Binding interaction between β-conglycinin/glycinin and cyanidin-3-O-glucoside in acidic media assessed by multi-spectroscopic and thermodynamic techniques

The structure-function relationships and techno-functions of β-conglycinin

β-conglycinin (β-CG) is a prominent storage protein belonging to the globulin family in soybean (Glycine max) seeds. Along with other soybean proteins, it serves as an important source of essential amino acids and high-quality nutrition. However, the digestibility and nutritional value of β-CG are key factors affecting the nutritional profile of soy-based foods. The heterotrimeric, secondary, and quaternary structures of β-CG, particularly the spatial arrangement of its α, α', and β subunits, influence its functional properties. Considering these aspects, β-CG emerges as a significant protein with diverse applications in the food and health sectors. Therefore, this review explores β-CG's composition, structure, function, health implications, and industrial uses. Salient discussions are presented on its molecular structure, nutrition, digestibility, allergenicity, and techno-functions including emulsification, solubility, gelling, and structure-function complexities. Overall, the multifaceted potential of β-CG in the healthcare sector and the food industry is evident.

Complexes of soybean protein fibrils and chlorogenic acid: Interaction mechanism and antibacterial activity

This study explored the mechanism of interaction between chlorogenic acid (CA) and protein fibrils (PF) as well as the effects of varying the CA/PF concentration ratio on antibacterial activity. Analysis of various parameters, such as ζ-potential, thioflavin T fluorescence intensity, surface hydrophobicity, and free sulfhydryl groups, revealed that the interaction between PF and CA altered the structure of PF. Fluorescence analysis revealed that hydrogen bonding and hydrophobic interactions were the primary interaction forces causing conformational rearrangement, resulting in a shorter, more flexible, and thicker fibril structure, as observed through transmission electron microscopy. Fourier-transform infrared spectroscopy, small-angle X-ray scattering, and X-ray diffraction analyses revealed that the characteristic fibril structure was destroyed when the CA/PF ratio exceeded 0.05. Notably, the CA-PF complexes inhibited the growth of Escherichia coli and Staphylococcus aureus and also exhibited antioxidant activity. Overall, this study expands the application prospects of CA and PF in the food industry.

Key residues involved in the interaction between chlorpyrifos and a chemosensory protein in Rhopalosiphum padi: Implication for tracking chemical residues via insect olfactory proteins

The development of advanced biosensors for tracking chemical residues and detecting environmental pollution is of great significance. Insect chemical sensory proteins, including chemosensory proteins (CSPs), are easy to synthesize and purify and have been used to design proteins for specific biosensor applications. Chlorpyrifos is one of the most commonly used chemicals for controlling insect pests in agriculture. This organophosphate is harmful to aquatic species and has long-term negative consequences for the ecosystem. CSPs can bind and carry a variety of environmental chemicals, including insecticides. However, the mechanism by which CSPs bind to insecticides in aphids has not been clarified. In this study, we discovered that RpCSP1 from Rhopalosiphum padi has a higher affinity for chlorpyrifos, with a Ki value of 4.763 ± 0.491 μM. Multispectral analysis revealed the physicochemical binding mechanism between RpCSP1 and chlorpyrifos. Computational simulation analysis demonstrated that the main factor promoting the development of the RpCSP1-chlorpyrifos complex is polar solvation energy. Four residues (Arg33, Glu94, Gln145, Lys153) were essential in facilitating the interaction between RpCSP1 and chlorpyrifos. Our research has improved knowledge of the relationship between CSPs and organophosphorus pesticides. This knowledge contributes to the advancement of biosensor chips for tracking chemical residues and detecting environmental pollution through the use of CSPs.

Complexation study of syringaldehyde complexed with serum albumin

As a major flavonoid polyphenolic compound in the stem of Hibiscus taiwanensis, syringaldehyde (SA) has numerous pharmacological effects. Nevertheless, owing to its less in-depth study, its application is limited. Within this work, the interactions between serum albumin and SA were elucidated by multispectral studies. The results of ultraviolet/visible absorption spectroscopy suggest that the conformation of serum albumin can be altered by binding with SA. Fluorescence spectroscopy indicates that SA forms complexes with serum albumin, quenching its fluorescence. This suggests that the fluorescent residues of serum albumin are situated at or near the binding site. Additionally, FT-IR results confirm that SA alters the secondary structure of BSA, specifically affecting the positions of both amide I and amide II bands. Via the computational biology analyses, it was confirmed that SA binds at the active site of serum albumin and nine residues form hydrophobic interactions. In addition, the cytotoxicity of SA to BRL-3A cells was also studied, and SA had almost no toxicity to the growth of BRL-3A cells. The complex has a higher α-amylase inhibition capacity than SA alone. To sum up, this work reveals that the interaction of SA with BSA induces a conformational alteration in BSA. It also proved that SA inhibits α-amylase more significantly and has great potential in hypoglycemia.

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.

Plant-Based Protein-Phenolic Interactions: Effect on different matrices and in vitro gastrointestinal digestion

This review summarizes the literature on the interaction between plant-based proteins and phenolics. The structure of the phenolic compound, the plant source of proteins, matrix properties (pH, temperature), and interaction mechanism (covalent and non-covalent) change the secondary structure, ζ-potential, surface hydrophobicity, and thermal stability of proteins as well as their functional properties including solubility, foaming, and emulsifying properties. Studies indicated that the foaming and emulsifying properties may be affected either positively or negatively according to the type and concentration of the phenolic compound. Protein digestibility, on the other hand, differs depending on (1) the phenolic concentration, (2) whether the food matrix is ​​solid or liquid, and (3) the state of the food-whether it is heat-treated or prepared as a mixture without heat treatment in the presence of phenolics. This review comprehensively covers the effects of protein-phenolic interactions on the structure and properties of proteins, including functional properties and digestibility both in model systems and real food matrix.

Recent advances in soybean protein processing technologies: A review of preparation, alterations in the conformational and functional properties

Currently, growing concerns about sustainable development and health awareness have driven the development of plant-based meat substitutes. Soybean proteins (SPs) are eco-friendly and high-quality food sources with well-balanced amino acids to meet consumer demand. The functionality and physicochemical attributes of SPs can be improved by appropriate processing and modification. With the burgeoning advances of modern processing technologies in the food industry, a multitude of functional foods and ingredients can be manufactured based on SPs. This review mainly highlights the conformational changes of SPs under traditional and emerging processing technologies and the resultant functionality modifications. By elucidating the relationship between processing-induced structural and functional alterations, detailed and systematic insights are provided regarding the exploitation of these techniques to develop different nutritional and functional soybean products. Some popular methods to modify SPs properties are discussed in this paper, including thermal treatment, fermentation, enzyme catalysis, high hydrostatic pressure, high-intensity ultrasound, atmospheric cold plasma, high-moisture extrusion, glycosylation, pulsed ultraviolet light and interaction with polyphenols. Given these processing technologies, it is promising to expand the application market for SPs and boost the advancement of the soybean industry.

Comparative analysis of the interaction between alpha-lactalbumin and two edible azo colorants equipped with different sulfonyl group numbers

Alpha-lactalbumin (α-La) is a crucial active component in whey protein. It would be mixed with edible azo pigments during processing. Spectroscopic analyses and computer simulations were used here to characterize the interaction between acid red 27 (C27) /acidic red B (FB) and α-La. Fluorescence, thermodynamics, and energy transfer showed the binding mechanism is a static quenching with a medium affinity. This binding process occurred spontaneously and was mainly driven by hydrophobic forces. Conformation analysis showed FB led to a greater change in the secondary structure of α-La compared with C27. C27 increased and FB decreased the surface hydrophobicity of α-La. The spatial structures of complexes were visualized with computer aid. The azo colorant binds to α-La easily and deeply with a smaller space volume and dipole moment and thereby affecting the α-La conformation and functionality. This study provides a theoretical basis for the application of edible azo pigments.

First insights into the binding mechanism and colour effect of the interaction of grape seed 11S globulin with malvidin 3-O-glucoside by fluorescence spectroscopy, differential colorimetry and molecular modelling

Recently, the search for alternative proteins endogenous to grapes to be used as wine colour protecting agents became an important research trend. In this study, the molecular interaction between the grape seed 11S globulin from winemaking by-product and malvidin-3-O-glucoside was investigated by fluorescence, differential colorimetry and molecular modelling. Fluorescence studies revealed the formation of grape seed protein- pigment complex whose KS was 8.5 × 104 M-1 and binding sites, n = 1.3. Malvidin-3-O-glucoside showed darker and more vivid bluish colour of in the presence of 11S globulin, suggesting the flavylium cation protection in a hydrophobic region of the protein. Docking analysis and molecular dynamics simulation indicated that malvidin-3-O-glucoside interacts mainly with the acidic subunit (40 kDa) of the 11S globulin monomer (60 kDa). An average of two hydrogen bonds and Van der Wall forces were the main interaction forces found for the protein-pigment complex, whose stability was confirmed by root-means-square deviation.

Enzymatic hydrolysates of soy protein promote the physicochemical stability of mulberry anthocyanin extracts in food processing

Soy protein papain hydrolysate (SPAH) and soy protein pepsin hydrolysate (SPEH) were used as protective agents for mulberry anthocyanin extracts (MAEs) to inhibit its color fading and enhance the anthocyanin stability at pH 6.3. Both SPAH and SPEH showed a significant protective effect on total anthocyanins in MAEs solutions. 1.0 mg/mL of SPEH presented the best protective effect on MAEs by increasing its half-life from 1.8 to 5.7 days. SPAH/SPEH-cyaniding-3-O-glucoside (C3G) interactions were investigated at pH 6.3 by fluorescence, Fourier-transform infrared spectroscopy (FT-IR), and Circular Dichroism (CD). Their association was mainly driven by hydrophobic interactions, and SPEH showed a higher binding affinity for C3G than SPAH, with a KA value of 2.62 × 105 M-1 at 300 K. The second structures of SPAH and SPEH were altered by C3G, with a decrease in the β-sheets and an increase in the turns and random coils.

Advances in dietary proteins binding with co-existed anthocyanins in foods: Driving forces, structure-affinity relationship, and functional and nutritional properties

Anthocyanins, which are the labile flavonoid pigments widely distributed in many fruits, vegetables, cereal grains, and flowers, are receiving intensive interest for their potential health benefits. Proteins are important food components from abundant sources and present high binding affinity for small dietary compounds, e.g., anthocyanins. Protein-anthocyanin interactions might occur during food processing, ingestion, digestion, and bioutilization, leading to significant changes in the structure and properties of proteins and anthocyanins. Current knowledge of protein-anthocyanin interactions and their contributions to functions and bioactivities of anthocyanin-containing foods were reviewed. Binding characterization of dietary protein-anthocyanins complexes is outlined. Advances in understanding the structure-affinity relationship of dietary protein-anthocyanin interaction are critically discussed. The associated properties of protein-anthocyanin complexes are considered in an evaluation of functional and nutritional values.

Interactions between Human Serum Albumin and Sulfadimethoxine Determined Using Spectroscopy and Molecular Docking

Sulfonamides are widely used antibiotics in agricultural production. However, the potential threat of these drugs to human health has increased global concern. Human serum albumin (HSA) is the main reservoir and transporter of exogenous small molecules in humans. In this study, the interaction between sulfadimethoxine (SMT) and human serum albumin (HSA) was studied using spectroscopy and computer simulation. Our results showed that the hydrogen bonding and van der Waals forces drove SMT to enter the binding site I of HSA spontaneously and resulted in the fluorescence quenching of HSA. The stability of the HSA–SMT complex decreased with an increase in temperature. The binding of SMT to HSA induced alterations in the secondary structure of HSA, where the content of α-helix decreased from 61.0% of the free state to 59.0% of the compound state. The π–π, π–σ, and π–alkyl interactions between HSA and SMT were found to play important roles in maintaining the stability of the complex.

Omnifarious fruit polyphenols: an omnipotent strategy to prevent and intervene diabetes and related complication?

Diabetes mellitus is a metabolic syndrome which cannot be cured. Recently, considerable interest has been focused on food ingredients to prevent and intervene in complications of diabetes. Polyphenolic compounds are one of the bioactive phytochemical constituents with various biological activities, which have drawn increasing interest in human health. Fruits are part of the polyphenol sources in daily food consumption. Fruit-derived polyphenols possess the anti-diabetic activity that has already been proved either from in vitro studies or in vivo studies. The mechanisms of fruit polyphenols in treating diabetes and related complications are under discussion. This is a comprehensive review on polyphenols from the edible parts of fruits, including those from citrus, berries, apples, cherries, mangoes, mangosteens, pomegranates, and other fruits regarding their potential benefits in preventing and treating diabetes mellitus. The signal pathways of characteristic polyphenols derived from fruits in reducing high blood glucose and intervening hyperglycemia-induced diabetic complications were summarized.

Complexation of rice glutelin fibrils with cyanidin-3-O-glucoside at acidic condition: Thermal stability, binding mechanism and structural characterization

The complexation of rice glutelin fibrils (RGFs) with cyanidin-3-O-glucoside (C3G) at acidic condition was investigated. The RGFs at pH 3.5 had a greatest protective effect on the thermal stability of C3G. The binding of C3G for RGFs was exothermic and driven by hydrophobic and electrostatic interactions. The RGFs exhibited a stronger binding interaction with C3G than rice glutelin (RG), resulting from the exposure of hydrophobic groups and positive charges on the fibrils surface, and thus RGFs exhibited better protective effect on C3G. The interaction with C3G resulted in the rearrangement of polypeptide chain, thereby reducing the β-sheet content. The larger aggregates were observed in RG/RGFs-C3G complexes due to protein-polyphenols aggregation. It was noteworthy that the pre-formed RGFs were restructured into entangled aggregates due to the interaction. This study proposed a novel protein fibril to protect anthocyanins, expanding the application of anthocyanins as stable and functional ingredients in acidic food systems.

Multi-spectroscopic and molecular docking studies of human serum albumin interactions with sulfametoxydiazine and sulfamonomethoxine

Sulfonamides are a kind of antibiotics which have been widely used as feed additives for livestock and poultry. However, sulfa drugs have raised worldwide concerns because of their adverse impact on human health. In this study, two sulfonamides, sulfametoxydiazine (SMD) and sulfamonomethoxine (SMM), were selected to explore the binding modes with human serum albumin (HSA). The spectroscopic approaches revealed that SMD or SMM could spontaneously enter into the binding site I of HSA through hydrogen bond interactions and van der Waals forces, and that SMD exhibited much stronger binding affinity toward HSA than SMM at different temperatures (p < 0.01, n = 3). The binding constants for SMD-HSA and SMM-HSA were determined to be (8.297 ± 0.010) × 10⁴ L·mol^-1 and (1.178 ± 0.008) × 10⁴ L·mol^-1 at 298 K, respectively. The interaction of SMD or SMM to HSA induced microenvironmental and conformational changes in HSA, where SMD had a greater effect on the α-helix content of HSA. Results from molecular docking implied that the amino acid residues of HSA, such as Arg222, Ala291 and Leu238, played key roles in the sulfonamide-HSA binding process. Meanwhile, hydrogen bonds might be a key factor contributing to the binding affinity of sulfa drugs and HSA. Additionally, the combined use of SMD and SMM led to an obvious variation in K_a values of binary systems (p < 0.01, n = 3). These findings might be helpful to understand the biological effects of sulfonamides in humans.

Glutathione S-transferases GhGSTF1 and GhGSTF2 involved in the anthocyanin accumulation in Gossypium hirsutum L

The glutathione S-transferases (GSTs) are important enzymes of secondary metabolism in plants. In this study, two putative GSTs, GhGSTF1 and GhGSTF2, were identified as anthocyanin-related GSTs by the transcriptome data of the leaves of Gossypium hirsutum L. TM-1 and T586. The quantitative real-time PCR showed that GhGSTF1 and GhGSTF2 were highly expressed in red leaves and stems of Gossypium hirsutum L. T586. Orthologous genes of GhGSTF2 in two Gossypium barbadense L. 3-79 and Xinhai21 contain bases deletion in N-terminal (GbGSTF2a) and C-terminal (GbGSTF2b) respectively. Among which, GhGSTF1 and GhGSTF2 can restore pigmentation in hypocotyls of Arabidopsis thaliana mutant tt19-7 while GbGSTF2a and GbGSTF2b cannot. Furthermore, in vitro assays showed the recombinant GhGSTF1 and GhGSTF2 had Glutathione S-transferase activities. Fluorescence quenching assays showed that Cya could obviously quench the fluorescence of GhGSTF1, GhGSTF2, GbGSTF2a and GbGSTF2b to lower levels as compared to C3G. Moreover, the transient dual-luciferase assays showed that the promoters of GhGSTF1 and GhGSTF2 could be activated by GhPAP1D at different levels. GUS staining assays showed that their promoters have different activities to light. This study indicated that GhGSTF1 and GhGSTF2 play important roles in anthocyanin accumulation and the regulatory mechanism of anthocyanin accumulation in allotetraploid Gossypium are complicated.

Nanoencapsulation of anthocyanins-loaded β-lactoglobulin nanoparticles: Characterization, stability, and bioavailability in vitro

This work aims to investigate the effect of desolvation on the stability and bioavailability of nanoparticles of β-lactoglobulin (β-Lg) and anthocyanins (AC) extracted from red raspberry pomace. Interactions between the substrates were also studied using multispectral approaches. β-Lg-nanoparticles were fabricated via heat treatment at 85 °C for 30 min before initiating the desolvation method at pH 7. This method generated monodisperse particles, nano-scale size of β-Lg, and AC-β-Lg ranged from 129.13 to 351.85 nm with square morphology obtained by SEM. The AC extract was encapsulated successfully during desolvation process into β-Lg-nanoparticles with encapsulation efficiency (EE %) of ~77%. Results also showed that AC (from 1 to 13 × 10^-4 M) quenched the fluorescence intensity of de-solvated β-Lg estimated to be 98%, and a binding among them occurred with a K_a-value of 7.59 × 10⁸ M^-1 at 25 °C. Addition of AC also gradually increased the antioxidant activity of β-Lg-nanoparticles with values of 82.51% at the highest AC-concentration (13 × 10^-4 M) loaded on β-Lg-nanoparticles. AC-loaded β-Lg nanoparticles was more stable in mouth (pH 6.8), simulated gastric (SG, pH 2), and simulated intestinal (SI, pH 6.9) by showing high retention rate (%) than that of AC unencapsulated. Overall, de-solvated-β-Lg increased the heat-stability and bioavailability of AC, which could be further utilized in various food and pharmaceutical matrices. These findings recommend that β-Lg nanoparticles could be appropriated as delivery systems for anthocyanins.

Probing the Interaction between Human Serum Albumin and 9-Hydroxyphenanthrene: A Spectroscopic and Molecular Docking Study

9-Hydroxyphenanthrene (9-OHPhe), the representative hydroxyl metabolite of phenanthrene, has generated increasing concern as it is potentially hazardous to organisms. Herein, multispectroscopic and molecular docking techniques were applied to investigate the molecular interaction of human serum albumin (HSA) with 9-hydroxyphenanthrene (9-OHPhe) under simulated physiological conditions. Steady-state fluorescence and time-resolved fluorescence spectral analysis showed that 9-OHPhe quenched HSA fluorescence through a mixed static and dynamic process. HSA can bind with 9-OHPhe to form a 1:1 complex, with binding constants of 1.28 × 10⁵, 1.36 × 10⁵, and 1.26 × 10⁵ L·mol^-1 at 298.15, 303.15, and 308.15 K, respectively. The strong binding between HSA and 9-OHPhe is spontaneous and entropy-driven. Molecular docking indicated that the optimal binding site of 9-OHPhe with HSA was located in the IA subdomain of HSA. Thermodynamic analysis and molecular docking results suggested that hydrophobic interactions and hydrogen bond force dominated the binding process of HSA with 9-OHPhe. Specifically, 9-OHPhe formed hydrophobic interactions with LEU134, LEU139, ILE142, LEU154, PHE157, ALA158, and TYR161 and formed a 1.86 Å hydrogen bond with LEU135. Circular dichroism spectral analysis showed that the α-helical content of HSA decreased from 52.3 to 50.9% after adding 9-OHPhe with a ratio of 1:1. The obtained results are hoped to provide basic data for understanding the potential effects of the hydroxyl metabolites of PAHs on functional biomacromolecules.