Influence of tea polyphenol and bovine serum albumin on tea cream formation by multiple spectroscopy methods and molecular docking

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.

Tailoring ternary complexes of lactoferrin, EGCG, and α-lactalbumin by assembly sequence strategies: Structural characterization, assembly mechanism, and emulsification elucidation

Three distinct ternary complexes (TC-M1, TC-M2, and TC-M3) based on lactoferrin (LF), (-)-epigallocatechin-3-gallate (EGCG), and α-lactalbumin (ALA) were prepared by varying the assembly sequence and EGCG concentrations (ranging from 0 to 2.0 mM). Structural characterization was performed using various spectroscopic techniques, while the assembly mechanisms were investigated through ITC and molecular docking. These ternary complexes were further evaluated as stabilizers in Pickering emulsions. Nephelometry and DLS analysis showed that TC-M1 exhibited the highest turbidity and largest particle size, followed by TC-M2 and TC-M3. FT-IR and fluorescence spectroscopy revealed strong binding between EGCG and both ALA and LF, enhancing the hydrophilicity and extending structure of proteins. ITC and molecular docking studies indicated spontaneous interactions primarily driven by hydrogen bonding and hydrophobic forces, with LF (Ka1 = 1.9 × 105 M-1) and ALA (Ka1 = 3.6 × 104 M-1) binding approximately 3.3 and 2.9 EGCG molecules, respectively. Pickering emulsions formed by these complexes demonstrated superior emulsification properties, with TC-M1 showing the smallest CI (10.09 % ± 0.19 %), particle size (1 to 2 μm), and higher MVI (1.2) and EI (2.5) at 2.0 mM EGCG, outperforming TC-M2 and TC-M3 in stability. Overall, the assembly sequence of LF, ALA, and EGCG, along with EGCG concentration, lays the foundation for designing protein-polyphenol-protein ternary complexes, offering enhanced stability and functionality for diverse EGCG delivery applications.

Comparative analysis of phytochemicals and antioxidant activities in seeds and sprouts of different varieties of radish (Raphanus sativus L.): TOPSIS-entropy weight method

Many bioactive components in plants are beneficial to health, and their contents in seeds and sprouts are much higher than those in mature parts. This study intended to uncover alterations in nutritional compositions of radish seeds following germination. It also aimed to evaluate the health-promoting potential of both radish (Raphanus sativus L.) seeds and sprouts by quantifying representative bioactive compounds and antioxidants across six varieties. The ultimate goal was to identify the optimal radish variety with these beneficial properties through the TOPSIS-entropy weight method. This study measured chlorophyll, carotenoids, anthocyanins, glucosinolates (GLSs), total phenol (TP), vitamin C content, and antioxidant capacities (POD: Peroxidase; PAL: Phenylalanine ammonia lyase; T-AOC: Total antioxidant capacity) in seeds and sprouts of radish grew for 7 days. The GLSs content in seeds was 3 to 6-fold higher than that in sprouts; while contents of anthocyanin, sugar, and TP were much higher in radish seeds than those in sprouts. Chlorophyll, carotenoid content, and POD activity were significantly higher in sprouts than in seeds. Combined with the ideal solution similarity ranking preference method (TOPSIS) entropy weight method, M (Man Tang Hong) was the optimal radish variety. Sprouts generally outperformed seeds in terms of overall phytochemical composition and antioxidant capacities, except for M. Therefore, more sprouts are recommended to be consumed in daily life without choosing specific radish variety. In conclusion, this study supports the health-promoting properties of radish based on a comprehensive deciphering of the nutritional profile of radish seeds and sprouts, both of which are good sources of bioactive compounds.

Studies of the binding mechanism between liquid smoke from tea tree branches and proteins in dry-cured tenderloin using 4D-DIA proteomics, synergistic multispectral analysis, and molecular docking techniques

This research investigates the impact of various concentrations of tea branch liquid smoke (TLS) on the protein structure of dry cured pork tenderloin using multispectral techniques, molecular docking, and 4D-DIA proteomics. The results reveal that TLS enhances the solubility of myofibrillar protein, with varying effects on tryptophan exposure based on the concentration. Notably, at 5 mL/kg, TLS inhibits myofibrillar protein unfolding. Raman spectroscopy demonstrates that higher TLS concentrations mitigate disruptions in hydrogen bonding and hydrophobicity. Guaiacol and furfural in TLS engage in π-stacking interactions with myosin, heightening myosin interaction with its carrier. 4D-DIA proteomics has revealed that TLS can down-regulate the expression of cytoplasmic and mitochondrial proteins, metabolic enzymes, and ligases, playing pivotal roles in metabolism and genetic information processing. These proteins, featuring membrane linkers and phosphatases, potentially impact peptide and amino acid biosynthesis, thereby affecting meat quality modifications.

Inhibitory Activity of Quercetin, Rutin, and Hyperoside against Xanthine Oxidase: Kinetics, Fluorescence, and Molecular Docking

INTRODUCTION

Quercetin (Qc), rutin (Ru), and hyperoside (Hyp) are three common polyphenols widely distributed in the plant kingdom.

METHODS

This study explored the inhibition and mechanisms of Qc, Ru, and Hyp against xanthine oxidase (XOD) by enzyme kinetic analysis, fluorescence analysis, and molecular docking. The inhibitory activities of the three polyphenols on XOD showed the following trend: quercetin > hyperoside > rutin, with IC50 values of 8.327 ± 0.36 μmol/L, 35.215 ± 0.4 μmol/L and 60.811 ± 0.19 μmol/L, respectively. All three polyphenols inhibited xanthine oxidase activity in a mixed-competitive manner. Synchronous fluorescence results demonstrated that three polyphenols binding to XOD were spontaneous and showed static quenching.

RESULTS

The binding of the three polyphenols to XOD is mainly driven by hydrogen bonding and van der Waals forces, resulting in the formation of an XOD-XA complex with only one affinity binding site. The binding sites of the three RSFQ phenolic compounds are close to those of tryptophan. Molecular docking showed that all three polyphenols enter the active pocket of XOD and maintain the stability of the complex through hydrogen bonding, hydrophobic interaction, and van der Waals forces.

CONCLUSION

The results provide a theoretical basis for quercetin, rutin, and hyperoside to be used as function factors to prevent hyperuricemia.

L-lysine enhances pork color through antioxidant activity and myoglobin conformational changes

This study aimed to investigate the effect of L-lysine (Lys) on the color of pork and reveal the possible mechanism. The results showed that the L* and a* values increased from 53.69 to 56.32, 56.39, and 56.47, and from 12.93 to 13.21, 13.24, and 13.52 with the addition of 0.1 %, 0.15 % and 0.2 % Lys, respectively. Meanwhile, the oxymyoglobin (Fe2+) levels increased from 21.14 % to 22.63 %, 23.83 %, and 23.53 %, while the metmyoglobin (Fe3+) levels decreased from 44.69 % to 40.28 %, 41.21 %, and 41.63 % with the addition of 0.1 %, 0.15 % and 0.2 % Lys, respectively. Additionally, the addition of Lys increased total sulfhydryl and active sulfhydryl contents, and decreased the levels of reactive oxygen species (ROS) (P<0.05). The particle size and the absolute value of the ζ-potential increased with the addition of Lys, reaching maximum values of 534.39 nm and -13.73 mV, respectively. The molecular dynamics results suggested that Lys can bind to myoglobin (Mb) through hydrophobic interactions and hydrogen bonds, forming a stable Lys-Mb complex, acting as a protective shield to prevent the entry of ROS and other oxidizing agents. Finally, the addition of 0.15 % Lys resulted in the highest surface hydrophobicity, which was 5.79 μg. The multispectral results indicated that Lys primarily induces changes in the secondary and tertiary structures of Mb through interactions with tyrosine residues. These changes stabilized the free-moving rings within the amino acid residues of Mb, thereby improving the structural stability of Mb and ultimately enhancing the color stability of pork. In summary, Lys improved meat color stability through a dual mechanism of antioxidation and interaction with Mb to alter its conformational stability.

Binding Mechanism of Nitro Musks to Human Lactoferrin: Multispectral Approach, Docking and Molecular Dynamics Simulation

Nitro musks are highly bioaccumulative and potentially carcinogenic, commonly used as additives in fabric softeners, detergents, and other household products. Furthermore, these substances have been detected in breast milk and human adipose tissue, posing a risk of direct exposure to pregnant women and infants. Human lactoferrin (HLF) is abundant in colostrum, and plays an important role in the non-specific immune system of the human body. In this study, the mechanisms of action of two nitro musk compounds, typical examples of synthetic musks, with HLF were investigated using molecular docking, dynamics simulation and multispectral methods. The fluorescence findings demonstrated that nitro musks quenched the intrinsic fluorescence of human lactoferrin through static quenching. Thermodynamic analysis of the binding parameters suggested that hydrophobic interactions acted synergistically in the formation of the complex. Moreover, analyses utilizing multispectral techniques, such as Fourier transform infrared (FTIR) spectroscopy, validated that the microenvironment and structure of HLF were altered in the presence of nitro musks. Finally, molecular docking and molecular dynamics simulations were employed to explore the specific binding mode of nitro musks with HLF and to assess the stability of the complex. These findings may provide a reference for assessing health risks to pregnant women and infants.

Apigenin analogs as α-glucosidase inhibitors: Molecular docking, biochemical, enzyme kinetic, and an in vivo mouse model study

Due to the high incidence of diabetes and its associated complications, diabetes is widely recognized as a serious global health problem. In diabetes treatment strategies, targeting α-glucosidase, a key carbohydratehydrolyzing enzyme, has emerged as a highly regarded approach. To develop novel α-glucosidase inhibitors, we successfully synthesized a series of apigenin analogs, collectively referred to as H1-H27 compounds and examined their inhibitory effects on α-glucosidase activity. H7 showed a remarkable inhibitory effect, surpassing that of the standard drug acarbose. Further analysis revealed that H7, H10, and H24 act as non-competitive inhibitors of α- glucosidase. In vivo experiments using a type 2 diabetes mouse model demonstrated the diverse therapeutic potential of H7; it effectively lowered blood sugar levels, improved glucose tolerance, and corrected lipid metabolism. In addition, H7 showed hepatoprotective effects, highlighting its ability to improve liver function. H7 also positively influenced the gut microbiota composition in diabetic mice, increasing diversity and richness. These results highlight the promising therapeutic effects of apigenin analogs, such as H7, for treating type 2 diabetes and show how they could provide numerous benefits, including effective inhibition of α-glucosidase, improved glucose control, correction of lipid metabolism, hepatoprotection, and modulation of the intestinal microbiota.

Effect of bacterial fermentation on the ability of myofibrillar proteins to bind esters and its potential mechanism: Based on protein metabolism and structural changes

The effect of fermentation strains (Lactiplantibacillus plantarum CQ01107 and Staphylococcus simulans CD207) on the binding properties of porcine myofibrillar proteins (MPs) to esters was investigated from two perspectives: metabolism degree and structural alterations. Results demonstrated that S. simulans could reduce the particle size and α-helix content of MPs, while simultaneously increasing the absolute zeta potential and active sulfhydryl content. This process decreased protein aggregation and facilitated the unfolding of MPs, thereby enhancing their binding to esters. Conversely, L. plantarum showed limited promotion, which might be related to its robust acid production and protein hydrolysis capacities. In addition, ethyl octanoate, with a longer carbon chain length, was found to have the highest binding capacity to MPs (28.38 %-41.59 %). Molecular docking results further revealed that the binding of the four esters to MPs was spontaneous, with ethyl octanoate exhibiting the lowest binding energy to MPs (-5.635 kcal/mol). The primary forces involved in the binding of the four selected esters to MPs were hydrophobic interactions, hydrogen bonding, and van der Waals forces. These findings can provide new insights into the mechanisms by which fermentation strains influence flavor formation in fermented foods.

Dairy and nondairy proteins as nano-architecture structures for delivering phenolic compounds: Unraveling their molecular interactions to maximize health benefits

Phenolic compounds are recognized for their benefits against degenerative diseases. Clinical and nutritional applications are limited by their low solubility, stability, and bioavailability, compromising their efficacy. Natural macromolecules, such as lipids, polysaccharides, and proteins, employed as delivery systems can efficiently overcome these limitations. In this sense, proteins are attractive due to their biocompatibility and dynamic structure properties, functional adaptability and self-assembly capabilities, offering stability, efficient encapsulation, and controlled release. This review explores the potential use of dairy proteins, caseins, and whey proteins, and, alternatively, nondairy proteins, gelatin, human serum albumin, maize zein, and soybean proteins, in building wall materials for the delivery of phenolic compounds. To optimize performance, aspects, such as protein-phenolic affinity and complex stability/activity, should be considered when designing particle nano-architecture. Molecular interactions between protein-phenolic compound complexes are, thus, further discussed, as well as the effects of temperature and pH and strategies to stabilize and preserve nano-architecture and retain phenolic compound activity. All proteins harbor one or more putative binding sites, shared or not, depending on the phenolic compound. Preservation techniques are still a case-to-case study, as no behavior patterns among different complexes are noted. Safety aspects necessary for the marketing of nanoproducts, such as characterization, toxicity assessments, and post-market monitoring as defined by the European Food Safety Authority and the Food and Drug Administration, are discussed, evidencing the need for a unified regulation. This review broadens our understanding and opens new opportunities for the development of novel protein-based nanocarriers to obtain more effective and stable products, enhancing phenolic compound delivery and health benefits.

Hybrid Albumin-Decorated Lipid-Nanocarrier-Mediated Delivery of Polyphenol-Rich Sambucus nigra L. in a Potential Multiple Antitumoural Therapy

The current research attempted to address the suitability of bioactive Sambucus nigra extract entrapped in albumin-decorated nanostructured lipid carriers (NLCs) as a promising "adjuvant" in improving tumour penetration for multiple antitumour therapy. The new hybrid albumin-decorated NLCs were characterised based on, e.g., the particle size, zeta electrokinetic potential, SambucusN entrapment efficiency, and fluorescence spectroscopy and tested for different formulation parameters. The antioxidant activity of NLC-SambucusN was significantly enhanced by a bovine serum albumin (BSA) polymer coating. According to the real-time cell analysis (RTCA) results, NLC-I-SambucusN-BSA behaved similarly to the chemotherapeutic drug, cisplatin, with cell viability for LoVo tumour cells of 21.81 ± 1.18%. The new albumin-NLC-SambucusN arrested cancer cells in G1 and G2 cycles and intensified the apoptosis process in both early and late phases. An advanced induction, over 50% apoptosis in LoVo colon cells, was registered for 50 μg/mL of NLC-II-SambucusN-BSA, a fourfold increase compared to that of untreated cells. RTCA and flow cytometry results showed that concentrations of the hybrid NLC-SambucusN up to 50 μg/mL do not affect the proliferation of normal HUVEC cells. This approach provides insightful information regarding the involvement of phytochemicals in future therapeutic strategies. Albumin-decorated NLCs can be considered a noteworthy strategy to be connected to antitumour therapeutic protocols.

Characterization of volatile compounds and identification of key aroma compounds in different aroma types of Rougui Wuyi rock tea

In this study, we characterized the aroma profiles of different Rougui Wuyi rock tea (RGWRT) aroma types and identified the key aroma-active compounds producing these differences. The roasting process was found to have a considerable effect on the aroma profiles. Eleven aroma compounds, including linalool, β-ionone, geraniol, indole, and (E)-nerolidol, strongly affected the aroma profiles. An RGWRT aroma wheel was constructed. The rich RGWRT aroma was found to be dominated by floral, cinnamon-like, and roasty aromas. Human olfaction was correlated with volatile compounds to determine the aromatic characteristics of these compounds. Most key aroma-active compounds were found to have floral, sweet, and herbal aromas (as well as some other aroma descriptors). The differences in key compounds of different aroma types were found to result from the methylerythritol phosphate, mevalonic acid and shikimate metabolic pathways and the Maillard reaction. Linalool, geraniol, and (E,E)-2,4-heptadienal were found to spontaneously bind to olfactory receptors.

Assessment on malvidin-3-glucoside interaction with TLR4 via multi-spectroscopic analysis and molecular docking

As one innate immune pattern recognition receptor, Toll-like receptor 4 (TLR4) recently has been considered as a critical player in glucolipid metabolism. Blueberries contain high level of anthocyanins, especially malvidin-3-glucoside (Mv-3-glc), which contribute the anti-inflammatory, hypoglycemic, and hypolipidemic effects. It is speculated that Mv-3-glc is able to possess these functions by binding to TLR4. Here, the noncovalent interactions of Mv-3-glc and TLR4 was explored through multi-techniques including fluorescence and ultraviolet-visible (UV-Vis) absorption spectroscopy, as well as molecular docking. The results demonstrated that Mv-3-glc was able to quench TLR4 intrinsic fluorescence effectively. A stable complex was formed spontaneously and the reaction was exothermic. The degree of binding of Mv-3-glc to TLR4 showed a strong dependence on the chemical concentration, temperature, and pH values. The negative signs for enthalpy (ΔH = -69.1 ± 10.8 kJ/mol) and entropy (ΔS = -105.0 ± 12.3 J/mol/K) from the interaction of the Mv-3-glc and TLR4 shows that the major driving forces are the hydrogen bonding and van der Waals' force, which is consistent with the molecular docking results. In addition, molecular docking predicted that the active center with specific amino acid residues, Phe126, Ser127, Leu54, Ile153, and Tyr131 was responsible for the site of Mv-3-glc binding to TLR4/myeloid differentiation protein-2 (MD-2). These findings confirmed that Mv-3-glc could bind to TLR4, which would be beneficial to understand the target therapeutic effects of blueberry anthocyanins on TLR4 in regulating glucolipid metabolism.

The effects of the interaction between cyanidin-3-O-glucoside (C3G) and walnut protein isolate (WPI) on the thermal and oxidative stability of C3G

This study explores the interaction between cyanidin-3-O-glucoside (C3G), a water-soluble pigment known for its diverse functional activities, and walnut protein isolate (WPI) as a potential stabilizing agent. Given the inherent instability of C3G, particularly its limited application in the food industry due to sensitivity to thermal and oxidative conditions, this research study aims to enhance its stability. According to the results of the fluorescence quenching experiment, C3G can efficiently quench WPI's intrinsic fluorescence through static quenching. Structural exploration revealed that C3G bound WPI via hydrophobic interaction force, with the number of bound C3G molecules (n) almost equivalent to 1. The ΔG value denoting change in Gibbs free energy for C3G binding with WPI was -8.05 kJ/mol, which indicated that the interaction between C3G and WPI is spontaneous. Moreover, the conformational structures of WPI were altered by C3G binding with a decrease in α-helix contents and an increase in β-turn, β-sheet, and random coil contents. The thermal degradation kinetics indicate that after interacting with WPI, the half-life of C3G increased by 1.62 times and 1.05 times at 80 and 95°C, respectively. The results of the oxidation stability test showed that the presence of WPI effectively reduced the discoloration and degradation of C3G caused by oxidation, and improved the oxidation stability of C3G. This study's findings will help to clarify the interaction mechanism between C3G and WPI, and broaden C3G's application scope in the food processing field.

Binding characteristics and conformational changes in alpha-2-macroglobulin by the dietary flavanone naringenin: biophysical and computational approach

In the present study, we investigated the interaction of alpha-2-macroglobulin (α2M) with naringenin using multi-spectroscopic, molecular docking, and molecular simulation approaches to identify the functional changes and structural variations in the α2M structure. Our study suggests that naringenin compromised α2M anti-proteinase activity. The results of absorption spectroscopy and fluorescence measurement showed that naringenin-α2M formed a complex with a binding constant of (kb)∼104, indicative of moderate binding. The value of ΔG° in the binding indicates the process to be spontaneous and the major force responsible to be hydrophobic interaction. The findings of FRET reveal the binding distance between naringenin and the amino acids of α2M was 2.82 nm. The secondary structural analysis of α2M with naringenin using multi-spectroscopic methods like synchronous fluorescence, red-edge excitation shift (REES), FTIR, and CD spectra further confirmed the significant conformational alterations in the protein. Molecular docking approach reveals the interactions between naringenin and α2M to be hydrogen bonds, van der Waals forces, and pi interactions, which considerably favour and stabilise the binding. Molecular dynamics modelling simulations also supported the steady binding with the least RMSD deviations. Our study suggests that naringenin interacts with α2M to alter its confirmation and compromise its activity.Communicated by Ramaswamy H. Sarma.

Identifying the temporal contributors and their interactions during dynamic formation of black tea cream

Tea cream formed in hot and strong tea infusion while cooling deteriorates quality and health benefits of tea. However, the interactions among temporal contributors during dynamic formation of tea cream are still elusive. Here, by deletional recombination experiments and molecular dynamics simulation, it was found that proteins, caffeine (CAF), and phenolics played a dominant role throughout the cream formation, and the contribution of amino acids was highlighted in the early stage. Furthermore, CAF was prominent due to its extensive binding capacity and the filling complex voids property, and caffeine-theaflavins (TFs) complexation may be the core skeleton of the growing particles in black tea infusion. In addition to TFs, the unidentified phenolic oxidation-derived products (PODP) were confirmed to contribute greatly to the cream formation.

Biomacromolecular carriers based hydrophobic natural products for potential cancer therapy

Cancer is the second leading cause of death worldwide. It was estimated that 90 % of cancer-related deaths were attributable to the development of multi-drug resistance (MDR) during chemotherapy, which results in ineffective chemotherapy. Hydrophobic natural products plays a pivotal role in the field of cancer therapy, with the potential to reverse MDR in tumor cells, thereby enhancing the efficacy of tumor therapy. However, their targeted delivery is considered a major hurdle in their application. The advent of numerous approaches for encapsulating bioactive ingredients in the nanodelivery systems has improved the stability and targeted delivery of these biomolecules. The manuscript comprehensively analyses the nanodelivery systems of bioactive compounds with potential cancer therapy applications, including liposomes, emulsions, solid lipid nanoparticles (NPs), and polymeric NPs. Then, the advantages and disadvantages of various nanoagents in the treatment of various cancer types are critically discussed. Further, the application of multiple-compbine delivery methods to overcome the limitations of single-delivery have need critically analyzed, which thus could help in the designing nanodrug delivery systems for bioactive compounds in clinical settings. Therefore, the review is timely and important for development of efficient nanodelivery systems involving hydrophobic natural products to improve pharmacokinetic properties for effective cancer treatment.

The Effect of Nanoscale Modification of Nisin by Different Milk-Derived Proteins on Its Physicochemical Properties and Antibacterial Activity

Nisin is used as a natural food preservative because of its broad-spectrum antimicrobial activity against Gram-positive bacteria. However, free nisin is susceptible to various factors that reduce its antimicrobial activity. Milk protein, a protein derived from milk, has self-assembly properties and is a good carrier of bioactive substances. In this study, lactoferrin-nisin nanoparticles (L-N), bovine serum albumin-nisin nanoparticles (B-N), and casein-nisin nanoparticles (C-N) were successfully prepared by a self-assembly technique, and then their properties were investigated. The studies revealed that lactoferrin (LF) and nisin formed L-N mainly through hydrophobic interactions and hydrogen bonding, and L-N had the best performance. The small particle size (29.83 ± 2.42 nm), dense reticular structure, and good thermal stability, storage stability, and emulsification of L-N laid a certain foundation for its application in food. Further bacteriostatic studies showed that L-N enhanced the bacteriostatic activity of nisin, with prominent inhibitory properties against Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus, which mainly disrupted the cell membrane of the bacteria. The above results broaden our understanding of milk protein-nisin nanoparticles, while the excellent antibacterial activity of L-N makes it promising for application as a novel food preservative, which will help to improve the bioavailability of nisin in food systems.

Study on the interaction and functional properties of Dolichos lablab L. protein-tea polyphenols complexes

Tea polyphenols (TP) and plant proteins are significant materials in the food industry, the interactions between them are beneficial for their stability, functional properties, and biological activity. In this study, the mechanism and interaction between Dolichos lablab L. protein (DLP) obtained from nine treatments and three tea polyphenol monomers (EGCG, ECG, and EGC) were investigated. The results showed that the fluorescence of DLP was noticeably quenched and exhibited static quenching after the addition of polyphenols. DLP exhibited 1-2 binding sites for EGCG and ECG, but weakly binding to EGC (<1). The binding sites of DLP-TP were found to be in close proximity to the tyrosine residues, primarily interacting through hydrophobic interactions, van der Waals forces, and hydrogen bonds. The antioxidant capacity of DLP-TP compound was significantly improved after digestion. ECG showed a strong resistance to intestinal digestion. Compared with ECG (653.456 μg/mL), the content of free tea polyphenols of 20/40 kHz-ECG after digestion was 732.42 μg/mL. DLP-TP complexes significantly improved the storage stability, thermal stability, and bioaccessibility of tea polyphenols. The interaction between TP and DLP, as a protein-polyphenol complex, has great potential for application in preparing emulsion delivery systems due to their antioxidant activity and improved stability.

Identification of umami peptides from Wuding chicken by Nano-HPLC-MS/MS and insights into the umami taste mechanisms

Wuding chicken is popular with consumers in China because of its umami taste. This study aimed to identify novel umami peptides from Wuding chicken and explore the taste mechanism of umami peptides. The molecular masses and amino acid compositions of peptides in Wuding chicken were identified by nano-scale liquid chromatography-tandem mass spectrometry (Nano-HPLC-MS/MS). The taste characteristics of the peptides synthesized by the solid-phase method were evaluated by sensory evaluation combined with electronic tongue technology. The secondary structure of the peptides was further analyzed by circular dichroism (CD), and the relationship between the structure and taste of the peptides was elucidated by molecular docking. The results showed that eight potential umami peptides were identified, among which FVT (FT-3), LDF (LF-3), and DLAGRDLTDYLMKIL (DL-15) had distinct umami tastes, and FT-3 had the highest umami intensity, followed by LF-3 and DL-15. The relative contents of β-sheets in the three umami peptides were 55.20%, 57.30%, and 47.70%, respectively, which were the key components of Wuding chicken umami peptides. In addition to LF-3 embedded in the cavity-binding domain of the TIR1, both FT-3 and DL-15 were embedded in the venus flytrap domain (VFTD) of the T1R3 to bind the umami receptor T1R1/T1R3. The main binding forces between the umami peptides and the umami receptor T1R1/T1R3 relied on hydrogen bonds and hydrophobic interactions, and the key amino acid residues of the combination of umami peptides and the umami receptor T1R1/T1R3 were Glu292, Asn235, and Tyr262.

Aggregation kinetics of green tea nanoparticles: Effects of pH, metal ions, and temperature

Colloidal nanoparticles in tea infusion are the link connecting micromolecular mechanism and macro-aggregation process of tea cream formation. In order to elucidate, the kinetics mechanism of green tea nanoparticles (gTNPs) aggregation, zeta-potentials, total average aggregation (TAA) rates, and critical coagulation concentration (CCC) in the presence of various pH and metal ions were investigated. Additionally, the effect of temperature on gTNPs aggregation was further explored. The results revealed that the TAA rate of gTNPs increased with decreasing pH values, the CCC of gTNPs increased in the order Mg2+  ≈ Ca2+  < Na+  ≈ K+ . The reason was that different positive ions changed the surface electric field strength of gTNPs to a different extent. Furthermore, it was indicated that low temperature could promote gTNPs aggregation in indirect way. Low temperature promoted the binding of epigallocatechin gallate (EGCG) and caffeine, and the combination between gTNPs and EGCG-caffeine complexes weakened the stability of gTNPs resulting from reduction in electrostatic repulsion. PRACTICAL APPLICATION: Tea is a popular beverage all over the world. This research revealed the mechanism of green tea nanoparticles aggregation and laid a theoretical foundation for the regulation of tea cream formation in tea beverage.

Elucidation of interactions between myofibrillar proteins and κ-carrageenan as mediated by NaCl level: Perspectives on multiple spectroscopy and molecular docking

The present study was aimed to investigate the intermolecular interaction between myofibrillar proteins (MP) and κ-carrageenan (KC) as mediated by KC concentration (0.1, 0.2, 0.3, and 0.4 %, w/w) and NaCl levels (0.3 and 0.6 M) based on the multiple spectroscopy and molecular docking. The results showed that the incorporation of KC increased the turbidity, zeta-potential, and surface hydrophobicity of MP-KC mixed sols with a dose-dependent manner, as well as significantly decreasing the protein solubility (P < 0.05), which indicated that the interaction between KC and MP promoted the expansion of protein structure and exposed more hydrophobic groups. Fluorescence spectra result revealed that the interaction between MP and KC was a static quenching in the fluorescence quenching process, which affected the aromatic amino acids residue microenvironment of MP. Moreover, the existence of KC decreased the α-helix contents of MP (P < 0.05), contributing to the transformation from random structure to organized configuration of MP. In addition, molecular forces, the molecular docking and thermodynamic parameters indicated that hydrophobic interactions, van der Waals force, and hydrogen bonding were considered as the main interaction forces between MP and KC. Furthermore, 0.6 M NaCl level rendered higher solubility and particle size, as well as lower turbidity and the surface hydrophobicity of MP-KC mixed sols than those with 0.3 M NaCl level (P < 0.05), which promoted the unfolding of MP molecule and subsequently increased the numbers of binding sites between MP and KC, facilitating the intermolecular interactions between MP and KC in mixed sols.

Interaction between Bovine Serum Albumin in Fresh Milk Cream and Encapsulated and Non-Encapsulated Polyphenols of Tamarillo

The fortification of dairy products with polyphenols is known to deliver additional health benefits. However, interactions between polyphenols may form complexes and cause a loss of functionality overall. This study aimed to investigate potential interactions between polyphenols, in encapsulated and non-encapsulated forms, extracted from tamarillo fruit and bovine serum albumin (BSA) from fresh milk cream. Fortification with tamarillo extract was made at 1, 2 and 3% (w/w), and the resultant changes in physicochemical, rheological and functional properties were studied. With an increase in fortification, the absorbance of protein-ligand in the protein-polyphenol complex was decreased by up to 55% and 67% in UV and fluorescent intensities, respectively. Chlorogenic acid and kaempferol-3-rutinoside were more affected than delphinidin-3-rutinoside and pelargonidin-3-rutinoside. Static quenching was the main mechanism in the fluorescence spectra. Tryptophan and tyrosine residues were the two major aromatic amino acids responsible for the interactions with BSA. There were at least three binding sites near the tryptophan residue on BSA. The rheological property remained unaffected after the addition of non-encapsulated tamarillo extracts. Antioxidant capacity was significantly decreased (p < 0.05) after the addition of encapsulated extracts. This may be explained by using a low concentration of maltodextrin (10% w/w) as an encapsulating agent and its high binding affinity to milk proteins.

Dynamic Formation of Green Tea Cream and the Identification of Key Components Using the "Knock-Out/Knock-In" Method

The composition of green tea cream is extremely complex, and identification of key components is a prerequisite for elucidating its microstructure formation mechanism. This study examined the dynamic changes in the content of components and properties of colloid particles during the formation process of tea cream by chemical analysis and dynamic laser scattering (DLS). A "knock-out/knock-in" method was developed and used to further explore the relationship between the interaction of these components and the microstructure formation of tea cream. The results revealed that polysaccharides, proteins, epigallocatechin gallate (EGCG), and caffeine were the main components involved in tea cream formation. These components participated in the formation process in the form of polysaccharide-protein and EGCG-caffeine colloidal particles. Consequently, there were synchronized dynamic changes in the levels of polysaccharides, proteins, EGCG, and caffeine. The "knock-out/knock-in" experiment revealed that the interactions between EGCG or caffeine and macro-molecule components were not the key factors in tea cream microstructure formation. However, it was found that the complexation between EGCG and caffeine played a crucial role in the formation of tea cream. The findings suggested that decreasing the concentrations of EGCG and caffeine could be useful in controlling tea cream formation during tea beverage processing and storage.

Probing the mechanism of interaction between capsaicin and myofibrillar proteins through multispectral, molecular docking, and molecular dynamics simulation methods

The interaction between myofibrillar proteins (MPs) and capsaicin (CAP) was investigated using multispectral, molecular docking, and molecular dynamics simulation methods. The resulting complex increased the hydrophobicity of the tryptophan and tyrosine microenvironment as revealed by fluorescence spectral analysis. The fluorescence burst mechanism study indicated that the fluorescence burst of CAP on the MPs was a static one (Kq = 1.386 × 10¹² m^-1s^-1) and that CAP could bind with MPs well (Ka = 3.31 × 10⁴ L/mol, n = 1.09). The analysis of circular dichroism demonstrated that the interaction between CAP and MPs caused a decrease in the α-helical structure of MPs. The complexes formed exhibited lower particle size and higher absolute ζ potential. Furthermore, hydrogen bonding, van der Waals forces, and hydrophobic interactions were found to be the primary factors facilitating the interaction between CAP and MPs, as suggested by molecular docking models and molecular dynamics simulations.

Molecular dynamics simulations on interactions of five antibiotics with luciferase of Vibrio Qinghaiensis sp.-Q67

A large number of antibiotics have been used in the medical industry, agriculture, and animal husbandry industry in recent years. It may cause pollution to the aquatic environment and ultimately threaten to human health due to their prolonged exposure to the environment. We aim to study the toxicity mechanism of enrofloxacin (ENR), chlortetracycline hydrochloride (CTC), trimethoprim (TMP), chloramphenicol (CMP), and erythromycin (ETM) to luciferase of Vibrio Qinghaiensis sp.-Q67 (Q67) by using toxicity testing combined with molecular docking, molecular dynamics, and binding free energy analysis. The curve categories for ENR were different from the other four antibiotics, with ENR being J-type and the rest being S-type, and the toxicity of these five antibiotics (pEC50) followed the order of ENR (7.281) > ETM (6.814) > CMP (6.672) > CTC (6.400) > TMP (6.123), the order of toxicity value is consistent with the the magnitude of the binding free energy (ENR (-47.759 kcal/mol), ETM (-46.821 kcal/mol), CMP (-42.905 kcal/mol), CTC (-40.946 kcal/mol), TMP (-28.251 kcal/mol)). The van der Waals force provided the most important contribution to the binding free energy of the five antibiotics in the binding system with Q67 luciferase. Therefore, the dominant factor for the binding of antibiotics to luciferase was shape compensation. The face-to-face π-π stacking interaction between the diazohexane structure outside the active pocket region and the indoles structure of Phe194 and Phe250 in the molecular structure was the main reason for the highest toxicity value of antibiotic ENR. The hormesis effect of ENR has a competitive binding relationship with the α and β subunits of luciferase. Homology modeling, molecular docking, molecular dynamics simulations and binding free energy calculations were used to derive the toxicity magnitude of different antibiotics against Q67, and insights at the molecular level. The conclusion of toxicological experiments verified the correctness of the simulation results. This study contributes to the understanding of toxicity mechanisms of five antibiotics and facilitates risk assessment of antibiotic contaminants in the aquatic environment.

Study on the Interaction Mechanism of Theaflavin with Whey Protein: Multi-Spectroscopy Analysis and Molecular Docking

The interaction mechanism of whey proteins with theaflavin (TF1) in black tea was analyzed using multi-spectroscopy analysis and molecular docking simulations. The influence of TF1 on the structure of bovine serum albumin (BSA), β-lactoglobulin (β-Lg), and α-lactoalbumin (α-La) was examined in this work using the interaction of TF1 with these proteins. Fluorescence and ultraviolet-visible (UV-vis) absorption spectroscopy revealed that TF1 could interact with BSA, β-Lg and α-La through a static quenching mechanism. Furthermore, circular dichroism (CD) experiments revealed that TF1 altered the secondary structure of BSA, β-Lg and α-La. Molecular docking demonstrated that the interaction of TF1 with BSA/β-Lg/α-La was dominated by hydrogen bonding and hydrophobic interaction. The binding energies were -10.1 kcal mol-1, -8.4 kcal mol-1 and -10.4 kcal mol-1, respectively. The results provide a theoretical basis for investigating the mechanism of interaction between tea pigments and protein. Moreover, the findings offered technical support for the future development of functional foods that combine tea active ingredients with milk protein. Future research will focus on the effects of food processing methods and different food systems on the interaction between TF1 and whey protein, as well as the physicochemical stability, functional characteristics, and bioavailability of the complexes in vitro or in vivo.

Effect of Catechin on Yolk Immunoglobulin Structure and Properties: A Polyphenol-Protein Interaction Approach

The preparation of the interaction between polyphenols and protein is of great significance for increasing added value and promoting the application of egg yolk immunoglobulin (IgY). This study systematically investigated the effect of catechin on yolk immunoglobulin structural characteristics and functional properties. The binding conditions, force types, molecular conformation, and residual microenvironment of the interaction between catechin and IgY were analyzed by molecular docking technology, UV-vis absorption and fluorescence spectroscopy studies. The results showed that the main binding forces in the complex were hydrogen bonding and van der Waals forces. After the interaction, fluorescence quenching occurred and the maximum emission wavelength was redshifted. The results showed that the microenvironment around IgY increased polarity, increased hydrophilicity and decreased hydrophobicity, and the structure of the peptide chain changed. The bacteriostatic thermal stability of the compound against Escherichia coli and Staphylococcus aureus was lower than that of catechin IgY. The bacteriostatic acid and base stability were higher than that of catechin and IgY. The antioxidant activity was catechin, complex, and IgY, in descending order. The antioxidant activity of catechin and complex was significantly higher than that of IgY. At the same concentration, the apparent viscosity of the three samples was complex, IgY and catechin, in descending order. G' was greater than G" indicating that elastic properties dominate in G". The G' and G" values of the complex were higher than those of the other groups. Rheological results indicated that the complex may have high physical stability. This study provides theoretical support for broadening the application field of IgY and suggest its properties change in the machining process. It also provides new ideas for the development of functional foods from poultry eggs.

Phenolic-protein interactions: insight from in-silico analyses – a review

Phenolic compounds are ubiquitous plant secondary metabolites that possess various biological activities and are known to interact with proteins, altering their structure and properties. Therefore, interactions between these compounds and proteins has gained increasing attention due to their potential benefits to human health and for exploitation by the food industry. Phenolic compounds and proteins can form complexes via covalent linkages and/or non-covalent interactions through hydrophobic, electrostatic, van der Waals forces and hydrogen bonding. This review describes possible mechanisms of phenol-protein complex formation, their physiological action and activities that are important in the food industry, and possible outcomes in the terms of molecular docking and simulation analysis. The conformational changes of the protein upon binding with polyphenols can lead to the folding or unfolding of the protein molecules, forming insoluble or soluble complexes. The concentration of polyphenols, their molecular weight and structure, ions/cofactors and conditions of the system determine the precipitation or solubilization of the complex, affecting their nutritional and functional properties as well as their bioactivities. In this regard, molecular docking and simulation studies of phenolic-protein interactions allows comprehensive virtual screening of competitive/non-competitive and site-specific/non-specific conjugation of phenolics with different protein targets and facilitates understanding the observed effects. The docking analysis of flavonoids with enzymes and milk proteins has indicated their potential application in producing nutraceuticals and functional foods. Thus, combining molecular docking and simulation studies with experimental techniques is vital for better understanding the reactions that take place during digestion to engineer and manufacture novel food ingredients with desirable pharmacological properties and as potential food additives.

Graphical Abstract

Structural Characterization and Evaluation of Interfacial Properties of Pea Protein Isolate-EGCG Molecular Complexes

Highlights

Pea protein isolate (PPI) and EGCG spontaneously formed complexes.

Protein–polyphenol complexation was mainly driven by hydrogen bonding.

The binding of EGCG influenced the structure and functionality of PPI.

PPI-EGCG complexes had better emulsifier properties than PPI.

Abstract

There is increasing interest in using plant-derived proteins in foods and beverages for environmental, health, and ethical reasons. However, the inherent physicochemical properties and functional performance of many plant proteins limit their widespread application. Here, we prepared pea protein isolate (PPI) dispersions using a combined pH-shift/heat treatment method, and then, prepared PPI-epigallocatechin-3-gallate (EGCG) complexes under neutral conditions. Spectroscopy, calorimetry, molecular docking, and light scattering analysis demonstrated that the molecular complexes formed spontaneously. This was primarily ascribed to hydrogen bonds and van der Waals forces. The complexation of EGCG caused changes in the secondary structure of PPI, including the reduction in the α-helix and increase in the β-sheet and disordered regions. These changes slightly decreased the thermal stability of the protein. With the accretion of EGCG, the hydrophilicity of the complexes increased significantly, which improved the functional attributes of the protein. Optimization of the PPI-to-EGCG ratio led to the complexes having better foaming and emulsifying properties than the protein alone. This study could broaden the utilization of pea proteins as functional ingredients in foods. Moreover, protein–polyphenol complexes can be used as multifunctional ingredients, such as antioxidants or nutraceutical emulsifiers.

Study on the mechanism of non-covalent interaction between rose anthocyanin extracts and whey protein isolate under different pH conditions

The non-covalent interaction between anthocyanin and dietary protein had an impact on their physicochemical property. The purpose of this study was to study the non-covalent interaction mechanism between rose anthocyanin extract (RAEs) and whey protein isolate (WPI), and further compare the interaction mechanism with pure anthocyanin (PC) and WPI. At pH 3.0 and pH 7.0, RAEs and WPI had non-covalent interactions in the two systems with two types of unequal and mutually influencing binding sites, and the interaction forces were both hydrogen bonds and van der Waals forces. Interestingly, PC and WPI also had non-covalent interactions in both systems, the number of which binding sites was about one type, and the forces were hydrogen bonds and van der Waals forces. In addition, a variety of spectral combination techniques indicated that RAEs and PC caused similar changes in the secondary structure of WPI.

Comparison of the chemical composition and antioxidant, anti-inflammatory, α-amylase and α-glycosidase inhibitory activities of the supernatant and cream from black tea infusion

Tea cream is a kind of turbid substance commonly existing in tea infusion and tea beverage upon cooling. Herein, a comparative study was conducted on the supernatant and cream from black tea infusion in terms of antioxidant, anti-inflammatory and enzyme inhibitory activities, and chemical composition. Ultraviolet-visible (UV-vis) spectrometry and high-performance liquid chromatography (HPLC) analysis showed that the contents of protein, polyphenols, theaflavins, thearubigins, theabrownins, and caffeine in cream were significantly higher than those in the supernatant. The contents of Al, Ca, Cu, and Fe elements in cream were higher than those in the supernatant. However, higher levels of monosaccharides and free amino acids were detected in the supernatant compared with cream. The ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) based metabolomics analysis revealed that the main marker compounds between the supernatant and the cream were organic acids, phenolic acids, and flavan-3-ols and their oxidation products, flavonol glycosides and amino acids. The cream showed better antioxidant and anti-inflammatory, as well as α-amylase and α-glycosidase inhibitory activities than the supernatant, because it contained higher contents of polyphenols than the supernatant. The present study expanded the new vision towards the cream of black tea infusion.

Insight on the microscopic binding mechanism of bisphenol compounds (BPs) with transthyretin (TTR) based on multi-spectroscopic methods and computational simulations

Thyroid hormones are involved in numerous physiological processes as regulators of metabolism, regulating organ growth, and mental state. Bisphenol compounds (BPs) are recognized as chemicals that interfere with endocrine balance. Because BPs have a similar structure to thyroxine, they can compete for binding to thyroid protein and disrupt the normal physiological activity of the thyroid system. In this study, three typical bisphenol compounds were selected to explore the interaction between BPs and TTR by computer simulations and multi-spectroscopic methods. The results revealed that BPs quenched the endogenous fluorescence of TTR via the combination of static quenching and non-radiative energy transfer, and the van der Waals forces and hydrogen bonding played a synergistic role in the binding process of BPs and TTR. Furthermore, the three-dimensional fluorescence spectroscopy, UV-vis spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy, which were employed to determine the conformation of protein, revealed that binding of BPs with TTR could induce conformational changes in TTR. In addition, the binding sites and the residues surrounding the BPs within the TTR were determined through molecular docking and molecular dynamics simulation. Therefore, this work provides new insights into the interaction between BPs and TTR to evaluate the potential toxicity of BPs.

Investigation of molecular mechanisms of interaction between myofibrillar proteins and 1-heptanol by multiple spectroscopy and molecular docking methods

In this study, we investigated the interaction between myofibrillar proteins (MPs) and selected alcohols (1-pentanol, 1-hexanol, and 1-heptanol). Only 1-heptanol exhibited the binding ability to MPs, and the binding ability significantly increased with increasing protein concentration (p < 0.05). In addition, both static and dynamic quenching occurred during the interaction, with a red shift of the maximum absorption peak in the synchronous fluorescence spectra indicating a change in the microenvironment of the MPs. The results of circular dichroism measurements suggested that the interaction between MPs and 1-heptanol altered the secondary structure of the MPs. Furthermore, thermodynamic analysis showed that hydrogen bonding and van der Waals forces dominated the interaction between MPs and 1-heptanol, which was confirmed by the results of molecular docking/dynamics simulations. This study provides an in-depth understanding of the interaction between MPs and alcohols, which can help to improve the flavor control in meat.

Fabrication and performance evaluation of pectin-fish gelatin-resveratrol preservative films

Resveratrol-loaded fish gelatin (FG)-low methoxyl pectin (LMP) composite films with different FG:LMP mass ratios were prepared and evaluated as food packaging materials. With increasing FG contents, the water solubility of the films decreased. Moreover, the UV (315-400 nm) blocking efficiency and opacity increased with increasing LMP contents. The elongation of the films at breaking and tensile strengths were adjusted using the ratio of FG and LMP. The lowest water vapour permeability was observed at an FG:LMP mass ratio of 2:1. All films exhibited good antioxidant properties and significantly delayed oil deterioration when used for beef tallow preservation. The release behaviour of resveratrol in 95% ethanol as a food simulant was determined by film composition. The fabricated films exhibit significant potential for beef tallow preservation applications. Furthermore, LMP can improve the stability of resveratrol-FG complexes and compete with resveratrol for binding FG to accelerate resveratrol release.

Modeling with Multiple Correlated Spectral Data Based on Approximating the Nonlinear Spectrum Induced by Scattering

In the spectral quantitative analysis of scattering solution, the improvement of accuracy is seriously restricted by the nonlinearity caused by scattering, and even the measurement will fail due to the influence of scattering. The important reasons are that the modeling variables are greatly affected by nonlinearity, and the information contained in the modeling data cannot represent the scattering characteristics. In this paper, a method is proposed, in which the spectral data of several optical pathlengths with equal space are combined as the modeling data set of a sample. These highly correlated spectral data contain relatively nonlinear information. The addition of the spectral data provides more options for the selection of principal components in modeling with PLS method. By giving lower weight to the corresponding wavelength which is greatly affected by scattering, the model is insensitive to scattering and the prediction accuracy is improved. Through the spectral quantitative analysis experiment on strong scattering material, the prediction accuracy of the model was 61.7% higher than that of the traditional method and was 58.5% higher than that of the variable sorting for normalization method. The feasibility of the method is verified.