scholarly journals Effects of High-Intensity Ultrasound Pretreatment on Structure, Properties, and Enzymolysis of Walnut Protein Isolate

Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 208
Author(s):  
Fei Zhao ◽  
Xiaosong Zhai ◽  
Xuemei Liu ◽  
Meng Lian ◽  
Guoting Liang ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Particle Size ◽  
High Intensity ◽  
Tertiary Structure ◽  
Fluorescence Emission ◽  
Protein Isolate ◽  
Random Coil ◽  
Degree Of Hydrolysis ◽  
Ζ Potential ◽  
Α Helix

The purpose of this paper was to investigate the effect of high-intensity ultrasonication (HIU) pretreatment before enzymolysis on structural conformations of walnut protein isolate (WPI) and antioxidant activity of its hydrolysates. Aqueous WPI suspensions were subjected to ultrasonic processing at different power levels (600–2000 W) and times (5–30 min), and then changes in the particle size, zeta (ζ) potential, and structure of WPI were investigated, and antioxidant activity of its hydrolysates was determined. The particle size of the particles of aqueous WPI suspensions was decreased after ultrasound, indicating that sonication destroyed protein aggregates. The ζ-potential values of a protein solution significantly changed after sonication, demonstrating that the original dense structure of the protein was destroyed. Fourier transform infrared spectroscopy indicated a change in the secondary structure of WPI after sonication, with a decrease in β-turn and an increase in α-helix, β-sheet, and random coil content. Two absorption peaks of WPI were generated, and the fluorescence emission intensity of the proteins decreased after ultrasonic treatment, indicating that the changes in protein tertiary structure occurred. Moreover, the degree of hydrolysis and the antioxidant activity of the WPI hydrolysates increased after sonication. These results suggest that HIU pretreatment is a potential tool for improving the functional properties of walnut proteins.

scholarly journals Effect of Oxidation on Quality of Chiba Tofu Produced by Soy Isolate Protein When Subjected to Storage

Foods ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1877
Author(s):  
Yue Xu ◽  
Zhongjiang Wang ◽  
Baokun Qi ◽  
Anqi Ran ◽  
Zengwang Guo ◽  
...  
Keyword(s):  
Loss Modulus ◽  
Structural Characteristics ◽  
Soy Protein Isolate ◽  
Protein Isolate ◽  
Sensory Properties ◽  
Random Coil ◽  
Carbonyl Content ◽  
New Type ◽  
Α Helix

Chiba tofu is a new type of vegetarian food prepared with soy protein isolate (SPI). According to factory feedback, the SPI stored in the factory storeroom in summer undergoes reactive oxidation, which changes the structure of SPI and further affects the quality of Chiba tofu. Consequently, the main objective of this study was to prepare Chiba tofu with SPI with different storage periods and evaluate the effect of different degrees of oxidation on structural characteristics of SPI and rheology, texture, microstructure and sensory properties of Chiba tofu. The carbonyl content and turbidity of SPI significantly increased, and the contents of free sulfhydryl (SH) and disulfide bond (S-S) simultaneously decreased with storage time. The oxidation changes the SPI conformation, leading to a transition of α-helix and β-turn to β-sheet and random coil during the storage periods. In the SDS–PAGE analysis, oxidation promoted the SPI molecules crosslinked and aggregated, which affected the quality of Chiba tofu. In short storage periods (0–12 days), SPI was relatively moderately oxidized when the carbonyl content was between 4.14 and 6.87 mmol/g. The storage and loss modulus of Chiba tofu both increased, the network was compact, and the hardness and springiness of Chiba tofu showed an increasing trend. Moreover, in longer storage periods (12–30 days), the SPI was relatively severely oxidized when the carbonyl content was between 7.24 and 9.14 mmol/g, which had an adverse effect on Chiba tofu rheological and texture properties, microstructure, and sensory properties. In sensory evaluation, Chiba tofu stored 12 days had the highest overall quality score than that stored on other days. This study is expected to provide an argument for the better industrial production of Chiba tofu.

scholarly journals Effects of High-Intensity Ultrasound Pretreatment on Structure, Properties, and Enzymolysis of Soy Protein Isolate

Molecules ◽  
2019 ◽  
Vol 24 (20) ◽  
pp. 3637 ◽  
Author(s):  
Fei Zhao ◽  
Xuemei Liu ◽  
Xiuzhen Ding ◽  
Haizhou Dong ◽  
Wentao Wang
Keyword(s):  
High Intensity ◽  
Near Infrared ◽  
Soybean Protein ◽  
Soy Protein Isolate ◽  
Radical Scavenging ◽  
Protein Isolate ◽  
Degree Of Hydrolysis ◽  
Soybean Protein Isolate ◽  
Near Infrared Spectra ◽  
Hydrolysis Of

The objective of this study was to investigate the effects of different high-intensity ultrasonication (HIU) pretreatment on the structure and properties of soybean protein isolate (SPI) as well as enzymatic hydrolysis of SPI by bromelain and antioxidant activity of hydrolysates. The HIU-treated SPI fractions showed a decrease in the proportion of α-helices and β-turns and an increase in the content of β-sheets and random coils based on Fourier-transform infrared spectroscopy. Near-infrared spectra and fluorescence spectra analyses provided support for the changes in secondary and tertiary structures of SPI after ultrasound treatment. The particle size of SPI decreased from 217.20 nm to 141.23 nm and the absolute zeta potential increased. Scanning electron microscopy showed that HIU treatment changed apparent morphology. Dynamic and static light scattering of ultrasonicated samples showed that SPI structure had changed from hard-sphere to hollow-sphere or polydisperse and monodisperse gaussian coils. HIU pretreatment significantly increased the hydroxyl-radical scavenging and the degree of hydrolysis of the SPI hydrolysates.

scholarly journals Structural and functional characterization of recombinant mouse annexin A11: influence of calcium binding

2003 ◽  
Vol 373 (2) ◽  
pp. 437-449 ◽  
Author(s):  
Emilio LECONA ◽  
Javier TURNAY ◽  
Nieves OLMO ◽  
Ana GUZMÁN-ARÁNGUEZ ◽  
Reginald O. MORGAN ◽  
...  
Keyword(s):  
Calcium Binding ◽  
Tertiary Structure ◽  
Random Coil ◽  
Tryptophan Residue ◽  
Tyrosine Residues ◽  
Recombinant Mouse ◽  
Structural And Functional Properties ◽  
N Terminus ◽  
Annexin A11 ◽  
Α Helix

Annexin A11 is one of the 12 vertebrate subfamilies in the annexin superfamily of calcium/phospholipid-binding proteins, distinguishable by long, non-homologous N-termini rich in proline, glycine and tyrosine residues. As there is negligible structural information concerning this annexin subfamily apart from primary sequence data, we have cloned, expressed and purified recombinant mouse annexin A11 to investigate its structural and functional properties. CD spectroscopy reveals two main secondary-structure contributions, α-helix and random coil (approx. 30% each), corresponding mainly to the annexin C-terminal tetrad and the N-terminus respectively. On calcium binding, an increase in α-helix and a decrease in random coil are detected. Fluorescence spectroscopy reveals that its only tryptophan residue, located at the N-terminus, is completely exposed to the solvent; calcium binding promotes a change in tertiary structure, which does not affect this tryptophan residue but involves the movement of approximately four tyrosine residues to a more hydrophobic environment. These calcium-induced structural changes produce a significant thermal stabilization, with an increase of approx. 14 °C in the melting temperature. Annexin A11 binds to acidic phospholipids and to phosphatidylethanolamine in the presence of calcium; weaker calcium-independent binding to phosphatidylserine, phosphatidic acid and phosphatidylethanolamine was also observed. The calcium-dependent binding to phosphatidylserine is accompanied by an increase in α-helix and a decrease in random-coil contents, with translocation of the tryptophan residue towards a more hydrophobic environment. This protein induces vesicle aggregation but requires non-physiological calcium concentrations in vitro. A three-dimensional model, consistent with these data, was generated to conceptualize annexin A11 structure–function relationships.

scholarly journals The Molecular Properties of Peanut Protein: Impact of Temperature, Relative Humidity and Vacuum Packaging during Storage

Molecules ◽  
2018 ◽  
Vol 23 (10) ◽  
pp. 2618 ◽  
Author(s):  
Xiaotong Sun ◽  
Hua Jin ◽  
Yangyang Li ◽  
Haiying Feng ◽  
Chunhong Liu ◽  
...  
Keyword(s):  
Secondary Structure ◽  
Functional Properties ◽  
Surface Hydrophobicity ◽  
Protein Isolate ◽  
Peanut Protein ◽  
Molecular Properties ◽  
Random Coil ◽  
Bivariate Correlation ◽  
Protein Particle ◽  
Α Helix

This study aimed to investigate the variation of molecular functional properties of peanut protein isolate (PPI) over the storage process and reveal the correlation between the PPI secondary structure and properties in the storage procedure. After storage, the molecular properties of PPI changed significantly (p < 0.05). Extending storage time resulted in a decrease in free sulfhydryl content, fluorescence intensity, surface hydrophobicity and emulsifying properties, which was accompanied by an increase in protein particle size. The results of infrared spectroscopy suggested the content decline of α-helix and β-sheet, and the content rise of β-turn and random coil. Based on bivariate correlation analysis, it was revealed that surface hydrophobicity and emulsifying activity of PPI was significantly affected by α-helix and by β-turn (p < 0.05), respectively. This research supplied more information for the relationship between the peanut protein’s secondary structure and functional properties over the stored process.

scholarly journals Secondary structure of NADPH: protochlorophyllide oxidoreductase examined by circular dichroism and prediction methods*

1996 ◽  
Vol 317 (2) ◽  
pp. 549-555 ◽  
Author(s):  
Simon J. BIRVE ◽  
Eva SELSTAM ◽  
Lennart B.-Å. JOHANSSON
Keyword(s):  
Secondary Structure ◽  
Fluorescence Emission ◽  
Random Coil ◽  
Prolamellar Body ◽  
Interfacial Region ◽  
Protochlorophyllide Oxidoreductase ◽  
Loop Region ◽  
Rossmann Fold ◽  
Α Helix ◽  
Β Sheet

To study the secondary structure of the enzyme NADPH: protochlorophyllide oxidoreductase (PCOR), a novel method of enzyme isolation was developed. The detergent isotridecyl poly(ethylene glycol) ether (Genapol X-080) selectively solubilizes the enzyme from a prolamellar-body fraction isolated from wheat (Triticum aestivumL.). The solubilized fraction was further purified by ion-exchange chromatography. The isolated enzyme was studied by fluorescence spectroscopy at 77 K, and by CD spectroscopy. The fluorescence-emission spectra revealed that the binding properties of the substrate and co-substrate were preserved and that photo-reduction occurred. The CD spectra of PCOR were analysed for the relative amounts of the secondary structures, α-helix, β-sheet, turn and random coil. The secondary-structure composition was estimated to be 33% α-helix, 19% β-sheet, 20% turn and 28% random coil. These values are in agreement with those predicted by the Predict Heidelberg Deutschland and self-optimized prediction method from alignments methods. The enzyme has some amino acid identity with other NADPH-binding enzymes containing the Rossmann fold. The Rossmann-fold fingerprint motif is localized in the N-terminal region and at the expected positions in the predicted secondary structure. It is suggested that PCOR is anchored to the interfacial region of the membrane by either a β-sheet or an α-helical region containing tryptophan residues. A hydrophobic loop-region could also be involved in membrane anchoring.

scholarly journals Effects of Cavitation Jet Treatment on the Structure and Emulsification Properties of Oxidized Soy Protein Isolate

Foods ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 2
Author(s):  
Mingyu He ◽  
Changling Wu ◽  
Lijia Li ◽  
Li Zheng ◽  
Tian Tian ◽  
...  
Keyword(s):  
Particle Size ◽  
Soy Protein ◽  
Activity Index ◽  
Soy Protein Isolate ◽  
Sulfhydryl Group ◽  
Stability Index ◽  
Surface Hydrophobicity ◽  
Protein Isolate ◽  
Atomic Force ◽  
Α Helix

This study examined the ability of cavitation jet processing to regulate the oxidation concentrations with 2,2’-azobis (2-amidinopropane) dihydrochloride (AAPH) (0.2, 1, and 5 mmol/L) and the structure and emulsification of soy protein isolate (SPI). The tested properties included particle size distribution, hydrophobic properties (sulfhydryl group (SH) and disulfide bond (S-S) contents, surface hydrophobicity (H0)), emulsifying properties (particle size and ζ-potential of emulsions, emulsification activity index (EAI), and emulsification stability index (ESI)), as well as conformational characteristics. The high shear force of cavitation jet treatment reduced the particle size of oxidized SPI and distributed uniformly. Cavitation jet (90 MPa)-treated SPI (AAPH with 1 mmol/L) demonstrated a high H0 (4688.70 ± 84.60), high EAI (71.78 ± 1.52 m2/g), and high ESI (86.73 ± 0.97%). The ordered secondary structure (α-helix and β-turn content) of SPI was enhanced by the cavitation jet. Meanwhile, the distribution of SPI-oxidized aggregates was observed under an atomic force microscope. Therefore, cavitation jet processing combined with oxidation treatment is an effective method to improve the characteristics of SPI and has potential industrial application prospects.

Effect of Heat Treatment on Gelatin Properties of Pepsin-Soluble Collagen from Chicken Bones

2018 ◽  
Vol 18 (1) ◽  
pp. 1-9
Author(s):  
Ye Mengliang ◽  
Mi Si ◽  
Zhang Chunhui ◽  
Yue Jianying ◽  
Jia Wei ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Profile Analysis ◽  
Random Coil ◽  
Degree Of Hydrolysis ◽  
Texture Profile ◽  
Physicochemical Composition ◽  
Heating Treatment ◽  
Higher Temperature ◽  
Collagen Hydrolysates ◽  
Α Helix

The aim of this study was to evaluate the physicochemical composition and gelatin properties of collagen hydrolysates obtained from chicken bones under different heat treatment temperatures (50, 70 and 90°C) and times (30, 60 and 90 min). Results showed that heat temperature can significantly improve the solubility of protein (from 37.8 to 72.1%). Degree of hydrolysis and SDS-PAGE analysis showed that the mean molecular weight of collagen hydrolysates at 50 and 70°C were higher than that of hydrolysates at 90°C, which indicating that the triple-helix structure of protein transmitted to chains and subsequently form protein-protein linkages during heating. FTIR analysis demonstrated that the relative content of β-sheet decreased and random coil increased significantly (P < 0.05), whereas α-helix and β-turn had no significant changes during heating treatment (P > 0.05). Collagen hydrolysates obtained at 90°C for 30 min indicated better gelatin properties (melting temperature, texture profile analysis and microstructure) when compared with that of hydrolysates obtained at 50 and 70°C. Therefore, heat treatment with a relatively higher temperature (90°C) and shorter time (30 min) is necessary to obtain hydrolyzed chicken bones collagen with good gelatin properties.

Highly efficient extraction of large molecular-weight keratin from wool in a water/ethanol co-solvent

2019 ◽  
Vol 90 (9-10) ◽  
pp. 1084-1093 ◽  
Author(s):  
Jiahao He ◽  
Duo Xu ◽  
Junyu Li ◽  
Linfeng Li ◽  
Wenbin Li ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Particle Size ◽  
Disulfide Bonds ◽  
Hydrophobic Interactions ◽  
Random Coil ◽  
High Yield ◽  
Mixed System ◽  
Wool Fibers ◽  
Cysteine Hydrochloride ◽  
Α Helix

A large number of wool fiber by-products, short and coarse wool fibers are difficult to spin and are disposed of by the wool industry, creating a burden on the environment. In this study, L-cysteine hydrochloride and sodium sulfite were used as reducing agents to extract keratin from natural wool in an ethanol-water mixed system. The molecular weight of the extracted keratin is up to 130 kDa with a high yield of 67%. It has been proven that the reducing agent destroyed partial disulfide bonds, ethanol destroyed partial hydrogen bonds and hydrophobic interactions, and the α-helix chain was converted into a β-folded chain and random coil after extraction by instrumental analysis using a Fourier transform infrared spectrometer and X-ray diffraction. The recombination of small keratin molecules can be proven by the increase in protein particle size and molecular weight via a particle size analyzer and SDS-PAGE respectively.

scholarly journals High-Pressure Homogenization Pretreatment before Enzymolysis of Soy Protein Isolate: the Effect of Pressure Level on Aggregation and Structural Conformations of the Protein

Molecules ◽  
2018 ◽  
Vol 23 (7) ◽  
pp. 1775 ◽  
Author(s):  
Fei Zhao ◽  
Daofang Zhang ◽  
Xiangyang Li ◽  
Haizhou Dong
Keyword(s):  
Antioxidant Activity ◽  
High Pressure ◽  
Antioxidant Activities ◽  
Soybean Protein ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Protein Isolate ◽  
Degree Of Hydrolysis ◽  
High Pressure Homogenization ◽  
Soybean Protein Isolate

The high-pressure homogenization (HPH) treatment of soybean protein isolate (SPI) before enzymatic hydrolysis using bromelain was investigated. Homogenization pressure and cycle effects were evaluated on the enzymatic degree of hydrolysis and the antioxidant activity of the hydrolysates generated. The antioxidant activity of SPI hydrolysates was analyzed by 1,1-dipheny-2-picrylhydrazyl (DPPH). The sizes and structures of the SPI-soluble aggregate after HPH treatment were analyzed using dynamic and static laser light scattering. The changes in the secondary structure, as measured by Fourier transform infrared spectroscopy (FTIR) and the macromorphology of SPI, were measured by scanning electron microscope (SEM). These results suggested that the HPH treatment (66.65%) could increase the antioxidant activities of the SPI hydrolysates compared with the control (54.18%). SPI hydrolysates treated at 20 MPa for four cycles obtained higher DPPH radical-scavenging activity than other samples. The control was predicted to be a hard sphere, and SPI treatment at 10 MPa was speculated to be Gaussian coil, polydisperse, and then the high-pressure treated SPI became a hollow sphere. Changes in the secondary structures showed protein aggregate formation and rearrangements. The image of SPI varied from a globular to a clump structure, as observed by the SEM. In conclusion, combining HPH treatment and enzymolysis could be an effective way to improve the antioxidant activity of the SPI.

scholarly journals Physicochemical Properties and Storage Stability of Food Protein-Stabilized Nanoemulsions

Nanomaterials ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 25 ◽  
Author(s):  
Yangyang Li ◽  
Hua Jin ◽  
Xiaotong Sun ◽  
Jingying Sun ◽  
Chang Liu ◽  
...  
Keyword(s):  
Corn Oil ◽  
Soybean Protein ◽  
Droplet Diameter ◽  
Protein Isolate ◽  
Random Coil ◽  
Food Protein ◽  
Soybean Protein Isolate ◽  
Bivariate Correlation ◽  
The Mean ◽  
Α Helix

This study investigated the preparation and properties of corn oil nanoemulsions stabilized by peanut protein isolate (PPI), rice bran protein isolate (RBPI), soybean protein isolate (SPI), and whey protein isolate (WPI). The mean droplet diameter of four protein-stabilized nanoemulsions prepared via ultrasound method was less than 245 nm. PPI-stabilized nanoemulsions showed better stability for 4 weeks, while the mean droplet diameter of RBPI-stabilized nanoemulsions had exceeded 1000 nm during the third week of storage. Fourier transform infrared and interfacial tension (IT) analysis showed that the higher level of disordered structure and lower IT of proteins made the stability of nanoemulsions better. Moreover, bivariate correlation analysis discovered that α-helix (p < 0.01) and β-turn (p < 0.05) of proteins were related to the mean droplet diameter of nanoemulsions, the random coil (p < 0.05) was related to the zeta potential of nanoemulsions. This study provided new idea for the relationship between the structure of protein and properties of protein-stabilized nanoemulsions.

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