Conformation Of Human Serum Albumin Research Articles

Association mechanism of bicalutamide and human serum albumin for potential clinical implications.

The binding mechanism of molecular interaction between bicalutamide and human serum albumin (HSA) in a pH7.4 phosphate buffer was studied using various spectroscopic techniques in combination with molecular modeling. Fluorescence data revealed that the fluorescence quenching of HSA by bicalutamide was a static quenching procedure. The binding constants and number of binding sites were evaluated at different temperatures. The thermodynamic parameters, ΔH and ΔS, were calculated to be 4.30 × 104J·mol-1 and 245 J·mol-1·K-1, respectively, suggesting that the binding of bicalutamide to HSA was driven mainly by hydrophobic interactions and hydrogen bonds. The displacement studies indicated neither Sudlow's site I nor II but subdomain IB as the main binding site for bicalutamide on HSA. The binding distance between bicalutamide and HSA was determined to be 3.54 nm based on the Förster theory. Analysis of circular dichroism, synchronous, and 3D fluorescence spectra demonstrated that HSA conformation was slightly altered in the presence of bicalutamide.

Insight into Sonodynamic Activities of Gold Nanoparticles with Different Morphologies

AbstractThe sonodynamic activities of gold nanoparticles (GNPs) with different morphologies, gold nanospheres (GNSs), gold nanoflowers (GNFs) and gold nanorods (GNRs), were explored by multi‐spectroscopic methods, in which the lesion degree of human serum albumin (HSA) was used as assessment index. The results revealed that three GNPs all had certain sonosensitivity but varying from different morphologies. It was also found that GNPs concentration and ultrasonic parameters were all critical influencing factors of sonodynamic injury HSA. Investigating the physical damage mechanism, the results indicated that the secondary and tertiary structure of HSA were compromised by ultrasound (US) combined with GNPs, so that the conformation of HSA was altered and the function was variously disturbed due to GNPs different morphologies. Studying the chemical damage mechanism, the results discovered that the yield of singlet oxygen (1O2) produced by GNPs with various morphologies combined with US was significant difference. Therefore, comprehensively analyzing the research results under different factors, the order of sonodynamic activities of GNPs was GNSs≈GNFs>GNRs. These findings may provide reference for the application of GNPs as sonosensitizers in sonodynamic therapy.

Evaluating the biomolecular interaction between delamanid/formulations and human serum albumin by fluorescence, CD spectroscopy and SPR: Effects on protein conformation, kinetic and thermodynamic parameters

Delamanid is an anti-tuberculosis drug used for the treatment of drug-resistant tuberculosis. Since delamanid has a high protein bound potential, even patients with low albumin levels should experience high and rapid delamanid clearance. However, the interaction between delamanid and albumin should be better controlled to optimize drug efficacy. This study was designed to evaluate the binding characteristics of delamanid to human serum albumin (HSA) using various methods: fluorescence spectroscopy, circular dichroism (CD), surface plasmon resonance (SPR), and molecular docking simulation. The fluorescence emission band without any shift indicated the interaction was not affected by the polarity of the fluorophore microenvironment. The reduction of fluorescence intensity at 344 nm was proportional to the increment of delamanid concentration as a fluorescence quencher. UV-absorbance measurement at the maximum wavelength (λmax, 280 nm) was evaluated using inner filter effect correction. The HSA conformation change was explained by the intermolecular energy transfer between delamanid and HSA during complex formation. The study, which was conducted at temperatures of 298 K, 303 K, and 310 K, revealed a static quenching mechanism that correlated with a decreased of bimolecular quenching rate constant (kq) and binding constant (Ka) at increased temperatures. The Ka was 1.75–3.16 × 104 M−1 with a specific binding site with stoichiometry 1:1. The negative enthalpy change, negative entropy change, and negative Gibbs free energy change demonstrated an exothermic-spontaneous reaction while van der Waals forces and hydrogen bonds played a vital role in the binding. The molecular displacement approach and molecular docking confirmed that the binding occurred mainly in subdomain IIA, which is a hydrophobic pocket of HSA, with a theoretical binding free energy of −9.33 kcal/mol. SPR exhibited a real time negative sensorgram that resulted from deviation of the reflex angle due to ligand delamanid-HSA complex forming. The binding occurred spontaneously after delamanid was presented to the HSA surface. The SPR mathematical fitting model revealed that the association rate constant (kon) was 2.62 × 108 s−1M−1 and the dissociation rate constant (koff) was 5.65 × 10−3 s−1. The complexes were performed with an association constant (KA) of 4.64 × 1010 M−1 and the dissociation constant (KD) of 2.15 × 10−11 M. The binding constant indicated high binding affinity and high stability of the complex in an equilibrium. Modified CD spectra revealed that conformation of the HSA structure was altered by the presence of delamanid during preparation of the proliposomes that led to the reduction of secondary structure stabilization. This was indicated by the percentage decrease of α-helix. These findings are beneficial to understanding delamanid-HSA binding characteristics as well as the drug administration regimen.

Multi-spectroscopic and theoretical analysis on the interaction between human serum albumin and Cm-E2O2-Cm gemini surfactants

Human serum albumin (HSA) is among the blood plasma proteins crucial for transporting various natural and pharmaceutical substances throughout the body. This research examined how the structure of HSA changes when exposed to Cm-E2O2-Cm gemini surfactants, which possess various advantageous properties, utilizing a combination of multispectral analysis and computational modeling techniques. The aggregation behavior of gemini surfactants in the presence of HSA was also investigated to demonstrate the HSA-Cm-E2O2-Cm complexation. The intrinsic fluorescence findings showed that gemini surfactants caused HSA fluorescence to diminish due to static quenching. The binding constants (Kb) for HSA-Cm-E2O2-Cm at varying temperatures were around 103 M−1, with approximately one binding site detected. In addition, the effect of gemini surfactants on the conformation of HSA was analyzed by performing UV–vis, extrinsic, synchronous, RRS and 3-D fluorescence, and CD experiments. The interactions’ binding sites and driving forces (also spontaneity) were calculated using molecular docking analysis, which agrees with site marker studies and thermodynamic parameter value results.

Influence of para-substituted benzaldehyde derivatives with different push/pull electron strength groups on the conformation of human serum albumin and toxicological effects in zebrafish

Excessive intake of benzaldehyde and its derivatives can cause irreversible damage to living organisms. Hence, benzaldehyde derivatives with different para-substitutions of push/pull electronic groups were chosen to investigate the effect of different substituent properties on the structure of human serum albumin (HSA). The binding constants, number of binding sites, major interaction forces, protein structural changes, and binding sites of benzaldehyde (BzH) and its derivatives (4-BzHD) with HSA in serum proteins were obtained based on multispectral and molecular docking techniques. The mechanism of BzH/4-BzHD interaction on HSA is mainly static quenching and is accompanied by the formation of a ground state complex. BzH/4-BzHD is bound to HSA in a 1:1 stoichiometric ratio. The interaction forces for the binding of BzH/4-BzHD to HSA are mainly hydrogen bonding and hydrophobic interaction, which are also accompanied by a small amount of electrostatic interactions. The effect of BzH/4-BzHD on HSA conformation follows: 4-Diethylaminobenzaldehyde (4-DBzH) > 4-Nitrobenzaldehyde (4-NBzH) > 4-Hydroxybenzaldehyde (4-HBzH) > 4-Acetaminobenzaldehyde (4-ABzH) > BzH, which means that the stronger push/pull electronic strength of the para-substituted benzaldehyde derivatives has a greater effect on HSA conformation. Furthermore, the concentration-lethality curves of different concentrations for BzH/4-BzHD on zebrafish verified above conclusion. This work provides a scientific basis for the risk assessment of benzaldehyde and its derivatives to the ecological environment and human health and for the environmental toxicological studies of benzaldehyde derivatives with different strengths of push/pull electron substitution.

Typical endocrine disruptors diethylstilbestrol and its analogues non-covalently bind to human serum albumin

Endocrine disruptors have received widespread attention from the scientific community. However, the structure-activity relationship of the binding between endocrine disruptors and proteins is still unclear. Therefore, this study investigated the structure-activity relationship between human serum albumin (HSA) and three types of estrogens, hexestrol (HX), diethylstilbestrol (DES), and dienestrol (DIS), which have slightly different structures. The binding constants of HX, DES and DIS with HSA at 298 K were 1.40×104, 3.84×104 and 4.46×104 M−1, respectively. The data of thermodynamic parameters confirmed that the entropy and enthalpy of the estrogens with HSA were positive, indicating that the binding was dominated by hydrophobic interaction. The results from photochemistry and electrochemistry showed that the binding of estrogens to HSA was more tightly regulated by the conjugation effect. The conjugation effect not only changed the binding behavior of estrogen to HSA, but also the selectivity of the binding sites of the three estrogens. These changes caused the main binding sites to become different, while also affecting the local conformation of HSA. This article provides theoretical guidance for predicting the biological safety of analogues of endocrine disruptors at the protein level.

Interaction and Binding Kinetics of Different Substituted Pyrazines with HSA: Based on Multispectral, Physiological Activity, and Molecular Dynamics Simulations

Pyrazine is a kind of compound containing pyrazine ring structure, which has attracted the attention of researchers because of its special aroma and healthcare function. It is currently used in spices, pharmaceuticals, food additives, and other industries. Human serum albumin (HSA) is a transport and storage protein in the human circulatory system. Previous research reported that pyrazine can interact with albumin, but the interaction between pyrazine and HSA has not been reported. Consequently, this study is based on the multispectral method and molecular dynamics (MD) simulation, exploring the interaction between different pyrazines and HSA. The results show that the four pyrazines mainly quench the endogenous fluorescence of HSA through the static quenching mechanism. Molecular docking indicates that hydrophobic forces play a major role in the binding of pyrazines with HSA. At the same time, synchronous fluorescence spectroscopy, circular dichroism (CD), three-dimensional fluorescence spectroscopy, and resonance light scattering (RLS) showed that each pyrazine compound can change the conformation of HSA. MD simulation results show that the combination of four pyrazines and HSA can enhance the stability of HSA. Among them, 2,3,5,6-tetramethylpyrazine (TTMP) and 2,3,5-trimethylpyrazine (TMTP) binding is the most stable and the most unstable combination with HSA, respectively. In addition, the four pyrazines could affect the physiological activity of HSA. This study is of great significance to explore the mechanism of action of pyrazine compounds in vivo and can provide useful information for the application of pyrazine compounds in food.

Protective effect of colchicine on albumin glycation and cellular oxidative stress: Insights into diabetic cardiomyopathy.

The present work elucidates the role of colchicine (COL) on albumin glycation and cellular oxidative stress in diabetic cardiomyopathy (DCM). Human serum albumin (HSA) was glycated with methylglyoxalin the presence of COL (2.5, 3.75, and 5 µM), whereas positive and negative control samples were maintained separately. The effects of COL on HSA glycation, structural and functional modifications in glycated HSA were analyzed using different spectroscopical andfluorescence techniques. Increased fructosamine, carbonyl, and pentosidine formation in glycated HSA samples were inhibited in the presence of COL. Structural conformation of HSA and glycated HSA samples was examined by field emission scanning electron microscopy, circular dichroism, Fourier transform infrared, and proton nuclear magnetic resonance analyses, where COL maintained both secondary and tertiary structures of HSA against glycation. Functional marker assays included ABTS•+ radical scavenging and total antioxidant activities, advanced oxidative protein product formation, and turbidimetry, which showed preserved functional properties of glycated HSA in COL-containing samples. Afterward, rat cardiomyoblast (H9c2 cell line) was treated with glycated HSA-COL complex (400 μg/mL) for examining various cellular antioxidants (nitric oxide, catalase, superoxide dismutase, and glutathione) and detoxification enzymes (aldose reductase, glyoxalase I, andII) levels. All three concentrations of COL exhibited effective anti-glycation properties, enhanced cellular antioxidant levels, and detoxification enzyme activities. The report comprehensively analyzes the potential anti-glycation and properties of COL during its initial assessment.

Interactions of Turmeric- and Curcumin-Functionalized Gold Nanoparticles with Human Serum Albumin: Exploration of Protein Corona Formation, Binding, Thermodynamics, and Antifibrillation Studies.

In order to better understand the bioavailability and biocompatibility of polyphenol-assisted surface-modified bioengineered nanoparticles in nanomedicine applications, here, we address a series of photophysical experiments to quantify the binding affinity of serum albumin toward polyphenol-capped gold nanoparticles. For this, two different gold nanoparticles (AuNPs) were synthesized via the green synthesis approach, where curcumin and turmeric extract act as reducing as well as capping agents. The size, surface charge, and surface plasmon bands of the AuNPs were highly affected by the adsorption of human serum albumin (HSA) during protein corona formation, which was investigated using dynamic light scattering (DLS), ξ-potential, ultraviolet-visible (UV-vis) spectroscopy, and transmission electron microscopy (TEM) measurements. Fluorescence-based methods, absorbance, and SERS experiments were carried out to evaluate the binding aspects of AuNPs with HSA. We found that the AuNPs show moderate binding affinity toward HSA (Kb ∼ 104 M-1), irrespective of the capping agents on the surface. Hydrophobic association, along with some contribution of electrostatic interaction, played a key role in the binding process. The binding interaction was more toward the subdomain IIA region of HSA, as indicated by the competitive displacement studies using site-specific binders (warfarin and flufenamic acid). Because of the large surface curvature of small-sized AuNPs, the secondary structural conformations of HSA were slightly altered, as revealed by circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopy, and surface-enhanced Raman scattering (SERS) measurements. Additionally, the findings of the binding interactions were re-evaluated using molecular dynamics (MD) simulation studies by determining the root-mean-square deviation (RMSD), root-mean-square fluctuation (RMSF), radius of gyration (Rg), and changes in the binding energy of HSA upon complexation with AuNPs. To determine the tentative evidence for pharmacokinetic administration, these biocompatible AuNPs were applied to inhibit the amyloid fibril formation of HSA and monitored by using the thioflavin T (ThT) assay, ANS fluorescence assay, fluorescence microscopic imaging, and FESEM. AuNPs were found to show better resistance toward fibrillation of the adsorbed protein.

Aggregation and cytotoxicity of food additive dye (Azorubine)-albumin adducts: a multi-spectroscopic, microscopic and computational analysis

Protein and peptide misfolding is a central factor in the formation of pathological aggregates and fibrils linked to disorders like Alzheimer’s and Parkinson’s diseases. Therefore, it’s essential to understand how food additives, particularly Azorubine, affect protein structures and their ability to induce aggregation. In this study, human serum albumin (HSA) was used as a model protein to investigate the binding and conformational changes caused by azorubine, a common food and drink colorant. The research revealed that azorubine destabilized the conformation of HSA at both physiological (pH 7.4) and acidic (pH 3.5) conditions. The loss of tryptophan fluorescence in HSA suggested significant structural alterations, particularly around aromatic residues. Far UV-CD analysis demonstrated disruptions in HSA's secondary structure, with a notable reduction in α-helical structures at pH 7.4. At pH 3.5, Azorubine induced even more extensive perturbations, resulting in a random coil conformation at higher azorubine concentrations. The study also investigated aggregation phenomena through turbidity measurements, RLS analysis, and TEM imaging. At pH 3.5, larger insoluble aggregates formed, while at pH 7.4, only conformational changes occurred without aggregate formation. Cytotoxicity assessments on neuroblastoma (SH-SY5Y) cells highlighted the concentration-dependent toxicity of albumin aggregates. Molecular dynamics simulations reaffirmed the stable interaction between azorubine and HSA. This research provides valuable insights into the mechanisms by which azorubine influences protein conformations. To further advance our understanding and contribute to the broader knowledge in this area, several future directions can be considered such as exploring other proteins, studying dose-response relationship, gaining mechanistic insights, biological relevance, toxicity assessment, identifying alternative food colorants, and mitigation strategies to prevent adverse effects of azorubine on serum proteins.Communicated by Ramaswamy H. Sarma

Assessment of the Binding of Pseudallecin A to Human Serum Albumin with Multi-Spectroscopic Analysis, Molecular Docking and Molecular Dynamic Simulation.

The binding of pseudallecin A (PA), a potential antibiotic with strong inhibitory activities against Gram-positive Escherichia coli and Gram-negative Staphylococcus aureus, to human serum albumin (HSA) was explored. The interaction between them was assessed by multi-spectroscopic analysis, binding site competitive analysis, molecular docking and molecular dynamic simulation, showing the results as follows: PA effectively quenched the innate fluorescence of HSA by a static quenching process, formed a complex at a molar ratio of approximately 1 : 1 and performed an effective non-radiative energy transfer; the binding of PA to HSA was a spontaneous exothermic reaction driven by enthalpy with strong affinity and had a slight effect on the conformation of HSA; PA bound at site III of HSA and hydrogen bonds were the major binding forces to maintain the stability of the PA-HSA complex. Molecular dynamic simulation was performed to calculate the root mean square deviation (RMSD), root mean square fluctuation (RMSF) and radius of gyration (Rg) for this complex and effectively supported the spectroscopic outcome. These results meant that the delivery and distribution of PA as a water-insoluble molecule can be efficiently accomplished via HSA in human blood and, it has a good potential for future drug application and pharmacological development.

Studies on the binding of curcumin and glycyrrhetinic acid to human serum albumin by multi-spectroscopic methods and molecular docking approaches

Human serum albumin (HSA) is the most prevalent and important carrier in plasma, and its interaction with drugs may have a significant effect on the efficacy of drugs. Curcumin (CU) and glycyrrhizic acid (GA) are excellent potential anti-cancer candidates, and studies have shown that the combined application of them can significantly enhance the anti-cancer effect. In order to investigate the interaction of binary systems (HSA-CU/GA) and ternary systems (HSA-CU-GA), we employed spectroscopic methods to study the interaction mechanism and binding affinity, and carried out molecular docking with docking tools. The fluorescence quenching spectrum showed that CU and GA all had fluorescence quenching effects on HSA, and the quenching mechanism were static quenching. The binding sites of CU and GA to HSA were both in site I, and the main force were van der Waals forces and hydrogen bonds. The presence of GA enhanced the affinity between CU and HSA, increased the bioavailability of CU and its stability in plasma. The circular dichroism (CD) and three-dimensional fluorescence experiments showed that CU and GA dramatically altered the conformation of HSA, and GA could enhance the influence of CU on the conformation of HSA. This study aimed at exploring the binding properties of CU/GA to HSA, and providing important theoretical support for their combined use.

Exploring the binding mechanism and adverse toxic effects of degradation metabolites of pyrethroid insecticides to human serum albumin: Multi-spectroscopy, calorimetric and molecular docking approaches.

Pyrethroid insecticides (PIs), a class of structurally similar non-persistent organic pollutants, can be degraded and metabolized to more toxic, and longer half-life products. In this study, the binding interaction mechanisms between human serum albumin (HSA) and the main degradation metabolites of PIs, 3-phenoxybenzoic acid (3-PBA) and 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA), were studied by theoretical simulation and experimental verification. Steady state fluorescence spectra showed that the fluorescence quenching mechanism was static. According to the binding constant, 4-F-3-PBA (1.53×105Lmol-1) was bound more strongly to HSA than 3-PBA (1.42×105Lmol-1) in subdomain ⅡA (site I). It was found by isothermal titration calorimetry that the metabolites and HSA spontaneously combined mainly through hydrogen bond and van der Waals interaction. Ultraviolet absorption spectra and circular dichroism spectra showed that the metabolites caused slight changes in the microenvironment and conformation of HSA. The above results were proved by molecular docking. The toxicity properties of the metabolites were further analyzed by software, and 4-F-3-PBA was found to be more toxic than 3-PBA. Considering the high exposure level of these metabolites in food, the environment and human body, it is necessary to further explore the toxicity of PIs metabolites.

Comparative investigation on interaction mechanism and native conformation of human serum albumin with organometallic iridium(III) complexes via spectroscopic and electrochemical approaches

Organometallic iridium(III) complexes, as high-efficient phototherapic drugs for cancer therapy and tumor treatment, have attracted widespread interest in diverse areas. To further clarify the biological functions of iridium(III) complexes, the interaction mechanism and native conformation of human serum albumin (HSA) affected by three organometallic iridium(III) complexes containing curcuminoid ligands were systematically and comparably investigated via various spectroscopic and electrochemical approaches. The results revealed that three iridium(III) complexes reacted with HSA tightly at its Sudlow's site I under the binding forces of van der Waals interaction, protonation, and hydrogen bond, leading to the hypochromic effect in the absorption spectrum of HSA and the static quenching in the intrinsic fluorescence of HSA. Three iridium(III) complexes disturbed the native conformation of HSA by reducing its α-helical content, finally reducing the melting temperature and the thermal stability of HSA. In comparison, the iridium(III) complex containing curcuminoid ligand with bigger spatial steric-hindrance effect and stronger chemical polarity was prone to binding with HSA more tightly and subsequently affecting its native conformation and biological function more prominently. This research finding reveals the interaction mechanisms of organometallic iridium(III) complexes with HSA and evaluates the function of curcuminoid ligands during their binding interactions, which pays the way for the targeted design and the potential application of novel iridium(III) complexes in biological fields.

Glycation reduces the binding dynamics of aflatoxin B1 to human serum albumin: a comprehensive spectroscopic and computational investigation

Aflatoxin B1 (AFB1), a potent mutagen, is synthesized by Aspergillus parasiticus and Aspergillus flavus. Human serum albumin (HSA) is a globular protein with diverse roles. As AFB1 is ingested with food and is transported in the body via blood, it becomes pertinent to comprehend the effect of the binding of this toxin on the structure and conformation of HSA, which may help to get insight into the toxic effect of the exposure of the mycotoxin. In this study, multi-spectroscopic approaches have been used to evaluate the binding efficiency of AFB1 with both the native HSA (nHSA) and the glycated HSA (gHSA). Steady-state fluorescence spectroscopy reveals the static type of fluorescence quenching in the fluorescence emission spectra of nHSA and gHSA in the presence of AFB1. The binding constant (Kb) is calculated to be 6.88 × 104 M−1 for nHSA, while a reduced Kb value of 2.95 × 104 M−1 has been obtained for gHSA. The circular dichroism study confirms the change in the secondary structure of nHSA and gHSA in the presence of AFB1, followed by alterations in the melting temperature (Tm) of nHSA and gHSA. In silico computational findings envisaged the amino acid residues and bonds involved in the binding of nHSA and gHSA with AFB1. The comprehensive study analyzes the binding effectiveness of AFB1 with nHSA and gHSA and shows reduced binding of AFB1 to gHSA. Communicated by Ramaswamy H. Sarma

Role of Polyanions and Surfactant Head Group in the Formation of Polymer-Colloid Nanocontainers.

This study was aimed at the investigation of the supramolecular systems based on cationic surfactants bearing cyclic head groups (imidazolium and pyrrolidinium) and polyanions (polyacrylic acid (PAA) and human serum albumin (HSA)), and factors governing their structural behavior to create functional nanosystems with controlled properties. Research hypothesis. Mixed PE-surfactant complexes based on oppositely charged species are characterized by multifactor behavior strongly affected by the nature of both components. It was expected that the transition from a single surfactant solution to an admixture with PE might provide synergetic effects on structural characteristics and functional activity. To test this assumption, the concentration thresholds of aggregation, dimensional and charge characteristics, and solubilization capacity of amphiphiles in the presence of PEs have been determined by tensiometry, fluorescence and UV-visible spectroscopy, and dynamic and electrophoretic light scattering. The formation of mixed surfactant-PAA aggregates with a hydrodynamic diameter of 100-180 nm has been shown. Polyanion additives led to a decrease in the critical micelle concentration of surfactants by two orders of magnitude (from 1 mM to 0.01 mM). A gradual increase in the zeta potential of HAS-surfactant systems from negative to positive value indicates that the electrostatic mechanism contributes to the binding of components. Additionally, 3D and conventional fluorescence spectroscopy showed that imidazolium surfactant had little effect on HSA conformation, and component binding occurs due to hydrogen bonding and Van der Waals interactions through the tryptophan amino acid residue of the protein. Surfactant-polyanion nanostructures improve the solubility of lipophilic medicines such as Warfarin, Amphotericin B, and Meloxicam. Surfactant-PE composition demonstrated beneficial solubilization activity and can be recommended for the construction of nanocontainers for hydrophobic drugs, with their efficacy tuned by the variation in surfactant head group and the nature of polyanions.

Study on the interaction of two quinazoline derivatives as novel PI3K/mTOR dual inhibitors and anticancer agents to human serum albumin utilizing spectroscopy and docking.

Interactions of human serum albumin (HSA) with two structurally similar quinazoline derivatives, S1 and S2 , which are potential anticancer drugs acting on PI3K/mTOR targets, were investigated in vitro utilizing multiple spectroscopy as well as molecular docking. The fluorescence quenching study demonstrated that HSA fluorescence could be statically quenched by S1 and S2 through the formation of an HSA-drug complex. Furthermore, the details of the binding site number, binding constant, as well as the thermodynamic parameters, were estimated at 298, 303, and 310 K. The results revealed that hydrogen bond interactions, as well as van der Waals forces, were the predominant factors responsible for binding HSA to S1 or S2 . Synchronous fluorescence and ultraviolet (UV) absorption spectra suggested that S1 and S2 had little effect on the polarity of the microenvironment and conformation of HSA. Energy transfer from HSA to S1 or S2 most probably occurred. The docking study revealed that S1 and S2 were able to bind to the hydrophobic cavity that was located in the HSA subdomain IIA and formed varying numbers of hydrogen bonds with amino acid residues nearby. Due to the subtle difference in the chemical structure, the binding of S1 and S2 to HSA was slightly different.

Thermodynamics of benzoquinone-induced conformational changes in nucleic acids and human serum albumin

Biological macromolecules such as proteins, nucleic acids, carbohydrates and lipids, play a crucial role in biochemical and molecular processes. Thus, the study of the structure-function relationship of biomolecules in presence of ligands is an important aspect of structural biology. The current communication describes the chemico-biological interaction between benzene metabolite para-benzoquinone (BQ) with B-form of nucleic acids (B-DNA) and human serum albumin (HSA). The binding ability of HSA towards bromocresol green (BCG) was significantly suppressed when exposed to increasing concentrations of BQ in the presence of various physiological buffers. Further, the native fluorescence of HSA was drastically reduced and the secondary structures of HSA were significantly compromised with increasing concentrations of BQ. In vitro and in silico studies also revealed that BQ binds to domains I and II of HSA and thus altering the conformation of HSA which may potentially affect plasma osmotic pressure, as well as the binding and transport of numerous endogenous and exogenous molecules. Similarly, BQ interacts directly to the GC region of B-DNA particularly in the minor groove which was also assessed by computational docking studies. Isothermal titration calorimetry data suggest higher binding affinity of BQ towards DNA than HSA. Various spectroscopic observations also suggest that BQ binds to DNA preferably in the minor grooves. Thus, the results revealed that BQ may play a key role in inducing mutagenicity, either by formation of adducts on GC regions or by accelerating oxidative damage to biomacromolecules through chemico-biological interactions.

Insights into the binding interaction of Reactive Yellow 145 with human serum albumin from a biophysics point of view

The interaction between Reactive Yellow 145 (RY145) and human serum albumin (HSA) under physiological conditions was studied by the methods of multiple spectroscopic, molecular docking, and molecular dynamic (MD) simulation. Fluorescence data revealed that the fluorescence quenching of HSA by RY145 resulted from the formation of the RY145–HSA complex. According to the modified Stern–Volmer equation, the effective quenching constants (KA) between RY145 and HSA at two different temperatures were obtained to be 114.15 × 104, and 52.55 × 104 L/mol, respectively. ΔH and ΔS were determined to be negative, showing that van der Waals force and hydrogen bonds were the governing intermolecular force in stabilizing the complex. The outcomes of UV– visible spectra, fluorescence spectroscopy, and CD spectra exhibited apparent modifications in the microenvironment and conformation of HSA, particularly for the secondary structure. The MD simulation and molecular docking supported experimental findings.

Unveiling interaction mechanisms between myricitrin and human serum albumin: Insights from multi-spectroscopic, molecular docking and molecular dynamic simulation analyses

Myricitrin is a natural polyhydroxy flavonoid and is mainly derived from the bark and leaves of the Chinese Bayberry tree (Myrica rubra). It has different pharmacological activities, including antioxidative, anti-inflammatory, hypoglycemic, antiviral, liver protection and cholagogue properties, and may be added to foods, pharmaceuticals, and cosmetic products for antioxidant purposes. In this study, the interaction mechanism between myricitrin and human serum albumin (HSA) was investigated using spectroscopic methods, molecular docking techniques, and molecular dynamic simulations. We showed that the HSA/myricitrin interaction exhibited a static fluorescence quenching mechanism, and that binding processes were spontaneous in nature, with the main forces exemplified by hydrogen bonding, hydrophobic interactions, and electrostatic interactions. Fluorescence spectroscopy, ultraviolet–visible (UV–vis) spectroscopy, synchronous fluorescence spectroscopy, three-dimensional (3D) fluorescence spectroscopy, micro-Fourier transform infrared spectroscopy (micro-FTIR), and circular dichroism (CD) spectroscopy showed that myricitrin binding altered the HSA conformation to some extent. Competitive binding and molecular docking studies showed that the preferred binding of myricitrin on HSA was in the sub-structural domain IIA (Site I); molecular dynamic simulations revealed that myricitrin interacted with HSA to produce a well stabilized complex, and it also generated a conformational change in HSA. The antioxidant capacity of the HSA-myricitrin complex was reduced when compared with free myricitrin. The identification of HSA-myricitrin binding mechanisms provides valuable insights for the application of myricitrin to the food and pharmaceutical industries.