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Yeast extract was separated by using ultrafiltration, gel filtration chromatography, and preparative high-performance liquid chromatography for analyzing the umami mechanism. 13 kinds of umami peptides were screened out from 73 kinds of peptides which were identified in yeast extract using nanoscale ultra-performance liquid chromatography-tandem mass spectrometry and virtual screening. The umami peptides were found to have a threshold range of 0.07-0.61 mM. DWTDDVEAR exhibited a strong umami taste with a pronounced enhancement effect for monosodium glutamate. Molecular docking studies revealed that specific amino acid residues in the T1R1 subunit, including Arg316, Ser401, and Asp315, played a critical role in the umami perception with these peptides. Overall, the study highlights the potential of natural flavor enhancers and provides insights into the mechanism of umami taste perception., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Shahtoosh, the down hair of the Tibetan antelope (Pantholops hodgsonii), is a kind of luxury fibre famous for its fineness and softness. Commercial poaching of the animal for its fibre has resulted in a dramatic decline in its population. Microscopic analysis is the most frequently used method for distinguishing shahtoosh, while the PCR-based DNA analysis method is a relatively objective approach. Here, we developed an MALDI-TOF-MS-based protein analysis method for shahtoosh fibre identification. Protein in animal fibres was lysed by SDS/dithiothreitol (DTT)/phosphate buffer. SDS-PAGE was employed to separate and purify the targeted protein. The protein in the gel was enzymatically digested by trypsin and then analysed by MALDI-TOF MS spectrometry. A species-specific peptide marker at 2606 m/z was found for shahtoosh identification. A fibre mixture of 5% shahtoosh mixed with cashmere can be detected with this method. Validation experiments with mixed dyed samples confirmed its ability to detect specific qualitative and quantitative markers. We hope that the method can be widely applied to inspections of shahtoosh and its processed products to minimize the illegal trading of shahtoosh., (Copyright © 2022 Elsevier B.V. All rights reserved.)

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.

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 β-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 N α H (3.62 ppm) and C α H (8.10 ppm) of 6-His residue disappeared in PEF-treated peptide. Molecule dynamics (MD) simulation verified that the distances of N α (H 78 )-C α (H 80 ) and H 82 -O 94 increased, whereas -OH and -C β (H 83 ) 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 N α H-C α H and imidazole group in histidine., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study aimed to evaluate the neuroprotective function of shrimp-derived peptides QMDDQ and KMDDQ. Biochemical results revealed that both peptides exhibited neuroprotective effects by increasing acetylcholine (ACh) content and inhibiting acetylcholinesterase (AChE) activity in PC12 cells; QMDDQ was more active than KMDDQ. COSY-NOESY spectroscopic data showed that the superior neuroprotective function of QMDDQ might be attributed to its N-terminal glutamine as it exhibited an extended spatial conformation, facilitating its interactions with AChE. QMDDQ can promote the basic energy metabolism of cells more than KMDDQ. The peptides showed neuroprotective ability due to the activation of the antiapoptosis and PKA/CREB/BNDF signaling pathway. QMDDQ was selected to investigate its memory-enhancing activity in scopolamine-induced amnesic mice, revealing memory protection in mice, as it improved their performance in the Morris water maze experiment. In addition, QMDDQ increased ACh content (4.98 ± 0.51 μg/mg prot) and decreased AChE activity (4.72 ± 0.11 U/mg prot) in the mouse hippocampus. These data indicate the systemic mechanism through which naturally derived QMDDQ improved neuroprotection and memory ability.

In this study, Alg-Gly-Ala-Val-Leu-His (RGAVLH) obtained from pine nut ( Pinus koraiensis Sieb. et Zucc.) protein was chosen to investigate the phenomenon of immunomodulatory activity improvement upon pulsed electric field (PEF) processing. The influence of electric field intensity on immunomodulatory activity of RGAVLH was evaluated using RAW 264.7 cells. It was found that RGAVLH can not only significantly ( p < 0.05) improve the capability of macrophage phagocytosis but also promote the production of nitric oxide. RGAVLH treated under an electric field intensity of 40 kV/cm exhibited the best immunomodulatory activity. The primary and secondary structures of PEF-treated peptides were analyzed by mid-infrared (MIR) spectroscopy, Raman spectroscopy, circular dichroism spectroscopy, and one-dimensional/two-dimensional nuclear magnetic resonance spectroscopy. After PEF treatment, the primary structure of RGAVLH was not influenced, as evaluated by MIR and Raman spectra. In addition, the content of β-sheet was decreased and active hydrogen was changed in PEF-treated RGAVLH solution. Moreover, the long-range connectivity between C α H (3.39 ppm) and N α H (8.24 ppm) was enhanced by PEF. Therefore, the improvement of the immunomodulatory activity of RGAVLH might result from the changes of the spatial state and spatial force in the peptide solution system.

A novel peptide from egg white, Asp-His-Thr-Lys-Glu (DHTKE), contains specific amino acids associated with iron binding. The present study aims to better understand the molecular basis of interactions between the DHTKE peptide and iron ions. The ultraviolet-visible and fluorescence spectra indicate an interaction between the DHTKE peptide and iron ions, which leads to the formation of a DHTKE-iron complex. Notably, Asp, Glu, His, and Lys in the DHTKE peptide play crucial roles in the formation of the DHTKE-iron complex, and the iron-binding site of the DHTKE peptide corresponds primarily to the amide and carboxyl groups. The DHTKE peptide can bind iron ions in a 1 : 2 ratio with a binding constant of 1.312 × 10 5 M -1 . Moreover, the DHTKE-iron complex belongs to thermodynamically stable nanoparticles that are present in the crystalline structure, which might be attributed to peptide folding induced by iron binding. Meanwhile, the DHTKE-iron complex exhibits a relatively high iron-releasing percentage and exerts excellent solubility in the human gastrointestinal tract in vitro. This suggests a potential application of peptides containing Asp, Glu, His, or Lys residues as potential iron supplements.

The Chemokine-like factor 1 (CKLF1) is a novel human cytokine and exhibits chemotactic activities on leukocytes. Two peptides named CKLF1-C27 and CKLF1-C19, were obtained from secreted CKLF1. In this study, a selective high-performance analytical method based on capillary zone electrophoresis (CZE) to investigate interactions between heparin and CKLF1-C27/CKLF1-C19 was developed. Samples containing CKLF1-C27/CKLF1-C19 and heparin at various ratios were incubated at room temperature and then separated by CZE with Tris-acetate buffer at pH 7.2. Both qualitative and quantitative characterizations of the binding were determined. The binding constants of the interactions between CKLF1-C27/CKLF1-C19 and heparin were calculated as (3.38 +/- 0.49) x 10(5) M(-1) and (1.10 +/- 0.02) x 10(5) M(-1) by Scatchard analysis. To study structural requirements, CKLF1-C19pm and CKLF1-C19km have been synthesized, and their interactions with heparin have been studied by CZE. We found that the Pro or Lys to Ala substitution within the residues of CKLF1-C19 (CKLF1-C19pm or CKLF1-C19km) strongly decreased or abolished its interaction with heparin, suggesting that the residues of Pro affect the affinity of CKLF1-C19 for heparin, and the residues of Lys of CKLF1-C19 play the important role for the interaction of CKLF1-C19 and heparin, respectively. The methodology presented should be generally applicable to study peptides and heparin interactions quantitatively and qualitatively., (Copyright (c) 2008 European Peptide Society and John Wiley & Sons, Ltd.)

Overexposure to ultraviolet light (UV) has become a major dermatological problem since the intensity of ultraviolet radiation is increasing. As an adaption to outside environments, amphibians gained an excellent peptide‐based defense system in their naked skin from secular evolution. Here, we first determined the adaptation and resistance of the dark‐spotted frogs (Pelophylax nigromaculatus) to constant ultraviolet B (UVB) exposure. Subsequently, peptidomics of frog skin identified a series of novel peptides in response to UVB. These UV‐induced frog skin peptides (UIFSPs) conferred significant protection against UVB‐induced death and senescence in skin cells. Moreover, the protective effects of UIFSPs were boosted by coupling with the transcription trans‐activating (TAT) protein transduction domain. In vivo, TAT‐conjugated UIFSPs mitigated skin photodamage and accelerated wound healing. Transcriptomic profiling revealed that multiple pathways were modulated by TAT‐conjugated UIFSPs, including small GTPase/Ras signaling and MAPK signaling. Importantly, pharmacological activation of MAPK kinases counteracted UIFSP‐induced decrease in cell death after UVB exposure. Taken together, our findings provide evidence for the potential preventive and therapeutic significance of UIFSPs in UV‐induced skin damage by antagonizing MAPK signaling pathways. In addition, these results suggest a practicable alternative in which potential therapeutic agents can be mined from organisms with a fascinating ability to adapt. [ABSTRACT FROM AUTHOR]

The extensive application of nuclear technology has increased the potential of uncontrolled radiation exposure to the public. Since skin is the largest organ, radiation‐induced skin injury remains a serious medical concern. Organisms evolutionally develop distinct strategies to protect against environment insults and the related research may bring novel insights into therapeutics development. Here, 26 increased peptides are identified in skin tissues of frogs (Pelophylax nigromaculatus) exposed to electron beams, among which four promoted the wound healing of irradiated skin in rats. Specifically, radiation‐induced frog skin peptide‐2 (RIFSP‐2), from histone proteolysis exerted membrane permeability property, maintained cellular homeostasis, and reduced pyroptosis of irradiated cells with decreased TBK1 phosphorylation. Subsequently, stearyl‐CoA desaturase 1 (SCD1) is identified, a critical enzyme in biogenesis of monounsaturated fatty acids (MUFAs) as a direct target of RIFSP‐2 based on streptavidin‐biotin system. The lipidomic analysis further assured the restrain of MUFAs biogenesis by RIFSP‐2 following radiation. Moreover, the decreased MUFA limited radiation‐induced and STING‐mediated inflammation response. In addition, genetic depletion or pharmacological inhibition of STING counteracted the decreased pyroptosis by RIFSP‐2 and retarded tissue repair process. Altogether, RIFSP‐2 restrains radiation‐induced activation of SCD1‐MUFA‐STING axis. Thus, the stress‐induced amphibian peptides can be a bountiful source of novel radiation mitigators. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the mechanism of PEF treatment on the regulation of pine nut peptide (VNAVLH) induced immune activity of RAW 264.7 based on C-terminal modification by molecular dynamics (MD). The results showed that PEF treatment can reduce the overall stability of pine nut peptides, enhance the flexibility of hydrophobic and positively charged residues in pine nut peptides, and make their residue structures more flexible. Active sites verification experiments showed that PEF treatment could improve the immune activity of histidine only when it was at C-terminal. Western blot and immunofluorescence analysis showed that PEF-treated VNAVLH could activate NF-κB pathway by promoting the nuclear translocation of NF-κB/p65 and the expression of IKKβ, and activate MAPK pathway by promoting the phosphorylation of JNK, ERK, and p38 in RAW 264.7. Furthermore, toll-like receptor 4 (TLR4), as the main receptor for VNAVLH to exert immune activity, exhibited a more prominent peptide-binding capacity and had more hydrogen-bonding sites to PEF-treated peptide compared to toll-like receptor 2 (TLR2). Therefore, enhanced immunoreactivity of VNAVLH may be due to the formation of a more stable complex with TLR4 after PEF treatment, which activates the MAPK/NF-κB signaling pathway causing an intracellular cascade response. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, to analyze the structural changes of the peptide Val-Asn-Ala-Val-Lys-His (VNAVKH) under PEF treatment and determine their response to amino acids, the atomic charge distribution, root mean square deviations (RMSD), root mean square fluctuation (RMSF), and atomic distance were analyzed using molecular dynamics (MD) simulations. The RMSF value under 40 kV/cm was significantly (P < 0.05) lower than that under other PEF conditions. However, calculations of the distances of the oxygen atom indicated that O 57 on Val and O 97 on His oxygen atoms became closer under all conditions. At 30 kV/cm, the changes were unique, and the α-C atom distance of C 44 on Val and C 82 on His decreased under all conditions. The results indicated that histidine was more sensitive and responsive after PEF treatment, and the peptide backbone was bent and exposed to some active atoms, which might lead to changes in biological activity. [Display omitted] • Multiple interactions of residues were identified by MD simulation. • The changes of residues could result in the bend of the peptides' backbone. • The bioactivities might be altered due to active atoms exposure on the residues. [ABSTRACT FROM AUTHOR]

This study was aimed to explore the mechanism of peptides antioxidant activity improvement treated by pulsed electric field (PEF). The pine nut ( Pinus koraiensis Sieb. et Zucc) peptides were used as the experimental materials. DPPH radical inhibition and cellular antioxidant activity (CAA) were applied to evaluate the peptides antioxidant activity. Structures of PEF-treated peptides were analyzed by mid-infrared (MIR) and circular dichroism (CD) spectroscopy. Peptides were indentified including Gln-Cys-His-Lys-Pro, Gln-Cys-His-Gln-Pro, Lys-Cys-His-Gln-Pro(KCHQP), and Lys-Cys-His-Lys-Pro. KCHQP was with the strongest DPPH radical scavenging of 89.10% ± 0.20%, and CAA units of 78.40 ± 1.71. Moreover, the DPPH radical scavenging of KCHQP was significantly increased from 89.10% ± 0.20% to 93.22% ± 0.09% under the PEF treatment conditions (pulse frequency 1800 Hz, and electric field intensity 15 kV/cm). The MIR and CD spectroscopy indicated that the structure of KCHQP was not changed by PEF. However, the zeta potential was reduced from 11.6 ± 0.28 mV to 0.4 ± 0.06 mV. This study enriched the resource of antioxidant peptides with indentified amino acid sequence. It provided a way to investigate mechanism of peptides antioxidant activity improvement treated by PEF. [ABSTRACT FROM AUTHOR]