Tryptophan Residues Of Bovine Serum Albumin Research Articles

Interaction mechanism of oseltamivir phosphate with bovine serum albumin: multispectroscopic and molecular docking study

Oseltamivir phosphate (OP) is an antiviral drug with potential risks to human health due to overuse, leading to serious consequences such as gastrointestinal disturbances, abnormal neuropsychiatric symptoms, and sudden death. Therefore, gaining an in-depth understanding of its interaction with proteins is crucial. We investigated the interaction between OP and bovine serum albumin (BSA) utilizing multispectral methods (i.e., fluorescence, ultraviolet absorption, circular dichroism) combined with molecular docking techniques. Fluorescence spectroscopy indicated that OP quenched BSA fluorescence by forming the OP-BSA complex. The Stern-Volmer constants (KSV) between OP and BSA were determined to be 3.06 × 103 L/mol, 2.36 × 103 L/mol, and 1.86 × 103 L/mol at 293 K, 298 K, and 303 K, respectively. OP occupies exclusively one binding site on BSA, and the fluorescent probe displacement measurements revealed that this is BSA site I. Thermodynamic data (∆H, ∆S, and ∆G) obtained by fitting the van’t Hoff equation were − 77.49 kJ/mol, -176.54 J/(mol∙K), and − 24.88 kJ/mol, respectively, suggesting that hydrogen bonding and van der Waals forces mainly participate in OP-BSA complex stabilization. Moreover, the reaction occurs spontaneously at room temperature. Synchronous fluorescence spectra indicated that OP interacts with tryptophan residue of BSA. The results of ultraviolet (UV) and 3D fluorescence spectroscopy indicated that the OP-BSA complex formation altered the microenvironment around amino acid residues. Circular dichroism spectra revealed that the addition of OP decreased the α-helix content of BSA by 7.13%. Docking analysis confirmed that OP binds to BSA site I through hydrogen bonding with amino acids VAL342, SER453, and ASP450. Finally, ADMET studies were conducted to explore the pharmacokinetics of OP as an antiviral drug.

Heterocyclic (pyrazine)carboxamide Ru(ii) complexes: structural, experimental and theoretical studies of interactions with biomolecules and cytotoxicity.

Treatments of N-(1H-benzo[d]imidazol-2-yl)pyrazine-2-carboxamide (HL1) and N-(benzo[d]thiazol-2-yl)pyrazine-2-carboxamide carboxamide ligands (HL2) with [Ru(p-cymene)Cl2]2 and [Ru(PPh3)3Cl2] precursors afforded the respective Ru(ii) complexes [Ru(L1)(p-cymene)Cl] (Ru1), [Ru(L2)(p-cymene)Cl] (Ru2), [Ru(L1)(PPh3)2Cl] (Ru3), and [Ru(L2)(PPh3)2Cl] (Ru4). These complexes were characterized by NMR, FT-IR spectroscopies, mass spectrometry, elemental analyses, and crystal X-ray crystallography for Ru2. The molecular structure of complex Ru2 contains one mono-anionic bidentate bound ligand and display pseudo-octahedral piano stool geometry around the Ru(ii) atom. The interactions with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) were investigated by spectroscopic techniques. The experimental binding studies suggest that complexes Ru1-Ru4 interact with DNA, primarily through minor groove binding, as supported by molecular docking results. Additionally, these complexes exhibit strong quenching of the fluorescence of tryptophan residues in BSA, displaying static quenching. The in vitro cytotoxicity studies of compounds Ru1-Ru4 were assessed in cancer cell lines (A549, PC-3, HT-29, Caco-2, and HeLa), as well as a non-cancer line (KMST-6). Compounds Ru1 and Ru2 exhibited superior cytotoxicity compared to Ru3 and Ru4. The in vitro cytotoxicity and selectivity of compounds Ru1 and Ru2 against A549, PC-3, and Caco-2 cell lines surpassed that of cisplatin.

Ultraviolet Resonance Raman Spectra of Serum Albumins.

The ultraviolet resonance Raman (UVRR) spectra of the two proteins bovine serum albumin (BSA) and human serum albumin (HSA) in an aqueous solution are compared with the aim to distinguish between them based on their very similar amino acid composition and structure and to obtain signals from tryptophan that has only very few residues. Comparison of the protein spectra with solutions of tryptophan, tyrosine, and phenylalanine in comparative ratios as in the two proteins shows that at an excitation wavelength of 220 nm, the spectra are dominated by the strong resonant contribution from these three amino acids. While the strong enhancement of two and one single tryptophan residue in BSA and HSA, respectively, results in pronounced bands assigned to fundamental vibrations of tryptophan, its weaker overtones and combination bands do not play a major role in the spectral range above 1800 cm-1. There, the protein spectra clearly reveal the signals of overtones and combination bands of phenylalanine and tyrosine. Assignments of spectral features in the range of Raman shifts from 3800 to 5100 cm-1 to combinations comprising fundamentals and overtones of tyrosine were supported by spectra of amino acid mixtures that contain deuterated tyrosine. The information in the high-frequency region of the UVRR spectra could provide information that is complementary to near-infrared absorption spectroscopy of the proteins.

Insights into the impacts of dissolved organic matter of different origins on bioaccumulation and translocation of per- and polyfluoroalkyl substances (PFASs) in wheat

Per- and polyfluoroalkyl substances (PFASs) have been found to be widely present in soil. Dissolved organic matter (DOM) in soil are supposed to greatly affect the bioavailability of PFASs in soil. Herein, hydroponic experiments were conducted to understand the impacts of two kinds of typical DOM, bovine serum albumin (BSA) and humic acid (HA), on the uptake and translocation of legacy PFASs and their emerging alternatives, perfluorooctane sulfonic acid (PFOS), perfluorooctane acid (PFOA), perfluorohexane sulfonic (PFHxS) and 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA) in wheat (Triticum aestivum L.). The results indicated that both HA and BSA significantly inhibited the bioaccumulation and translocation of PFASs in the roots and shoots of wheat, and the impacts of BSA were greater than HA. This difference was explained by the greater binding affinities of the four PFASs with BSA than with HA, as evidenced by the equilibrium dialysis and isothermal titration calorimetry (ITC) analyses. It was noting that inhibition impacts of the BSA-HA mixture (1:1) were lower than BSA alone. The results of Fourier transform infrared (FT-IR) spectroscopy and excitation-emission matrix (EEM) fluorescence spectroscopy suggested that HA could bind with the fluorescent tryptophan residues in BSA greatly, competing the binding sites with PFASs and forming a cover on the surface of BSA. As a result, the binding of PFASs with BSA-HA complex was much lower than that with BSA, but close to HA. The results of this study shed light on the impacts of DOM in soil on the bioaccumulation and translocation of PFASs in plants.

The role of metal ions in the behavior of bovine serum albumin molecules under physiological environment

Metal ions released from metallic implants can affect the conformation and structural stability of proteins in biological fluids, which eventually affects the biocompatibility of implants. The present study aimed at understanding the interactions between the metal ions (Mn2+, Fe2+, Fe3+, Co2+, Cu2+, and Zn2+) and bovine serum albumin (BSA) molecules in physiological context. The structural information of BSA molecules and the microenvironment of functional groups were investigated using UV, Raman, and circular dichroism spectroscopy. The results revealed that addition of Fe3+, Fe2+, and Cu2+ ions alters the tertiary structure of BSA molecules and exposes the aromatic heterocyclic hydrophobic group of BSA amino acid residues. The addition of Fe3+ and Cu2+ ions results in increased viscosity and decreased intensity of the water peak in the BSA solution. Furthermore, Fe3+ and Cu2+ ions evidently promote the α-helix to β-sheet transformation of BSA molecules due to decreased disulfide bond stability. Tryptophan residues of BSA and metal ions containing BSA (Me+/BSA) solutions were found to be in a hydrophilic environment. Moreover, the addition of metal ions to BSA results in several of tyrosine residues acting as hydrogen-bond donors. Coomassie brilliant blue staining revealed that the addition of Cu2+ ions promotes the aggregation of BSA molecules. The findings of this study will be helpful for evaluating the biocompatibility of metallic implants.

Preparation of SiO2/YPO4:Nd/SiO2 composite microspheres with near-infrared luminescence and surface functionalization

In this study, the core/shell/shell-structured SiO2/YPO4:Nd/SiO2 composite microspheres with near-infrared luminescence property were prepared by sol-gel method. The morphology and structure of the as-prepared microspheres were observed by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and infrared spectroscopy (IR). These tests show that the composite microspheres have a sandwich structure. The diameter of the core SiO2 microspheres is ~ 220 nm, the intermediate layer thickness of rare-earth phosphate is ~ 5 nm, and the outer SiO2 layer is ~ 20 nm thick. The core/shell/shell microspheres are emitted at 1063 nm in the near-infrared region, which attributes to optical transparent windows of biological tissues. Meanwhile, the interaction between the composite microspheres and bovine serum albumin (BSA) was investigated. The results showed that the composite microspheres could quench the emission intensity of BSA by binding the tryptophan residues in BSA. The synthesized core/shell/shell composite microspheres may be used as near-infrared luminescence probes in the field of biological tissue imaging.

Spectroscopic and theoretical methods to probe protein–ligand binding

Protein-ligand binding studies have gained considerable attention owing to its application in biomedical research. The present study discusses the application of spectroscopic and theoretical methods to probe the interaction between a model ligand, 1, 3-diphenylisobenzofuran (DPBF) and bovine serum albumin (BSA). The quenching of the intrinsic fluorescence of BSA arising from tryptophan residue in the presence of DPBF is monitored to follow the nature and mechanism associated with the binding process. The binding affinity and number of binding sites have been investigated. Synchronous fluorescence and UV–Vis spectroscopic studies have been carried out to follow the changes in the fluorophore micro-environment and binding mechanism. Theoretical methods such as fluorescence resonance energy transfer (FRET) and molecular docking are also employed to predict the binding mechanism, binding modes, binding sites and the distance between the tryptophan residue in BSA and DPBF.

Effect of adiphenine hydrochloride on the structure of bovine serum albumin: Spectroscopic and docking study

The interaction of adiphenine hydrochloride (ADP) with bovine serum albumin (BSA) has been investigated by fluorescence, time resolved fluorescence, UV–visible, FTIR and tensiometric technique. Molecular docking has also been done to show the available binding sites on BSA for ADP. Critical micelle concentration (cmc), surface excess (Γmax), the minimum area per molecule (Amin), and molar free energy at the maximum adsorption attained at cmc (Gmin) were evaluated to study the interfacial properties of ADP. Fluorescence spectroscopy was used to observe the effective quenching mechanism between BSA and ADP which was further confirmed by time-resolved fluorescence spectroscopy. Different thermodynamic parameters such as molar enthalpy (ΔH), molar Gibbs free energy (ΔG), and molar entropy contribution (ΔS) were evaluated by using van’t Hoff equation which showed that the binding mechanism was enthalpy driven and the major forces involved between ADP and BSA interaction are van der Waals and hydrogen bonding. UV–vis spectroscopy results showed the complex formation between ADP and BSA. Synchronous fluorescence spectra reveal that there is a slight effect of ADP on the fluorescence intensity of tyrosine but a significant effect on tryptophan residue of BSA. FTIR results suggested the ADP induced conformational changes in BSA. In addition, the molecular docking and competitive binding results showed that the ADP molecule binds with BSA on Sudlow site I (subdomain IIA). The esterase-like enzymatic activity study revealed that the ADP inhibits the enzymatic activity of BSA.

Self-assembly of the mixed systems based on cationic surfactants and different types of polyanions: The influence of structural and concentration factors

Mixed systems based on cationic surfactants with a cyclic head group (morpholinium bromide (Mor-16) and triphenylphosphonium bromide (TPPB-16)) and pH-dependent polyanions with different natures (polyacrylic acid (PAA) and bovine serum albumin (BSA)) were formed. The critical aggregation concentration, sizes, zeta-potential, solubilization capacity, aggregation number of the mixed systems were determined by the complex of modern, complementary physicochemical methods. It has been shown that the nature of the polyanions and the head group of surfactant play important role in the formation of complexes. By several methods it has been shown that the addition of PAA to Mor-16 solution leads to a significant decrease in the CAC compared to single surfactant by one to two orders of magnitude, while the addition of fixed amount of BSA to Mor-16 system does not affect the aggregation threshold. For mixed PAA-TPPB-16 system only slight changes in CAC value compared to CMC of single TPPB-16 system were revealed by different techniques. The particle size in the mixed BSA-surfactant systems is about 10 nm, while in PAA-surfactant systems the size is determined by the nature of the surfactant head group. By the synchronous fluorescence method it has been shown that the interaction of BSA with surfactant occurred through the tryptophan residues of BSA. The presence of aromatic ring in the surfactant structure can be a key factor in increasing the binding efficiency in the surfactant-BSA systems.

Effect of chain length on the interactions of sodium N-alkyl prolinates with bovine serum albumin: a spectroscopic investigation and molecular docking simulations

The interaction of anionic surfactants with serum albumin has emerged as an important area of research and is considered as a model for gaining fundamental insight into surfactant-protein binding, which is useful in both chemical and biological applications. This study involves the interactions of three synthesized proline-based anionic surfactants of varying chain lengths (C8, C10, and C12) with bovine serum albumin (BSA) using different techniques, including fluorescence, 1H NMR, and FT-IR spectroscopy. The study indicated that the binding of the proline surfactants with BSA followed a static quenching process, with an increase in binding ability upon increasing chain length. FT-IR studies revealed a change in the secondary structure of BSA upon binding with the proline surfactant, while 1H NMR investigations indicated the proximity of the long alkyl chain of the surfactant with tryptophan residues of BSA. Molecular docking studies performed on the three proline surfactants with BSA revealed that the surfactants were able to bind in the vicinity of both tryptophan residues (Trp-213 and Trp-134) with an increase in the free energy of binding while increasing the chain length from C8 to C12. Therefore, this study provided a whole view about the interaction of BSA with anionic proline derived surfactants, which can be used as potential ingredients in pharmaceutical products.

Experimental and ONIOM computational evaluation of DNA- and BSA-binding and cytotoxic activity of a mononuclear Pd(II) complex with piroxicam

Binding studies of a new mononuclear Pd(II) complex, trans-[Pd(Pir)2] (Pir− is piroxicam), with fish sperm deoxyribonucleic acid (FS-DNA) and bovine serum albumin (BSA) were investigated. The results reveal that the complex interacts with FS-DNA by two binding modes, viz., electrostatic and minor groove binding. The interaction of the Pd(II) complex with BSA changes the polarity of the microenvironment around the tyrosine and tryptophan residues of BSA. An in vitro cytotoxicity study of the effect of the complex on K562 cell lines indicates that the complex exhibits the best cell growth-inhibitory effect among the reported oxicam complexes with an IC50 value of 11.7μM. Also, the Pd(II) complex shows a remarkable increase in the cytotoxic activity in comparison to Pir− and Pd(OAc)2. Molecular docking was also used for modeling the binding of the Pd(II) complex to DNA and BSA. In addition, hybrid QCH/MM ONIOM (the Our own N-layered Integrated molecular Orbital and molecular Mechanics) method, based on the quantum mechanics/molecular mechanics (QM/MM) methodology, was carried out to investigate the interaction of the Pd(II) complex with DNA and BSA. Based on the QM/MM calculations, the variation in the structural parameters due to insertion of the Pd(II) complex into the minor grooves of DNA were determined. In addition, the QM/MM calculations were used to interpret the interaction of the Pd(II) complex with DNA using the calculated UV spectrum of the complex in different environments.

Insight into the Interaction between the HIV-1 Integrase Inhibitor Elvitegravir and Bovine Serum Albumin: A Spectroscopic Study

The interaction between the anti-HIV drug Elvitegravir (EVG) and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy and UV-visible absorption spectra. The mechanism for quenching the fluorescence of BSA by EVG is discussed. It was found that EVG can quench the intrinsic fluorescence of BSA through a static quenching procedure. The quenching type, association constant, and number of binding sites were investigated. The binding constant of EVG with BSA was calculated at different temperatures based on fluorescence quenching results. The thermodynamic parametersΔHθ,ΔGθ, andΔSθwere determined. The positiveΔSθand negativeΔHθandΔGθvalues showed that a spontaneous interaction may involve both roles of hydrophobic interaction and hydrogen bonding. The interaction of BSA with EVG was also confirmed by UV absorption spectra. The average distance,r, between donor (BSA) and acceptor (EVG) was obtained according to Förster’s theory of nonradiation energy transfer. Synchronous fluorescence and three-dimensional fluorescence spectra were used to investigate the conformational change of BSA molecules that occur upon addition of EVG and showed, upon binding, a possibility of increasing hydrophobicity around tryptophan residues of BSA.

Photophysical properties and in vitro cytotoxicity studies of new Ru(ii) carbonyl complexes and mixed geometrical Ru(ii)–Ni(ii) complex in HS-DNA/BSA protein and human lung (A549) and liver (HepG2) cells

Two new ruthenium(II) carbonyl complexes have been synthesized from [RuHCl(CO)(PPh3)3] and 2-hydroxy-1-naphthaldehydethiosemicarbazone [H2-(Nap-tsc)]. The stoichiometric reaction afforded two different complexes (1 and 2) exhibiting different structural motifs. In complex 1, the ligand coordinated through the N(2) nitrogen and thiolate sulphur by forming a strained four member chelate ring by leaving three donor sites (phenolic oxygen, N1 nitrogen and terminal nitrogen) uncoordinated. However, in complex 2, it coordinated as an ONS tridentate with the formation of a six member and a five member ring. In order to utilize the three unutilized donor sites in complex 1, it was reacted further with [NiCl2(PPh3)2], which resulted in the formation of a new hetero bimetallic complex 3 wherein all the donor atoms of the ligand were utilized. The complexes have been characterized analytically and spectroscopically and X-ray diffraction (1, 3) and have also been evaluated for their binding affinity with HS-DNA. The electrostatic binding of the complexes with DNA was evident from absorption and fluorescence titration experiments. The binding interaction between the complexes 1–3 and bovine serum albumin (BSA) was studied by absorption, fluorescence and synchronous spectra at room temperature. From the results, it is inferred that complex 2 had a better binding ability with the tryptophan residues of BSA. The mechanism of complex interaction was found as static quenching. The in vitro cytotoxicity of metal complexes (1–3) has been evaluated by colorimetric assay (MTT assay).

Investigation of the Interaction between Nitrite Ion and Bovine Serum Albumin Using Spectroscopic and Molecular Docking Techniques

AbstractThe interaction between nitrite ion and bovine serum albumin (BSA), in an aqueous environment, was studied using spectroscopic methods, including fluorescence quenching technique, synchronous fluorescence, UVVis spectrophotometry and Resonance Rayleigh Scattering (RRS), and molecular docking technique. The experimental results showed that nitrite ion effectively quenched the intrinsic fluorescence of BSA with the static quenching. The ion‐BSA binding constant was determined to be 3.69×103 L mol−1. As the results showed the stoichiometry of binding nitrite ion to BSA was 1 : 1. Furthermore the thermodynamic parameters and nature of the binding force were calculated. The negative ΔHo and ΔSo values of reaction between nitrite ion and BSA indicated the predominant forces in the ion‐BSA interactions are hydrogen bonding interactions. Based on the Förster’s theory of non‐radiative energy transfer, the binding distance between nitrite ion and the inner tyrosine and tryptophan residue of BSA were determined to be 2.16 nm. Furthermore binding site of this ion on BSA was carried out by molecular docking technique.

Assessing the interaction of Hecameg® with Bovine Serum Albumin and its effect on protein conformation: A spectroscopic study

Interaction of the nonionic surfactant Hecameg® with the plasma protein Bovine Serum Albumin (BSA), and its effect on protein conformation, has been studied using spectroscopic techniques such as steady-state and time-resolved fluorescence and circular dichroism. A weak interaction of the surfactant with BSA is reflected by changes in the intrinsic fluorescence of BSA in either steady-state or time-resolved measurements. The fluorescence intensity data allowed us to determine the corresponding binding curve, which suggests a sequential binding mechanism, in which the surfactant first occupies the hydrophobic sites of the inner protein cavity and then, condenses onto the surface hydrophobic sites of BSA via a cooperative mechanism. Additional fluorescence data obtained by synchronous, three-dimensional and anisotropy experiments show that the surfactant mainly interacts with the tryptophan residues of BSA, which seem to experience motional restriction as a result of this interaction. Time-resolved fluorescence data, which were analyzed using the modified Stern–Volmer equation, also support the above mechanism. Finally, far-UV circular dichroism studies indicated that the secondary structure of the protein remains almost unaltered even for BSA to surfactant molar ratio as high as 1 to 100.

Research on the Interaction between Pheophorbide and Bovine Serum Albumin

The interaction between natural pheophorbide (a superior photosensitizer) and bovine serum albumin (BSA) in physiological condition is investigated by means of UV-Vis, fluorescence and synchronous fluorescence spectra so as to provide the basis for clinical use. Natural pheophorbide was isolated from silkworm excrement. BSA in pH 7.4 Tris buffer mixed with different concentration of pheophorbide was kept at certain temperature for 3 h or under illumination by laser at 630 nm for 20 min. UV-Vis absorption of BSA was enhanced and its fluorescence was quenched by pheophorbide. Illumination of laser at 630 nm intensified the quenching. The mechanism is deemed as mainly static quenching. The binding constants Ka at 300, 310, 320 K are separately 6.93×1012,7.40×1012,6.82×1012 L/mol/s respectively. Number of binding sites n is 1; the binding distance R is 3.70 nm, and that suggests non-radiation energy transfer from BSA to pheophorbide. The thermodynamic parameters of the binding reaction are H=36.7 kJ/mol, S=213 J/mol/K, and G negative value, and indicates that hydrophobic force plays a predominant role in the process, and it is a spontaneous interaction. Synchronous fluorescence spectra show that pheophorbide mainly interacts with tryptophan residue of BSA and leads to the promotion of hydrophobic force. Pheophorbide can bind to serum protein and be transported in vivo, makes no destruction to molecular structure of serum protein, but causes its conformational alteration.

Norfloxacin Zn(II)-based complexes: acid base ionization constant determination, DNA and albumin binding properties and the biological effect against Trypanosoma cruzi

Zn(II) complexes with norfloxacin (NOR) in the absence or in the presence of 1,10-phenanthroline (phen) were obtained and characterized. In both complexes, the ligand NOR was coordinated through a keto and a carboxyl oxygen. Tetrahedral and octahedral geometries were proposed for [ZnCl2(NOR)]·H2O (1) and [ZnCl2(NOR)(phen)]·2H2O (2), respectively. Since the biological activity of the chemicals depends on the pH value, pH titrations of the Zn(II) complexes were performed. UV spectroscopic studies of the interaction of the complexes with calf-thymus DNA (CT DNA) have suggested that they can bind to CT DNA with moderate affinity in an intercalative mode. The interactions between the Zn(II) complexes and bovine serum albumin (BSA) were investigated by steady-state and time-resolved fluorescence spectroscopy at pH 7.4. The experimental data showed static quenching of BSA fluorescence, indicating that both complexes bind to BSA. A modified Stern-Volmer plot for the quenching by complex 2 demonstrated preferential binding near one of the two tryptophan residues of BSA. The binding constants obtained (K b ) showed that BSA had a two orders of magnitude higher affinity for complex 2 than for 1. The results also showed that the affinity of both complexes for BSA was much higher than for DNA. This preferential interaction with protein sites could be important to their biological mechanisms of action. The analysis in vitro of the Zn(II) complexes and corresponding ligand were assayed against Trypanosoma cruzi, the causative agent of Chagas disease and the data showed that complex 2 was the most active against bloodstream trypomastigotes.

Interaction of bovine serum albumin with a psychotropic drug alprazolam: Physicochemical, photophysical and molecular docking studies

The interaction between alprazolam (Alp) and bovine serum albumin (BSA) has been investigated under physiological conditions by UV–vis, steady state as well as time-resolved fluorescence, circular dichroism (CD) spectroscopic and molecular docking studies. The binding constant K of Alp to BSA was found to be 1.8×105Lmol−1 from absorption data. Fluorometric studies suggested the formation of the Alp–BSA complex, while time-resolved fluorescence studies showed that the binding of Alp by BSA was mainly static and the effective rate constant is found to be 2.33×1013Lmol−1s−1. According to the modified Stern–Volmer equation, the Stern–Volmer quenching constants (KSV) between Alp and BSA at four different temperatures 295, 303, 308, 313K were obtained to be 1.19×105, 1.05×105, 0.99×105 and 0.90×105Lmol−1, respectively. The change in enthalpy (ΔH) and entropy (ΔS) were calculated to be −11.66 and 57.64Jmol−1K−1, respectively, indicating that the interaction was hydrophobic in nature. Site marker competitive experiments suggested that the binding of Alp to BSA primarily took place in sub-domain IIA, whereas the binding distance (r) between Alp and the tryptophan residue of BSA was obtained to be 1.87nm by Förster's theory of non-radiative energy transfer. The conformational studies by CD spectroscopy showed that the presence of Alp decreased the α-helical content of BSA and induced the unfolding of the polypeptide of the protein. The change in conformation was also supported by excitation–emission matrix spectroscopy (EEMS) studies. The molecular docking experiment supports the above results and effectively proves the binding of Alp to BSA.

Investigation of the Interaction Between N-benzyl Piperidones and Bovine Serum Albumin by Spectroscopic Approaches

Fluorescence and ultraviolet spectroscopies were applied to investigate the interaction between five N-benzyl piperidones (NBP) and bovine serum albumin (BSA) under imitated physiological conditions. The experimental results show that these NBPs have a static fluorescence quenching effect on the endogenous fluorescence of BSA at the temperatures 302 and 310 K. According to the fluorescence quenching theory, the Stern–Volmer quenching constant (KSV), the binding constant (Ka), and the number of binding sites (n) were obtained. Also, the effect of substituents on the binding capacity between NBP and BSA is in the order: C6H5 < 4-CH3OC6H4 < 4-CH3C6H4 < 2,4-Cl2C6H3 < 4-ClC6H4. The corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were obtained at two different temperatures and indicate that hydrogen bonding and van der Waals forces play main roles in stabilizing the BSA–NBP complex. The binding distance between the tryptophan residue in BSA and NBP was found to be much <7 nm based on the Forster theory of non-radiation energy transfer. The effect of NBP on the conformation of BSA was analyzed as well by synchronous fluorescence spectroscopy.

Systematic investigation on the interaction of bovine serum albumin with ZnO nanoparticles using fluorescence spectroscopy

Zinc oxide (ZnO) nanoparticles with average size of ∼7.5nm were synthesized to investigate their interaction with bovine serum albumin (BSA) at different temperatures. Fluorescence quenching, synchronous and polarization spectroscopy along with UV–vis absorption, circular dichroism and resonance light scattering spectroscopy techniques were used to establish the interaction mechanism between ZnO and BSA. The obtained results confirmed that the ZnO nanoparticles (NPs) quench the fluorophore of BSA by forming ground state complex in the solution. The fluorescence quenching data was also used to determine binding sites and binding constants at different temperatures. The calculated thermodynamic parameters (ΔG°, ΔH°, and ΔS°) suggest that the binding process occurs spontaneously by involving hydrogen bond and van der Waals interactions. The synchronous fluorescence spectra reveal that the microenvironment close to both the tyrosine and tryptophan residues of BSA is perturbed and that the hydrophobicity of both the residues is increased in the presence of ZnO NPs. Resonance light scattering, circular dichroism, and fluorescence polarization spectra suggest the formation of BSA–ZnO complex and conformational changes in BSA. The calculated distance between the BSA and ZnO NPs suggests that the energy transfer from excited state of BSA to ZnO NPs occurs with high efficiency.