Use of a combination of the MD simulations and NMR spectroscopy to determine the regulatory mechanism of pulsed electric field (PEF) targeting at C-terminal histidine of VNAVLH

Production of bioactive peptides by high-voltage pulsed electric field: Protein extraction, mechanism, research status and collaborative application

Bioactive peptides exhibit a variety of potential applications in the fields of medicine, food and cosmetics. However, studies have shown that the traditional preparation is characterized by low efficiency, substantial pollution, limited activities and poor purity, which constrains their further application. High-voltage pulsed electric field (HPEF) technology, as a physical non-thermal processing method, shows unique advantages in bioactive peptide preparation. Through comprehensive analysis, this paper reveals the main principle of HPEF technology, the extraction of proteins (break up cellular tissue), the structural changes of proteins, enzymes and bioactive peptides after treatment, the improvement of bioactive peptides' functional properties and the potential in promoting bioactive peptides' large-scale production. Besides, this paper introduces the application of other non-thermal processing technologies, artificial intelligence and nanotechnology, providing new ways of thinking for the efficient preparation and application of bioactive peptides and establishes a theoretical foundation for the application and promotion of HPEF technology.

Molecular dynamics insights into pulsed electric field-induced structural and functional changes in polygalacturonase

Pulsed electric field (PEF) is one of the emerging non-thermal sterilization technologies which can be applied to fruit juice preservation. The PEF process can also affect the activity and structure of enzymes and other natural macromolecules in fruit juice, including polygalacturonase (PG), an undesired enzyme which can dissolve the turbidity state of juice. However, the precise molecular mechanisms driving this phenomenon remain elusive. In this study, molecular dynamics simulations were used to investigate the effects of PEF on PG. It was found that with electric field strength <1 V/nm, the structural change of the protein is insignificant and could be restored within a few nanoseconds. However, with electric field strength >1 V/nm, most of the secondary structure is lost, the internal hydrogen bonds are broken and the hydrophobic core is exposed irreversibly. The relative positions of the active sites of the PG are also changed. The experimental results also showed that the activity of PG decreased with the increase of electric field strength. This study reveals the basic mechanism of the interaction between PEF and PG, suggesting PEF can potentially be used for enzyme control in fruit juice preservation.

Digestive and Absorptive Properties of the Antarctic Krill Tripeptide Phe-Pro-Phe (FPF) and Its Auxiliary Memory-Enhancing Effect

Aging and stress have contributed to the development of memory disorders. Phe-Pro-Phe (FPF) was identified with high stability by mass spectrometry from simulated gastrointestinal digestion and everted gut sac products of the Antarctic krill peptide Ser-Ser-Asp-Ala-Phe-Phe-Pro-Phe-Arg (SSDAFFPFR) which was found to have a positive impact on memory enhancement. This study investigated the digestive stability, absorption, and memory-enhancing effects of FPF using nuclear magnetic resonance spectroscopy, simulated gastrointestinal digestion, in vivo fluorescence distribution analysis, mouse behavioral experiments, acetylcholine function, Nissl staining, immunofluorescence, and immunohistochemistry. FPF crossed the blood-brain barrier into the brain after digestion, significantly reduced shock time, working memory errors, and reference memory errors, and increased the recognition index. Additionally, FPF elevated ACh content; Nissl body counts; and CREB, SYN, and PSD-95 expression levels, while reducing AChE activity (P < 0.05). This implies that FPF prevents scopolamine-induced memory impairment and provides a basis for future research on memory disorders.

Advances in Research on the Activity Evaluation, Mechanism and Structure-Activity Relationships of Natural Antioxidant Peptides

Antioxidant peptides are a class of biologically active peptides with low molecular weights and stable antioxidant properties that are isolated from proteins. In this review, the progress in research on the activity evaluation, action mechanism, and structure-activity relationships of natural antioxidant peptides are summarized. The methods used to evaluate antioxidant activity are mainly classified into three categories: in vitro chemical, in vitro cellular, and in vivo animal methods. Also, the biological effects produced by these three methods are listed: the scavenging of free radicals, chelation of metal ions, inhibition of lipid peroxidation, inhibition of oxidative enzyme activities, and activation of antioxidant enzymes and non-enzymatic systems. The antioxidant effects of natural peptides primarily consist of the regulation of redox signaling pathways, which includes activation of the Nrf2 pathway and the inhibition of the NF-κB pathway. The structure-activity relationships of the antioxidant peptides are investigated, including the effects of peptide molecular weight, amino acid composition and sequence, and secondary structure on antioxidant activity. In addition, four computer-assisted methods (molecular docking, molecular dynamics simulation, quantum chemical calculations, and the determination of quantitative structure-activity relationships) for analyzing the structure-activity effects of natural peptides are summarized. Thus, this review lays a theoretical foundation for the development of new antioxidants, nutraceuticals, and cosmetics.

Functionalization of pine kernel protein by pH-shifting combined with ultrasound treatments: Further improvement with increasing acidity

As a novel plant protein, developing various aspects of pine kernel protein (PKP) functionality is essential to meet the demand for protein-rich foods. To achieve this, the PKP was functionalized by a combination of pH-shifting and ultrasound techniques. The solubility, emulsification and droplet stability of the PKP in the pH range suitable to food (pH 3 to 7) were further investigated. The pH 12-shifting was an effective strategy to increase the solubility of PKP under extreme acidic and neutral conditions, characterized by a higher content of β-sheets and random coils, a greater exposure of free sulfhydryl and hydrophobic groups. Furthermore, appropriate ultrasonic power (250 W) further improved the solubility of PKPs by disrupting intermolecular hydrogen and hydrophobic bonds. As the ambient acidity increased, the emulsions exhibited higher viscoelasticity and stronger protein interactions. Especially at pH 3, the oil droplets stabilized by U250-PKP-12 (PKP treated with 250 W ultrasound-assisted pH 12-shifting) were homogeneously dispersed and surrounded by dense protein, maintaining small particle size and large electrostatic repulsion, and there was no apparent creaming or phase separation in the emulsions after 10 days of storage. Thus, the functionality of PKP after pH-shifting combined with ultrasonic treatments is further enhanced by increasing the environmental acidity.

C-Terminal Modification on the Immunomodulatory Activity, Antioxidant Activity, and Structure–Activity Relationship of Pulsed Electric Field (PEF)-Treated Pine Nut Peptide

In this study, a novel peptide VNAVL was synthesized by removing the C-terminal histidine on the basis of a bioactive peptide VNAVLH obtained from pine nut (Pinus koraiensis Sieb. et Zucc) protein. The effects of removing histidine on antioxidant activity, immunomodulatory activity, and secondary structure of the PEF-treated peptide were discussed. Compared with VNAVLH, VNAVL only exhibited lower antioxidant activity, but no immunomodulatory activity to release TNF-α, IL-6, and NO by activating RAW 264.7 cells. In addition, both antioxidant and immune activities of VNAVLH were significantly more sensitive to treatment with 40 kV/cm than other field intensities, whereas VNAVL was not sensitive to field strength changes. CD spectra and DSSP analysis verified that both peptides consisted of a β structure and random coil, but the ability of VNAVL to transform the random coil via PEF treatment is weaker than that of VNAVLH. Therefore, PEF treatment might expose the key active site located on the C-terminal histidine by altering the secondary structure of the peptide.

Mechanism of Ser-Ala-Gly-Pro-Ala-Phe treatment with a pulsed electric field to improve ethanol-induced gastric mucosa injury in mice

This paper focused on the mechanism of Ser-Ala-Gly-Pro-Ala-Phe (SAGPAF) treatment to improve gastric mucosal injury in mice. A gastric mucosa injury model induced by ethanol was established, and the superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, nitric oxide (NO) content and myeloperoxidase (MPO) level were determined. We performed macroscopic and histopathological evaluation of the gastric organs. Moreover, we analyzed the mechanism of SAGPAF treatment by western blotting. Compared with the model group, the SOD activity and NO content in the medium-dose and high-dose SAGPAF groups of treated with 10 kV cm^-1 field intensity were significantly increased. The MDA content and MPO level were decreased significantly. They significantly reduced the gastric mucosal injury induced by ethanol (21.17 ± 3.51% and 13.99 ± 2.00%) and the histopathological scores (3.83 ± 0.40 and 4.33 ± 0.37) (P < 0.05). Western blotting analysis showed that SAGPAF after pulsed electric field (PEF) treatment improved gastric injury by reducing protein phosphorylation. These findings provided strong evidence that PEF-treated SAGPAF enhanced the gastric mucosal barrier function by inhibiting the activation of the mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signaling pathways, reducing the ethanol-induced inflammatory response and oxidative stress.