Insight into the Molecular Interaction of Cloxyquin (5-chloro-8-hydroxyquinoline) with Bovine Serum Albumin: Biophysical Analysis and Computational Simulation.
ABSTRACT: Cloxyquin is a potential therapeutic compound possessing various bioactivities, especially antibacterial, antifungal, cardioprotective, and pain relief activities. Herein, the interaction mechanism between cloxyquin and bovine serum albumin (BSA) has been elucidated in order to fulfill its pharmacokinetic and pharmacodynamic gaps essential for further development as a therapeutic drug. Multi-spectroscopic and biophysical model analysis suggested that cloxyquin interacts with BSA via a static process by ground-state complex formation. Its binding behavior emerged as a biphasic fashion with a moderate binding constant at the level of 104 M-1. Thermodynamic analysis and molecular docking simulation concurrently revealed that hydrophobic interaction is a major driving force for BSA-cloxyquin complexation. Binding of cloxyquin tends to slightly enlarge the monomeric size of BSA without a significant increase of aggregate fraction. Cloxyquin preferentially binds into the fatty acid binding site 5 (FA5) of the BSA via hydrophobic interaction amongst its quinoline scaffold and Phe550, Leu531, and Leu574 residues of BSA. The quinoline ring and hydroxyl moiety of cloxyquin also form the ?-? interaction and the hydrogen bond with Phe506. Our data indicate a potential function of serum albumin as a carrier of cloxyquin in blood circulation.
Project description:Protein fibrillation is a leading cause of innumerable neurodegenerative diseases. The exact underlying mechanism associated with the formation of fibrils is yet to be known. Recently, the role of metal ions resulting into fibrillation of proteins has gained attention of the scientific community. In this piece of work, we have investigated the effect of the aluminum (Al) metal ion on the kinetics of aggregation of bovine serum albumin (BSA) protein under physiological conditions by employing several biophysical and microscopic techniques. Quenching of tryptophan fluorescence was observed along with 9 nm blue shift, demonstrating BSA becomes more hydrophobic during unfolding pathway of thermal denaturation. Moreover, ANS (8-Anilino-1-naphthalene sulfonic acid) binding shows quenching in fluorescence intensity with increasing time of incubation at 65 °C, suggesting unfolding leading to the disruption of hydrophobic patches in BSA. Besides, Thioflavin T intensity indicated a significant acceleration in BSA fibrillation at a ratio of 1:1 and 1:2 of BSA and Al (III) metal ion respectively. In addition, circular dichroism (CD) spectroscopy study revealed the transition of BSA from ?-helical conformation to the ?-sheet rich structure. Molecular docking analysis demonstrated significant binding affinity (-1.2 kcal/mol) of Al (III) with BSA involving Phe501, Phe506, Val575, Thr578, Gln579, Leu531 residues. Transmission electron microscopy (TEM) reaffirm augmentation of thermal-induced BSA fibril formation in the presence of Al (III) metal ions. This study highlights the metal chelating potency as the possible therapeutic target for neurological diseases.
Project description:Understanding the interactions of trityl radicals with proteins is required to expand their biomedical applications. In this work, we demonstrate that the Finland trityl radical CT-03 binds to bovine serum albumin (BSA) in aqueous solution. Upon binding with BSA, CT-03 exhibits a much broader electron paramagnetic resonance (EPR) signal and this line broadening can be reversed by proteolysis of the BSA. The binding induces a red-shift of the maximal UV-Vis absorbance wavelength of CT-03 around 470 nm, likely due to localization of CT-03 in the relatively hydrophobic region of the protein. The interaction between CT-03 and BSA is driven by a hydrophobic interaction with an estimated binding constant of 2.18 ×105 M-1 at 298 K. Furthermore, only one CT-03 is bound to each molecule of BSA and the binding site is determined to be the sub-domain IIA (Sudlow's site I). This protein binding of the trityl probe to albumin can be used to study the structure and function of albumin and also must be considered for its use as an in vivo imaging agent or spin label.
Project description:Background:The binding interaction between bovine serum albumin (BSA) and roflumilast (ROF) was explored in this study. The binding of drugs to albumin plays a vital role in their pharmacokinetics and pharmacodynamics in vivo. The mechanisms involved in the interaction between BSA and ROF was studied using multi-spectroscopic experimental and computational approaches. Materials and methods:Spectrofluorometric experiments were used to determine the method of quenching involved and the conformational changes in the BSA. UV-visible spectroscopy synchronous and three-dimensional fluorescence spectroscopy were used to further explore the binding interaction mechanism. Results:The results suggested that the intrinsic fluorescence of BSA was quenched due to the formation of a static complex between ROF and BSA. Conformational changes in BSA were determined based on its interaction with ROF. The thermodynamic results suggested that the interaction between ROF and BSA was spontaneous and a hydrophobic interaction occurred between them. Site I of BSA was suggested as the site of interaction between ROF and BSA based on the site marker experiments. Conclusion:The molecular simulation results and the experimental outcomes were complimentary to each other and helped to identify the binding site and nature of bonds involved in the interaction between ROF and BSA.
Project description:The interaction of baicalein with bovine serum albumin (BSA) was investigated with the help of spectroscopic and molecular docking studies. The binding affinity of baicalein towards BSA was estimated to be in order of 105 M-1 from fluorescence quenching studies. Negative ?H° (-5.66±0.14 kJ/mol) and positive (?S°) (+79.96±0.65 J/mol K) indicate the presence of electrostatic interactions along with the hydrophobic forces that result in a positive ?S°. The hydrophobic association of baicalein with BSA diminishes in the presence of sodium dodecyl sulfate (SDS) due to probable hydrophobic association of baicalein with SDS, resulting in a negative ?S° (-40.65±0.87 J/mol K). Matrix-assisted laser desorption ionization/time of flight (MALDI--TOF) experiments indicate a 1:1 complexation between baicalein and BSA. The unfolding and refolding phenomena of BSA were investigated in the absence and presence of baicalein using steady-state and fluorescence lifetime measurements. It was observed that the presence of urea ruptured the non-covalent interaction between baicalein and BSA. The presence of metal ions (Ag+, Mg2+, Ni2+, Mn2+, Co2+and Zn2+) increased the binding affinity of ligand towards BSA. The changes in conformational aspects of BSA after ligand binding were also investigated using circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopic techniques. Site selectivity studies following molecular docking analyses indicated the binding of baicalein to site 1 (subdomain IIA) of BSA.
Project description:This study investigated the interaction between eupatorin and bovine serum albumin (BSA) using ultraviolet-visible (UV-vis) absorption, fluorescence, synchronous fluorescence, circular dichroism (CD) spectroscopies, and molecular modeling at pH 7.4. Results of UV-vis and fluorescence spectroscopies illustrated that BSA fluorescence was quenched by eupatorin via a static quenching mechanism. Thermodynamic parameters revealed that hydrophobic and electrostatic interactions played major roles in the interaction. Moreover, the efficiency of energy transfer, and the distance between BSA and acceptor eupatorin, were calculated. The effects of eupatorin on the BSA conformation were analyzed using UV-vis, CD, and synchronous fluorescence. Finally, the binding of eupatorin to BSA was modeled using the molecular docking method.
Project description:The interaction of afatinib (AFB) with bovine serum albumin (BSA) was examined via fluorescence and UV-Vis spectroscopy. Spectrofluorimetric measurements revealed that AFB can strongly quench the BSA intrinsic fluorescence through producing a non-fluorescent complex. This quenching mechanism was thoroughly investigated with regard to the type of quenching, binding constant, number of binding locations and the fundamental thermodynamic parameters. Subsequently, the association constant of AFB with BSA was computed at three different temperatures and was found to range from 7.34 to 13.19 x10(5) L mol(-1). Thermodynamic parameters calculations demonstrated a positive ?S? value with both negative ?H? and ?G? values for AFB-BSA complex, which in turn infers that a spontaneous binding is taking place with both electrostatic bonding and hydrophobic interactions participating in the binding of AFB and BSA. Similarly, the UV absorption spectra of AFB-BSA system were studied and confirmed the interaction. Conformational alteration of the protein upon binding to AFB was elaborated with the aid of three dimensional fluorescence measurements as well as synchronous fluorescence spectra.
Project description:The study of the interaction of persistent organic pollutants with biosubstrates helps to unravel the pathways for toxicity, however, few mechanistic data are present in the literature for these systems. We analyzed the binding of paraquat (PQ) and diquat (DQ) herbicides to natural calf thymus DNA and a DNA G-quadruplex by spectrophotometric titrations, ethidium bromide exchange tests, viscometry, and melting experiments. The interaction with bovine serum albumin (BSA) protein was studied spectrofluorimetrically at different temperatures. The retention of the targets on positive, negative, and neutral micellar aggregates and liposomes was analyzed by ultrafiltration experiments. Despite some favorable features, PQ and DQ only externally bind natural DNA and do not interact with DNA oligonucleotides. Both herbicides bind bovine serum albumin (BSA). PQ binds BSA mainly according to an electrostatics-driven process. However, ultrafiltration data also show that some hydrophobic contribution participates in the features of these systems. The practical problems related to unfavorable spectroscopic signals and inner filter effects are also discussed. Overall, both herbicides show a low affinity for nucleic acids and weak penetration into liposomes; in addition, the equilibrium constants values found for BSA system suggest optimal conditions for transport in the body.
Project description:The effect of a naphthalimide pharmacophore coupled with diverse substituents on the interaction between naphthalimide-polyamine conjugates 1-4 and bovine serum albumin (BSA) was studied by UV absorption, fluorescence and circular dichroism (CD) spectroscopy under physiological conditions (pH = 7.4). The observed spectral quenching of BSA by the compounds indicated that they could bind to BSA. Furthermore, caloric fluorescent tests revealed that the quenching mechanisms of compounds 1-3 were basically static type, but that of compound 4 was closer to a classical type. The Ksv values at room temperature for compound-BSA complexes-1-BSA, 2-BSA, 3-BSA and 4-BSA were 1.438 × 10?, 3.190 × 10?, 5.700 × 10? and 4.745 × 10?, respectively, compared with the value of MINS, 2.863 × 10? at Ex = 280 nm. The obtained quenching constant, binding constant and thermodynamic parameter suggested that the binding between compounds 1-4 with BSA protein, significantly affected by the substituted groups on the naphthalene backbone, was formed by hydrogen bonds, and other principle forces mainly consisting of charged and hydrophobic interactions. Based on results from the analysis of synchronous three-dimensional ?uorescence and CD spectra, we can conclude that the interaction between compounds 1-4 and BSA protein has little impact on the BSA conformation. Calculated results obtained from in silico molecular simulation showed that compound 1 did not prefer either enzymatic drug sites I or II over the other. However, DSII in BSA was more beneficial than DSI for the binding between compounds 2-4 and BSA protein. The binding between compounds 1-3 and BSA was hydrophobic in nature, compared with the electrostatic interaction between compound 4 and BSA.
Project description:Introduction: Ascorbyl palmitate (AP) is an example of natural secondary food antioxidant, which has been used for oxidative rancidity prevention in food industry. In this study, the interaction of AP with bovine serum albumin (BSA) was investigated. Methods: The mechanism of BSA interaction with AP was investigated using spectroscopic methods (UV-Vis, fluorescence). The thermodynamic parameters including enthalpy change (ΔH), entropy change (ΔS), and Gibb's free energy (ΔG) were calculated using Van't Hoff equation at different temperatures. Results: The experimental results showed that UV-Vis absorption spectra of BSA decreased upon increasing AP concentration, indicating that the AP can bind to BSA. Formation of the AP-BSA complex was approved by quenching of fluorescence and the quenching mechanism was found to be resultant from dynamic procedure. The positive values of both ΔH and ΔS showed that hydrophobic forces were the major binding forces. The negative value of ΔG demonstrated that AP interacts with BSA spontaneously. Molecular docking results confirmed that AP binds to BSA through hydrophobic forces. Conclusion: The attained results showed that AP can bind to BSA and effectively distributed into the bloodstream.
Project description:The binding interactions of the surfactants: anionic sodium dodecyl sulphate (SDS), cationic cetyltrimethylammonium bromide (CTAB), non-ionic octyl glucoside (OG), and zwitterionic 3-[Hexadecyl(dimethyl)ammonio]-1-propanesulfonate (HPS), with bovine serum albumin (BSA) were investigated by computer simulation. The results disclosed that the surfactants bound stably between hydrophobic subdomain IIA and IIIA where tryptophan-213 residue, an important intrinsic fluorophore in BSA is housed. The interactions of the surfactants with the BSA were electrostatic and hydrophobic interactions. The head-groups of SDS, HPS and OG formed hydrogen bonds with the BSA, while that of CTAB was shielded from intermolecular hydrogen-bonding due to intervening methyl groups. Subsequently, molecular dynamics (MD) simulation of the protein-surfactant complexes revealed that hydrogen bonds formed by OG were stronger than those of SDS and HPS. However, the decomposed force-field energies showed that OG had the least interaction energy with the BSA. In addition to MD simulation, it was found by density functional theory (DFT) that the differences in the coulomb interaction energies can be attributed to charge distribution in the surfactants. Overall, free energies calculated by linear interaction energy (LIE) proved that the binding of each surfactant was dominated by differences between van der Waals interactions in bound and free states.