Trifluoroethanol-induced conformational change of tetrameric and monomeric soybean agglutinin: role of structural organization and implication for protein folding and stability

Development of Novel Nanocarriers by Ultrasound and Ethanol-Assisted Soy Protein Isolate: Enhancing the Resistance of Lutein to Environmental Stress

The aim of this work was to investigate the effects of the processing sequence of ultrasound and ethanol on the physicochemical properties of soy protein isolate (SPI), which were further evaluated for the morphology and stability of SPI-lutein coassembled nanoparticles. The results showed that the sequence of ultrasound followed by ethanol treatment was the optimal one. The samples were subjected to ultrasonication followed by subunit disassembly and reassembly induced by 40% (v/v) ethanol, with the resulting molecular unfolding and subsequent aggregation being attributed to intramolecular hydrogen bonds. The recombined nanoparticles had smaller particle size (142.43 ± 2.91 nm) and turbidity (0.16 ± 0.01), and the exposure of more hydrophobic groups (H0 = 6221.00 ± 130.20) induced a shift of SPI structure toward a more ordered direction. The homogeneous and stable particle provided excellent stability for the loading of lutein. The bioaccessibility (from 25.48 ± 2.35 to 65.85 ± 1.78%) and release rate of lutein were modulated in gastrointestinal digestion experiments. Our discoveries provide a new perspective for the development of combined physicochemical modification of proteins as nanocarriers in functional foods.

Ultra-high-pressure passivation of soybean agglutinin and safety evaluations

Soybean agglutinin (SBA) is a heat-sensitive anti-nutritional factor (ANF). It affects nutrient absorption and causes organism poisoning. This study explored the SBA passivation ability and mechanism by ultra-high pressure (HHP), a non-thermal food processing technology. The results indicated that more than 500 MPa HHP treatment reduced the SBA activity by destroying its secondary and tertiary structures. Also, the cell and animal experiments showed that HHP treatment reduced the cytotoxicity of SBA, improved the mice's body weight, and alleviated liver, kidney, and digestive tract damage in Vivo. These results demonstrated that HHP had a high passivation efficiency against the SBA, thereby HHP promoting the safety of soybean products. This study provided supporting evidence for ultra-high-pressure treatment applications in soybean processing.

Inactivation of Soybean Trypsin Inhibitor by Dielectric-Barrier Discharge Plasma and Its Safety Evaluation and Application

The trypsin inhibitor (TI) is one of the most important anti-nutritive elements in soybeans. As a new nonthermal technology, dielectric-barrier discharge (DBD) cold plasma has attracted increasing attention in food processing. In this research, we investigated the effect of dielectric-barrier discharge (DBD) plasma treatment on soybean trypsin inhibitor content and its structure, evaluated TI toxicity and the safety of its degradation products after treatment with DBD technology in vitro and in vivo, and applied the technology to soybean milk, which was analyzed for quality. Using the statistical analysis of Student’s t-test, the results demonstrated that DBD plasma treatment significantly decreased the content of TI (33.8 kV at 1, 3, or 5 min, p < 0.05, p < 0.01, p < 0.001) and destroyed the secondary and tertiary structures of TI. TI was toxic to Caco-2 cells and could inhibit body weight gain, damage liver and kidney functions, and cause moderate or severe lesions in mouse organ tissues, whereas these phenomena were alleviated in mice treated with degradation products of TI after DBD plasma treatment under the optimal condition (33.8 kV at 5 min). The content of TI in DBD-treated soymilk was also significantly reduced (p < 0.001), while the acidity, alkalinity, conductivity, color, and amino acid composition of soymilk were not affected, and there were no statistical differences (p > 0.05). In summary, DBD plasma is a promising non-thermal processing technology used to eliminate TI from soybean products.

Structural changes and exposed amino acids of ethanol-modified whey proteins isolates promote its antioxidant potential

Whey protein isolates (WPI) were treated with different ethanol level (20, 40, 60, and 80%, v/v) to promote structural unfolding and subsequent aggregation. In general, protein aggregation gradually increased with increasing ethanol level in a dose-dependent manner, which was implied by notably increased turbidity and gradually decreased solubility. The formation of aggregates, which were confirmed by the results of circular dichroism spectrum and total sulfhydryl content, were promoted mainly through disulfide bonds and intra-molecular hydrogen bonds. Moreover, ethanol treated WPI (E-WPI) had significantly enhanced antioxidant activities over native WPI, which was mainly attribute to the higher contents of specific amino acids (such as hydrophobic amino acids, aromatic amino acids, and sulfur-containing amino acids), and E-WPI prepared with moderate ethanol concentration (40% in our present study) exhibited the highest antioxidant activities. These results reveal that antioxidant activities of WPI can be increased by ethanol treatment and are possibly achieved through molecular unfolding of native WPI.

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Ethanol treatment caused unfolding and aggregation of whey protein isolate (WPI).

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Aggregation enhanced with increasing ethanol concentration (EC).

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Medium EC (40%, v/v) rendered the highest antioxidant activities of WPI.

Solvent Perturbation of Protein Structures - A Review Study with Lectins

Use of organic molecules as co-solvent with water, the ubiquitous biological solvent, to perturb the structure of proteins is popular in the research area of protein structure and folding. These organic co-solvents are believed to somehow mimic the environment near the cell membrane. Apart from that they induce non-native states which can be present in the protein folding pathway or those states also may be representative of the off pathway structures leading to amyloid formation, responsible for various fatal diseases. In this review, we shall focus on organic co-solvent induced structure perturbation of various members of lectin family. Lectins are excellent model systems for protein folding study because of its wide occurrence, diverse structure and versatile biological functions. Lectins were mainly perturbed by two fluoroalcohols - 2,2,2- trifluoroethanol and 1,1,1,3,3,3-hexafluoroisopropanol whereas glycerol, ethylene glycol and polyethylene glycols were used in some cases. Overall, all native lectins were denatured by alcohols and most of the denatured lectins have predominant helical secondary structure. But characterization of the helical states and the transition pathway for various lectins revealed diverse result.

The Status of Edge Strands in Ferredoxin-Like Fold

There is an opinion in professional literature that edge-strands in β-sheet are critical to the processes of amyloid transformation. Propagation of fibrillar forms mainly takes place on the basis of β-sheet type interactions. In many proteins, the edge strands represent only a partially matched form to the β-sheet. Therefore, the edge-strand takes slightly distorted forms. The assessment of the level of arrangement can be carried out based on studying the secondary structure as well as the structure of the hydrophobic core. For this purpose, a fuzzy oil drop model was used to determine the contribution of each fragment with a specific secondary structure to the construction of the system being the effect of a certain synergy, which results in the construction of a hydrophobic core. Studying the participation of β-sheets edge fragments in the hydrophobic core construction is the subject of the current analysis. Statuses of these edge fragments in β-sheets in ferredoxin-like folds are treated as factors that disturb the symmetry of the system.

Biomacromolecules enabled dendrite-free lithium metal battery and its origin revealed by cryo-electron microscopy

Metallic lithium anodes are highly promising for revolutionizing current rechargeable batteries because of their ultrahigh energy density. However, the application of lithium metal batteries is considerably impeded by lithium dendrite growth. Here, a biomacromolecule matrix obtained from the natural membrane of eggshell is introduced to control lithium growth and the mechanism is motivated by how living organisms regulate the orientation of inorganic crystals in biomineralization. Specifically, cryo-electron microscopy is utilized to probe the structure of lithium at the atomic level. The dendrites growing along the preferred < 111 > crystallographic orientation are greatly suppressed in the presence of the biomacromolecule. Furthermore, the naturally soluble chemical species in the biomacromolecules can participate in the formation of solid electrolyte interphase upon cycling, thus effectively homogenizing the lithium deposition. The lithium anodes employing bioinspired design exhibit enhanced cycling capability. This work sheds light on identifying substantial challenges in lithium anodes for developing advanced batteries.

Inspired by the role of proteins in regulating eggshell mineralization, here Tao, Liu and colleagues apply trifluoroethanol modified eggshell membrane to combat lithium dendrite. Cryo-electron microscopy reveals that the growth along the most favored crystallographic direction is suppressed.