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pH-driven method is an effective strategy to prepare complex protein. This study provides guidance on how to select acidifiers and alkalizers from view of Hofmeister ion effects. Cations and anions regulated the molecular structure (particle size, surface charge, protein folding/unfolding, structural orderliness) of complex rapeseed proteins (CRPs) mainly via electrostatic and hydrogen bond. No evident changes were found in the molecular weight distribution, but their distribution on oil/air-water interface varied greatly. Various techno-functional properties of CRPs were synergistically improved: Citrate3− and Na+ increased the emulsifying activity index of CRPs from 80 to 102.21 m2/g; Citrate3−, K+ and Na+ made the foaming stability of CRPs close to 80 % after 60 min of storage. Moreover, the oil/water-holding and gel properties of CRPs were regulated effectively. These findings demonstrate the key role of Hofmeister ion effects in improving CRPs properties, contributing to develop, select, and apply novel acidifiers and alkalizers during pH-driven treatment. [Display omitted] • Cations usually showed more obvious Hofmeister effects than that of anions. • Citrate3− and Na+ synergistically improved the emulsifying activity index of CRPs. • Citrate3−, K+ and Na+ synergistically improved the foaming stability of CRPs. • K+ and CH 3 COOH2− synergistically contribute to form protein-based gels. • Cations and anions mainly regulated the role of electrostatic and hydrogen bond. [ABSTRACT FROM AUTHOR]

This work aims to verify the feasibility of improving protein function by regulating its hydrophobicity and reveal the relationship between structure and function. Whey protein (WP) and zein were the source of hydrophilic and hydrophobic polypeptide chains to prepare complex proteins (CPs) with much different structure and function. The results showed that the water- and oil-holding capacities, emulsifying properties and gel properties of CPs can be significantly improved via changing WP-zein ratio. All these can be attributed to the changes in protein hydrophobicity, which not only regulated the binding strength of protein to water and oil, but also modified their molecular structure (surface characteristics, availability of free thiols, α-helix, β-sheet, random coil and the formation of disulfide bonds). Notably, optimal protein hydrophobicity varies greatly among different functional properties. Overall, the techno-functional properties of protein can be improved via tuning its hydrophobicity, which may provide novel sights in protein modification. [Display omitted] • Protein hydrophobicity can be regulated via changing whey protein (WP)-zein ratio. • Zein interacts with WP to form stable complex and changes protein conformation. • Increase in WP ratio transforms main force from non-covalent bonds to covalent bonds. • Techno-functional properties of protein can be improved via tuning its hydrophobicity. • Optimal protein hydrophobicity varies greatly among different functional properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Molecular docking was employed to screen antioxidant peptides. • Density Functional Theory was used to assess three significant antioxidant peptides. • Peptide FFDR modulated the Nrf2 pathway downstream genes CAT, SOD and GSH-Px. • Additionally, peptide FFDR was also shown to improve the cellular redox balance. The aim of the study was to identify potent antioxidant peptides sourced from coix seed, analyze the structure–activity relationship through molecular docking and quantum chemical calculation. Molecular docking results showed that among thirteen peptides selected in silico , eight had favourable binding interaction with the Keap1-Kelch domain (2FLU). Promising peptides with significant binding scores were further evaluated using quantum calculation. It was shown that peptide FFDR exhibited exceptional stability, with a high energy gap of 5.24 eV and low Highest Occupied Molecular Orbitals (HOMO) and Lowest Unoccupied Molecular Orbitals (LUMO) values. Furthermore, FFDR displayed the capacity to enhance the expression of Nrf2-Keap1 antioxidant genes (CAT, SOD, GSH-Px) and improved cellular redox balance by increasing reduced glutathione (GSH) while reducing oxidized glutathione (GSSG) and malonaldehyde (MDA) levels. These findings highlight the potential of coix seed peptides in developing novel, effective and stable antioxidant-based functional foods. [ABSTRACT FROM AUTHOR]

The aim of this study was to purify and identify antioxidant peptides from watermelon seed protein hydrolysates (WSPHs-I: Mw < 1 kDa) and further evaluate their cytoprotective effects against H 2 O 2 -induced oxidative stress in HepG2 cells. After purification by Sephadex G-15 and semi-preparative reversed-phase high performance liquid chromatography (RP-HPLC), five peptides, RDPEER (P1), KELEEK (P2), DAAGRLQE (P3), LDDDGRL (P4), and GFAGDDAPRA (P5) were sequenced by LC-MS/MS and synthesized with solid-phase synthesis method. These peptides showed desirable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity (IC 50 : 0.216 ± 0.01-0.435 ± 0.03), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity (IC 50 : 0.54 ± 0.02-1.23 ± 0.03), and oxygen radical absorbance capacity (ORAC) (82.36 ± 1.2-130.67 ± 2.2 μM TE/mg). Among them, peptide P1 exhibited the strongest antioxidant capacity. Moreover, the results suggested that peptide P1 may protect HepG2 cells from H 2 O 2 -induced oxidative damage by significantly inhibiting reactive oxygen species (ROS), [Ca 2+ ]i, malondialdehyde (MDA) levels and increasing antioxidative enzyme activities., 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.)