Interaction mechanism of flavonoids and bovine β-lactoglobulin: Experimental and molecular modelling studies

Interactions between β-lactoglobulin and polyphenols: Mechanisms, properties, characterization, and applications

β-lactoglobulins (βLGs) have a wide range of applications in food because of their ability to emulsify, foam, and gel. This makes them good functional additives. However, their performance depends on temperature, pH, and mineral levels, so their functional qualities are limited in particular applications. How polyphenols (PPs) interact with βLG is crucial for the functional characteristics and quality of dietary compounds. In most food systems, a spontaneous interaction between proteins and PPs results in a "protein-PP conjugate," which is known to affect the sensory, functional, and nutraceutical qualities of food products. The βLG-PP conjugates can be used to enhance the quality of food. This article emphasizes analytical techniques for describing the characteristics of βLG-PP complexes/conjugates. It also goes over the functions of βLG-PP conjugates, including their solubility, thermal stability, emulsifying, and antioxidant qualities. The majority of βLG-PPs interactions is due to non-covalent (H-bonding, electrostatic interactions) or covalent bonds that are mostly caused by βLG or PP oxidation through enzymatic or non-enzymatic mechanisms. Furthermore, the conformation or type of proteins and PPs, as well as environmental factors like pH and temperature, have a significant impact on proteins-PPs interactions. Higher thermal stability, antioxidant activities, and superior emulsifying capabilities of the βLG-PP conjugates make them useful as innovative additives to enhance the quality and functions of food products.

Understanding interactions between four main fishy compounds and grass carp myofibrillar proteins using the SPME-GC-MS, multiple spectroscopy, and molecular docking

The interaction mechanism between four fishy compounds and myofibrillar proteins of grass crap was explored using solid phase microextraction-gas chromatography-mass spectrometry, multispectroscopy, and molecular docking. The result showed that the binding abilities of myofibrillar protein for the fishy compounds decreased in the order of decanal, octanal, hexanal, and 1-octen-3-ol. The interaction between myofibrillar proteins and four fishy compounds affected the aromatic amino acid residue microenvironment. The predominant binding force of myofibrillar proteins to the three aldehydes was hydrophobic, while those to 1-octen-3-ol were hydrogen bonds and van der Waals forces, and binding sites of these compounds occurred near tryptophan and tyrosine. A significant reduction in α-helical content and surface hydrophobicity in grass carp myofibrillar protein upon interaction with the four fishy compounds. Molecular docking confirmed that the different functional groups and chain lengths of the fishy components resulted in different binding sites and binding free energies with grass carp protein.

Interactions between food matrices and odorants: A review

Currently, although odorants of various foods have been thoroughly studied, the regulation of food aromas is still difficult due to the interaction between odorants and food matrices. These complex matrices in food may interact with odorants to change the volatility of odorants, which in turn affect food aroma. Clarifying the interaction between them are promising for predicting food aroma formation, which will provide valuable support for a high-efficiency food industry. Herein, the research progresses on interactions between food matrices and odorants are reviewed. First, the analysis methods and their advantages and disadvantages are introduced and discussed emphatically, including sensory-analysis methods, characterization methods of the volatility changes of odorants, and the research methods of interaction mechanism. Further, the research advances of interactions among proteins, carbohydrates, lipids, and polyphenols with odorants are summarized briefly. Finally, the existing problems are discussed and the research prospects are proposed.

Influence of phloretin on acrolein-induced protein modification and physicochemical changes in a dairy protein model

Acrolein (ACR) is an α,β-unsaturated aldehyde with high reactivity towards nucleophiles in proteins. In this study, a typical phenolic compound phloretin (Phl) was employed to counteract protein modification induced by ACR (1 mM) in whey protein isolate (WPI, 10 mg/mL). The addition of Phl (2 mM) significantly reduced ACR-induced surge of protein carbonyls (from 1.65 to 0.65 μmol/mg protein) and loss of protein total sulfhydryl content (from 0.28 to 0.24 μmol/mg protein) whilst contributing to further reductions in protein surface hydrophobicity and intrinsic fluorescence. The incorporation of ACR into WPI was effectively interrupted by Phl as visualized by Western blot. Only 2.87 % of ACR remained in the presence of 2 mM Phl with the generation of Phl-ACR adducts, suggesting Phl could partially alleviate protein modification by scavenging of ACR. These findings could have important implications for employment of natural phenolic nucleophiles against the adverse effects of ACR towards dietary proteins.

Unveiling differential interaction pattern for iminium and alkanolamine forms of Sanguinarine with β-Lactoglobulin protein

A comparative study on the interaction of two tautomeric forms of sanguinarine (SANG), an alkaloid with therapeutic properties, with β-lactoglobulin (β-LG) protein was explored using spectroscopic and computational methods. The spectroscopic study reveals a high binding affinity for alkanolamine to monomeric β-LG (at pH = 9) as compared to iminium to dimeric β-LG (at pH = 6.2). Temperature dependent fluorescence study provides thermodynamic parameters for the binding process. Circular dichroism spectra showed changes in the secondary structure of the protein with major conformational transition from α-helix to β-sheets. Molecular docking and MD simulation validate the stable protein-drug complex during a 200 ns simulation period. All results clearly depict the differential interactions of two forms of SANG with β-LG protein. Overall, the characterization of SANG binding interactions with the whey milk protein provides valuable insights for pharmacological research and design of novel drug carriers based on β-LG protein.

Deciphering the conformational changes induced by high-risk nsSNPs in β-lactoglobulin

Whey protein from bovine milk is highly valued in the food and pharmaceutical industries because of its high protein content and abundance of essential amino acids. The relationship between whey protein and the β-lactoglobulin (BLG) gene has been extensively discussed because BLG is the most abundant whey protein, making up approximately 50 % of the total whey protein in bovine milk. In recent years, researchers have been interested in this gene because of its critical role in healthy milk production, and any genetic polymorphism in this gene may deteriorate the milk quality. In the current study, we identified several deleterious and damaging non-synonymous single nucleotide polymorphisms (nsSNPs) in BLG and analyzed their destabilizing effects using different computational algorithms. Cumulative results from all tools and evolutionary conservation profiles of BLG suggested that four nsSNPs, G17A, W19C, F136S, and C119R, were the most deleterious and could affect the structural integrity of the protein. Detailed molecular dynamics simulation analysis revealed that all variants induced major structural alterations, that affected the ability of the protein to interact with natural and synthetic ligands. Particularly, the G17A, F136S, and C119R variants induced large conformational changes in the EF loop and main α-helix of BLG, which may affect the access of natural and synthetic ligands to the central calyx of BLG. We hope that the suggested nsSNPs will guide future studies and assist researchers in improving the quality of bovine milk.

Postharvest ripening of newly harvested corn: Weakened interactions between starch and protein

The effects of postharvest ripening of corn on the mechanisms of starch and protein interactions were investigated using molecular dynamics and several chemical substances. Sodium dodecyl sulfate (SDS) treatment all significantly affected the starch content, molecular weight of proteins, relative crystallinity, pasting characteristics and dynamic viscoelasticity in samples before and after postharvest ripening. In the corn that had not undergone postharvest ripening, there were also significant electrostatic interactions and hydrogen bonds between starch and protein. In addition, molecular dynamics had demonstrated that the forces between starch and protein in corn were mainly hydrophobic interactions, electrostatic interaction, and hydrogen bonds. Compared with zein, corn glutelin was more tightly bound to starch. The binding energy of starch to both proteins was reduced in after postharvest-ripened corn. This study laid a rationale for investigating the change mechanism of corn postharvest ripening quality and improving processing property and edible quality of corn.

Inactivation mechanisms on pectin methylesterase by high pressure processing combined with its recombinant inhibitor

High pressure processing (HPP) juice often experiences cloud loss during storage, caused by the activity of pectin methylesterase (PME). The combination of HPP with natural pectin methylesterase inhibitor (PMEI) could improve juice stability. However, extracting natural PMEI is challenging. Gene recombination technology offers a solution by efficiently expressing recombinant PMEI from Escherichia coli and Pichia pastoris. Experimental and molecular dynamics simulation were conducted to investigate changes in activity, structure, and interaction of PME and recombinant PMEI during HPP. The results showed PME retained high residual activity, while PMEI demonstrated superior pressure resistance. Under HPP, PMEI's structure remained stable, while the N-terminus of PME's α-helix became unstable. Additionally, the helix at the junction with the PME/PMEI complex changed, thereby affecting its binding. Furthermore, PMEI competed with pectin for active sites on PME, elucidating. The potential mechanism of PME inactivation through the synergistic effects of HPP and PMEI.

Deciphering the binding behavior and interaction mechanism of apigenin and α-glucosidase based on multi-spectroscopic and molecular simulation studies

This study investigated the molecular mechanism underlying the binding interaction between apigenin (API) and α-glucosidase (α-glu) by a combination of experimental techniques and computational simulation strategies. The spontaneously formation of stable API-α-glu complex was mainly driven by hydrogen bonds and hydrophobic forces, leading to a static fluorescence quenching of α-glu. The binding of API induced secondary structure and conformation changes of α-glu, decreasing the surface hydrophobicity of protein. Computational simulation results demonstrated that API could bind into the active cavity of α-glu via its interaction with active residues at the binding site. The important roles of key residues responsible for the binding stability and affinity between API and α-glu were further revealed by MM/PBSA results. In addition, it can be found that the entrance of active site tended to close after API binding as a result of its interaction with gate keeping residues. Furthermore, the structural basis for the binding interaction behavior of API was revealed and visualized by weak interaction analysis. The findings of our study revealed atomic-level mechanism of the interaction between API, which might shed light on the development of better inhibitors.

Developing Lipase Inhibitor as a Novel Approach to Address the Rice Bran Rancidity Issue─A Critical Review

Rice bran is a valuable byproduct from the food processing industry, which contains abundant protein, essential unsaturated fatty acids, and numerous bioactive compounds. However, its susceptibility to rancidity greatly restricts its wide utilization. Many strategies have been proposed to delay the rancidity of rice bran, but most of them have their respective limitations. Here, we proposed that developing rice ban lipase peptide inhibitors represents an alternative and promising prescription for impeding the rancidity of rice bran, in contrast to the conventional stabilization approaches for rice bran. For this reason, the rancidity mechanisms of rice bran and the research progress of rice bran lipases were discussed. In addition, the feasibility of utilizing in silico screening and phage display, two state-of-the-art technologies, in the design of the related peptide inhibitors was also highlighted. This knowledge is expected to provide a theoretical basis for opening a new avenue for stabilizing rice bran.

Interaction mechanism of okra (Abelmoschus esculentus L.) seed protein and flavonoids: Fluorescent and 3D-QSAR studies

The binding capacity of 10 flavonoids with okra seed protein (OSP) was studied by fluorescence spectroscopy. The structure of flavonoids had an obvious impact on binding performance. The binding ability of flavanone was lower than that of flavone, isoflavone and dihydrochalcone. The binding capacity of flavonoid glycoside was superior to that of the corresponding flavonoid aglycone. The binding ability was positively correlated with the number of phenolic hydroxyl groups on the B ring. The steric field and electrostatic field model constructed by 3D-QSAR method could well explain the above interaction behavior. Thermodynamic analysis suggested that the quenching mechanism of OSP caused by flavonoids was static quenching, and the binding-site number was 1. In addition, hydrogen bonding and van der Waals force dominated this interaction. The 3D and synchronous fluorescence spectra showed that there was no significant change in the polarity of the environment around tryptophan and tyrosine residues during binding.

Deciphering the interaction mechanism and binding mode between chickpea protein isolate and flavonoids based on experimental studies and molecular simulation

Chickpea protein isolate (CPI) is a promising novel plant protein, and protein-flavonoid system has also been applied in various food products. However, the interaction mechanism between CPI and flavonoids remains to be elucidated. In this paper, the affinity behavior between flavonoids and CPI was explained by constructing the three-dimensional quantitative structure-activity relationship (R2 = 0.988, Q2 = 0.777). Subsequently, four representative flavonoids were selected for further study. Multi-spectroscopy analysis showed that the sequence of affinity for CPI was puerarin > apigenin > naringenin > epigallocatechin gallate. Meanwhile, flavonoids altered the secondary structure and spatial conformation of CPI, leading to the static quenching of CPI. Additionally, thermodynamic analysis indicated that hydrogen bonding and van der Waals forces were the main driving forces for complex binding. Molecular docking and molecular dynamics simulations further explored the binding sites and conformations of complexes. This study provides theoretical guidance for in-depth research on the interaction patterns between biomacromolecules and small molecules in food matrices.

Reducing Antigenicity and Improving Antioxidant Capacity of β-Lactoglobulin through Covalent Interaction with Six Flavonoids

β-lactoglobulin (β-LG) is a pivotal nutritional and functional protein. However, its application is limited by its antigenicity and susceptibility to oxidation. Here, we explore the impact of covalent modification by six natural compounds on the antigenicity and antioxidant characteristics of β-LG to explore the underlying interaction mechanism. Our findings reveal that the covalent interaction of β-LG and flavonoids reduces the antigenicity of β-LG, with the following inhibition rates: epigallocatechin-3-gallate (EGCG) (57.0%), kaempferol (42.4%), myricetin (33.7%), phloretin (28.6%), naringenin (26.7%), and quercetin (24.3%). Additionally, the β-LG-flavonoid conjugates exhibited superior antioxidant capacity compared to natural β-LG. Our results demonstrate that the significant structural modifications from α-helix to β-sheet induced by flavonoid conjugation elicited distinct variations in the antigenicity and antioxidant activity of β-LG. Therefore, the conjugation of β-LG with flavonoids presents a prospective method to reduce the antigenicity and enhance the antioxidant capacity of β-LG.

Understanding molecular interaction between thermally modified β-lactoglobulin and curcumin by multi-spectroscopic techniques and molecular dynamics simulation

This study elucidated the binding of curcumin (CUR) onto preliminary thermally modified β-lactoglobulin (β-LG). β-LG at pH 8.1 was heated at 75 °C, 80 °C and 85 °C for 10 min to construct denatured proteins (β-LG75, β-LG80, β-LG85). Steady and time-resolved fluorescence studies uncovered that CUR quenched proteins in simultaneous static and dynamic mode. Pre-heating β-LG improved its binding with CUR and the strongest affinity occurred in β-LG80. Fluorescence resonance energy transfer (FRET) analysis indicated that binding distance between CUR and β-LG80 was the smallest and energy transfer was the most efficient. β-LG80 had the highest surface hydrophobicity. Fourier-transform infrared (FT-IR) spectroscopy and differential scanning calorimeter (DSC) confirmed that CUR transferred from crystal to amorphous state after association with protein and revealed the contribution of hydrogen bonds. Combination of β-LG80 with CUR retained the antioxidant capacity of each component. Molecular dynamics simulation demonstrated enhanced hydrophobic solvent accessible surface area of β-LG80 compared with native protein. Data obtained from this study may provide useful information for comprehensively understanding the ability of β-lactoglobulin to bind hydrophobic substances under different environmental conditions like high temperature and alkaline medium.

Application of Molecular Simulation Methods in Food Science: Status and Prospects

Molecular simulation methods, such as molecular docking, molecular dynamic (MD) simulation, and quantum chemical (QC) calculation, have become popular as characterization and/or virtual screening tools because they can visually display interaction details that in vitro experiments can not capture and quickly screen bioactive compounds from large databases with millions of molecules. Currently, interdisciplinary research has expanded molecular simulation technology from computer aided drug design (CADD) to food science. More food scientists are supporting their hypotheses/results with this technology. To understand better the use of molecular simulation methods, it is necessary to systematically summarize the latest applications and usage trends of molecular simulation methods in the research field of food science. However, this type of review article is rare. To bridge this gap, we have comprehensively summarized the principle, combination usage, and application of molecular simulation methods in food science. We also analyzed the limitations and future trends and offered valuable strategies with the latest technologies to help food scientists use molecular simulation methods.

Noncovalent interaction mechanism and functional properties of flavonoid glycoside-β-lactoglobulin complexes

The interaction of flavonoid glycosides with milk protein and effects on the functional properties of flavonoid glycoside-β-lactoglobulin complexes are still inexplicit. The noncovalent interactions between flavonoid glycosides including quercetin (QE), quercitrin (QI), and rutin (RU) with β-lactoglobulin (β-LG) were determined by computer molecular docking and multispectral technique analysis. The fluorescence quenching results indicated that the flavonoid glycosides formed stable complexes with β-LG by the static quenching mechanism. The computer molecular docking and thermodynamic parameters analysis conclude that the main interaction of β-LG-QE was via hydrogen bonding, while for β-LG-QI and β-LG-RU it is via hydrophobic forces. The order of binding affinity to β-LG was QE (37.76 × 10⁴ L mol^-1) > RU (16.80 × 10⁴ L mol^-1) > QI (11.17 × 10⁴ L mol^-1), which indicated that glycosylation adversely affected the colloidal complex binding capacity. In this study, the physicochemical properties of the protein-flavonoid colloidal complex were determined. The analysis by circular dichroism spectroscopy demonstrated that flavonoid glycosides made the protein structure looser by inducing the secondary structure of β-LG to transform from the α-helix and β-sheet to random coils. The hydrophobicity of β-LG decreased due to binding with flavonoid glycosides, while functional properties including foaming, emulsification, and antioxidant capacities of β-LG were improved due to the noncovalent interactions. This study presents a part of the insight and guidance on the interactive mechanism of flavonoid glycosides and proteins and is helpful for developing functional protein-based foods.

Encapsulation of calcium carbonate with a ternary mixture of sodium caseinate/gelatin/xanthan gum to enhance the dispersion stability of solid/oil/water emulsions

Calcium carbonate (CaCO3) has poor suspension stability, which severely limits its application in food processing and products. The solid/oil/water (S/O/W) emulsion stabilized by sodium caseinate (NaCas), gelatin (GEL), and xanthan gum (XG) ternary composite was to improve the dispersion stability of CaCO3 in emulsions. Particle size, Zeta potential, physical stability, and microstructure were determined to characteristic the stability of the S/O/W emulsions. Shear rheological and tribological analyses were used to characterize the rheological properties of S/O/W emulsions. X-ray diffraction (XRD), Infrared spectral analysis (FTIR), and molecular docking were used to characterize the molecular interactions, which was to explore the influence of the W phase on the system stability. It was found that when the NaCas concentration was 2 wt% and the S/O phase addition was 5%, the particle size distribution was uniform, and the physical stability was improved. CLSM and Cryo-SEM results showed that the S/O/W emulsions could embedded CaCO3 in the system, and formed a dense three-dimensional network space structure. The viscosity of the system increased and even agglomeration occurred with NaCas concentration increased, and the stability of the emulsion decreased. XRD results confirmed that the CaCO3 was partially covered due to physical embedding. Infrared spectral analysis and molecular docking results showed electrostatic, hydrophobic interaction, and hydrogen bond interaction between NaCas, GEL, and XG, which could improve the stability of S/O/W emulsions. The results showed that the S/O/W emulsions delivery system is an effective way to promote the application of CaCO3.

Interaction Mechanism of Mangiferin and Ovalbumin Based on Spectrofluorimetry and Molecular Docking

Mangiferin (MAG) is a kind of polyphenol with many bioactivities. However, its application in medicines and functional foods is restricted because of its poor aqueous solubility and stability. The construction of a MAG/protein complex is an effective way to solve this bottleneck. In this study, the interaction of MAG and ovalbumin (OVA) was systematically investigated by spectrofluorimetry, and their binding mode was clarified based on molecular docking. The results suggested that MAG could cause the static fluorescence quenching of OVA with the quenching constant ( Kq) of >2 × 1010 L/(mol·s). Their binding performance increased with increasing temperature, and the binding-site number ( n) was close to 1. The thermodynamic analysis indicated that the binding was a spontaneous process, which was mainly driven by hydrophobic force. During this process, there was no apparent change in the microenvironment surrounding the tyrosine and tryptophan residues of OVA. The molecular docking results demonstrated the hydrophobic interaction and hydrogen bonding in the complex, which well-confirmed the results of the fluorescence experiments.

Beta-Lactoglobulin as a Model Food Protein: How to Promote, Prevent, and Exploit Its Unfolding Processes

Bovine milk beta-lactoglobulin (BLG) is a small whey protein that is a common ingredient in many foods. Many of the properties of BLG relevant to the food industry are related to its unfolding processes induced by physical or chemical treatments. Unfolding occurs through a number of individual steps, generating transient intermediates through reversible and irreversible modifications. The rate of formation of these intermediates and of their further evolution into different structures often dictates the outcome of a given process. This report addresses the main structural features of the BLG unfolding intermediates under conditions that may facilitate or impair their formation in response to chemical or physical denaturing agents. In consideration of the short lifespan of the transient species generated upon unfolding, this review also discusses how various methodological approaches may be adapted in exploring the process-dependent structural modifications of BLG from a kinetic and/or a thermodynamic standpoint. Some of the conceptual and methodological approaches presented and discussed in this review can provide hints for improving the understanding of transient conformers formation by proteins present in other food systems, as well as when other physical or chemical denaturing agents are acting on proteins much different from BLG in complex food systems.

Prediction of flavor and retention index for compounds in beer depending on molecular structure using a machine learning method

In order to make a preliminary prediction of flavor and retention index (RI) for compounds in beer, this work applied the machine learning method to modeling depending on molecular structure. Towards this goal, the flavor compounds in beer from existing literature were collected. The database was classified into four groups as aromatic, bitter, sulfury, and others. The RI values on a non-polar SE-30 column and a polar Carbowax 20M column from the National Institute of Standards Technology (NIST) were investigated. The structures were converted to molecular descriptors calculated by molecular operating environment (MOE), ChemoPy and Mordred, respectively. By combining the pretreatment of the descriptors, machine learning models, including support vector machine (SVM), random forest (RF) and k-nearest neighbour (kNN) were utilized for beer flavor models. Principal component regression (PCR), random forest regression (RFR) and partial least squares (PLS) regression were employed to predict the RI. The accuracy of the test set was obtained by SVM, RF, and kNN. Among them, the combination of descriptors calculated by Mordred and RF model afforded the highest accuracy of 0.686. R 2 of the optimal regression model achieved 0.96. The results indicated that the models can be used to predict the flavor of a specific compound in beer and its RI value.

Improved color stability of anthocyanins in the presence of ascorbic acid with the combination of rosmarinic acid and xanthan gum

This study investigated the protective effect and mechanism of action of combined use of rosmarinic acid (RA) and xanthan gum (XG) on the stability of anthocyanins (ACNs) in the presence of l-ascorbic acid (pH 3.0). The addition of RA and XG, alone and in combination, significantly enhanced the color stability of ACNs, and the combined use of RA and XG showed the best effect. FTIR, 1H NMR, AFM and computational molecular simulation analyses revealed that the improvement in ACN stability following the combined addition of RA and XG was due to intermolecular interactions such as hydrogen bonding and van der Waals forces. In the ACN-RA-XG ternary complexes, XG had stronger binding interactions with ACNs than RA. Our findings provide a valuable potential to enhance the stability of ACNs in the presence of ascorbic acid with the combined use of RA and XG.

Prediction and evaluation of the 3D structure of Macadamia integrifolia antimicrobial protein 2 (MiAMP2) and its interaction with palmitoleic acid or oleic acid: An integrated computational approach

This study investigated the physicochemical properties and 3D structure of Macadamia integrifolia antimicrobial protein 2 (MiAMP2) and its interaction with palmitoleic acid (POA) or oleic acid (OA) in macadamia oil. The 3D structure of MiAMP2 was constructed for the first time by ab initio modelling using the TrRosetta server. The results showed that MiAMP2 was highly hydrophilic and had seven disulfide bonds and higher α-helix and β-sheet/turn contents. Molecular simulation showed that the hydrophobic pocket of MiAMP2 created a favourable environment for the binding of POA and OA. Free energy landscape and independent gradient model (IGM) analyses revealed that hydrogen bonds and van der Waals forces were the major driving forces stabilizing complexes formed by MiAMP2 and POA or OA. The present study provides a theoretical basis and new insight for the future development and utilization of macadamia nut protein in the food industry.

Interaction mechanism of kafirin with ferulic acid and tetramethyl pyrazine: Multiple spectroscopic and molecular modeling studies

Ferulic acid (FA) and tetramethyl pyrazine (TMP) are intrinsic bioactive compounds in baijiu, and kafirin is the major protein of sorghum, which is the raw material of baijiu. In this study, the interactions of kafirin-FA and kafirin-TMP were investigated by multiple spectroscopic and molecular modeling techniques. Fluorescence spectra showed that intrinsic fluorescence of kafirin drastically quenched because of the formations of kafirin-FA and kafirin-TMP complexes. The CD studies indicated that the combination with FA or TMP decreased the α-helix content of kafirin slightly. The shifts and intensity changes of UV-Vis, FTIR and fluorescence spectra confirmed the formations of complexes. Moreover, the molecular docking and molecular dynamics studies showed that hydrophobic interactions and hydrogen bonds played major roles in the formations of kafirin-FA and kafirin-TMP complexes, and the formations of complexes made kafirin structures more compact. This work is of great importance for further quality improvement in baijiu and alcoholic beverages.

Interaction of vitamin B12 with β-lactoglobulin: a computational study

The β-Lactoglobulin (βLG) is a major whey protein that has the potential to bind various ligands; hence it is used as a model protein in protein-ligand interaction studies. Vitamin B12 is an essential nutrient for the human body, which helps in the synthesis of DNA, proteins, and the production of red blood cells. Binding interaction of vitamin B12 with βLG will help to understand the potency of βLG as a transporter for vitamin B12. Our experimental findings already showed that βLG binds with vitamin B12 successfully (Swain et al., 2020). Nevertheless, to further support our experimental results firmly, here, we have employed computational tools such as molecular docking and molecular dynamics (MD) simulation. The molecular docking technique was used to elucidate the probable binding sites and binding affinity of vitamin B12 on βLG. The docked complex of vitamin B12 with βLG was subjected to MD simulation to investigate its stability and other interaction properties over a time frame. The study revealed that the compound is stable, and vitamin B12 imposes no change to the secondary structure of the βLG. The computational results agree reasonably well with our experimental study.

Kinetic interactions of nanocomplexes between astaxanthin esters with different molecular structures and β-lactoglobulin

The influence of different fatty acid carbon chains on the kinetic interactions of nanocomplexes between esterified astaxanthin (E-Asta) and β-lactoglobulin (β-Lg) were investigated by multi-spectroscopy and molecular modeling techniques. We synthesized ten different E-Asta bound to β-Lg and formed nanocomplexes (< 300 nm). Fluorescence spectroscopy showed moderate affinities (binding constants Ka = 10³-10⁴ M^-1). Docosahexaenoic acid astaxanthin monoester (Asta-C22:6) had the strongest binding affinity towards β-Lg (Ka = 3.77 × 10⁴ M^-1). The fluorescence quenching of β-Lg upon binding of E-Asta displayed a static mechanism, with binding sites (n) equal to 1. Fourier transform infrared spectroscopy and ultraviolet-visible absorption spectroscopy revealed that E-Asta might enter the β-Lg hydrophobic cavity, leading to unfolding of the peptide chain skeleton. In summary, β-Lg and E-Asta can form stable nanocomplex emulsions to achieve an effective delivery process for E-Asta.