The antioxidant peptides from walnut protein hydrolysates and their protective activity against alcoholic injury.

In this study, walnut protein was hydrolyzed, separated by ultrafiltration, purified by RP-HPLC, identified by LC-MS/MS, and screened by molecular docking to finally obtain three novel antioxidant peptides HGEPGQQQR (1189.584 Da), VAPFPEVFGK (1089.586 Da) and HNVADPQR (949.473 Da). These three peptides exhibited excellent cellular antioxidant activity (CAA) with EC50 values of 0.0120 mg mL-1, 0.0068 mg mL-1, and 0.0069 mg mL-1, respectively, which were superior to that of the positive control GSH (EC50: 0.0122 mg mL-1). In the ethanol injury model, three antioxidant peptides enhanced the survival of cells treated with ethanol from 47.36% to 62.69%, 57.06% and 71.64%, respectively. Molecular docking results showed that the three antioxidant peptides could effectively bind to Keap1, CYP2E1 and TLR4 proteins. These results suggested that walnut-derived antioxidant peptides could be potential antioxidants and hepatoprotective agents for application in functional foods.

Investigation into the Relationship between Spermidine Degradation and Phenolic Compounds Biosynthesis in Barley Seedlings under Ultraviolet B Stress.

Barley germination under ultraviolet B (UV-B) illumination stress induces effective accumulation of phenolic compounds in the barley. Spermidine can enhance the biosynthesis of phenolic compounds and alleviate the oxidative damage caused by UV-B. To better understand the function of spermidine, inhibitors of enzymes that are involved in the degradation of spermidine and the synthesis of gamma-aminobutyric acid (GABA), the product of spermidine degradation, were applied to barley germinated under UV-B treatment. The results showed a more severe oxidative damage, and a decrease in phenolic acid contents were observed when spermidine degradation was inhibited. However, GABA application did attenuate an increase in electrolyte permeability and MDA content caused by UV-B induced oxidative damage and improved the respiration rate. Meanwhile, GABA application can elevate the accumulation of phenolic compounds by ca. 20%, by elevating the activities of some key enzymes. Furthermore, the application of GABA, together with the inhibitor of spermidine degradation, can alleviate its suppression of the synthesis of phenolic acids, and resistance to UV-B stress. In conclusion, spermidine alleviated oxidative damage and enhanced the accumulation of phenolic compounds using its degradation product.

Unnatural amino acids: promising implications for the development of new antimicrobial peptides.

The increasing incidence and rapid spread of bacterial resistance to conventional antibiotics are a serious global threat to public health, highlighting the need to develop new antimicrobial alternatives. Antimicrobial peptides (AMPs) represent a class of promising natural antibiotic candidates due to their broad-spectrum activity and low tendency to induce resistance. However, the development of AMPs for medical use is hampered by several obstacles, such as moderate activity, lability to proteolytic degradation, and low bioavailability. To date, many researchers have focussed on the optimization or design of novel artificial AMPs with desired properties. Unnatural amino acids (UAAs) are valuable building blocks in the manufacture of a variety of pharmaceuticals, and have been used to develop artificial AMPs with specific structural and physicochemical properties. Rational incorporation of UAAs has become a very promising approach to endow AMPs with strong and long-lasting activity but no toxicity. This review aims to summarize key approaches that have been used to incorporate UAAs to develop novel AMPs with improved properties and better performance. It is anticipated that this review will guide future design considerations for UAA-based antimicrobial applications.

Identification and functional analysis of three novel osteogenic peptides isolated from tilapia scale collagen hydrolysate.

On the basis of our previous study that 133 peptides were identified from the tilapia scale peptide-calcium chelate, the potential osteogenic peptide monomers through the calcium-binding properties of peptides and molecular docking were screened, and the osteogenic activity and active mechanism of the peptides were further researched in this study. Three highly osteogenic peptides GPAGPHGPVG (844.4191 Da), APDPFRMY (995.4534 Da), and TPERYY (827.3813 Da) were screened. Molecular docking showed that the three osteogenic peptides had the same interaction sites in the epidermal growth factor receptor (EGFR), namely ARG 285, GLN 8, GLY 317, THR 406, and HIS 409. Compared to the blank control group, within 50 µg/mL of GPAGPHGPVG, APDPFRMY, and TPERYY increased the proliferation of MC3T3-E1 cells by changing the cell proportion in the S and G2/M phases, and the alkaline phosphatase (ALP) activity of MC3T3-E1 cells treated with 50 µg/mL of the three active peptides increased by 25%, 37%, and 56%, respectively. The three active peptides at 10 µg/mL concentration significantly promoted the mineralization of osteoblasts, and the mineralized calcium nodules increased by 166%, 161%, and 111%, respectively. TPERYY significantly increased the expression of osteogenic genes (osteocalcin (OCN), type I collagen (Col I α) and transcription factor (OSX)). Moreover, TPERYY significantly increased the mRNA and protein expression of ß-catenin to 1.39 and 2.6 times of the blank control group, respectively, while decreased the mRNA and protein expression of glycogen synthesis kinase (GSK3ß) to 1.6 and 2.3 times of the blank control group, respectively. This study provides a theoretical basis for using GPAGPHGPVG, APDPFRMY, and TPERYY peptides as functional foods to prevent osteoporosis.

Effect of Amino Acids on Folates Accumulation in Wheat Seedlings during Germination under Red Light Radiation.

Deficiency of folates can cause various health problems, and germination is a potential way to enrich folates in grain-based food materials. In the present study, the effects of six amino acids (phenylalanine, tyrosine, tryptophan, glutamate, γ-aminobutyric acid, and p-aminobenzoic acid) on folate accumulation during wheat germination under red light radiation were investigated, and an optimized combination of amino acids for promoting folate enrichment was established. The results showed that applying phenylalanine, tyrosine, tryptophan, glutamate, or p-aminobenzoic acid to wheat seedlings during germination can significantly increase the content of total folates through activating the synthesis of the precursors for folate synthesis (pterin and p-aminobenzoic acid) or condensation of these two moieties. Meanwhile, up-regulation of corresponding genes was observed by measuring their expressions to investigate the mechanism for promoting the accumulation of folates. The highest content of folates (ca. 417 µg/100 g DW) was observed when the germinated wheat was cultured with a mixture of 1.5 mM phenylalanine, 0.5 mM tyrosine, 0.5 mM tryptophan, 0.75 mM p-aminobenzoic acid, and 0.5 mM glutamic acid, which was 50% higher than the control seedlings. This study established a promising and practical approach to enhance the accumulation of folates in wheat seedlings.

DDAH1 Protects against Acetaminophen-Induced Liver Hepatoxicity in Mice.

In many developed countries, acetaminophen (APAP) overdose-induced acute liver injury is a significant therapeutic problem. Dimethylarginine dimethylaminohydrolase 1 (DDAH1) is a critical enzyme for asymmetric dimethylarginine (ADMA) metabolism. Growing evidence suggests that liver dysfunction is associated with increased plasma ADMA levels and reduced hepatic DDAH1 activity/expression. The purpose of this study was to investigate the involvement of DDAH1 in APAP-mediated hepatotoxicity using Ddah1-/- and DDAH1 transgenic mice. After APAP challenge, Ddah1-/- mice developed more severe liver injury than wild type (WT) mice, which was associated with a greater induction of fibrosis, oxidative stress, inflammation, cell apoptosis and phosphorylation of JNK. In contrast, overexpression of DDAH1 attenuated APAP-induced liver injury. RNA-seq analysis showed that DDAH1 affects xenobiotic metabolism and glutathione metabolism pathways in APAP-treated livers. Furthermore, we found that DDAH1 knockdown aggravated APAP-induced cell death, oxidative stress, phosphorylation of JNK and p65, upregulation of CYP2E1 and downregulation of GSTA1 in HepG2 cells. Collectively, our data suggested that DDAH1 has a marked protective effect against APAP-induced liver oxidative stress, inflammation and injury. Strategies to increase hepatic DDAH1 expression/activity may be novel approaches for drug-induced acute liver injury therapy.

Proteins from leguminous plants: from structure, property to the function in encapsulation/binding and delivery of bioactive compounds.

Leguminous proteins are important nutritional components in leguminous plants, and they have different structures and functions depending on their sources. Due to their specific structures and physicochemical properties, leguminous proteins have received much attention in food and nutritional applications, and they can be applied as various carriers for binding/encapsulation and delivery of food bioactive compounds. In this review, we systematically summarize the different structures and functional properties of several leguminous proteins which can be classified as ferritin, trypsin inhibitor, ß-conglycinin, glycinin, and various leguminous proteins isolates. Moreover, we review the development of leguminous proteins as carriers of food bioactive compounds, and emphasize the functions of leguminous protein-based binding/encapsulation and delivery in overcoming the low bioavailability, instability and low absorption efficiency of food bioactive compounds. The limitations and challenges of the utilization of leguminous proteins as carriers of food bioactive compounds are also discussed. Possible approaches to resolve the limitations of applying leguminous proteins such as instability of proteins and poor absorption of bioactive compounds are recommended.

The formation of phycocyanin-EGCG complex for improving the color protection stability exposing to light.

Phycocyanin (PC) is a natural pigment-protein complex in food dye applications. In this study, a phycocyanin-epigallocatechin gallate (EGCG) complex (PE) was prepared and the effects of EGCG on the structure and color stability of PC were evaluated. The fluorescence results showed that the binding number n was 62.1 ± 3.41 (EGCG/PC) and the binding constant K was 4.39 (±0.2) × 105 M-1, indicating a weak-binding interaction. Fourier transform-infrared analysis showed that EGCG caused structural changes in PC by partially uncoiling α-helix and increasing ß-sheet content. The EGCG induced a PC association at a reaction molar ratio above 40:1 (EGCG/PC). Moreover, EGCG protected phycocyanobilin against color fading, making PE more stable relative to PC under 8-days storage in light. This study provides a novel scheme to stabilize PC by forming a complex with polyphenols, which will facilitate the PC application as a natural blue pigment in food.

Self-Assembly of Phycoerythrin with Oligochitosan by Electrostatic Interaction for Stabilization of Phycoerythrin.

Phycoerythrin (PE) is a natural water-soluble pigment protein with characteristic phycobilins and is sensitive to thermal and light environmental changes. In this study, PE was extracted from Porphyra haitanensis and PE-oligochitosan complexes (POC) were fabricated by a self-assembly approach. The effects of cationic oligochitosan on the binding interaction, structure, size distribution, and color stability of PE were evaluated. The stoichiometric number n was calculated to be 21.67 ± 2.65 (oligochitosan/PE) and the binding constant K was (6.47 ± 0.48) × 105 M-1. Cationic oligochitosan could electrostatically interact with PE and affect the PE structure by increasing the α-helix content. In addition, high concentrations of oligochitosan led to the formation of dense phycoerythrin protein granules. Moreover, at a reaction ratio of 20.0:1 (oligochitosan/PE), being approximately the predicted stoichiometric number n, the thermal stability (40-80 °C), natural light stability, and ultraviolet light irradiation (254 nm) stability of the POC were improved. This study provides an approach to reduce the susceptibility of PE upon environmental changes by forming a stable self-assembly complex, which will promote the application of PE as a natural pigment protein in food and chemical applications.

Chaotrope-Controlled Fabrication of Ferritin-Salvianolic Acid B- Epigallocatechin Gallate Three-Layer Nanoparticle by the Flexibility of Ferritin Channels.

Phytoferritin has a natural cagelike architecture for carrying bioactive molecules, and it is uniquely suited to function as a carrier due to its multiple interfaces and channels. In this study, a novel approach was proposed to prepare ferritin-salvianolic acid B-epigallocatechin gallate (EGCG) three-layer nanoparticles (FSE) through the steric hindrance of ferritin channels. Urea (30 mM) could expand the ferritin channel size evidenced by the improved iron release rate vo and promote the EGCG penetration into the ferritin cavity without disassembly of the ferritin cage. The encapsulation ratio of EGCG was 16.0 ± 0.14% (w/w). Salvianolic acid B attached to the outer interface of ferritin through weak bonds with a binding constant of (2.91 ± 0.04) × 105 M-1. The FSE maintained a spherical structure with a diameter of 12 nm. Moreover, when subjected to heat (40-70 °C) there was a significant increase in the stability of EGCG in the FSE due to the binding of salvianolic acid B. Through this interesting approach, two molecules are simultaneously attached and encapsulated in ferritin in a multilayer form under moderate conditions, which is conducive to the protection of unstable molecules for potential encapsulation and delivery utilization.

Fabrication of a ferritin-casein phosphopeptide-calcium shell-core composite as a novel calcium delivery strategy.

Plant ferritin has a natural cage-like nanospace for carrying bioactive ingredients. By taking advantage of the calcium binding ability of casein phosphopeptide (CPP) and the cage-like conformation of plant ferritin, a ferritin-CPP shell-core complex (FC) was fabricated with the reversible self-assembly character of ferritin induced by a pH 2.0/7.0 transition strategy. The FC-calcium composite (FCC) was further fabricated by binding of the FC with calcium ions. When the same amount of calcium was loaded, the calcium binding capacity of the FCC was 28.13 ± 1.65%, which was significantly higher than that of ferritin and CPP alone. Fluorescence and Fourier transform infrared analysis indicated that the CPP encapsulation and the calcium binding in the FCC influenced the ferritin structure. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) results showed that the spherical morphology and the 12 nm-diameter size were sustained in the FC and FCC. Moreover, the FCC as a transport carrier could increase the precipitation time of calcium phosphate, and the encapsulated calcium could be released in a more sustained manner as compared with ferritin and CPP under simulated in vitro gastrointestinal conditions. This study presents a novel calcium delivery strategy based on the ferritin cage and CPP, which will improve the applicability of ferritin and CPP and enhance the bioavailability of calcium ions.

Insights for the New Function of N,N-Dimethylpyrrolidone in Preparation of a High-Voltage Spinel LiNi0.5Mn1.5O4 Cathode.

The solid-state method is extensively applied to the synthesis of electrode materials for its simplicity and low cost. However, particles obtained using the traditional solid-state method exhibited a large, uneven particle size and a severe aggregation phenomenon, leading to an unsatisfactory electrochemical performance. Here, spinel LiNi0.5Mn1.5O4 (LNMO) with good dispersion was synthesized using the solid-state method with the addition of N,N-dimethylpyrrolidone (NMP). During the LNMO preparation process, NMP is effective in refining and optimizing the particle size and suppressing the aggregation phenomenon. Meanwhile, the N element migration phenomenon was also observed in the bulk of LNMO, and it was beneficial for extending solid-solute reactions as demonstrated by in situ X-ray diffraction. LNMO prepared with NMP (LNMO-N-x) exhibited a higher discharge voltage and capacity (115.3 mA h g-1 at 2 C) compared with LNMO (105.8 mA h g-1). These results reveal the function of NMP in the preparation of LNMO and the effect of the physical characteristic changes on structure and phase transition in a working battery, and it can be easily incorporated into other electrode materials; if well engineered, it will contribute a lot to the further applications of lithium ion batteries.

Ultrasensitive electrochemiluminescence biosensor for the detection of tumor exosomes based on peptide recognition and luminol-AuNPs@g-C3N4 nanoprobe signal amplification.

Highly sensitive determination of tumor exosomes is significant for early diagnosis of cancers and precision therapy. Herein, a sandwich peptide-based electrochemiluminescence (ECL) biosensor was developed for determination of phosphatidylserine (PS)-positive exosomes, a promising biomarker for early diagnosis of ovarian malignancy. A PS-specific binding peptide with high affinity was immobilized on Au nanoflowers (AuNFs) modified biosensing interface for recognition and capture of exosomes. Meanwhile, g-C3N4 nanosheet loaded with luminol capped AuNPs (Lum-AuNPs@g-C3N4) nanocomposite was used as the ECL signal nanoprobe. The g-C3N4 nanosheets with large surface area were not only utilized as the carrier to immobilize more peptides for recognition of exosomes but also used to catalyze co-reactant H2O2 decomposition to achieve the ECL signal amplification of luminol-H2O2 system. Under optimal conditions, the biosensor showed superior performances compared with most currently available methods, including wider linear range across 5 orders of magnitude and a lower detection limit (LOD) down to 39 particles µL-1. Moreover, the biosensor could be applicable for determination of exosomes in complex biological samples. This study indicates the combination of peptide recognition with nanoprobe as a label for signal amplification in sandwich ECL biosensing is a great promising strategy for sensitive and cost-effective determination of exosomes.

The structure and stability analysis of the pea seed legumin glycosylated by oligochitosan.

BACKGROUND: The functionality of pea proteins is relatively weak relative to that of soybean proteins, which limits the application of pea proteins in food and nutritional applications. Glycosylation is a promising approach to influence the protein structure and in turn change the functional properties of pea proteins. RESULTS: In this study, the effect of transglutaminase-induced oligochitosan glycosylation on the structural and functional properties of pea seed legumin was studied. Different oligochitosan-modified legumin complexes (OLCs) were prepared by applying different molar ratios of legumin to oligochitosan (1:1 to 1:4) induced by transglutaminase (10 U g-1 protein). Results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), glucosamine, and free amino analysis showed that the legumin could be covalently bonded with the oligochitosan and were influenced by the applying dose of the oligochitosan. Infrared spectroscopy, fluorescence, and scanning electron microscopy analysis indicated that the structure of the different OLC samples could be changed to different extents. Moreover, although the emulsifying activity decreased, the emulsification stability, thermal stability, and in vitro digestive stability of the OLCs were remarkably improved relative to that of the untreated legumin. CONCLUSION: Oligochitosan glycosylation could change the structure of the legumin and consequently improve its emulsification stability, thermal stability, and in vitro digestive stability. This study will facilitate the legumin functionalization by the glycosylation approach to fabricate protein-oligochitosan complex for potential food and nutritional applications. © 2020 Society of Chemical Industry.

Efficient Synthesis of Structured Phospholipids Containing Short-Chain Fatty Acids over a Sulfonated Zn-SBA-15 Catalyst.

Catalytic production of structured phospholipids (SPLs) containing short-chain fatty acids (SCFAs) in an efficient heterogeneous manner is of great importance from the standpoint of food engineering. Herein, a bifunctionalized sulfonated Zn-SBA-15 catalyst was studied for SPL synthesis through interesterification of soybean lecithin with ethyl propionate or methyl butyrate. Various characterization techniques such as pyridine Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy were conducted to determine the physicochemical properties, so as to build the possible structure-reactivity relationship of the catalyst. In screening tests with commercial Amberlyst-15 or other SBA-15-type materials, the as-prepared sample showed promising catalytic performance probably owing to its mesoporous structure and cooperative role of Brönsted and Lewis acid sites. Notably, the sample was easily separated and recycled without obvious deactivation. In general, the investigated catalyst was regarded as one of the promising alternatives to otherwise expensive biocatalysts for SCFA-containing SPL production.

Double-Interface Binding of Two Bioactive Compounds with Cage-Like Ferritin.

Ferritin is a cage-like carrier protein with multiple interfaces, allowing for the encapsulation and delivery of biologically active molecules. In this study, hesperetin was covalently conjugated to the outer surface of ferritin to fabricate hesperetin covalently modified ferritin (HFRT) at pH 9.0. This conjugation resulted in a binding equivalent of hesperetin to ferritin of 12.33 ± 0.56 nmol/mg. After covalent binding, the free amino content of HFRT decreased and the secondary and tertiary structures of HFRT were changed relative to the structure of control ferritin. In addition, HFRT successfully retained the cage-like structure of ferritin and exhibited reversible self-assembly property regulated by pH shifts. Taking advantage of this property, quercetin was encapsulated into the inner surface of HFRT with an encapsulation ratio of 14.0 ± 1.36% (w/w). The modification with hesperetin improved the digestive stability of ferritin and enhanced the stability of encapsulated quercetin against thermal treatment compared to unmodified ferritin. This study explored the functions of the double interfaces of ferritin by covalent and non-covalent binding of two different bioactive compounds. The results can help guide the functionalization of the ferritin cage as a nanocarrier in food application.

NaCl treatment on physio-biochemical metabolism and phenolics accumulation in barley seedlings.

Phenolics are important secondary metabolites in plants with strong antioxidant effects. Seeds germination and exogenous stimulation could activate endogenous enzymes to enhance the content of phenolic acids and flavonoids. Barley seeds geminated under NaCl (1-20 mM) treatment to evaluate the accumulation of phenolics in this study. Results showed that NaCl treatment significantly enhanced the growth of seedlings, especially bud length. NaCl treatment up-regulated genes and proteins expression of phenylalanine ammonia lyase (PAL), cinnamate-4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL), resulting in the enhancement of their activities. As a result, phenolic acids and flavonoids contents increased by 11.19% and 32.54%, respectively, in which gallic acid, protocatechuic, fisetin, myricetin and quercetin were affected mostly. Moreover, NaCl treatment enhanced 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging capacity. Hence, NaCl stimulated the synthesis of phenolic components via enhancing gene, protein expression and the activity of key enzymes.

Black phosphorus quantum dots as novel electrogenerated chemiluminescence emitters for the detection of Cu2.

For the first time, electrochemiluminescence (ECL) emission was observed from black phosphorus quantum dots (BPQDs) in the presence of K2S2O8 as the co-reactant. The potential application of BPQDs ECL in analytical chemistry was also demonstrated using Cu2+ as an example.

Coencapsulation and Stability Evaluation of Hydrophilic and Hydrophobic Bioactive Compounds in a Cagelike Phytoferritin.

Enrichment of multiple bioactive components with different characters into one food substrate simultaneously is a challenge. In this study, the hydrophilic epigallocatechin gallate (EGCG) and the hydrophobic quercetin were simultaneously enriched in the cavity of phytoferritin from red bean seed deprived of iron (apoRBF), a cagelike protein. The interactions of apoRBF with EGCG and quercetin were evaluated by UV/visible absorption, fluorescence, and circular dichroism technologies. By combination of the reversible assembly and urea induced approaches, both EGCG and quercetin were successfully coencapsulated in apoRBF to fabricate four kinds of apoRBF-EGCG-quercetin nanocomplexes FEQ (FEQ1, FEQ2, FEQ3, and FEQ4) with good solubility in aqueous solution. All FEQ samples maintained the typically spherical morphology of ferritin cage with a diameter around 12 nm. Among the four FEQ samples, the FEQ1 prepared by involving a pH 2.0/6.7 transition scheme was more effective in encapsulating EGCG and quercetin molecules than that by the urea induced method. Furthermore, all FEQs facilitated the stability of EGCG and quercetin molecules relative to free ones, and simultaneous coencapsulation of EGCG and quercetin could significantly improve the quercetin stability as compared with that of the free one and quercetin-loaded ferritin (p < 0.05), respectively. This work provides a new scheme to design and fabricate the ferritin based carrier for encapsulation of multiple bioactive components, and it is beneficial for the intensification of multifunction in one food substrate.

Physiological and Metabolic Responses of a Novel Dunaliella salina Strain to Myo-inositol1.

Dunaliella salina is well known for its ability to accumulate large amounts of ß-carotene. Myo-inositol (MI) enhances the biomass production of D. salina, but the underlying mechanisms were unclear. The present study showed that the concentration of exogenous MI decreased gradually and reached a constant level at the 4th day of cultivation. MI enhanced the contents of total colored carotenoids and the activity of photosystem II. Metabolic profiles were significantly changed after the addition of exogenous MI, as revealed by multivariate statistical analysis. The metabolites could be categorized into four groups based on the relative levels in different samples. Exogenous MI increased the levels of most detected sugars, amino acids, and total saturated and unsaturated fatty acids. Based on the physiological and metabolic analyses, a hypothetical growth-promoting model that MI promotes the growth of D. salina TG by increasing the levels of key metabolites and possibly enhancing photosynthesis, was proposed. This study provides valuable information for understanding the growth-promoting mechanisms of MI in D. salina from the metabolic perspective.