Probing the binding of fluoxetine hydrochloride to human serum albumin by multispectroscopic techniques

Insights into the binding of buspirone to human serum albumin using multi-spectroscopic and molecular docking techniques

Buspirone is an anxiolytic drug that plays a significant role in managing anxiety disorders and alleviating their symptoms as well. Several techniques were utilized to study the interaction between buspirone and human serum albumin under physiological conditions, including UV-vis absorption spectroscopy, fluorescence emission spectroscopy, circular dichroism, Fourier transform infrared spectroscopy (FT-IR), equilibrium dialysis, and molecular docking. The results of this study demonstrated that buspirone quenched the intrinsic fluorescence of human serum albumin through a mixed mechanism. Moreover, the binding constants (Kb), the quenching constants (Ksv), and thermodynamic parameters were calculated at various temperatures. The binding process of buspirone to human serum albumin showed a cooperative binding pattern, confirmed by the Scatchard diagram and Hill coefficient. Molecular docking results showed that buspirone interacted with the IIA, IIIA, and IIB subdomains of human serum albumin and slightly changed its conformation. It was also found that hydrophobic forces played a major role in this interaction. This study consequently proves that BSH as a drug can be transported by blood albumin. Additionally, due to its ratiometric response in absorbance upon binding to a biological target, HSA can be used as a molecular probe to follow biomolecular interactions.

Multi-Spectroscopic, thermodynamic and molecular docking studies to investigate the interaction of eplerenone with human serum albumin

The binding of small molecular drugs with human serum albumin (HSA) has a crucial influence on their pharmacokinetics. The binding interaction between the antihypertensive Eplerenone (EPL)and HSA was investigated using multi-spectroscopic techniques for the first time. These techniques include UV-Vis spectroscopy, Fourier Transform Infrared (FT-IR), native fluorescence spectroscopy, synchronous fluorescence spectroscopy and molecular docking approach. The fluorescence spectroscopic study showed that EPL quenched HSA inherent fluorescence. The mechanism for quenching of HSA by EPL has been determined to be static in nature and confirmed by UV absorption and fluorescence spectroscopy. The modified Stern-Volmer equation was used to estimate the binding constant (K_b ) as well as the number of bindings (n). The results indicated that the binding occurs at a single site (Kb;2.238 x 10³ L mol^-1 at 298 K). The enthalpy and entropy changes (∆H and ∆S) were 58.061 and 0.258 K J mol^-1 , respectively, illustrating that the principal intermolecular interactions stabilizing the EPL-HSA system are hydrophobic forces. Synchronous fluorescence spectroscopy revealed that EPL binding to HSA occurred around the tyrosine residue (Tyr) and this agreed with the molecular docking study. The FRET analysis confirmed the static quenching mechanism. The esterase enzyme activity of HSA was also evaluated showing its decrease in the presence of EPL. Furthermore, docking analysis and site-specific markers experiment revealed that EPL binds with HSA at subdomain IB (site III).

Multi-Spectroscopic, thermodynamic and molecular dynamic simulation studies for investigation of interaction of dapagliflozin with bovine serum albumin

Dapagliflozin (DAPA) is a selective sodium-glucose cotransporter-2 inhibitor that reduces renal glucose reabsorption. The drug has recently become a crucial milestone in the management of diabetes and heart failure. In this study, the interaction of DAPA with bovine serum albumin (BSA) was investigated for the first time using various fluorescence spectroscopic techniques, UV-absorption spectroscopy, molecular docking, and molecular dynamic (MD) simulation. The fluorescence spectroscopic titration study performed at different temperatures showed that DAPA quenched the fluorescence of BSA through a combination of dynamic and static mechanisms, which was confirmed by UV absorption, fluorescence-resonance energy transfer measurements, and MD simulation. The binding thermodynamic parameters demonstrated that the binding stoichiometry between BSA and DAPA was 1:1. Competitive binding experiments using site-specific markers as well as molecular docking studies showed that DAPA binds to site I on BSA. The positive values of enthalpy change (ΔH) and entropy change (ΔS) revealed that hydrophobic forces played a predominant role in the binding of DAPA to BSA, whereas the negative value of Gibbs free energy change (ΔG) indicated the spontaneity of the interaction. Moreover, the synchronous fluorescence spectroscopy has shown that DAPA binding to the protein molecule occurs in the vicinity of the tryptophan residue. These findings were confirmed by the molecular docking and MD simulation studies.

Multi-spectroscopic and molecular docking studies for binding interaction between fluvoxamine and human serum albumin

In the present study, different spectroscopic techniques have been used to study the binding interaction between the antidepressant drug fluvoxamine and human serum albumin under simulated physiological conditions (pH 7.4). The utilized spectroscopic techniques include fluorescence emission spectroscopy, synchronous fluorescence spectroscopy, UV-Vis absorption spectroscopy, Fourier Transform Infrared spectroscopy (FT-IR), and molecular modeling methods. The obtained results revealed that the formation of a complex between human serum albumin and fluvoxamine was responsible for quenching the native fluorescence of human serum albumin. The results indicated that the quenching mechanism between human serum albumin and fluvoxamine was static. Besides, the binding constant (K), number of binding sites (n), thermodynamic parameters (ΔH, ΔS, and ΔG), and binding forces were calculated at three different temperatures (298, 310, and 318 K). These data proposed that hydrophobic forces were the principal intermolecular forces stabilizing the complex. From the molecular docking results, it could be deduced that fluvoxamine was inserted into sub-domain II A (site I) of human serum albumin and led to a slight change in human serum albumin conformation.

Antidepressant drug-protein interactions studied by spectroscopic methods based on fluorescent carbon quantum dots

A highly sensitive fluorescent carbon quantum dots (CDs) was designed to measure the interaction of antidepressant drugs and serum albumins (SA). In present investigation the interaction of bovine serum albumin (BSA) and human serum albumin (HSA) with antidepressant drugs viz. amitryptiline hydrochloride (AMT), chlorpromazine hydrochloride (CPZ) and desipramine hydrochloride (DSP) bioconjugated on CDs have been studied by different spectroscopic techniques i.e., Fluorescence, UV-Visible, Dynamic light scattering (DLS) and FT-IR. The CDs were prepared by one-pot method using glucose and PEG-200. The developed CDs showed blue luminescence under irradiation with ultra-violet. The Stern-Volmer quenching constant (K sv ) indicates the presence of static quenching mechanism. The apparent binding constant K a between antidepressant drugs with complex of SA-CDs have been determined. These results illustrated that CPZ shows strong binding with HSA. As further analyzed by FT-IR spectroscopy and DLS technique, the results suggested induced conformational changes on SA, thus confirming the experimental and theoretical results. Thus, a thorough knowledge of the energetics of drug-protein affinities in presence of CDs as attempted in this work is vital in giving way for appropriate drug delivery.

Characterization of the binding mechanism and conformational changes of bovine serum albumin upon interaction with aluminum-maltol: a spectroscopic and molecular docking study

The widespread use of aluminum in the treatment of drinking water, food, agriculture and pharmaceuticals has greatly increased the risk of human exposure to excess aluminum, which is a serious health hazard to human beings.

Multispectroscopic and molecular modeling studies on the interaction of copper-ibuprofenate complex with bovine serum albumin (BSA)

Bovine serum albumin (BSA) represents the well recognized model protein for investigations of diverse intermolecular reactions in studies on pharmacological activities of modern drugs. In the present work, the interaction between copper ibuprofenate ([Cu2(IBU)4]) and BSA under simulative physiological conditions was investigated by the using of diverse spectral methods including fluorescence, UV-vis absorption, CD spectroscopy and also molecular docking. The obtained results showed that there was a strong fluorescence quenching of BSA by [Cu2(IBU)4] (2.964E+4 M^-1 at room temperature). Using the continuous variation method, a single class of binding sites, (1:1), for [Cu2(IBU)4] on BSA was put in evidence. The Stern-Volmer analysis of fluorescence quenching data shows the presence of the static quenching mechanism. The binding constants K_b were calculated and the thermodynamic parameters ∆G°, ∆H° and ∆S° were given. The obtained thermodynamic values and the change observed in the alpha-helical content signature suggests that hydrogen bonding and hydrophobic forces play a major role in the [Cu2(IBU)4]-BSA binding interaction. Site marker competitive experiments indicated that the binding of [Cu2(IBU)4] to BSA primarily took place in sub-domain IIA that this observation were substantiated by molecular docking studies. The results of CD and UV-vis spectroscopy showed for the first time that the presence of [Cu2(IBU)4] increased the ɑ-helical content of BSA (from 48.56% to 55.71%) and conformational changes of BSA molecules.

Association of iminium and alkanolamine forms of the benzo[c]phenanthridine alkaloid chelerythrine with human serum albumin: photophysical, thermodynamic and theoretical approach

Association of isoforms of chelerythrine (CHL) with HSA.

Decrease of the affinity of theophylline bind to serum proteins induced by flavonoids and their synergies on protein conformation

In this study, the single and simultaneous interactions of theophylline and flavonoids with human serum albumin (HSA) were studied by multi-spectroscopic and molecular docking approaches. The influences of flavonoids on the binding constant (K_b) and the binding distance (r) of theophylline bind to HSA were determined and the changes of HSA conformation caused by the synergies of theophylline and flavonoids were investigated. Because theophylline, rutin and baicalin are all bond to the same binding site, the competitive bind of theophylline and flavonoids to HSA leads to the reduction of the K_a value of theophylline binding to HSA. The addition of rutin and baicalin can increase the value of r of theophylline binding to HSA, which further confirm the existence of the competitive bind of theophylline and flavonoids to HSA. Additionally, the results of synchronous fluorescence, three-dimensional fluorescence and circular dichroism spectra indicate that the presence of rutin and baicalin can give rise to the further changes of HSA conformation. These results suggest that the intake of flavonoid-rich food and beverages can increase the serum concentrations of theophylline and induce a high incidence of toxic symptom in clinic.

Competitive binding of (-)-epigallocatechin-3-gallate and 5-fluorouracil to human serum albumin: A fluorescence and circular dichroism study

Combination therapy with more than one therapeutic agent can improve therapeutic efficiency and decrease drug resistance. In this study, the interactions of human serum albumin (HSA) with individual or combined anticancer drugs, (-)-epigallocatechin-3-gallate (EGCG) and 5-fluorouracil (FU), were investigated by fluorescence and circular dichroism (CD) spectroscopy. The results demonstrated that the interaction of EGCG or FU with HSA is a process of static quenching and EGCG formed a more stable complex. The competitive experiments of site markers suggested that both anti-carcinogens mainly bound to site I (subdomain IIA). The interaction forces which play important roles in the binding process were discussed based on enthalpy and entropy changes. Moreover, the competition binding model for a ternary system was proposed so as to precisely calculate the binding parameters. The results demonstrated that one drug decreased the binding affinity of another drug with HSA, resulting in the increasing free drug concentration at the action sites. CD studies indicated that there was an alteration in HSA secondary structure due to the binding of EGCG and FU. It can be concluded that the combination of EGCG with FU may enhance anticancer efficacy. This finding may provide a theoretical basis for clinical treatments.

Spectroscopic and molecular modeling study on the separate and simultaneous bindings of alprazolam and fluoxetine hydrochloride to human serum albumin (HSA): with the aim of the drug interactions probing

The objective of the present research is to study the interaction of separate and simultaneous of alprazolam (ALP) and fluoxetine hydrochloride (FLX) with human serum albumin (HSA) in phosphate buffer (pH 7.4) using different kinds of spectroscopic, cyclic voltammetry and molecular modeling techniques. The absorbance spectra of protein, drugs and protein-drug showed complex formation between the drugs and HSA. Fluorescence analysis demonstrated that ALP and FLX could quench the fluorescence spectrum of HSA and demonstrated the conformational change of HSA in the presence of both drugs. Also, fluorescence quenching mechanism of HSA-drug complexes both separately and simultaneously was suggested as static quenching. The analysis of UV absorption data and the fluorescence quenching of HSA in the binary and ternary systems showed that FLX decreased the binding affinity between ALP and HSA. On the contrary, ALP increased the binding affinity of FLX and HSA. The results of synchronous fluorescence and three-dimensional fluorescence spectra indicated that the binding of drugs to HSA would modify the microenvironment around the Trp and Tyr residues and the conformation of HSA. The distances between Trp residue and the binding sites of the drugs were estimated according to the Förster theory, and it was demonstrated that non-radiative energy transfer from HSA to the drugs occurred with a high probability. Moreover, according to CV measurements, the decrease of peak current in the cyclic voltammogram of the both drugs in the presence of HSA revealed that they interacted with albumin and binding constants were calculated for binary systems which were in agreement with the binding constants obtained from UV absorption and fluorescence spectroscopy. The prediction of the best binding sites of ALP and FLX in binary and ternary systems in molecular modeling approach was done using of Gibbs free energy.

Molecular modeling and spectroscopic studies on the interaction of the chiral drug venlafaxine hydrochloride with bovine serum albumin

This study was designed to examine the interaction of racemic antidepressant drug "S,R-venlafaxine hydrochloride (VEN)" with bovine serum albumin (BSA) under physiological conditions. The mechanism of interaction was studied by spectroscopic techniques combination with molecular modeling. Stern-Volmer analysis of fluorescence quenching data shows the presence of the static quenching mechanism. The thermodynamic parameters indicated that the hydrogen bonding and weak van der Waals interactions are the predominant intermolecular forces stabilizing the complex. The number of binding sites (n) was calculated. Through the site marker competitive experiment, VEN was confirmed to be located in subdomain IIIA of BSA. The binding distance (r=4.93 nm) between the donor BSA and acceptor VEN was obtained according to Förster's non-radiative energy transfer theory. According to UV-vis spectra and CD data binding of VEN leaded to conformational changes of BSA. Molecular docking simulations of S and R-VEN revealed that both isomers have similar interaction and the same binding sites, from this point of view S and R isomers are equal.

Differential interactions of the broad spectrum drugs artemisinin, dihydroartemisinin and artesunate with serum albumin

Artemisinin is a drug, widely used in malaria treatment. As the binding affinity of artemisinin and its derivatives dihydroartemisinin and artesunate to blood serum proteins might influence the effectiveness of the drug, binding of artemisinin and derivatives to serum albumin was studied under near physiological conditions. Binding kinetics indicate a simple, single-step association process for all artemisinin derivatives. The determined changes in enthalpy and entropy upon drug binding clearly indicate that hydrophobic forces are most important for artemisinin and dihydroartemisinin binding, whereas binding of artesunate is governed by both hydrophilic and hydrophobic forces. Key residues, which are most likely involved in binding of the respective compounds, were identified in subsequent protein/drug docking studies. The obtained results not only explain differences in between artemisinin and derivatives but generally illustrate how slight modifications in a drug can significantly affect principles underlying drug binding to target proteins.

Comparative studies on the interaction of genistein, 8-chlorogenistein, and 3',8-dichlorogenistein with bovine serum albumin

Chlorination can significantly enhance the antioxidant and antitumor activity of genistein. In this paper, genistein, 8-chlorogenistein, and 3',8-dichlorogenistein were selected to investigate the binding to bovine serum albumin (BSA) using fluorescence spectroscopy and circular dichroism (CD). The results showed that chlorination, especially at position 3', had significant effects on the binding constant value of chlorinated genistein derivatives to BSA; however, the binding site and the binding number were slightly affected. The thermodynamic parameters indicated that hydrophobic and electrostatic forces played important roles in the binding process and the enhanced binding affinity mainly associated with the increase of the hydrophobicity caused by the chlorine atom substitution. Furthermore, the CD data demonstrated that the conformation of BSA was slightly altered in the presence of genistein, 8-chlorogenistein, and 3',8-dichlorogenistein, with different reduced α-helix contents. The results obtained herein will be of biological significance in toxicology investigation and genistein derivative drug design.