Human Serum Albumin Complex Research Articles

Exploring the interaction between the antiallergic drug, tranilast and human serum albumin: Insights from calorimetric, spectroscopic and modeling studies

The interaction of tranilast (TRN), an antiallergic drug with the main drug transporter in human circulation, human serum albumin (HSA) was studied using isothermal titration calorimetry (ITC), fluorescence spectroscopy and in silico docking methods. ITC data revealed the binding constant and stoichiometry of binding as (3.21±0.23)×106M−1 and 0.80±0.08, respectively, at 25°C. The values of the standard enthalpy change (ΔH°) and the standard entropy change (ΔS°) for the interaction were found as −25.2±5.1kJmol−1 and 46.9±5.4Jmol−1K−1, respectively. Both thermodynamic data and modeling results suggested the involvement of hydrogen bonding, hydrophobic and van der Waals forces in the complex formation. Three-dimensional fluorescence data of TRN–HSA complex demonstrated significant changes in the microenvironment around the protein fluorophores upon drug binding. Competitive drug displacement results as well as modeling data concluded the preferred binding site of TRN as Sudlow’s site I on HSA.

Understanding the Regioselective Hydrolysis of Human Serum Albumin by Zr(IV)-Substituted Polyoxotungstates Using Tryptophan Fluorescence Spectroscopy

The interaction between human serum albumin (HSA) and a series of Zr(IV)-substituted polyoxometalates (POMs) (Lindqvist type POM ((nBu4N)6[{W5O18Zr (μ-OH)}2]·2H2O, Zr2-L2), two Keggin type POMs ((Et2NH2)10[Zr(PW11O39)2]·7H2O, Zr1-K2 and (Et2NH2)8[{α-PW11O39Zr(μ-OH)(H2O)}2]·7H2O, Zr2-K2), and two Wells-Dawson type POMs (K15H[Zr(α2-P2W17O61)2]·25H2O, Zr1-WD2 and Na14[Zr4(P2W16O59)2(μ3-O)2(OH)2(H2O)4]·10H2O, Zr4-WD2) was investigated by tryptophan (Trp) fluorescence spectroscopy. The fluorescence data were analyzed using the Tachiya model, ideally suited for multiple binding site analysis. The obtained quenching constants have the same order of magnitude for all the measured POM:protein complexes, ranging from 1.9 × 105 M−1 to 5.1 × 105 M−1. The number of bound POM molecules to HSA was in the range of 1.5 up to 3.5. The influence of the ionic strength was studied for the Zr1-WD2:HSA complex in the presence of NaClO4. The calculated quenching constant decreases upon increasing the ionic strength of the solution from 0.0004 M to 0.5004 M, indicating the electrostatic nature of the interaction. The number of POM molecules bound to HSA increases from 1.0 to 4.8. 31P NMR spectroscopy provided evidence for the stability of all investigated POM structures during the interaction with HSA.

Structural basis of non-steroidal anti-inflammatory drug diclofenac binding to human serum albumin.

Human serum albumin (HSA) is the most abundant protein in plasma, which plays a central role in drug pharmacokinetics because most compounds bound to HSA in blood circulation. To understand binding characterization of non-steroidal anti-inflammatory drugs to HSA, we resolved the structure of diclofenac and HSA complex by X-ray crystallography. HSA-palmitic acid-diclofenac structure reveals two distinct binding sites for three diclofenac in HSA. One diclofenac is located at the IB subdomain, and its carboxylate group projects toward polar environment, forming hydrogen bond with one water molecule. The other two diclofenac molecules cobind in big hydrophobic cavity of the IIA subdomain without interactive association. Among them, one binds in main chamber of big hydrophobic cavity, and its carboxylate group forms hydrogen bonds with Lys199 and Arg218, as well as one water molecule, whereas another diclofenac binds in side chamber, its carboxylate group projects out cavity, forming hydrogen bond with Ser480.

Spectroscopic study on the interaction of resveratrol and pterostilbene with human serum albumin

The interaction of human serum albumin (HSA) with two stilbene compounds, resveratrol and pterostilbene was investigated using fluorescence, UV–visible absorption, Fourier transform infrared spectroscopic methods and molecular modeling technique. The intrinsic fluorescence of HSA was quenched significantly by resveratrol and pterostilbene. Analysis of fluorescence quenching data of HSA by the two compounds using Stern–Volmer and modified Stern–Volmer methods showed the formation of ground state complexes of HSA with resveratrol and pterostilbene. The binding analysis showed that the binding constant for resveratrol as 4.47×106 and 0.299×102M−1s−1 for pterostilbene revealing the high binding affinity of resveratrol to HSA. The conformational changes of HSA were investigated using synchronous fluorescence and Fourier transform infrared spectroscopy. The efficiency of energy transfer and the distance between HSA and resveratrol/pterostilbene were calculated. The binding of resveratrol/pterostilbene was modeled by molecular docking, which is in accordance with the experimental data.

Enhancement of the binding affinity of methylene blue to site I in human serum albumin by cupric and ferric ions.

In this work, the binding characteristics of methylene blue (MB) to human serum albumin (HSA) and the influence of Cu(2+) and Fe(3+) on the binding affinity of MB to HSA were investigated using fluorescence, absorption, circular dichroism (CD) spectroscopy and molecular modelling. The results of competitive binding experiments using the site probes ketoprofen and ibuprofen as specific markers suggested that MB was located in site I within sub-domain IIA of HSA. The molecular modelling results agreed with the results of competitive site marker experiments and the results of CD spectra indicated that the interaction between MB and HSA caused the conformational changes in HSA. The binding affinity of MB to HSA was enhanced but to a different extent in the presence of Cu(2+) and Fe(3+), respectively, which indicated that the influence of different metal ions varied. Enhancement of the binding affinity of MB to HSA in the presence of Cu(2+) is due to the formation of Cu(2+)-HSA complex leading to the conformational changes in HSA, whereas in the presence of Fe(3+), enhancement of the binding affinity is due to the greater stability of the Fe(3+)-HSA-MB complex compared with the MB-HSA complex.

Studies on drug-human serum albumin binding: the current state of the matter.

Human serum albumin (HSA) is the major plasma protein with vital functions acting as depot and career for many endogenous (fatty acids, bilirubin, etc.) and exogenous substances (drugs, nutrients, etc.) in the blood. Binding to HSA controls the free, active concentration of the drug and may affect considerably the overall pharmacodynamic and pharmacokinetic profile. Studies on drug - protein binding are important from both theoretical and practical point of view as they allow better understanding of the processes underlying drug disposition and elimination and the effect of several pathological states or co-administered drugs on drug delivery and efficacy. The present review focuses on the current state of drug - HSA binding studies. The major functions and consequences of drug - protein binding are described. The X-ray structure of HSA is discussed focusing on the location and the architecture of the primary drug and fatty acids binding sites. Some of the most commonly used methods for drug - HSA binding assay are presented together with examples for their application. The most extensive studied topics in the area are discussed including quantitative characterization of drug - HSA complexation, identification of the binding sites, stereoselectivity of drug - HSA interactions, and thermodynamic characterization of the binding process. A short section is devoted to in silico prediction of drug - HSA binding as an important step in drug design and development.

Study of interaction between human serum albumin and three phenanthridine derivatives: Fluorescence spectroscopy and computational approach

Over the past decades, phenanthridine derivatives have captured the imagination of many chemists due to their wide applications. In the present work, the interaction between phenanthridine derivatives benzo [4,5]imidazo[1,2-a]thieno[2,3-c]quinoline (BTQ), benzo[4,5]imidazo[1,2-a]furo[2,3-c]quinoline (BFQ), 5,6-dimethylbenzo[4,5]imidazo[1,2-a]furo[2,3-c]quinoline (DFQ) and human serum albumin (HSA) were investigated by molecular modeling techniques and spectroscopic methods. The results of molecular modeling simulations revealed that the phenanthridine derivatives could bind on both site I in HSA. Fluorescence data revealed that the fluorescence quenching of HSA by phenanthridine derivatives were the result of the formation of phenanthridine derivatives–HSA complex, and the binding intensity between three phenanthridine derivatives and HSA was BTQ>BFQ>DFQ. Thermodynamics confirmed that the interaction were entropy driven with predominantly hydrophobic forces. The effects of some biological metal ions and toxic ions on the binding affinity between phenanthridine derivatives and HSA were further examined.

Probing the anticancer-drug-binding-induced microenvironment alterations in subdomain IIA of human serum albumin

The binding interaction of anticancer drug (using 5-fluorouracil (FU) as an example) with the model protein human serum albumin (HSA), and the FU-binding-induced microenvironment alterations in subdomain IIA of HSA molecule were studied by a combination of spectroscopic techniques and molecular docking method. The results indicated that the nature of forces involved in binding interaction between HSA and FU molecule were mainly van der Waal’s forces and hydrogen bonding interactions. These interactions resulted in the formation of FU–HSA complex, making the local microenvironment in subdomain IIA of the protein more hydrophobic than its native state. Moreover, the interaction caused the large conformation changes of HSA, leading to the increase of the compact α-helix structures at low concentration of FU (less than 150μM). However, the high concentration of FU (higher than 150μM) made the compact α-helix structure decreasing, probably due to the protein undergoing some sort of distortion. Molecular docking study revealed that FU could enter the inside a hydrophobic cavity of subdomain IIA (Sudlow’s site I) in proximity of Trp214 residue with the formation of specific hydrogen bonding with Trp214 and Lys199 residues, causing the fluorescence quenching of Trp214 through a static quenching mechanism. The study essentially provides an effective way for investigating the microenvironment alterations of protein induced by the drug molecules, and this approach can further be used in development of biomedicines and assessment of the safety-engineered drug delivery.

Enhancing the copper(II) complexes cytotoxicity to cancer cells through bound to human serum albumin

We use Schiff-base salicylaldehyde benzoylhydrazone (HL) as the ligand for copper(II), resulting in the complexes [CuCl(L)]·H2O (C1), [CuNO3(L)]·H2O (C2) and [CuBr(L)]2 (C3). We characterize the Cu(II) compounds' interactions with human serum albumin (HSA) using fluorescence spectroscopy and molecular docking. These studies revealed that Cu(II) compounds propensity bound to IIA subdomain of HSA possible by hydrophobic interactions and hydrogen bond. Cu(II) compounds produce intracellular reactive oxygen species (ROS) in cancer cells. Complexes of HSA and copper(II) compounds enhance about 2-fold cytotoxicity in cancer cells but do not raise cytotoxicity levels in normal cells in vitro. Compared with C3 alone, HSA–C3 complex promotes HepG2 cell apoptosis and has a stronger capacity to promote cell cycle arrest at the G2/M phase of HepG2.

Comprehensive two-dimensional gas chromatography and three-dimensional fluorometry for detection of volatile and bioactive substances in some berries

The volatile fractions of Cape gooseberry and blueberry were determined by headspace solid-phase microextraction coupled with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (HS-SPME/GC×GC-TOFMS). The highest amount of alcohol (51.8%), ester (32.8%) and carboxylic acid (6.9%) was in blueberry in comparison with gooseberry and oppositely ketones (14.7%), aldehydes (9.9%) and terpenes (8%) were found in gooseberry. The bioactive compounds and antioxidant capacities were higher in blueberries than in gooseberries. Three dimensional fluorescence emission spectrometry (3D-FL) was applied to determine and to compare experimentally found binding parameters of berries extracts with human serum albumin (HSA). The fluorescence quenching of HSA by polyphenols from berries was a result of the formation of a polyphenol–HSA complex. The binding abilities of berries were highly correlated with the bioactivity of polyphenols and volatile substances. The cluster analysis (CA) and linear discriminant analysis (LDA) was applied to differentiate the berries samples according to their type.

Study on the interaction of antiviral drug ‘Tenofovir’ with human serum albumin by spectral and molecular modeling methods

This study was designed to examine the interaction of Tenofovir (Ten) with human serum albumin (HSA) under physiological conditions. The binding of drugs with human serum albumin is a crucial factor influencing the distribution and bioactivity of drugs in the body. To understand the action mechanisms between Ten and HSA, the binding of Ten with HSA was investigated by a combined experimental and computational approach. UV–vis results confirmed that Ten interacted with HSA to form a ground-state complex and values of the Stern–Volmer quenching constant indicate the presence of a static component in the quenching mechanism. As indicated by the thermodynamic parameters (positive ΔH and ΔS values), hydrophobic interaction plays a major role in the Ten–HSA complex. Through the site marker competitive experiment, Ten was confirmed to be located in site I of HSA. Furthermore, UV–vis absorption spectra, synchronous fluorescence spectrum and CD data were used to investigate the structural change of HSA molecules with addition of Ten, the results indicate that the secondary structure of HSA molecules was changed in the presence of Ten. The experimental results were in agreement with the results obtained via molecular docking study.

Spectroscopy and molecular docking studies on the binding of propyl gallate to human serum albumin

The interaction of propyl gallate (PG) with human serum albumin (HSA) was investigated by fluorescence, far-UV CD and FT-IR spectroscopic methods as well as molecular docking. Fluorescence emission spectra demonstrated that the HSA fluorescence was quenched by PG through static quenching and energy transfer with the binding constants in the order of 105Lmol−1. The thermodynamic parameters (ΔH=−29.64KJmol−1, ΔS=2.7Jmol−1K−1) indicated that both hydrophobic force and hydrogen bond interactions played a leading role in the formation of PG–HSA complex. The results also showed the existence of a single binding site, which was located in subdomain IIA (site I) as revealed by molecular docking and competitive binding experiments. Molecular docking studies further showed the participation of several amino acids in PG–HSA complexation, which stabilized by H-bonding systems. The synchronous fluorescence spectra showed that the binding of drug caused the environment of tryptophan residues became more polar. FT-IR and CD spectroscopic further showed that drug complexation altered protein conformation by a major reduction of α-helix inducing a partial protein destabilization.

Study the interactions between human serum albumin and two antifungal drugs: Fluconazole and its analogue DTP

Binding affinities of fluconazole and its analogue 2-(2,4-dichlorophenyl)-1,3-di(1H-1,2,4-triazol-yl)-2-propanol (DTP) to human serum albumin (HSA) were investigated under approximately human physiological conditions. The obtained result indicated that HSA could generate fluorescent quenching by fluconazole and DTP because of the formation of non-fluorescent ground-state complexes. Binding parameters calculated from the Stern–Volmer and the Scatchard equations showed that fluconazole and DTP bind to HSA with binding affinities of the order 104L/mol. The thermodynamic parameters revealed that the binding was characterized by negative enthalpy and positive entropy changes, suggesting that the binding reaction was exothermic. Hydrogen bonds and hydrophobic interaction were found to be the predominant intermolecular forces stabilizing the drug–protein. The effect of metal ions on the binding constants of fluconazole–HSA complex suggested that the presence of Mg2+ and Zn2+ ions could decrease the free drug level and extend the half-life in the systematic circulation. Docking experiments revealed that fluconazole and DTP binds in HSA mainly by hydrophobic interaction with the possibility of hydrogen bonds formation between the drugs and the residues Arg 222, Lys 199 and Lys 195 in HSA.

Fluorescence enhancing of 5,10,15,20-tetraphenylporphyrin in complex with human serum albumin and gold nanorods

Using absorption and fluorescence spectroscopy methods we obtained the results demonstrating alterations in spectral characteristics in supramolecular system composed of gold nanorods (AuNR) (10 x 38 nm) and complexes of human serum albumin (HSA) and 5, 10, 15, 20-tetraphenylporphyrin (TPP). TPP fluorescence (max = 636 and 658 nm) was found to enhance. The dependence of fluorescence enhancing in time was of nonlinear nature. Maximum TPP fluorescence enhancing value was as high as 16% and it was achieved in 7 min after mixing the components. Simultaneously with TPP fluorescence enhancing we observed a decrease in HAS own fluorescence (max = 340 nm) and optical density reduction in maximum of longitudinal localized plasmon band of AuNR (max = 752 nm).

In vitro study on the interaction of Mn(II)-DiAmsar with human serum albumin (HSA) and bovine serum albumin (BSA) by spectroscopic and molecular docking methods

Understanding the interaction between protein and manganese(II) Diamine sarcophagine (Mn(II)-DiAmsar) has significant implications for biological applications of Mn(II)-DiAmsar. To this aim, at first, Mn(II)-DiAmsar was synthesized and characterized. In the next step, the interaction between Mn(II)-DiAmsar and protein [human serum albumin (HSA) and bovine serum albumin (BSA)] was investigated by Fourier transform infrared (FT-IR), UV–Visible (UV–Vis), fluorescence spectroscopies, and cyclic voltammetry (CV) under the physiological conditions in Tris buffer solution adjusted to pH 7.4. FT-IR spectra revealed that the conformation and microenvironment of HSA and BSA were changed in the presence of Mn(II)-DiAmsar. Mn(II)-DiAmsar could strongly quench the intrinsic fluorescence of HSA and BSA by static quenching. The hydrogen bonding and weak van der Waals interaction plays a major role in stabilizing the Mn(II)-DiAmsar–HSA (BSA) complex. The binding site number n apparent binding constant Ka, and corresponding thermodynamic parameters ∆G°, ∆H° and ∆S° at different temperatures were calculated. The distance R between the donor (HSA and BSA) and acceptor (Mn(II)-DiAmsar) has been obtained utilizing fluorescence resonance energy transfer (FRET). Finally, the molecular docking was performed to explore the possible binding sites and assess the microenvironment around the bounded Mn(II)-DiAmsar with HSA and BSA. Our results clarified that Mn(II)-DiAmsar complex could bind to HSA and BSA effectively and could be a useful guideline for further biological applications.

Interaction of the La(III)–Morin Complex with Human Serum Albumin

Lanthanum (La) is one of the most reactive rare earth elements, whose carbonate had been approved by the FDA for marketing as a treatment drug for hyperphosphatemia. In this paper, a complex of La with the natural active compound morin was synthesized and identified. The interaction between synthesized complex (LaMO) and human serum albumin (HSA) was studied by multiple spectroscopic methods. It was found that LaMO has an efficient interaction with HSA through hydrogen bonds and van der Waals forces, with formation of the LaMO–HSA complex in its ground state. The reaction led to quenching of HSA’s fluorescence and the quenching follows a static quenching mechanism. The binding constants, reference state enthalpy change (ΔH θ), Gibbs energy change (ΔG θ) and entropy change (ΔS θ) were calculated at four different temperatures. Fluorescence probe techniques were used to identify the binding location. The results showed that LaMO competes with warfarin for Sudlow’s site I in subdomain IIA of HSA, an acknowledged site marker. Meanwhile, circular dichroism spectrum measurements revealed changes of HSA’s secondary structure in the presence of LaMO, which implies that LaMO is potentially bioactive. The study involves research about the pharmacologic mechanism of rare earth metal coordination compounds and can provide basic data for their safety evaluation.

Probing the Binding of 4β-(Benzoyl-thioureido)-4-deoxypodophyllotoxin to Human Serum Albumin by Molecular Spectroscopy

The binding interaction of 4β-(benzoyl-thioureido)-4-deoxypodophyllotoxin (HY-1) with human serum albumin (HSA) was investigated by fluorescence, UV–visible absorption, and circular dichroism (CD) spectroscopies. The results indicated that binding of HY-1 to HSA caused strong fluorescence quenching of HSA through a static quenching mechanism, hydrogen bond and van der Waals contacts are the major forces in the stability of the HY-1–HSA complex, and the process of the binding of HY-1 with HSA was driven by the enthalpy (ΔH = −41.60 kJ·mol−1). The energy transfer from HSA to HY-1 occurs with high probability. The effect of HY-1 on the conformation of HSA was further analyzed by synchronous fluorescence and CD spectra techniques. The results show that presence of HY-1 decreases the α-helix content of HSA and induces the slight unfolding of the polypeptides of this protein. Additionally, the presence of metal ions (e.g. Zn2+, Cu2+, Fe3+, Co2+, and Ni2+) was found to decrease the binding constant between HY-1 and HSA.

Spectroscopic and molecular docking techniques study of the interaction between oxymetholone and human serum albumin

In this study, the binding of oxymetholone (OXM), a doping drug, to human serum albumin (HSA) was explored at pH 7.40 by spectroscopic methods including spectrofluorimetry, three dimensional excitation–emission matrix (3D EEM), UV–vis absorption, resonance rayleigh scattering (RRS) and molecular docking. The fluorescence results showed that there was a considerable quenching of the intrinsic fluorescence of HSA upon binding to OXM by static quenching mechanism. The Stern–Volmer quenching constants (KSV) between OXM and HSA at three different temperatures 295, 303, 308K, were obtained as 4.63×104, 3.05×104 and 1.49×104Lmol−1, respectively. Furthermore this interaction was confirmed by UV–vis spectrophotometric and RRS techniques. The binding site number, n, apparent binding constant, Kb, and corresponding thermodynamic parameters (ΔS, ΔH and ΔG) were measured at different temperatures. The Van der Waals and hydrogen-bond forces were found to stabilize OXM–HSA complex. The distance (r) between the donor and acceptor was obtained from Förster׳s theory of fluorescence resonance energy transfer (FRET) and found to be 1.67nm. The 3D EEM showed that OXM slightly changes the secondary structure of HSA. Furthermore, the molecular docking was employed for identification of drug binding sites and interaction of OXM with amino acid residues.

Interaction Between Ginkgolic Acid and Human Serum Albumin by Spectroscopy and Molecular Modeling Methods

The interaction of ginkgolic acid (15:1, GA) with human serum albumin (HSA) was investigated by FT–IR, CD and fluorescence spectroscopic methods as well as molecular modeling. FT–IR and CD spectroscopic showed that complexation with the drug alters the protein’s conformation by a major reduction of α-helix from 54 % (free HSA) to 46–31 % (drug–complex), inducing a partial protein destabilization. Fluorescence emission spectra demonstrated that the fluorescence quenching of HSA by GA was by a static quenching process with binding constants on the order of 105 L·mol−1. The thermodynamic parameters (ΔH = −28.26 kJ·mol−1, ΔS = 11.55 J·mol−1·K−1) indicate that hydrophobic forces play a leading role in the formation of the GA–HSA complex. The ratio of GA and HSA in the complex is 1:1 and the binding distance between them was calculated as 2.2 nm based on the Forster theory, which indicates that the energy transfer from the tryptophan residue in HSA to GA occurs with high probability. On the other hand, molecular docking studies reveal that GA binds to Site II of HSA (sub-domain IIIA), and it also shows that several amino acids participate in drug–protein complexation, which is stabilized by H-bonding.

Site-specific recognition of fluorescein by human serum albumin: A steady-state and time-resolved spectroscopic study

The increased interest in using fluorescein as a fluorescent probe in biology and medicine is associated with its distinct absorption and fluorescence signals that are transparent to biological samples. Herein, we characterize the binding mechanism of fluorescein inside human serum albumin which is used as a carrier and protector for fluorescein in medical applications. Binding of fluorescein in human serum albumin causes partial fluorescence quenching of the sole tryptophan residue in the protein (W214). The estimated W214-fluorescein distance (2.42 nm) and the calculated quenching rate constant (kq = 5.13 × 1012 M−1 s−1), both indicate binding of fluorescein in subdomain IIA. A site-competitive experiment shows that fluorescein is located in the warfarin binding pocket. The estimated binding constant (K = 10,000 M−1) points to a moderate binding strength of the fluorescein–human serum albumin complex that should not affect the fluorescein release to the target when used as a probe.