Binding thermodynamics of synthetic dye Allura Red with bovine serum albumin

Exploring the Interactions of Soybean 7S Globulin with Gallic Acid, Chlorogenic Acid and (-)-Epigallocatechin Gallate

In this study, the noncovalent interaction mechanisms between soybean 7S globulin and three polyphenols (gallic acid (GA), chlorogenic acid (CA) and (-)-epigallocatechin gallate (EGCG)) were explored and compared using various techniques. Fluorescence experiments showed that GA and EGCG had strong static quenching effects on 7S fluorescence, and that of CA was the result of multiple mechanisms. The interactions caused changes to the secondary and tertiary structure of 7S, and the surface hydrophobicity was decreased. Thermodynamic experiments showed that the combinations of polyphenols with 7S were exothermic processes. Hydrogen bonds and van der Waals forces were the primary driving forces promoting the binding of EGCG and CA to 7S. The combination of GA was mainly affected by electrostatic interaction. The results showed that the structure and molecular weight of polyphenols play an important role in their interactions. This work is helpful for developing products containing polyphenols and soybean protein.

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.

New look at the metabolism of nonsteroidal anti-inflammatory drugs: influence on human serum albumin antioxidant activity

Body's homeostasis is dependent on many factors, such as maintaining balance between free radicals formation and degradation. Human serum albumin (HSA) also plays an important role in homeostasis. The aim of this study was thermodynamic analysis of the interaction between ketoprofen (KET), naproxen (NPX), diclofenac (DIC) and HSA, as well as the effect of drug-albumin binding on HSA antioxidant activity using calorimetric and spectrophotometric techniques. Based on the calorimetric analysis it has been shown that accompanied by hydrophobic interaction drugs-albumin binding is an exoenergetic reaction. All analyzed drugs and HSA showed the ability to react with free radicals such as a radical cation, formed as a result of the reaction between 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and potassium persulfate (K₂S₂O₈). Using ABTS assay a synergistic effect of ketoprofen (KET) and naproxen (NPX) on HSA antioxidant activity was observed while the effect of diclofenac (DIC) binding with albumin was probably additive. Because some medications including KET, NPX and DIC belong to over the counter (OTC) non-steroidal anti-inflammatory drugs (NSAIDs), it is necessary to understand their influence on HSA antioxidant activity.Communicated by Ramaswamy H. Sarma.

Comparison of Losartan and Furosemide Interaction with HSA and Their Influence on HSA Antioxidant Potential

Serum albumin (HSA) is the most important protein in human body. Due to the antioxidant activity, HSA influences homeostasis maintenance and transport of drugs as well as other substances. It is noteworthy that ligands, such as popular drugs, modulate the antioxidant activity of HSA. The aim of this study was to analyze the influence of losartan (LOS) and furosemide (FUR) on HSA antioxidant properties as well as the interaction between these drugs and protein using calorimetric and spectroscopic methods. LOS and FUR showed the high affinity for human serum albumin, and the binding reactions between them were spontaneous and exothermic. LOS and FUR, separately and together in the system, have no significant impact on the secondary HSA structure; however they have significant impact on the tertiary HSA structure. LOS and FUR mixed with HSA have the ability to scavenge free radicals, and the ligand(s)-HSA interactions were synergistic.

Kinetic and thermodynamic of lactoferrin - Ethoxylated-nonionic surfactants supramolecular complex formation

Understanding nonionic surfactant-protein interactions is fundamental from both technological and scientific points of view. However, there is a complete absence of kinetic data for such interactions. We employed surface plasmon resonance (SPR) to determine the kinetic and thermodynamic parameters of bovine lactoferrin-Brij58 interactions at various temperatures under physiological conditions (pH 7.4). The adsorption process was accelerated with increasing temperature, while the desorption rate decreased, resulting in a more thermodynamically stable complex. The kinetic energetic parameters obtained for the formation of the activated complex, [bLF-Brij58]^‡, indicated that the potential energy barrier for [bLF-Brij58]^‡ formation arises primarily from the reduction in system entropy. [bLF-Brij58]^○ formation was entropically driven, indicating that hydrophobic interactions play a fundamental role in bLF interactions with Brij58.

Thermodynamic and kinetic insights into the interactions between functionalized CdTe quantum dots and human serum albumin: A surface plasmon resonance approach

To explore in vivo application of quantum dots (QDs), it is essential to understand the dynamics and energetics of interactions between QDs and proteins. Here, surface plasmon resonance (SPR) and molecular docking were employed to investigate the kinetics and thermodynamics of interactions between human serum albumin (HSA) and CdTe QDs (~3 nm) functionalized with mercaptopropionic acid (MPA) or thioglycolic acid (TGA). Kinetic analysis showed that HSA-QD interactions involved transition-complex formation. Despite the structural similarities between MPA and TGA, the [HSA-CdTe@TGA]^‡ formation by association of free HSA and QDs demanded 70% more energy and higher entropic gain (E_a-TGA^‡= 65.10 and T∆S_a-TGA^‡= 28.62 kJ mol^-1) than the formation of [HSA-CdTe@MPA]^‡ (E_a-MPA^‡ = 38.13 and T∆S_a-MPA^‡ = 0.53kJ mol^-1). While the [HSA-CdTe@MPA]^° dissociation required higher energy and lower entropy loss (E_d-MPA^‡ = 49.96 and T∆S_d-MPA^‡ = - 32.18kJ mol^-1) than the [HSA-CdTe@TGA]^° dissociation (E_d-TGA^‡= 30.78 and T∆S_d-TGA^‡= - 51.12 kJ mol^-1). The stability of [HSA-QDs]^° was independent of the temperature and functionalizing group. However, the enthalpic and entropic components were highly affected by the substitution of MPA (ΔH° = - 11.83 and TΔS° = 32.72 kJ mol^-1) with TGA (ΔH° = 34.31 and TΔS° = 79.73 kJ mol^-1). Furthermore, molecular docking results indicated that the metal site on the QDs contributes to the stabilization of [HSA-QDs]^°. Therefore, differences in QD functionalization and surface coverage densities can alter the HSA-QD interaction, thus their application.

Extraction of Pb(II) from wheat samples via dual-frequency ultrasound-assisted enzymatic digestion and the mechanisms of its interactions with wheat proteins

A novel dual-frequency ultrasound-assisted enzymatic digestion (DUED) technique was used to extract Pb(II) from certified reference materials (CRMs) of wheat flour. Following this, the interactions of Pb(II) with wheat proteins were investigated to provide evidence for the selection of enzyme species. The results showed that the simultaneous use of α-amylase and flavourzyme resulted in the recovery of 97.9% of Pb(II) in 6 min under a 40 kHz ultrasonic bath combined with a 20 kHz ultrasonic probe. The exopeptidase activity of the flavourzyme was found to be the main contributor to the extraction of Pb(II) from the CRMs. Additionally, the proposed method exhibited a low detection limit (8.2 ng/g) and high recoveries of real samples (93.4%-112.2%) with RSD less than 7.33%. Furthermore, the oxygen-containing groups of wheat proteins, the nitrogen-containing groups of albumins and globulins, and the sulfur-containing groups of gliadins and glutenins were found to offer coordination sites for Pb(II).

Calorimetric and spectroscopic detection of the interaction between a diazo dye and human serum albumin

Dye effluents are one of the main causes of water pollution. Azo dyes, the most widely applied colorants, are particularly difficult to degrade. Exposure of such dyes to the aquatic environment is hazardous to human health and biota due to their intrinsic harmful mutagenic and carcinogenic properties. Congo Red (CR) is an anionic and synthetic diazo dye, which is recalcitrant to the biodegradative process and metabolizes to produce a potential carcinogen. Research on the interaction of this toxic dye with serum albumin, as a transport protein, is of paramount significance because the physiological and toxicological behaviours of the dye in vivo are associated with its interactive characteristics with the proteins. In this regard, a detailed binding profile of CR with human serum albumin (HSA) was studied using isothermal titration calorimetry (ITC) along with various spectroscopic and microscopic methods. The thermodynamic results from ITC indicated that the CR-HSA non-covalent interaction occured primarily due to favorable entropy and unfavorable enthalpy with a Ka of 106 M-1 at lower concentrations and 105 M-1 at higher concentrations. Steady-state fluorescence data revealed that the intrinsic fluorescence of HSA was quenched in the presence of CR via the static quenching mechanism. Using Förster's non-radioactive energy transfer theory (FRET), the specific binding distance r (2.73 nm) between the donor (Trp-214 from HSA) and the acceptor (CR) was calculated. Our preliminary results indicated that CR had a high affinity to HSA, which can have significant implications in the distribution and elimination of this toxic dye upon exposure.

Ultrasonically synthesis of Mn- and Cu- @ ZnS-NPs-AC based ultrasound assisted extraction procedure and validation of a spectrophotometric method for a rapid preconcentration of Allura Red AC (E129) in food and water samples

This study is devoted on Allura Red as food colorant preconcentration and determination in beverage, fruit juice and drink water samples is based on usage of Mn- and Cu- @ ZnS-NPs-AC as new sorbent for ultrasound-assisted-dispersive solid-phase microextraction (UA-DSPME) combined with ultraviolet-visible spectrophotometric based method (UV-Vis). Contribution of volume of eluent, pH, sorbent mass and sonication time on response following conduction of 28 experiments were optimized and investigated while their significantly justified according to p-value. Values of "Prob > F" less than 0.0500 is proportional with their significant influence on recovery of analyte. Under the optimum conditions 0.14 mL of THF; pH of 2.5; 8 mg of sorbent and 3 min sonication time guide and help achievement of limit of quantification (LOQ) and limit of detection (LOD) of 6.08 and 20.26 ng mL^-1, respectively. The accuracy of method was validated according to calculation of recovery following spiking 400 and 600 ng mL^-1 to blank solution and recovery as more reliable indication of accuracy 93.41 and 102.17% recoveries with RSD < 3.5%, which demonstrate the successful applicability of present method for real sample analysis. The maximum sorbent capacity was 50.0 mg g^-1 based on Langmuir isotherm as best model with high correlation coefficient. Combination of UA-DSPME and UV-Vis lead to higher sensitivity and lower cost for accurate and repeatable monitoring of Allura Red level in beverage, fruit juice and drink water samples with acceptable recovery and reasonable RSD%.

New LC-MS/MS Method for the Analysis of Allura Red Level in Takeaway Chinese Dishes and Urine of an Adult Chinese Population

Allura red is a widely used synthetic food dye. In this study, we developed and validated a LC-MS/MS method for the quantification of allura red in three popular takeaway Chinese dishes (braised pork, soy sauce chicken, sweet and sour pork) and human urine samples. High levels of allura red ranging from 2.85 to 8.38 mg/g wet weight were detected in the surveyed Chinese dishes. Of 113 participants who frequently consume the surveyed Chinese dishes (>once a week in the past 2 years), the median of their urinary allura red level was 22.29 nM/mM creatinine (95% CI = 19.48-25.03) . Risk assessment using Cox proportional hazard models showed that a 10-fold increase in urinary allura red was positively associated with high blood pressure (odds ratio of 1.75 (95% CI = 0.78-3.96)). Our findings provide new insights for the potential risk of hypertension for long-term allura red overconsumption.