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.

Characterization of a synergistic antioxidant synthetic peptide from sea cucumber and pine nut.

We compared antioxidant activity of the synthetic peptide Val-Leu-Leu-Tyr-Gln-Asp-His-Cys-His (VLLYQDHCH), sea cucumber peptide Val-Leu-Leu-Tyr (VLLY) and pine seed peptide Gln-Asp-His-Cys-His (QDHCH). The structure-activity relationship was analyzed based on radical scavenging ability and Raman, circular dichroism (CD) and nuclear magnetic resonance spectroscopy (NMR). Based on RP-HPLC, the contents of peptides in simulated gastrointestinal tract and digestive juices in rat intestinal sac were determined, and their absorption stability were explored. These results showed that the DPPH clearance rate of VLLYQDHCH was 45.90% higher than the sum of VLLY and QDHCH at 3 mmol/L. The α-helix, ß-sheet and random coil of VLLYQDHCH increased, ß-turn decreased, and the active hydrogen site shifted. After simulated digestion and absorption, the retention rate of VLLYQDHCH was 80.86 ± 0.88% in simulated stomach and 45.75 ± 0.97% in simulated intestine. There was no significant difference in the absorption rates of the three peptides (P > 0.05). This research provided a new idea for the development of safe and green food-derived animal-plant protein antioxidant peptides.

Research advances and application of pulsed electric field on proteins and peptides in food.

Proteins or peptides are essential nutrients required by the human body because some essential amino acids cannot be biosynthesized. In this context, food industry is urged to find method to meet the demands of high protein yield and high bioactive protein/peptide production. Pulsed electric fields (PEF) possess high potential and a promising future in the processing and activity performance enhancement of protein/peptides. PEF processing, as food preservation technology, has ongoing from laboratory and pilot plant scale level to the industrial level, however, there was a lack of knowledge on the effects of PEF on proteins and peptides. In the last few years, the increasing number of studies demonstrated that PEF processing is effective in extracting protein, inactivating most endogenous enzymes in foods, improving peptides' biological activities. We provide an overview of existing and potential applications of PEF on proteins and peptides in food and suggest that the change in structures and functions of proteins/ protein hydrolysates (food component proteins/peptides and enzymes) in PEF processing is receiving considerable attention and may provide a basis for elucidating influence mechanism of PEF processing on protein/peptides and for further improving its application accuracy and range, which thereby could become a key technology for protein-based foods in the future.

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.

In this study, the targeted regulatory mechanism of pulsed electric field (PEF) was explored for antioxidant activity improvement in four peptides, RGAVIH, RGAVLH, VNAVIH, and VNAVLH, of the pine nut (Pinus koraiensis Sieb. et Zucc). The VNAVLH peptide exhibited the best antioxidant activity and the ß-sheet content decreased to a minimum value at 40 kV/cm. Moreover, the chemical shifts of hydrogen atoms of 2-H Asn and 6-H His shifted to a higher magnetic field. The connectivity between NαH (3.62 ppm) and CαH (8.10 ppm) of 6-His residue disappeared in PEF-treated peptide. Molecule dynamics (MD) simulation verified that the distances of Nα(H78)-Cα(H80) and H82-O94 increased, whereas -OH and -Cß(H83) got closer in histidine residue after applying the electric field force. Therefore, the antioxidant activity enhancement of VNAVLH might due to the targeted regulation of PEF treatment on NαH-CαH and imidazole group in histidine.

Tryptophan targeted pulsed electric field treatment for enhanced immune activity in pine nut peptides.

To investigate immune activity of pine nut peptides treated by PEF technology and mechanism of targeting immunoactive sitesits, immune regulatory active was evaluated by RAW 264.7 cells model and the structures of pine nut peptides were researched by fluorescence, CD, and 1D/2D NMR spectrum. These consequences showed the ability of macrophages to phagocytosis neutral red and the production of nitric oxide (NO) were improved after PEF treatment. KWFCT treated by PEF treatment with 40 kV/cm obtained the best immunocompetence. The CD spectroscopy showed that PEF could transform the secondary structures of pine nut peptides. The short-range correlation between Cγ H (1.65 ppm) and Cα H (3.35 ppm), and long-range correlation between Cα H (3.37 ppm) and Nα H (8.07 ppm) were enhanced by PEF treatment. PEF treatment of tryptophan in the pine nut peptides enhanced the immunological activity of the pine nut peptides. PRACTICAL APPLICATIONS: Bioactive peptides derived from food proteins have been extensively studied in recent years. However, little research has been done on the immunoactive peptide of pine nut source. PEF treatment is promising for improving certain properties of foods while maintaining the flavor, color, taste, and nutritional value of the food. This research demonstrated that PEF treatment increased the immunological activity of KWFCT and KWFM. The primary structure of KWFCT and KWFM did not change after PEF treatment, but the secondary structure was transformed into each other. A new perspective on the PEF action site is proposed, which is beneficial to the application of PEF technology.