Comparative study of the interactions between ovalbumin and three alkaloids by spectrofluorimetry

Aggregation and Growth Mechanism of Ovalbumin and Sodium Carboxymethylcellulose Colloidal Particles under Thermal Induction

Ovalbumin (OVA)/sodium carboxymethylcellulose (CMC) colloidal particles were prepared with different compactness and morphologies by regulating the interaction between proteins and polysaccharides during heating. Electrostatic interactions between the amine groups of OVA (-NH₃⁺) and carboxyl groups of CMC (-COO^-) enhanced complex formation. The protein conformation change benefited the hydrophobic interaction between the particles. Proteins in colloidal particles were unfolded/folded under thermal induction to form aggregates having more β-sheet structures. When the OVA/CMC ratio was 1:2, the initially loosely connected OVA/CMC aggregation changed into a uniform sphere between 25 and 90 °C. The mass ratio of OVA to CMC within the final colloidal particle (90 °C) was about 1:1.4. The OVA/CMC particle stability was maintained with hydrogen bonding, hydrophobicity, and disulfide bond. When OVA levels were predominant, OVA and CMC developed an approximately hollow sphere. Moreover, the final colloidal particle composition showed the OVA-to-CMC ratio as 3:1 (w/w). OVA bound into colloidal particle pores to increase compactness. Moreover, OVA and CMC bound to the colloidal particle while the particle shrank, thereby increasing the compactness of colloidal particles. There was a significant decrease in ABTS^•+ scavenging activity of curcumin compared with that of the particles with a ratio of 1:2. Thus, the rational adjustment of the structure of colloidal particles could effectively enhance their functional characteristics, providing a new way for the controlled release of the active ingredients.

Interaction of haemin with albumin-based macroporous cryogel: Adsorption isotherm and fluorescence quenching studies

Albumin-based cryogels for capturing haemin were synthesised by crosslinking different biomolecules, bovine serum albumin (BSA) and ovalbumin (OVA). The impact of the protein and coupling agent concentrations on cryogel’s mechanical properties, swelling ratios and polymerisation yields, as well as autoclaving as a post-treatment on the cryogel, were studied. We found that BSA (50 mg/ml) and the crosslinker (N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride, 46 mg/ml) formed a cryogel with optimum physical characteristics at a comparatively low protein concentration. The cryogel’s mechanical stability was increased using a double-layer cryogel approach by crosslinking the BSA proteins at subzero temperature inside an acrylamide and hydroxyethyl methacrylate premade cryogels. Batch binding and kinetic adsorption isotherms of haemin on the cryogels were assessed to evaluate their binding capacity toward the porphyrin molecule. The results showed that single-layer cryogels (BSA and OVA) had a higher capacity (∼0.68 mg/ml gel) and higher reaction rate constant towards haemin adsorption than double-layer gels. In contrast, the double-layer cryogels had higher mechanical strength than single-layer gels. The experimental results suggested that the cryogels followed the Freundlich model and the pseudo-second-order isotherm for batch adsorption and kinetics, respectively. The interaction between haemin and the gels was studied by fluorescence quenching. We found between 1.1 and 1.6 binding sites for different cryogels.

Interaction Mechanism between OVA and Flavonoids with Different Hydroxyl Groups on B-Ring and Effect on Antioxidant Activity

Ovalbumin (OVA) is a common carrier with high efficiency to deliver flavonoids. The aim of this study was to investigate the interaction mechanism of OVA and four flavonoids (quercetin (Que), myricetin (Myri), isorhamnetin (Ish), and kaempferol (Kaem)) with similar structures by fluorescence spectra, SDS−PAGE, FT−IR, and molecular docking analysis, and the effect on the antioxidant abilities of flavonoids was also evaluated. Results indicated that the antioxidant activity of flavonoids was positively correlated to the number of phenolic hydroxyl groups of on the B-ring, and weakened when the C-3′ position was replaced by a methoxy group. The addition of OVA enhanced the antioxidant activity of Que/Kaem, while it masked the antioxidant activity of Myri. The formation of Que/Myri/Ish/Kaem−OVA complexes was a spontaneous exothermic process driven mainly by hydrogen bond and van der Waals force, which could result in the change in OVA conformation and induce the transformation of α-helix to β-sheet. Among these, Kaem exhibited the strongest binding ability with OVA, and showed the greatest impact on the secondary and conformational structure of OVA, followed by Que. The hydroxylation of C-3′ and methoxylation of C-5′ weaken the interaction of Kaem with OVA. Molecular docking analysis suggested that Que, Myri, Ish, and Kaem formed six, three, five, and four hydrogen bonds with OVA, and the number of hydrogen bonds was not positively correlated with their binding constants. Our findings can provide a theoretical basis for the application of OVA on improving the antioxidant activity of flavonoids, and may help to explain the delivery efficiency of OVA on different bioactive constituents.

Ovalbumin/carboxymethylcellulose colloids: Particle compactness and interfacial stability

A protein/polysaccharide colloidal particle was prepared via combined complex coacervation and heat-induction. When the ratio of ovalbumin (OVA) to carboxymethylcellulose (CMC) was at 1:2, loose flexible particles (low D_f) with low surface hydrophobicity were obtained. Conversely, dense and compact particles (high D_f) were easily formed at a higher OVA/CMC ratio. Only in the appropriate OVA/CMC ratio, pH will have a greater impact on the colloidal particles. At the pH value of 4.4, the OVA/CMC ratio had a greater impact on the colloidal particles compared to pH. The emulsion stabilized by loose particles had a mean particle size of 3888 nm and was easily flocculated and creamed. On the other hand, compact particles formed a stable emulsion, which had a higher exponent of Δr² (0.867) and could resist flocculation during the 7 days storage. As such, the results showed that stable emulsion could be realized by utilizing compact particles as emulsifiers.

Bioactive compounds: Application of albumin nanocarriers as delivery systems

Enriched products with bioactive compounds (BCs) show the capacity to produce a wide range of possible health effects. Most BCs are essentially hydrophobic and sensitive to environmental factors; so, encapsulation becomes a strategy to solve these problems. Many globular proteins have the intrinsic ability to bind, protect, encapsulate, and introduce BCs into nutraceutical or pharmaceutical matrices. Among them, albumins as human serum albumin (HSA), bovine serum albumin (BSA), ovalbumin (OVA) and α-lactalbumin (ALA) are widely abundant, available, and applied in many industrial sectors, becoming promissory materials to encapsulate BCs. Therefore, this review focuses on researches about the main groups of natural origin BCs (namely phenolic compounds, lipids, vitamins, and carotenoids), the different types of nanostructures based on albumins to encapsulate them and the main fields of application for BCs-loaded albumin systems. In this context, phenolic compounds (catechins, quercetin, and chrysin) are the most extensively BCs studied and encapsulated in albumin-based nanocarriers. Other extensively studied subgroups are stilbenes and curcuminoids. Regarding lipids and vitamins; terpenes, carotenoids (β-carotene), and xanthophylls (astaxanthin) are the most considered. The main application areas of BCs are related to their antitumor, anti-inflammatory, and antioxidant properties. Finally, BSA is the most used albumin to produced BCs-loaded nanocarriers.

Utilization of diverse protein sources for the development of protein-based nanostructures as bioactive carrier systems: A review of recent research findings (2010-2021)

Consumer awareness of the relationship between health and nutrition has caused a substantial increase in the demand for nutraceuticals and functional foods containing bioactive compounds (BACs) with potential health benefits. However, the direct incorporation of many BACs into commercial food and beverage products is challenging because of their poor matrix compatibility, chemical instability, low bioavailability, or adverse impact on food quality. Advanced encapsulation technologies are therefore being employed to overcome these problems. In this article, we focus on the utilization of plant and animal derived proteins to fabricate micro and nano-particles that can be used for the oral delivery of BACs such as omega-3 oils, vitamins and nutraceuticals. This review comprehensively discusses different methods being implemented for fabrications of protein-based delivery vehicles, types of proteins used, and their compatibility for the purpose. Finally, some of the challenges and limitations of different protein matrices for encapsulation of BACs are deliberated upon. Various approaches have been developed for the fabrication of protein-based microparticles and nanoparticles, including injection-gelation, controlled denaturation, and antisolvent precipitation methods. These methods can be used to construct particle-based delivery systems with different compositions, sizes, surface hydrophobicity, and electrical characteristics, thereby enabling them to be used in a wide range of applications.

Interaction of two peptide drugs with biomacromolecules analyzed by molecular docking and multi-spectroscopic methods

Peptide drugs, which are mainly used for the treatment of AIDS, myeloma, and breast cancer, have evolved rapidly owing to their high efficacy and low side effects. The interaction mechanisms of two peptide drugs with two biological macromolecules (protein and DNA), which are of great significance in disease prevention and drug design, were investigated using molecular docking, fluorescence spectroscopy, circular dichroism (CD) spectroscopy, UV-visible spectroscopy and viscosity measurements. The interaction between a series of common drugs and ovalbumin (OVA) was simulated by molecular docking, and two peptide drugs with the highest energy values, namely atazanavir and carfilzomib, were selected; the binding energy values of these drugs with OVA were -59.20 and -55.93 kcal/mol, respectively. The K_b values of the interaction of the two drugs with OVA/DNA were in the range of 10⁴-10⁷ M^-1, and the binding affinity of the drugs was stronger with OVA than with DNA. Hydrogen bonds and van der Waals forces were very important for the binding between drugs and OVA through molecular docking studies, and it was consistent with experimental results (ΔH < 0, ΔH < 0). The synchronous fluorescence spectrum showed that the interaction caused a change to the original structure of OVA, and atazanavir had a greater effect on OVA than carfilzomib. CD spectrum analysis also demonstrated that the conformation of OVA changed slightly. The interaction between atazanavir and DNA was mainly driven by hydrophobic forces (ΔH > 0 and ΔH > 0), whereas the major interaction forces involved in the binding of carfilzomib with DNA were hydrogen bonds and van der Waals forces. DNA melting studies, UV-visible spectroscopy, CD spectroscopy and viscosity measurements established that the interaction between the drugs and DNA was groove binding.

Medicinal plant compounds as promising inhibitors of coronavirus (COVID-19) main protease: an in silico study

The novel Coronavirus (COVID-19) has spread rapidly across the globe and has involved more than 215 countries and territories. Due to a lack of effective therapy or vaccine, urgent and concerted efforts are needed to identify therapeutic targets and medications. COVID-19 main protease represents a major target for drug treatment to inhibit viral function. The present study sought to evaluate medicinal plant compounds as potential inhibitors of the COVID-19 main protease using molecular docking and molecular dynamic analysis. The PDB files of COVID-19 main protease and some medicinal plant compounds were retrieved from the Protein Data Bank (http://www.rcsb.org) and Pubchem server, respectively. The Gromacs software was used for simulation studies, and molecular docking analysis was done using Autodock 4.2. The COVID-19 main protease simulation, compared with some phytochemicals docked to the COVID-19 main protease, were analyzed. Glabridin, catechin, and fisetin had the greatest tendency to interact with the COVID-19 main protease by hydrogen and hydrophobic interactions. Docking of these phytochemicals to COVID-19 main protease led to an increase in the radius of gyration (Rg), decrease in the Root mean square fluctuation (RMSF), and induced variation in COVID-19 main protease secondary structure. The high tendency interaction of glabridin, catechin, and fisetin to COVID-19 main protease induced conformational changes on this enzyme. These interactions can lead to enzyme inhibition. This simulated study indicates that these phytochemicals may be considered as potent inhibitors of the viral protease; however, more investigations are required to explore their potential medicinal use.Communicated by Ramaswamy H. Sarma.

Delineating the interaction mechanism of glabridin and ovalbumin by spectroscopic and molecular docking techniques

The interaction between ovalbumin (OVA) and isoflavonoid glabridin (GB) was investigated using spectroscopic and molecular docking techniques. Fluorescence spectroscopy revealed that GB was bound to OVA mainly due to hydrogen bonding and hydrophobic forces. FT-IR spectroscopy showed that the combination of GB and OVA resulted in a decrease in the β-sheet content of OVA and an increase in the α-helix and extended-chain content. All these experimental results were supported and clarified by molecular docking simulations. GB binding was able to inhibit chemical denaturant-induced structural changes in OVA as observed by intrinsic tryptophan and ANS fluorescence. Moreover, GB-OVA complex increased the aqueous solubility of GB by about 4.45 times at pH 7.0. These results provided insights into the interaction between GB and OVA that contributes to the utilization of GB in the food and pharmaceutical industries.

Repurposing of genistein as anti-sickling agent: elucidation by multi spectroscopic, thermophoresis, and molecular modeling techniques

Sickle cell disease (SCD) is a major medical problem in which mono-therapeutic interventions have so far shown only limited effectiveness. We studied the repurpose of genistein, which could prevent sickle hemoglobin from polymerizing under hypoxic conditions in this disease. Genistein an important nutraceutical molecule found in soybean. The present study examines the repurposing genistein as an anti- sickling agent. Genistein shows inhibition of Hb S polymerization as well as a sickle reversal. Also, we have explored the interaction of the genistein with sickle hemoglobin (Hb S), using fluorescence, far-UV-CD spectroscopy, MicroScale Thermophoresis (MST), FTIR, combined with molecular modeling computations. The quenching constant decreases with increasing temperature, a characteristic that coincides with the static type of quenching mechanism. Temperature-dependent fluorescence measurements and molecular modeling studies reveal that apart from the hydrogen bonding, electrostatic interactions also play a crucial role in genistein and Hb S complex formation. In silico, distribution prediction of adsorption, digestion, metabolism, excretion, and toxicity (ADME/Tox) based on physical and chemical properties show that genistein is nontoxic and has ideal drug properties. The helicity and thermophoretic mobility of Hb S was a change in the presence of genistein, which leads to the destabilizing the Hb S polymer was examined using CD and MST, respectively. Our results open up the possibility for a promising therapeutic approach for the SCD by repurposed genistein as an anti-sickling agent.Communicated by Ramaswamy H. Sarma.

Retardation of some drugs in thin-layer chromatographic systems with impregnated silica gel plates with hen's egg white and bovine serum albumin

The influence of impregnation the chromatographic plate adsorbent layer, silica, with hen's egg white albumin (OVA) or bovine serum albumin (BSA) on the retention of some popular medicines (paracetamol, aminophenazone, theophylline, caffeine, acetanilide, ciprofloxacin, tramadol, acetylsalicylic acid, acebutolol) is investigated. The effect of composition and buffer pH of the mobile phase on solute separation selectivity is also studied. The chromatographic systems with and without above mentioned albumins and their influence on investigated drug retention are compared. In general, it has been turned out that retention of tested medicines in systems with the sorbent impregnated with albumin significantly increase relative to those with non-impregnated.

Molecular interaction of sulfonamides and ovalbumin, an allergenic egg protein, exploring biophysical, theoretical and biological studies

Biophysical, theoretical and biological in vitro studies were carried out to evaluate the interaction of the main allergen protein of egg white (ovalbumin, OVA) with sulphonamides (SA): sulphathiazole (S1), sulfaquinoxaline (S2), sulfadimethoxine (S3) and sulfamethazine (S4). The binding constants for the OVA-SA supramolecular complexes ranged from 1.20 to 30.66 × 10⁵ M^-1, observing the following order of affinity: S1 > S2 > S4 > S3. The preferential forces in the stabilization of the OVA complexes with S2 and S3 were hydrogen bonds and Van der Waals forces, whereas for OVA-S1 and OVAS4, were electrostatic interactions. Interaction process led to a change in the native structure of the protein, which may potentiate its natural allergenicity. Cations Ca(II), Mg(II) and Fe(III) favor the interaction of OVA with S1 and S2. The theoretical studies performed were consistent with the spectroscopic data. Finally, it was found that the interaction process for sulfonamides evaluated with OVA change the inhibition activity profile these antibiotics against strains of Escherichia coli ATCC 25922 and Bacillus megaterium APFSG3isox, but not the minimal inhibitory concentration values.

Albumin nanoscience: homing nanotechnology enabling targeted drug delivery and therapy

Albumin is a biocompatible, non-immunogenic and versatile drug carrier system. It has been widely used to extend the half-life, enhance stability, provide protection from degradation and allow specific targeting of therapeutic agents to various disease states. Understanding the role of albumin as a drug delivery and distribution system has increased remarkably in the recent years from the development of albumin-binding prodrugs to albumin as a drug carrier system. The extraordinary surface property of albumin makes it possible to bind various endogenous and exogenous molecules. This review succinctly deals with several albumin-drug conjugates and nanoparticles along with their preparation techniques and focuses on surface-modified albumin and targeting of albumin formulation to specific organs and tissues. It also summarizes research efforts on albumin nanoparticles used for delivering drugs to tumor cells and describes their role in permeation through tumor vasculature and in receptor mediated endocytosis, which is also described in this review. The versatility of albumin and ease of preparation makes it a suitable drug carrier system, swhich is the major objective of this review.

Structural dynamics studies on the binding of aflatoxin B1 to chicken egg albumin using spectroscopic techniques and molecular docking

Aflatoxin B₁, a mycotoxin produced by large number of Aspergillus species including Aspergillus flavus and Aspergillus parasiticus, has been described as the most potent carcinogenic mycotoxin. In this study, we have used a multiple spectroscopic and molecular docking approach to investigate the interaction of aflatoxin B₁ (AFB₁) with chicken egg albumin (CEA). Fluorescence spectroscopy, UV-Vis spectroscopy, and three-dimensional fluorescence spectroscopic techniques were employed to gain insight into the conformational changes in CEA in the presence of AFB₁. Fluorescence spectroscopy revealed ligand-induced quenching in the fluorescence emission spectra of CEA upon binding with AFB₁. Hyperchromic effect was observed in case of the ground state complex formation between CEA and AFB₁ by UV-Vis spectroscopy. To gain further comprehension into the site of binding of AFB₁ to CEA, competitive site marker displacement assay was performed using warfarin site marker. The magnitude of ΔG value calculated from fluorescence-based method was negative which confirmed spontaneous process. The results obtained suggest that the binding is enthalpy driven and van der Waals force and hydrogen bonds are stabilizing the AFB₁-CEA complex. Three-dimensional fluorescence studies also confirmed the quenching in the fluorescence intensity around tryptophan residues in CEA. Circular dichroism assessment revealed reduction in the alpha helical content of CEA in the presence of AFB₁. Molecular docking studies showed hydrophobic interaction, van der Waals forces, and hydrogen bonds as major forces present in interaction between CEA and AFB₁. The overall study confirms conformational and structural alteration in the protein due to binding of AFB₁.Communicated by Ramaswamy H. Sarma.

Potential of isoquercitrin as antisickling agent: a multi-spectroscopic, thermophoresis and molecular modeling approach

Sickle cell disease is an inherited disease caused by point mutation in hemoglobin (β-globin gene). Under oxygen saturation, sickle hemoglobin form polymers, leading to rigid erythrocytes. The transition of the blood vessels is altered and initiated by the adhesion of erythrocytes, neutrophils and endothelial cells. Sickle Hemoglobin (HbS) polymerization is a major cause in red blood cells (RBC), promoting sickling and destruction of RBCs. Isoquercitrin, a medicinal bioactive compound found in various medicinal plants, has multiple health benefits. The present study examines the potential of isoquercitrin as an anti-sickle agent, showing a significant decrease in the rate of polymerization as well as sickling of RBCs. Isoquercitrin-induced graded alteration in absorbance and fluorescence of HbS, confirmed their interaction. A negative value of ΔG° strongly suggests that it is a spontaneous exothermic reaction induced by entropy. Negative ΔH° and positive ΔS° predicted that hydrogen and hydrophobic binding forces interfered with a hydrophobic microenvironment of β6Val leading to polymerization inhibition of HbS. HbS-Isoquercitrin complex exhibits helical structural changes leading to destabilization of the HbS polymer as confirmed by CD spectroscopy. MST and DSC results indicate greater changes in thermophoretic mobility and thermal stability of sickle hemoglobin in the presence of isoquercitrin, respectively. These findings were also supported by molecular simulation studies using DOCK6 and GROMACS. Hence, we can conclude that isoquercitrin interacts with HbS through hydrogen bonding, which leads to polymerization inhibition. Consequently, isoquercitrin could potentially be used as a medication for the treatment of sickle cell disease.Communicated by Ramaswamy H. Sarma.

New insights into the binding interaction of food protein ovalbumin with malachite green dye by hybrid spectroscopic and molecular docking analysis

Communicated by Ramaswamy H. Sarma.

Preparation of Complexes between Ovalbumin Nanoparticles and Retinoic Acid for Efficient Induction of Tolerogenic Dendritic Cells

The induction of antigen-specific immunotolerance has been gathering attention concerning the therapy of allergy and autoimmune diseases. Tolerogenic dendritic cells (tDCs) play crucial roles in immunotolerance therapy because they induce anergic responses for auto-reactive helper T cells, and also enhance differentiation to regulatory T cells to maintain tolerance against auto-antigens. All-trans retinoic acid (ATRA) is one of the representative molecules used to induce tDCs. We have proposed a simple formulation of ovalbumin nanoparticles complexed with ATRA (OVA/RA NPs). OVA/RA NPs were taken up by DCs and successfully induced phenotypes of tDCs.

pH and heat induced structural changes of chicken ovalbumin in relation with antigenic properties

Ovalbumin is the major egg white protein known to induce allergic reactions in humans. A comprehensive evaluation of the structural and antigenicity features of ovalbumin subjected to different pH and heat treatments was performed by combining fluorescence spectroscopic measurements, ELISA and in silico prediction. The intrinsic fluorescence spectra indicated modification of the ovalbumin tertiary structure depending on pH and applied temperature. The heat treatment caused the alteration of ovalbumin structure, which exhibited gradual hydrophobic exposure. The in depths check of ovalbumin molecular model, after performing molecular dynamics simulations, indicated the slight transition toward a typical β-strand dominant structure with the temperature increase. Moreover the immunoenzymatic test was employed to estimate the effect of the pH and thermal treatment on the stability of ovalbumin epitopes. Only a 5.5% reduction of the residual antigenicity was observed when heat treating the ovalbumin samples at pH 7.0, whereas a significant reduction (over 82%) of the antigenicity was obtained at pH 9.5 and temperatures over 80°C. Both pH and thermal treatment affected the conformation of ovalbumin. The reduced recognition of the modified native ovalbumin by specific antibodies at alkaline pH is most probably a consequence of significant changes in the local conformation of the epitopes.

Complexes of green tea polyphenol, epigalocatechin-3-gallate, and 2S albumins of peanut

2S albumins of peanuts are seed storage proteins, highly homologous in structure and described as major elicitors of anaphylactic reactions to peanut (allergens Ara h 2 and Ara h 6). Epigallocatechin-3-gallate (EGCG) is the most biologically potent polyphenol of green tea. Non-covalent interactions of EGCG with proteins contribute to its diverse biological activities. Here we used the methods of circular dichroism, fluorescence quenching titration, isothermal titration calorimetry and computational chemistry to elucidate interactions of EGCG and 2S albumins. Similarity in structure and overall fold of 2S albumins yielded similar putative binding sites and similar binding modes with EGCG. Binding affinity determined for Ara h 2 was in the range described for complexes of EGCG and other dietary proteins. Binding of EGCG to 2S albumins affects protein conformation, by causing an α-helix to β-structures transition in both proteins. 2S albumins of peanuts may be good carriers of physiologically active green tea catechin.

Interactions of epigallo-catechin 3-gallate and ovalbumin, the major allergen of egg white

Polyphenols, the potent plant secondary metabolites, have beneficial effects on human health, but the mechanism(s) by which these effects are exerted is not well understood. Here, we present the detailed analysis of the interactions between the major green tea catechin, epigallo-catechin 3-gallate (EGCG), and the major dietary protein and allergen, ovalbumin (OVA). We show that EGCG binds to the pocket that partly overlaps with the previously identified IgE-binding region in OVA, and that this interaction induces structural changes in the allergen. Moreover, our ex vivo studies reveal that OVA binds IgE and stimulates degranulation of basophils, and that its uptake by monocytes proceeds at a slower rate in the presence of EGCG. This study provides further evidence in support of the proposed mechanism by which EGCG interactions with the food allergens contribute to its diverse biological activities and may impair antigen uptake by antigen-presenting cells.