Binding Sites Of Bovine Serum Albumin Research Articles

Aggregation behavior, interaction forces and physico-chemical parameters of cetyltrimethylammonium chloride in aqueous solution of bovine serum albumin: Impacts of short-chain alcohols and temperature

To better understand the molecular interactions between cetyltrimethylammonium chloride (CTAC) and bovine serum albumin (BSA), we report the alteration of the physicochemical characteristics of CTAC in aqueous BSA solutions in the presence of different alcohols. The analyses were performed using the conductivity method at temperatures ranging from 298.15 to 323.15 K, with 5 K intervals. The critical micelle concentration (CMC) values of the BSA + CTAC systems were found to change with variations in alcohol types, solvent compositions, and temperatures. The CMC values grew with the rising of alcohol contents. The negative free energy changes (∆Gm0) indicated the spontaneous association of the systems in all solvents media. The magnitudes of ∆Hm0 and ∆Sm0, determined from the micellization of the systems, indicated the presence of electrostatic, ion-dipole, and hydrophobic forces. The thermodynamics of transfer (free energy (∆Gm,tr0), enthalpy (∆Hm,tr0), entropy (∆Sm,tr0)), and compensation parameters (∆Hm0,∗ and Tc)—were also calculated, which provided significant insights into the potential interactions between CTAC and BSA in the presence of various alcohol additives. Furthermore, molecular docking studies suggested the binding of CTAC to different BSA binding sites with varying affinities.

Synthesis, characterization, and BSA binding studies of newfangled 2-phenylacetohydrazide derivatives

Five 2-phenylacetohydrazide derivatives (BPAH = N′-benzylidene-2-phenylacetohydrazide, HBPAH = N’-(2-hydroxybenzylidene)-2-phenylacetohydrazide), PPAH = 2-phenyl-N′-3-phenylallylideneacetohydrazide, FMPAH = N’-(furan-2-ylmethylene)-2-phenylaceto hydrazide and EPAH = N′-ethylidene-2-phenylacetohydrazide were synthesized by the condensation of 2-phenylacetohydrazide with the corresponding aldehyde. The synthesized compounds were characterized by FTIR, 1D, and 2D NMR spectroscopy. The structure of the BPAH and PPAH were analyzed by single crystal X-ray diffraction analysis and in both crystallized compounds, the molecules adopted trans geometry around the –CN- (imine) functional group. To explore the pharmacological significance of these compounds, the binding ability of these compounds with Bovine Serum Albumin (BSA) was investigated using fluorescence spectroscopy. BPAH and PPAH showed the highest binding ability while EPAH, HBPAH, and FMPAH had lower binding ability to BSA molecules. Thermodynamic parameters ΔG, ΔH°, and ΔS° demonstrated that interactions of BSA with compounds BPAH, EPAH, FMAH, and HBPAH were exothermic while for PPAH it was endothermic. The negative enthalpy and entropy of the compounds BPAH, EPAH, FMAH, and HBPAH indicated that van der Waals' forces and hydrogen bonding played a major role in stabilizing the BSA binding with the molecules. Hydrophobic interactions were predominant in the binding of PPAH with BSA tends to interact with two sets of BSA binding sites with an increase in temperature.

Induced Circular Dichroism Analysis of Thermally Induced Conformational Changes on Protein Binding Sites Under a Crowding Environment.

Protein-ligand interactions in crowded cellular environments play a crucial role in biological functions. The crowded environment can perturb the overall protein structure and local conformation, thereby influencing the binding pathway of protein-ligand reactions within the cellular milieu. Therefore, a detailed understanding of the local conformation is crucial for elucidating the intricacies of protein-ligand interactions in crowded cellular environments. In this study, we investigated the feasibility of induced circular dichroism (ICD) using 8-anilinonaphthalene-1-sulfonic acid (ANS) for local conformational analysis at the binding site in a crowding environment. Bovine serum albumin (BSA) concentration-dependent measurements were performed to assess the feasibility of ANS-ICD for analyzing protein interior binding sites. The results showed distinct changes in the ANS-ICD spectra of BSA solutions, indicating their potential for analyzing the internal conformation of proteins. Moreover, temperature-dependent measurements were performed in dilute and crowding environments, revealing distinct denaturation pathways of BSA binding sites. Principal component analysis of ANS-ICD spectral changes revealed lower temperature pre-denaturation in the crowded solution than that in the diluted solution, suggesting destabilization of binding sites owing to self-crowding repulsive interactions. The established ANS-ICD method can provide valuable conformational insights into protein-ligand interactions in crowded cellular environments.

Structure and energetics of serum protein complex of tea adulterant dye Bismarck brown Y using experimental and computational methods

Tea, a widely consumed aromatic beverage, is often adulterated with dyes such as Bismarck brown Y (C.I. 21000) (BBY), Prussian blue, and Plumbago, which pose potential health risks. The objective of this study is to analyze how the food dye BBY interacts with serum protein, bovine serum albumin (BSA). This study investigated the BBY-BSA interaction at the molecular level. Fluorescence spectroscopy results showed that the quenching of BSA by BBY is carried out by dynamic quenching mechanism. The displacement assay and molecular docking studies revealed that BBY binds at the flavanone binding site of BSA with hydrophobic interactions. Circular Dichroism results indicate the structural stability of the protein upon BBY binding. Molecular dynamics simulations demonstrated the stability of the complex in a dynamic solvent system, and quantum mechanics calculations showed slight conformational changes of the diaminophenyl ring due to increased hydrophobic interaction. The energetics of gas phase optimized and stable MD structures of BBY indicated similar values which further confirmed that the conformational changes were minor, and it also exhibited a moderate binding with BSA as shown by the MM/PBSA results. This study enhances our understanding of the molecular-level interactions between BBY and BSA, emphasizing the critical role of hydrophobic interactions.

Complexity of the Role of Various Site-Specific and Selective Sudlow Binding Site Drugs in the Energetics and Stability of the Acridinedione Dye-Bovine Serum Albumin Complex: A Molecular Docking Approach.

Molecular docking (Mol.Doc) techniques were employed to ascertain the binding affinity of two resorcinol-based acridinedione dyes (ADR1 and ADR2) with the widely studied globular protein Bovine Serum Albumin (BSA) in the presence of site-selective binding drugs by Autodock Vina 4.2 software. Docking of various feasible conformers of ADR1 dye with BSA was found to be energetically more favored than ADR2 dye, even though both these dyes differ in the 9th position of the basic dye structure. Analysis of dyes with BSA establishes the location of dye in all of the binding sites of BSA, predominantly through conventional and nonconventional hydrogen-bonding (HB) interactions. The coexistence of hydrophobic interactions resulted in the stability of various conformers generated. The introduction of site I and site II (Sudlow site binding drugs) into ADR1-BSA and ADR2-BSA complexes effectively destabilizes the dye-protein complex; however, the drugs do not displace ADR dyes completely from their selective binding domains. Site II binding drugs effectively destabilize the binding ability of the dye-protein complex rather than site I drugs. However, docking of site I drug 3-carboxyl-4-methyl-5-propyl-2-furanpropanic acid (CMPF) largely destabilizes the ADR1-protein complex, whereas indomethacin (INDO) enhances the binding affinity of the ADR2-protein complex. Interestingly, simultaneous docking of ADR dyes to the BSA-drug complex results in larger stability of the protein-drug complex through HB interactions rather than hydrophobic interactions. Both ADR1 and ADR2 dyes predominantly occupy the Sudlow binding sites of BSA, and the introduction of either site I or site II binding drugs does not displace the dye efficiently from the corresponding binding sites, rather the drugs are effectively displaced toward other binding domains apart from their specific site-binding domains of BSA. Through Mol.Doc techniques, we authenticate that the interactions in host-guest complex systems involving competing ligands are established in depth, wherein the dye as well as the amino acid (AA) moieties in BSA act as both HB donor and acceptor sites apart from several hydrophobic interactions coexisting toward the stability.

Spectroscopic studies on binding of ibuprofen and drotaverine with bovine serum albumin

The interaction between ibuprofen (analgesic) and drotaverine (smooth muscle relaxant) drugs with bovine serum albumin (BSA) was investigated using both experimental (UV–Vis, fluorescence, and circular dichroism spectroscopy) and theoretical (molecular mechanics) methods. Both drugs quench the intrinsic fluorescence of BSA through static processes. The binding constant of the BSA–drotaverine complex is found to be relatively higher than that of the BSA–ibuprofen complex. The binding distance between BSA and ibuprofen/drotaverine was calculated to be 1.7 and 3.1 nm, respectively. Both fluorescence and circular dichroism spectral studies confirmed conformational changes in the BSA upon binding with these drugs. From both displacement competition studies and molecular docking, it was found that drotaverine can displace ibuprofen at higher concentrations, but ibuprofen can bind to other sites on the BSA. Circular dichroism showed that drotaverine has a stabilizing effect on the secondary structure of BSA in the presence of ibuprofen, which on its own leads to an increase in the disordered fraction at high concentrations.These observations imply that concurrent administration of these two drugs can be effective as a combination therapy in the management of pain due to primary dysmenorrhea, even when the disease tends to gain resistance to the NSAIDs; their competition for the BSA binding sites should be taken into account.

4-Dimethylamino-beta-nitrostyrene, a fluorescent solvatochromic probe to estimate the apparent dielectric constant in serum albumin: Experimental and molecular dynamics studies

The spectroscopic properties of 4-dimethylamino-beta-nitrostyrene (DANS) were theoretically and experimentally correlated with the polarity of organic solvents and applied to estimate the overall apparent dielectric constant in the binding sites of bovine serum albumin (BSA). The linear correlation between McRae's solvent polarity function and the wavelength of maximum emission (R2 = 0.8899) showed the suitability of DANS as a fluorescent solvatochromic probe. The interaction between BSA and DANS was evaluated (Ka = 3.1 × 104 mol−1 L), and based on the DANS/BSA emission, the apparent dielectric constant of BSA was estimated (ε = 5.5 ± 0.8). The experimental and theoretical absorption and emission maxima were correlated using density-functional theory. Molecular dynamics was used to calculate the mean electrostatic energy between DANS and the organic solvent molecules. These results were associated with the experimental fluorescence and applied to the BSA/DANS system, resulting in electrostatic energy (−37 kJ mol−1). The application of this model generated a dielectric constant of 5.8 ± 1.3 to BSA, which was consistent with the values obtained by McRae's solvent polarity function. The mean electrostatic energy of DANS in BSA binding sites was calculated directly from molecular dynamics simulations and resulted in −40 ± 2, −47 ± 3, and −48 ± 3 kJ mol−1 for sites I, II, and III. These results showed that the environment offered by the site I presented the value of electrostatic energy closest to the obtained with the solvatochromic model. In conclusion, DANS can be used to estimate the apparent polarity of albumins.

Binding behavior of ibuprofen-based ionic liquids with bovine serum albumin: Thermodynamic and molecular modeling studies

• Nine ibuprofen-based ionic liquids containing cations amino acid alkyl esters [AAOR] were synthesized and characterized. • The [AAOR][Ibu] are not toxic against mouse fibroblasts and keratinocytes. • Ibu-ILs bind spontaneously to bovine serum albumin with moderate affinities (Ka 1–3.7 × 10 5 L/mol) at 25 °C. • Depending on their structures, [AAOR] showed differences at the preferred binding site of bovine serum albumin. Ionic liquids based on active-pharmaceutical ingredients are an attractive alternative to classical drugs because they are able to overcome problems with drug solubility and polymorphism, hence bioavailability and as well as to propose different routes of administration and/or improve the pharmacokinetics of the drug. In this manuscript, we report the synthesis of nine amino acid alkyl esters of ibuprofen [AAOR][Ibu]. The estimated half-maximum inhibitory constants toward murine embryotic fibroblasts and human dermal keratinocytes are in the millimolar range, which makes them practically not toxic. The conversion of ibuprofen into ionic liquids does not affect the binding affinity of ibuprofen to bovine serum albumin (BSA). Molecular modeling studies have shown that bulky cations such as L-PheOEt and L-PheOPr are able to bind effectively in three different BSA binding sites. On the other hand, smaller cations preferably bind to Sudhow’s site I, the same that binds ibuprofen.

Supramolecular Arrangement and DFT analysis of Zinc(II) Schiff Bases: An Insight towards the Influence of Compartmental Ligands on Binding Interaction with Protein.

We report, for the first time, a detailed crystallographic study of the supramolecular arrangement for a set of zinc(II) Schiff base complexes containing the ligand 2,6‐bis((E)‐((2‐(dimethylamino)ethyl)imino)methyl)‐4‐R‐phenol], where R=methyl/tert‐butyl/chloro. The supramolecular study acts as a pre‐screening tool for selecting the compartmental ligand R of the Schiff base for effective binding with a targeted protein, bovine serum albumin (BSA). The most stable hexagonal arrangement of the complex [Zn−Me] (R=Me) stabilises the ligand with the highest FMO energy gap (ΔE=4.22 eV) and lowest number of conformations during binding with BSA. In contrast, formation of unstable 3D columnar vertebra for [Zn−Cl] (R=Cl) tend to activate the system with lowest FMO gap (3.75 eV) with highest spontaneity factor in molecular docking. Molecular docking analyses reported in terms of 2D LigPlot+ identified site A, a cleft of domains IB, IIIA and IIIB, as the most probable protein binding site of BSA. Arg144, Glu424, Ser428, Ile455 and Lys114 form the most probable interactions irrespective of the type of compartmental ligands R of the Schiff base whereas Arg185, Glu519, His145, Ile522 act as the differentiating residues with ΔG=−7.3 kcal mol−1.

Effect of Tetraphenylborate on Physicochemical Properties of Bovine Serum Albumin.

The binding interactions of bovine serum albumin (BSA) with tetraphenylborate ions ([B(Ph)4]−) have been investigated by a set of experimental methods (isothermal titration calorimetry, steady-state fluorescence spectroscopy, differential scanning calorimetry and circular dichroism spectroscopy) and molecular dynamics-based computational approaches. Two sets of structurally distinctive binding sites in BSA were found under the experimental conditions (10 mM cacodylate buffer, pH 7, 298.15 K). The obtained results, supported by the competitive interactions experiments of SDS with [B(Ph)4]− for BSA, enabled us to find the potential binding sites in BSA. The first site is located in the subdomain I A of the protein and binds two [B(Ph)4]− ions (logK(ITC)1 = 7.09 ± 0.10; ΔG(ITC)1 = −9.67 ± 0.14 kcal mol−1; ΔH(ITC)1 = −3.14 ± 0.12 kcal mol−1; TΔS(ITC)1 = −6.53 kcal mol−1), whereas the second site is localized in the subdomain III A and binds five ions (logK(ITC)2 = 5.39 ± 0.06; ΔG(ITC)2 = −7.35 ± 0.09 kcal mol−1; ΔH(ITC)2 = 4.00 ± 0.14 kcal mol−1; TΔS(ITC)2 = 11.3 kcal mol−1). The formation of the {[B(Ph)4]−}–BSA complex results in an increase in the thermal stability of the alfa-helical content, correlating with the saturation of the particular BSA binding sites, thus hindering its thermal unfolding.

Physicochemical nature of sodium dodecyl sulfate interactions with bovine serum albumin revealed by interdisciplinary approaches

To rigorously characterize the interactions of sodium dodecyl sulfate (SDS) with bovine serum albumin (BSA) a set of experimental methods, namely isothermal titration calorimetry, conductometric titration, steady-state fluorescence spectroscopy, differential scanning calorimetry and circular dichroism spectroscopy, supported by in silico analysis have been applied. The influence of pH and temperature on the binding mode has been revealed. At a low molar ratio of SDS to BSA up to ca. 16:1, there are at least two structurally distinct binding sites in BSA. The formation of SDS-BSA complexes is an enthalpy-driven process in which the van der Waals interactions play a crucial role. The first binding site, located close to the Trp-134 residue within the sub-domain IA, is pH-independent and binds two molecules of SDS per one molecule of BSA whereas the total number of SDS molecules bound to the second site of albumin is affected by temperature and pH. The saturation of the first binding site of BSA (ca. 0.009 mg of SDS per 1 mg of BSA) is sufficient to thermally stabilize the helical conformation of BSA. The presented results have important structural and thermodynamic implications to understand the influence of a widely used anionic surfactant on globular protein functionality in modern branches of chemistry.

Exploring the interactions of acenaphthene with bovine serum albumin: Spectroscopic methods, molecular modeling and chemometric approaches

The interaction of acenaphthene (ACN), a widespread environmental pollutant, with bovine serum albumin (BSA) was explored using spectroscopic methods, molecular modeling and chemometric approaches. The multivariate curve resolution-alternating least squares (MCR-ALS) analysis decomposed the overlapped excitation-emission matrix (EEM) spectra of mixture of ACN and BSA successfully and extracted spectral profiles of pure BSA, ACN and BSA-ACN complex. Based on fluorescence quenching analysis, ACN quenched the inherent fluorescence of BSA remarkably via a static mechanism. The obtained value of binding constant (Kb = 3.82 × 105 L mol−1) revealed a high binding affinity of ACN to BSA which facilitates its distribution by blood circulation system. Furthermore, the binding parameters values revealed that one binding site in BSA was involved in BSA-ACN complex. FT-IR, UV–Vis and CD spectra showed that the conformation of BSA was altered in presence of ACN slightly. Molecular docking simulation suggested that ACN was located in the IA region of BSA and the main interactions between ACN and BSA, are van der Waals forces. The obtained results provide some insight into interactions between ACN and serum albumins at the molecular level.

Molecular insight on the binding of stevia glycosides to bovine serum albumin

The interaction of the steviol and its glycosides (SG), steviolbioside, and rebaudioside A, with bovine serum albumin (BSA) was studied by absorption and fluorescence spectroscopy techniques alongside molecular docking. The stevia derivatives quenched the fluorescence of BSA by a dynamic quenching mechanism, indicating the interaction between the stevia derivatives and BSA. The binding constant (Kb) of steviol was 100-1000-fold higher than those of SG. The stevia derivative/BSA binding reaction was spontaneous and involved the formation of hydrogen bonds and van der Waals interactions between steviol and steviolbioside with BSA, and water reorganization around the rebaudioside A/BSA complex. Molecular docking pointed out the FA1 and FA9 binding sites of BSA as the probable binding sites of steviol and SG, respectively. In conclusion, steviol enhanced hydrophobicity and small size compared to SG may favor its binding to BSA. As steviol and its glycosides share binding sites on BSA with free fatty acids and drugs, they may be competitively displaced from plasma albumin under various physiological states or disease conditions. These findings are clinically relevant and provide an insight into the pharmacokinetics and pharmacodynamics of the stevia glycosides.

Interaction of acridinedione dye with a globular protein in the presence of site selective and site specific binding drugs: Photophysical techniques assisted by molecular docking methods

Photophysical investigations and molecular docking studies of photoinduced electron transfer (PET) based fluorophores of acridine family with a globular protein, Bovine Serum Albumin (BSA) bound to non-narcotic drugs like phenylbutazone (PB) and flufenamic acid (FA) were carried out in aqueous solution. PB and FA are site specific and site selective drugs, wherein PB predominantly binds at the site (I) whereas FA selectively orients towards site (II) of BSA. Acridinedione (AD) dyes, both resorcinol and dimedone based are hydrophobic in nature and exhibits a combination of both hydrophobic and hydrogen-bonding interactions that are based on the binding sites in BSA. The extent of displacement of AD from the binding sites of BSA by PB and FA are elucidated and established from variation in the fluorescence lifetime and relative amplitude distribution of free and dye bound in site (I) and site (II). The extent of binding affinity of PB-BSA and FA-BSA in the presence of AD is minimal when compared to other site I and II drugs. This is attributed to AD dye bound to several amino acid residues present in BSA such that the dye prefers multiple binding sites in BSA even in the presence of FA and PB. Further, the dye bound to several amino acid residues of BSA ascertains the combination of hydrogen-bonding, hydrophobic interactions, pi-pi and pi-alkyl interaction apart from the binding through sites (I) and (II) from molecular docking methods. The combination of fluorescence tools with molecular modelling techniques provides an excellent approach in determining the stability of these complexes containing competitive guest molecules in the presence of a fluorescence probe and the binding characteristics of dye in a micro heterogeneous environment.

DNA/BSA binding of a new oxovanadium (IV) complex of glycylglycine derivative Schiff base ligand

In this study, a new oxovanadium (IV) Schiff base complex was synthesized by the reaction of {[5-(triethylammoniummethyl)salicylaldehyde]chloride}triethylammonium and vanadyl sulfate. The complex was characterized by elemental analysis, FT-IR and UV–Vis spectroscopy. The interaction between the complex and bovine serum albumin (BSA) was studied by absorption and emission titration methods. The quality of the spectral changes and the large calculated value of both the binding constant (Kb = 7.53 × 104 M−1) and the Stern-Volmer quenching constant (KSV = 7.65 × 104 M−1) proved the strong affinity of the complex to BSA. The static quenching mechanism was confirmed by comparing the calculated Kb values at four different temperatures. The negative changes in enthalpy and Gibbs free energy, proved that the BSA-complex binding is exothermic and spontaneous. The fluorescence data also indicated 1:1 binding stoichiometry of the complex on one binding site of BSA. Competitive experiments with site markers (phenylbutazone and ibuprofen) and synchronous measurements identified site I of BSA as the main binding site. Molecular docking results confirmed the binding pocket of site I (subdomain IIA) as the binding site. In the second part of the work, the binding of the complex to fish sperm DNA (FS-DNA) was investigated by UV–Vis absorption spectroscopy, fluorescence spectroscopy, viscosity measurement and cyclic voltammetry. The Stern-Volmer quenching and bimolecular quenching rate constants (KSV = 6.13 × 102 M−1, kq = 6.13 × 1010 M−1S−1) were calculated. Absorption and emission studies could present types of interactions for example groove binding and electrostatic. A minor changes in viscosity showed a groove binding mode. In cyclic voltammogram study, decrease in current and also shift of peak potentials positively after adding DNA supported a partial intercalation mode. Theoretical docking study proposed the minor groove as the main part for DNA-complex binding.

Poziotinib and bovine serum albumin binding characterization and influence of quercetin, rutin, naringenin and sinapic acid on their binding interaction.

Serum albumin is the major transporter protein present in systemic circulation and the ability to transport ligands can be influenced in presence of other ligands. This interaction can influence the pharmacodynamic and pharmacokinetic property of certain ligands. Spectroscopic and molecular docking studies were conducted to understand the poziotinib binding interaction to bovine serum albumin (BSA). Further, influence of different flavonoids (quercetin, rutin, naringenin and sinapic acid) on displacing poziotinib from BSA binding sites was also studied. The BSA and poziotinib followed a static quenching mechanism as the Stern-Volmer constant showed decrease (7.6×104-6.0×104) when the temperature increased from 298K to 310K. The BSA and poziotinib interaction was spontaneous and enthalpy driven. Involvement of Van der Waals forces and hydrogen bonding in the binding interaction was suggested on the basis of thermodynamic study results. Conformational changes were suggested in the BSA on its interaction with poziotinib based on fluorescence experimental data. The binding constant for BSA-poziotinib showed a maximum decrease in presence of quercetin followed by naringenin, rutin and sinapic acid respectively. Site displacement studies suggested binding of poziotinib site I of BSA.

Investigation of the Interaction of Chrysene and Bovine Serum Albumin by Multispectroscopic Method

The interaction mechanisms of chrysene with bovine serum albumin (BSA) were studied by multispectroscopy and molecular docking method. The quenching mechanism, binding constants, thermodynamic parameters and binding force of chrysene with BSA were investigated. The results indicated that the fluorescence of BSA was quenched by chrysene through a static quenching procedure. The binding constants K b and number of binding sites n were 3.97 × 104 M–1 and 1.0 at 298 K, respectively, which indicated that the binding of chrysene and BSA was moderate and there was one main binding site in BSA for chrysene. The thermodynamic parameters including entropy change (ΔH) and enthalpy change (ΔS) were 40.2 kJ mol–1 and 223.0 J mol–1 K–1, respectively, which revealed that the main binding force of chrysene to BSA was hydrophobic interaction. This result was in accordance with the results from the molecular docking. The binding distance r was 2.60 nm, which suggested that the energy transfer from BSA to chrysene occurred with high possibility. The results of synchronous fluorescence spectra, three-dimensional fluorescence spectra and circular dichroism spectra indicated that the binding of chrysene to BSA induced conformation changes of BSA.

How does cholinium cation surpass tetraethylammonium cation in amino acid-based ionic liquids for thermal and structural stability of serum albumins?

In this study, we report how similarly two serum albumins (bovine serum albumin (BSA) and human serum albumin (HSA)) respond in the presence of different concentration of aromatic amino acid based ionic liquids (AAILs), which are cholinium tryptophan [CHO][Trp]IL and tetraethylammonium tryptophan [TEA][Trp]IL. Extended results of thermodynamic stability indicate the extent to which both serum albumins differ in their thermal stability despite having structural similarity in presence of AAILs. To efficiently quantify the results, biomolecular interactions studies were carried out between serum albumins and AAILs with the help of differential scanning calorimetry (DSC), dynamic light scattering (DLS) and various spectroscopic techniques. DSC results illustrated that both AAILs are increasing the thermal stability of BSA and HSA, as per transition temperature (Tm) values, BSA (65.51 to 72.46 °C) and HSA (65.46 to 75.97 °C) have more thermal stability in the presence of [CHO][Trp]IL as compare to [TEA][Trp]IL, BSA (65.51 to 69.75 °C) and HSA (65.46 to 72.08 °C). Secondary structure results obtained using Dichroweb software and selcon calculations. Furthermore, to illustrate the specific binding of AAIL's cations or anions with the binding sites of BSA and HSA, the molecular docking studies were also performed using Molegro trail version v 6.0.

Spectroscopic demonstration of sinapic acid methyl ester complexes with serum albumins.

The methyl ester of sinapic acid (MESA) is a molecule with confirmed antioxidant properties. It is important to establish whether it can be transported across humans and animals. Therefore, we investigated MESA interactions with serum albumins, namely, human serum albumin (HSA), bovine serum albumin (BSA), rabbit serum albumin (RSA), and sheep serum albumin (SSA). Experiments were performed in a pH range from 5.9 to 10.7 using absorption and fluorescence techniques. It was found that MESA formed complexes with every albumin in the entire pH range under examination, which was confirmed by the appearances of new absorption and fluorescence complex bands. Fluorescence intensities were much higher (up to 20 times) and lifetimes were up to 340 times as compared to those for unbound MESA. The quenching experiments at pH 7.4 showed that the stoichiometry for every albumin was 1 : 1; the binding constant was the highest for HSA, which reached 52 000 M−1. The obtained results suggested that MESA preferred the hydrophobic binding sites in albumins. The analysis of the fluorescence spectra and fluorescence lifetimes showed two possibly different binding sites in BSA, RSA, and SSA as well as three binding sites in HSA.

Characterization of the binding of cyanidin-3-glucoside to bovine serum albumin and its stability in a beverage model system: A multispectroscopic and chemometrics study

Anthocyanins as one of the main natural groups of food colorants undergo quick color fading, which can be diminished through protein association. The stabilization of cyanidin-3-glucoside (CYG) through binding to bovine serum albumin (BSA) was investigated at pH 3.0 using atomic force microscopy and differential scanning calorimetry along with UV–Vis absorption, steady-state fluorescence, circular dichroism, and three-dimensional emission spectral analyses merged with the multivariate curve resolution-alternative least square method. The stabilized CYG molecules were found at the site II of BSA with combined static and dynamic quenching mechanisms. Approximately 93% of the BSA binding sites were occupied in the BSA-CYG complex through hydrogen bonds and van der Waals forces with the binding constant and stoichiometry ratio of 1.88 × 105 M−1 and 1:13, respectively. The results also revealed that CYG molecules caused partial unfolding of the BSA structure, while it was not enough for significant alteration of denaturation temperature. The binding results also indicated that the reduction of H2O2-induced-CYG oxidation rate (34.78%) at pH 3.0 was mainly driven via the BSA-hemiketal association, although the colored species of CYG had a greater affinity towards BSA in the equilibrated system at pHs 1.0 and 5.0.