Structure Of Bovine Serum Albumin Research Articles

Characterization of the covalent binding of cyanidin-3-glucoside to bovine serum albumin and its inhibition mechanism for advanced nonenzymatic glycosylation reactions.

Nonenzymatic glycosylation of proteins can generate advanced glycosylation end products, which are closely associated with the pathogenesis of certain chronic physiological diseases and aging. In this study, we characterized the covalent binding of cyanidin-3-glucoside (C3G) to bovine serum albumin (BSA) and investigated the mechanism by which this covalent binding inhibits the nonenzymatic glycosylation of BSA. The results indicated that the covalent interaction between C3G and BSA stabilized the protein's secondary structure. Through liquid chromatography-electrospray ionization tandem mass spectrometry analysis, we identified the covalent binding sites of C3G on BSA as lysine, arginine, asparagine, glutamine, and cysteine residues. This covalent interaction significantly suppressed the nonenzymatic glycosylation of BSA, consequently reducing the formation of nonenzymatic glycosylation products. C3G competitively binds to nonenzymatic glycosylation sites (e.g., lysine and arginine) on BSA, thereby impeding the glycosylation process and preventing the misfolding and structural alterations of BSA induced by fructose. Furthermore, the covalent attachment of C3G to BSA preserves the secondary structure of BSA and hinders subsequent nonenzymatic glycosylation events.

Binding and displacement study of gentamicin, 5-fluorouracil, oxytetracycline and rolitetracycline with (BSA: Drug2) complex using spectroscopic and calorimetric techniques: Biophysical approach

Understanding of energetics of interactions between drug and protein is essential in pharmacokinetics and pharmacodynamics study. The binding affinity (K) helps in investigating how tightly or loosely drug is bound to protein. The binding, displacement, conformational change and stability study of drugs- gentamicin (GM), 5-Fluorouracil (5FU), oxytetracycline (OTC) and rolitetracycline (RTC) with bovine serum albumin (BSA) has been carried out in presence of each other drug by fluorescence, UV–visible spectroscopy, molecular docking, circular dichroism techniques and thermal denaturation method. The site marker study and docking methods have confirmed that 5FU and GM are able to bind at site 1 and OTC and RTC at site II of BSA. The order of their binding affinities with BSA for the binary system were as GM <5FU < OTC < RTC with the order of 102 < 103 < 105 < 105–6 M−1. The displacement study has shown that higher affinity drug decreases the equilibrium constant of another drug already in bound state with BSA if both these drugs are having the same binding site. Therefore 5FU, GM (binding site 1) drugs were not able to displace OTC and RTC (binding site 2) and vice-versa as they are binding at two different sites. The binding constant values were found to be decreasing with increasing temperature for all the systems involved which suggests static or mixed type of quenching, however can only confirmed with the help of TCSPC technique. The ΔG0 (binding energy) obtained from docking method were in accordance with the ITC method. From molecular docking we have determined the amino acid residues involved in binding process for binary and ternary systems by considering first rank minimum binding energy confirmation. From CD it has been observed that RTC causes most conformational change in secondary and tertiary structure of BSA due to the presence of pyrrole ring. OTC-RTC with higher affinity showed highest melting temperature Tm values while low affinity drugs in (5FU-GM) combination showed lowest Tm value. 5FU showed large endothermic denaturation enthalpy ΔHd0 due to the presence of highly electronegative fluorine atom in the pyridine analogue.

BSA Binding and Aggregate Formation of a Synthetic Amino Acid with Potential for Promoting Fibroblast Proliferation: An In Silico, CD Spectroscopic, DLS, and Cellular Study.

This study presents the chemical synthesis, purification, and characterization of a novel non-natural synthetic amino acid. The compound was synthesized in solution, purified, and characterized using NMR spectroscopy, polarimetry, and melting point determination. Dynamic Light Scattering (DLS) analysis demonstrated its ability to form aggregates with an average size of 391 nm, extending to the low micrometric size range. Furthermore, cellular biological assays revealed its ability to enhance fibroblast cell growth, highlighting its potential for tissue regenerative applications. Circular dichroism (CD) spectroscopy showed the ability of the synthetic amino acid to bind serum albumins (using bovine serum albumin (BSA) as a model), and CD deconvolution provided insights into the changes in the secondary structures of BSA upon interaction with the amino acid ligand. Additionally, molecular docking using HDOCK software elucidated the most likely binding mode of the ligand inside the BSA structure. We also performed in silico oligomerization of the synthetic compound in order to obtain a model of aggregate to investigate computationally. In more detail, the dimer formation achieved by molecular self-docking showed two distinct poses, corresponding to the lowest and comparable energies, with one pose exhibiting a quasi-coplanar arrangement characterized by a close alignment of two aromatic rings from the synthetic amino acids within the dimer, suggesting the presence of π-π stacking interactions. In contrast, the second pose displayed a non-coplanar configuration, with the aromatic rings oriented in a staggered arrangement, indicating distinct modes of interaction. Both poses were further utilized in the self-docking procedure. Notably, iterative molecular docking of amino acid structures resulted in the formation of higher-order aggregates, with a model of a 512-mer aggregate obtained through self-docking procedures. This model of aggregate presented a cavity capable of hosting therapeutic cargoes and biomolecules, rendering it a potential scaffold for cell adhesion and growth in tissue regenerative applications. Overall, our findings highlight the potential of this synthetic amino acid for tissue regenerative therapeutics and provide valuable insights into its molecular interactions and aggregation behavior.

Inhibition and Mechanism of Protein Nonenzymatic Glycation by Lactobacillus fermentum.

Lactobacillus fermentum (L. fermentum) was first evaluated as a potential advanced glycation end-product (AGE) formation inhibitor by establishing a bovine serum albumin (BSA) + glucose (glu) glycation model in the present study. The results showed that the highest inhibition rates of pentosidine and total fluorescent AGEs by L. fermentum were approximately 51.67% and 77.22%, respectively, which were higher than that of aminoguanidine (AG). Mechanistic analysis showed that L. fermentum could capture methylglyoxal and glyoxal, inhibit carbonyl and sulfhydryl oxidation, reduce the binding of glucose and amino groups, increase total phenolic content and antioxidant activity, and release intracellular substances to scavenge free radicals; these abilities were the basis of the antiglycation mechanism of L. fermentum. In addition, L. fermentum significantly prevented conformational changes in proteins during glycation, reduced protein cross-linking by 35.67%, and protected the intrinsic fluorophore. Therefore, the inhibition of L. fermentum on glycation mainly occurs through antioxidation, the capture of dicarbonyl compounds, and the protection of the BSA structure. These findings collectively suggest that Lactobacillus is an inhibitor of protein glycation and AGE formation and has the potential for nutraceutical applications.

Bovine serum albumin-liposome stabilized high oil-phase emulsion: Effect of liposome ratio on interface properties and stability

This study aimed to solve the issue of poor lipophilicity of natural bovine serum albumin (BSA) by combining with liposomes (Lips) to stabilize high oil-phase emulsions (HOPEs). The interaction between BSA and Lips was mainly driven by hydrophobic forces, followed by hydrogen bonding. The secondary structure and tertiary structure of BSA were characterized and indicated that the addition of Lips promoted the structural expansion of BSA exposing the hydrophobic groups inside. Interfacial adsorption behaviours were assessed through dynamic interfacial tension, three-phase contact angle, and quartz crystal microbalance with dissipation. These results indicated that BSA-Lips crosslinking improved wettability, promoting adsorption and rearrangement at the oil-water interface, thereby resulting in a dense interfacial layer. The emulsifying efficacy of BSA-stabilized HOPEs also displayed a distinct Lips dependency. Varying the BSA-to-Lips ratio transformed their consistency from flowing to semi-solid, reinforcing the gel network. Under optimal conditions (BSA: Lips = 1:1), the droplet size of BSA-Lips stabilized HOPEs reached a minimum with a highly uniform distribution. Moreover, a 1:1 BSA to Lips ensured outstanding storage, thermal, and centrifugal stability for the HOPEs. This work provides valuable references for the interaction between protein and Lips, guiding the development of highly stable HOPEs stabilizers.

5-methyl-salicylaldoxime based ionic liquids for non-destructive separation of protein and cadmium

Confronting with explosive cadmium contaminations to environment, non-destructive separation of protein with cadmium for protecting food safety is hardpressed. Ionic liquids (ILs) are benign bio-compatible stabilizer of proteins with considerable metal affinity, while their application in separation of cadmium from protein is limited owing to their comparative metal affinities with protein. Accordingly, we firstly synthesize 1-methyl-3 (salicylaldoxime-5-methyl) imidazole hexafluorophosphate ([Salenmim][PF6]) to enhance cadmium extraction with hydroxyl and oxime groups as ligands of cadmium. Structure of [Salenmim][PF6] is confirmed by 1H NMR, 13C NMR, 31P NMR, 19F NMR, FT-IR, Raman spectra, and theoretical simulations. [Salenmim][PF6] can remove 85.31 % of Cd2+ from bovine serum albumin (BSA) at pH of 2.0. X-ray photoelectron spectroscopy (XPS) of BSA and [Salenmim][PF6] before and after Cd2+ extraction illustrate that Cd2+ generally bonds with C = N and O-H of [Salenmim][PF6] to achieve detachment of Cd2+ from BSA. Molecular docking of BSA and Cd2+ indicates that 4 amino acids residues listed as ASP561, ASP562, LYS563, and GLU564 coordinate with Cd2+ with coordinate number close to 1, further confirmed as 1.48 by isothermal titration calorimetry (ITC) analysis. DFT calculations of [Salenmim][PF6] with Cd2+ demonstrate that energy gap between HOMO orbital localized at benzene ring is 1.6860 eV higher than LUMO orbital, faciliating formation of [Salenmim][PF6]-Cd2+ complex. Finally, there are no changes in secondary and tertiary structure of BSA and no ILs residual observed after [Salenmim][PF6] assisted Cd2+ extraction. This work firstly reports a method for synthesis of [Salenmim][PF6] with high affinity to cadmium and systemically reveals how do structure of [Salenmim][PF6] enhance heavy metal removal from proteins, providing a possible strategy for heavy metal extraction from proteins.

Serum albumin hydrogels designed by protein Re-association for self-powered intelligent interactive systems

Advancements in protein structural engineering have made it possible to design protein materials that can mediate between humans and intelligent systems, manifesting a combination of characteristics such as elastic recovery, electrical conductivity, and stability. This work describes the design of a hydrogel using bovine serum albumin (BSA), based on protein-protein interactions and sulfhydryl-alkene click reactions. The multiple α-helices of BSA were intertwined together by the multi-armed olefin derivatives, acting like Lego blocks to form a gel network and locking in bound water and ions, thus imparting mechanical recovery characteristics (demonstrating 80 % recovery after the compressive strain and 638 % after tensile strain), electrical conductivity, resistance to freezing (maintaining mechanical properties after being frozen at -20 °C for 48 h), biocompatibility (the cell viability of mouse pre-osteoblast-like cells in the hydrogels was 97.5 %), antimicrobial properties, and biodegradability to the BSA hydrogels. A multi-channel wireless signal acquisition system based on BSA hydrogel devices designed for bioenergy conversion and harvesting was developed for the real-time detection of human motion along with a human-mechanics interaction system for manipulating robotic gestures with simple human finger movements. This restructuring of the BSA structure represents a significant advancement in the systematic exploration of protein structures and the development of protein materials. These applications serve as a secure bridge between humans and energy storage devices.

Multiple spectroscopic and computational studies on binding interaction of 2-phenylamino-4-phenoxyquinoline derivatives with bovine serum albumin

Binding characteristics of potent non-nucleoside HIV-1 reverse transcriptase inhibitors, 4-(2′,6′-dimethyl-4′-formylphenoxy)-2-(5″-cyanopyridin-2″ylamino) quinoline (1) and 4-(2′,6′-dimethyl-4′-cyanophenoxy)-2-(5″-cyanopyridin-2″ylamino) quinoline (2), to bovine serum albumin (BSA) under simulative physiological conditions were investigated by multiple spectroscopic and computational methods. The experimental results demonstrated that (1) and (2) bound to BSA at site III (subdomain IB), and quenched BSA fluorescence through a static quenching process. The binding interaction of (1) or (2) to BSA forms stable complexes with the binding constants (Kb) at the level of 104 L/mol and the number of binding site was determined to be 1 for both systems, indicating that new synthesized compounds occupied one site in BSA with moderate binding affinities. Based on the analysis of the thermodynamic parameters, it can be indicated that the main binding forces for interaction between BSA and both compounds were hydrogen bonding and van der Waals force. Synchronous fluorescence results revealed that the interaction of two compounds with BSA led to modifications in the microenvironment surrounding tryptophan residue of BSA. Circular dichroism spectra demonstrated alterations in the secondary structure of BSA induced by (1) and (2). Moreover, the experimental data of molecular docking and molecular dynamics (MD) simulations supported the results obtained from multiple spectroscopic techniques, confirming the binding interactions between both compounds and BSA.

A chondroitin sulfate purified from shark cartilage and bovine serum albumin interaction activity

Chondroitin sulfate (CS) was extracted and purified from shark cartilage, and its interaction with bovine serum albumin (BSA) were studied. The content of chondroitin sulfate in shark cartilage was 29.97 % using the 1,9-dimethyl-methylene blue method. The molecular weight of CS was determined to be 62.464 kDa by high-performance gel permeation chromatography. UV and FT-IR spectroscopy identified the characteristics of CS and its functional group information. NMR spectroscopy and disaccharide derivatization revealed that CS was predominantly composed of disulfated disaccharides, specifically ΔDi4,6S. Fluorescence quenching experiments indicated that the interaction between CS and BSA exhibited static quenching, with a binding site number of 1. The binding process was primarily mediated by van der Waals forces and hydrogen bonds. Furthermore, synchronous and 3D fluorescence spectroscopy demonstrated that CS had minimal impact on the polarity and hydrophobicity of the microenvironment surrounding Tyr and Trp residues. UV–vis absorption and circular dichroism (CD) spectroscopy demonstrated the altered structure of BSA. The molecular docking analysis revealed that CS formed hydrogen bonds and salt bridges with BSA, predominantly binding to the IIA substructure domain of BSA. Investigating the interaction between CS and BSA holds the potential for enhancing its applications in drug delivery and tissue engineering endeavors.

Changes in Secondary Structure and Properties of Bovine Serum Albumin as a Result of Interactions with a Gold Surface.

The front cover artwork is provided by Prof. Barbara Jachimska's group at the Jerzy Haber Institute of Catalysis and Surface Chemistry, PAS. The image represents the process of changes in the secondary structure of Bovine Serum Albumin (BSA) as a result of its interactions with a gold surface. Read the full text of the Research Article at 10.1002/cphc.202300505.

Revisiting the conformational transition model for the pH dependence of BSA structure using photoluminescence, circular dichroism, and ellipsometric Raman spectroscopy

Changes in pH affect metabolic pathways, primarily by modulating enzyme conformations, which is why a detailed analysis of pH-driven conformational transitions is required to understand the underlying biochemistry of diseases and biological organisms. In this work, we examined the pH-driven conformational dynamics of Bovine Serum Albumin (BSA), within the framework of the Foster Model. Circular Dichroism and Raman Optical Activity showed the conversion of helical into β-rich structures in the acid and basic regions, while an opening of BSA tertiary structure was shown by the upsurging of accessibility of ANS-BSA binding sites and the increasing of random contributions at regions F and B. We could then revisit the Foster Model by introducing two additional intermediate conformational states and structural reorganization at extreme pH values. This expanded model opens up new possibilities concerning protein-molecule interactions, promising far-reaching implications for fields such as drug design and biomaterials.

Application of the switchSENSE® technology for real-time study of pesticides interaction with biological molecules

Organochlorine pesticides have been extensively utilized in agriculture and pest control, and still contributing to numerous health issues. However, the mechanism underlying the transportation of these compounds through animal and human body is not well understood. The switchSENSE® technology is an original and powerful tool in biosensing, which demonstrates high sensitivity in detecting a variety of biological interaction which involves proteins, nucleic acids and small molecules. There has been a growing interest in using switchSENSE® technology for detecting interactions between proteins and environmental pollutants in recent years. Therefore, the aim of this study is to refine and enhance the methodology of the switchSENSE® technology to facilitate characterization of real time interaction between biological transport molecule, bovine serum albumin (BSA), and organochlorine pesticides. Using this technology, we noticed the conformational change in structure and protein hydrodynamic diameter (DH) of BSA in response to Chlordecone (CLD) and Dichlorodiphenyltrichloroethane (DDT). We also identified the possible obstacles, that should be resolved in future researches.

Insight into the effect of synthesis parameters on the properties of graphene quantum dots for theranostic application

Ultra-small size and tunable optical properties of graphene quantum dots (GQDs) make them potentially suitable for theranostic applications. This investigation focuses on the effect of process parameters for the synthesis of GQDs of desirable optical properties for biomedical applications. The effect of the raw materials (graphene oxide sheets, glucose, and starch), reaction temperature (170 to 200 °C), and reaction time (3 to 6 h) was investigated on GQDs prepared through hydrothermal treatment. The dispersion of GQDs was characterized using dynamic light scattering (DLS), UV–visible, fluorescence, Raman, and X-ray photon spectroscopic techniques. The effect of the solution temperature and pH on the fluorescence properties of GQDs was also studied. The small hydrodynamic diameter (8.57 ± 1.47 nm) was observed with GQDs prepared from glucose using hydrothermal treatment time of 4 h at 190 °C (GQDs-D). The GQDs-D showed blue fluorescence (λem= 460 nm) with a quantum yield (QY) 67.09 ± 1.25%. The fluorescence characteristic of the GQDs was unchanged up to 6 months during storage at room temperature. GQDs-D revealed their antioxidant nature with a DPPH scavenging activity of 15.08 ± 2.07%. Despite having relatively low DPPH scavenging activity, excellent hemocompatibility (0.23 ± 0.04%) and colloidal stability against bovine serum albumin (BSA) showed GQDs-D as a safe nanocarrier for theranostic application. This was further substantiated with circular dichroism (CD) spectroscopy, which exhibited a preserved α-helical structure of BSA by GQDs-D. High-resolution transmission electron microscopic image of GQDs-D showed an average particle size of 5.70 nm and homogeneous particle distribution between 2–8 nm. Conclusively, all the results revealed the potential of GQDs-D for theranostic application.

Spectroscopic and computational approaches to investigate the binding mechanism of multi-purpose dye pararosaniline with serum albumin protein

Pararosaniline (PRN) is a significant carcinogenic threat to human, animal, and environmental health and is classified as a Category 2B carcinogen. Investigating the binding interactions of PRN with Bovine Serum Albumin (BSA) is crucial to understand the toxic effects of this carcinogenic dye within the body. This study examined the interaction between PRN and BSA using various spectroscopic techniques and computational methods. Fluorescence spectroscopy was used to determine the thermodynamic parameters required to form the complex and the stability and interactions between them were examined through molecular docking and dynamic simulations. Conformational analysis of the PRN-BSA complex was conducted through Circular Dichroism and Dynamic Light Scattering studies, corroborated by Molecular Dynamics results. The experimental results underscored the dynamic nature of this interaction, showcasing effective binding at physiological temperatures without inducing major conformational alterations in BSA structure. The stability of the complex was attributed to strong hydrophobic interactions with specific amino acid residues in subdomain IB of domain I, as well as notable van der Waals interactions between the dye and water molecules. A detailed energetic assessment of the stable complexation was monitored through MM/PBSA and QM calculations, aligning well with the experimental results. This study provides critical insights into the underlying mechanism of the interaction between PRN and BSA, which can further aid in understanding the toxic effects and potential bioavailability of similar molecules.

Experimental and hypothetical appraisal on inhibition of glucose-induced glycation of bovine serum albumin by quercetin

BackgroundThe specificity of protein functions depends on its folding ability into a functional structure. Protein folding is an essential systemic phenomenon that prevents incorrect folding which could result in harmful aggregation. This harmful aggregation of proteins causes neurodegenerative diseases and systemic amyloidosis. Experimental and theoretical approaches were used in this study to explicate the probable mechanisms of action of quercetin in inhibition of glucose-induced glycation through estimations of percentage glycated protein, inhibited induced protein aggregation, and unoxidized bovine serum albumin thiol groups and assessments of molecular interactions of quercetin with the structures of bovine serum albumin, amyloid beta-peptide (1–42) and 3D amyloid-beta (1–42) fibrils retrieved from the protein databank (http://www.rcsb.org). ResultsThe results showed quercetin inhibited the formation of glycated protein, protein aggregation, and thiol oxidation in a concentration-dependent manner where 200 μg/ml showed the highest inhibition while 50 μg/ml depicted the least inhibition in all the studied assessments. From the docking analysis, it was observed that quercetin had a significantly higher binding affinities − 8.67 ± 0.09 kcal/mol, − 5.37 ± 0.05 kcal/mol and − 5.93 ± 0.13 kcal/mol for the bovine serum albumin, amyloid beta-peptide (1–42) and 3D amyloid-beta (1–42) fibrils respectively compared to the glucose, the inducer. Quercetin and glucose interacted with amino acid residues at the BSA subdomain IIA thus providing a clue that quercetin may impose its inhibition through the binding domain. Also, it is important to mention that the phytochemicals shared a similar interaction profile as that of glucose with the amyloid-beta. ConclusionsThese findings established the beneficial effects of quercetin as a potential agent that could alleviate hyperglycaemic-initiated disorders associated with elevated serum glucose levels.

AN IN SILICO PHARMACOKINETIC INVESTIGATION OF ORGANIC LUMINOGENS: UNDERSTANDING THE NIR AIEGENS AND THEIR INTERACTIONS WITH SERUM ALBUMINS

Objective: Fluorescence imaging (FLI) is accepted as a highly effective method for visualizing bioanalytics directly and gaining insight into complicated biological structures and processes. In this context, newly tailored organic molecules, which have the potential to be used in FLI, especially near-infrared (NIR) regions supported by aggregation-induced emission luminogens (AIEgens), are a rapidly developing area of study. Herein, using ADMET and molecular docking analyses, we examined the pharmacokinetic properties of both model (D2-A2-D2) and newly designed (Dn-An-Dn) organic luminogens to interact with blood proteins, namely bovine serum albumin (BSA) and human serum albumin (HSA), which have emerged as a versatile carrier of several therapeutic agents against preliminary cancer and infectious diseases. Material and Method: The structural properties of the examined luminogens were computed using the Gaussian 09 software package. The DFT/B3LYP/6-31G(d,p) level was then utilized for geometry optimization and accurately determining electronic structures and molecular properties. Lipinski's rule of five was applied to predict the drugability of the compounds using the SwissADME web tool. Molinspiration was used for further validation of these properties and additional bioactivity parameters. Toxicity parameters were evaluated with OSIRIS Property Explorer (v.4.5.1). Molecular docking simulations of the luminogen-albumin complexes were performed using SAMSON 2022 R2 modeling platform and implemented Autodock-vina extension. The X-ray crystal structures of bovine serum albumin (BSA, PDB ID: 4F5S) and human serum albumin (HSA, PDB ID: 4L9Q) were obtained from the Protein Data Bank. Visualization of the docking interactions was conducted using Discovery Studio Visualizer 2021. Result and Discussion: The compounds D1-A1-D1 and D1-A4-D1 stood out concerning molecular weight (MW) and ClogPo/w values, making them promising candidates for drug design. An analysis of lipophilicity revealed that these two compounds displayed high miLogP values, indicating a high degree of lipophilicity, which is generally beneficial for drug delivery. They also exhibited moderate bioactivity based on GPCR ligand and protease inhibitor (PI) parameters. On the other hand, D4-A3-D4 showcased paramount interaction with bovine serum albumin (BSA), while D5-A3-D5 demonstrated the highest binding affinity with human serum albumin (HSA).

Spectroscopic study of drug–drug interactions: influence of two over-the-counter drugs on the albumin binding affinities of carbamazepine and its major metabolite

BackgroundMultidrug regimens can increase the risk of drug–drug interactions at the level of albumin binding especially for drugs with narrow therapeutic windows such as carbamazepine (CBZ). This risk is particularly heightened for CBZ which is mainly metabolized to the active carbamazepine-10,11-epoxide (CBZE) that has been identified as contributory to both the therapeutic efficacy and severity of toxicity in CBZ-treated individuals. The objective of this study was to investigate the binding affinities of albumin with CBZ and CBZE, and to explore the influence of two competing over-the-counter medicines on the binding characteristics. CBZE was synthesized by epoxidation of CBZ and characterized using IR, NMR and mass spectrometry. The influence of paracetamol and ascorbic acid on the albumin complexes of CBZ and CBZE was investigated using absorption and IR spectrophotometry.ResultsProtein–ligand complexation produced progressive hyperchromic changes in 278 nm band of bovine serum albumin (BSA) with formation constants of 10.28–10.44 and 12.66–13.02 M−1 for CBZ and CBZE, respectively. Thermodynamic considerations confirmed both binding processes as endothermic, spontaneous and driven by hydrophobic interactions. The presence of ascorbic acid increased the binding constants of both CBZ-BSA and CBZE-BSA complexes by non-competitive interference mechanism. Similarly, paracetamol increased the affinity of CBZ for albumin but then competitively interfered with the CBZE-BSA complex. The ratio of albumin binding affinities of CBZ–CBZE varied from 0.81 in the absence of competing drug to 1.29 and 1.0 with paracetamol and ascorbic acid, respectively. IR study confirmed that both CBZ and CBZE induced a reduction from the 67.34% α-helical content of free BSA to 42.56 and 56.43%, respectively. Competitive binding in the presence of either paracetamol or ascorbic acid induced further reduction in the α-helical content of BSA in the complexes. The most extensive perturbation in the secondary structure of BSA (22.78% α-helical content) which was observed with CBZE-BSA complex in the presence of paracetamol is probably due to the increased interaction of the protein for the analgesic.ConclusionThe study has revealed potential interference of paracetamol or ascorbic acid with the albumin binding of carbamazepine and its major metabolite.

Serum albumin acted as an effective carrier to improve the stability of bioactive flavonoid.

The health-improving functions of bioactive flavonoids in vitro and in vivo are often limited by their low stability, which could be counteracted by the application of proteins as carriers of flavonoids. Clarification of the mechanism of protein-ligand interaction is crucial for the encapsulation of bioactive components. Herein, common plasma proteins [i.e., bovine serum albumin (BSA), human serum albumin (HSA), human immunoglobulin G (IgG) and fibrinogen (FG)] were compared for their binding characteristics to quercetin, the main component of flavonoids in human diet, in the absence and presence of free Cu2+ (anaccelerator for flavonoids' instability) using multi-spectroscopic and computational methods. As a flexible open structure of proteins, both BSA and HSA were found to be the most promising carriers for quercetin and Cu2+ with an affinity on the order of 104M-1. HSA-diligand complex (i.e., HSA-quercetin-Cu2+) was successfully generated when both quercetin and Cu2+ were added to the HSA solution. The stability and free radical scavenging activity of bioactive quercetin during incubation was promoted in the HSA-diligand complex relative to quercetin-Cu2+ complex. Quercetin/Cu2+ system could induce the formation of reactive oxygen species such as hydrogen peroxide (H2O2) and hydroxide radical (·OH), which were significantly suppressed upon HSA binding. Consistently, the cytotoxicity of the quercetin/Cu2+ system to endothelial cells was reduced in the HSA-diligand complex. These results demonstrate the possibility of developing serum albumin-based carriers for the protection of bioactive flavonoids in their nutritional application.

Ascorbic and salicylic acids modulate the binding interactions of an emergency contraceptive pill levonorgestrel to a model transport protein: Insights from spectroscopy and molecular docking analysis

Serum proteins generally help to transport and distribute drug molecules within the body. In this study, the binding characteristics of bovine serum albumin (BSA) with levonorgestrel (LVG), an emergency contraceptive pill, and the influences of ascorbic acid (ASC) and salicylic acid (SAL) on the binding behaviour and protein structure were elucidated using multi-spectroscopic techniques and molecular docking. The results showed that levonorgestrel decreased BSA intrinsic fluorescence via static quenching mechanism. Binding constant (Ka) values for BSA-LVG complexes were 103 to 104 M-1, indicating their high stabilities. Site probing/docking analysis indicated LVG bound between BSA subdomains IIA and IIIA. UV–visible absorption, Fourier Transform-Infrared and 3D fluorescence spectroscopies affirmed LVG-induced changes in BSA structure, especially in α-helix and β-sheet contents. ASC and SAL influenced BSA conformation for LVG binding and reduced the Ka values by 3.37 and 5.43-folds, respectively. LVG altered the microenvironments of tyrosine residues, interacted with Arg-217, Lys-221, Val-292, Glu-443 etc. within the binding domains. The process was spontaneous (ΔG<0), entropy driven (TΔS>ΔH) and involved van der Waals forces and hydrogen bonding. The findings of the study offered details on the binding interaction between BSA and LVG, and also indicated that prior intake of ASC or SAL could suppress the binding affinity of BSA for levonorgestrel.

Unveiling the Three-Step Model for the Interaction of Imidazolium-Based Ionic Liquids on Albumin.

The effect of the ionic liquids (ILs) 1-methyl-3-tetradecylimidazolium chloride ([C14MIM][Cl]), 1-dodecyl-3-methylimidazolium chloride ([C12MIM][Cl]), and 1-decyl-methylimidazolium chloride ([C10MIM][Cl]) on the structure of bovine serum albumin (BSA) was investigated by fluorescence spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, small-angle X-ray scattering (SAXS), and molecular dynamics (MD) simulations. Concerning the fluorescence measurements, we observed a blue shift and a fluorescence quenching as the IL concentration increased in the solution. Such behavior was observed for all three studied imidazolium-based ILs, being larger as the number of methylene groups in the alkyl chain increased. UV-vis absorbance measurements indicate that even at relatively small IL/protein ratios, like 1:1 or 1:2, ([C14MIM][Cl]) is able to change, at least partially, the sample turbidity. SAXS results agree with the spectroscopic techniques and suggest that the proteins underwent partial unfolding, evidenced by an increase in the radius of gyration (Rg) of the scattering particle. In the absence and presence of ([C14MIM][Cl]) = 3 mM BSA Rg increases from 29.1 to 45.1 Å, respectively. Together, these results indicate that the interaction of BSA with ILs is divided into three stages: the first stage is characterized by the protein in its native form. It takes place for protein/IL ≤ 1:2, and the interaction is predominantly due to the electrostatic forces provided by the negative charges on the surface of BSA and the cationic polar head of the ILs. In the second stage, higher IL concentrations induce the unfolding of the protein, most likely inducing the unfolding of domains I and III, in such a way that the protein's secondary structure is kept almost unaltered. In the last stage, IL micelles start to form, and therefore, the interaction with protein reaches a saturation point and free micelles may be formed. We believe that this work provides new information about the interaction of ILs with BSA.