drug binding to heme-HSA results in a significant rearrangement of the heme pocket, implying that the conformational adaptability of HSA involves more than the immediate vicinity of the drug binding site. As a whole, the present spectroscopic investigation supports the notion that HSA could be considered as the prototype of monomeric allosteric proteins.

Interaction of anthracycline disaccharide with human serum albumin: Investigation by fluorescence spectroscopic technique and modeling studies

Anthracyclines are considered to be some of the most effective anticancer drugs for cancer therapy. However, drug resistance and cardiotoxicity of anthracyclines limit their clinical application. An 3′-azido disaccharide analogue of daunorubicin, 7-[4- O-(2,6-dideoxy-3- O-methyl-α- l- arabino-hexopyranosyl)-3-azido-2,3,6-trideoxy-α- l- lyxo-hexopyranosyl]daunorubicinone (ADNR-3), was shown to exhibit 10-fold better activity than parent compound daunorubicin against the drug-resistant cells and completely overcomes the drug resistance with same IC 50 in both drug-resistant and drug-sensitive cells. In this paper, the interactions between ADNR-3 and human serum albumin (HSA) have been studied by spectroscopic techniques. By the analysis of fluorescence spectrum and fluorescence intensity, it was observed that the ADNR-3 has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The association constants of ADNR-3 with HSA were determined at different temperatures based on fluorescence quenching results. The negative Δ H and positive Δ S values in case of ADNR-3–HSA complexes showed that both hydrogen bonds and hydrophobic interactions play a role in the binding of ADNR-3 to HSA. Furthermore, synchronous fluorescence spectroscopy data and UV–vis absorbance spectra have suggested that the association between ADNR-3 and HSA changed the molecular conformation of HSA and the hydrophobic interactions play a major role in ADNR-3–HSA association. Moreover, the study of computational modeling indicated that ADNR-3 could bind to the site I of HSA and hydrophobic interaction was the major acting force for the second type of binding site, which was in agreement with the thermodynamic analysis. The distance, r, between donor (HSA) and acceptor (ADNR-3) was obtained according to the Förster's theory of non-radiation energy transfer. In addition, the effects of common ions on the binding constants of ADNR-3–HSA complexes were also investigated.