Protein Secondary Structure Research Articles

Identification of a novel MEF2C::SS18L1 fusion in childhood acute B-lymphoblastic leukemia

PurposeLeukemia-associated fusion genes are closely related to the occurrence, development, diagnosis, and treatment of leukemia. DNA microarrays and second-generation sequencing have discovered multiple B-ALL fusion genes. We identified a novel MEF2C::SS18L1 fusion gene in a child diagnosed with B-ALL. This study investigates the oncogenicity and prognosis of this fusion gene in B-ALL.MethodsA child with B-ALL who has a MEF2C::SS18L1 fusion is reported as a newly discovered case. Compared the breakpoints, structural domains, clinical phenotypes, and differential expression genes of MEF2C::SS18L1 and MEF2D::SS18.Using “ONCOFUSE” software, the carcinogenicity of MEF2C::SS18L1 is predicted. Using whole transcriptome sequencing, we analyze the breakpoints and the secondary structure of the fusion protein. Further, we compared the structures, differentially expressed genes, and clinical phenotypes of MEF2D and MEF2C fusion genes by DESeq, GO functional enrichment, and flow cytometry immunophenotyping analysis.ResultsWhole transcriptome sequencing identified a MEF2C::SS18L1 fusion transcript in a 3-year-old child with B-ALL. The MADS box, MEF structural domain, HJURP_C structural domain, and TAD I structural domain of MEF2C, and the QPGY structural domain of SS18L1, make up the fusion protein. “Oncofuse” found a 0.99 Bayesian probability that the fusion gene drives cancer. The breakpoint positions, fusion protein secondary structures, differentially expressed genes, and clinical characteristics of this patient were identical to those with MEF2D::SS18 fusion gene.ConclusionWe identified a novel MEF2C::SS18L1 fusion gene in childhood ALL, which shares similar structural and clinical characteristics with MEF2D::SS18. Further studies with more samples should be conducted in future.

Mechanism by which exogenous H2O2 improves main secondary metabolites contents in post-harvest fresh Ginkgo leaves through induced physiological responses mimicking stress

Ginkgo (Ginkgo biloba L.) is widely cultivated for leaves containing flavonoids and ginkgolides with various bioactivities, achieving global sales of preparations exceeding $10 billion. Improving the secondary metabolites contents in Ginkgo leaves holds significant importance for health and socioeconomic aspects. In natural settings, moderate stress boosts the biosynthesis and accumulation of secondary metabolites. However, controlling stress during growth to improve secondary metabolites contents in Ginkgo leaves is impractical due to the multiple, complex, and uncontrollable field conditions. To address the trouble, this study employed exogenous hydrogen peroxide (H2O2), an essential substance that stress affects secondary metabolism, at concentrations of 20, 200, and 2000 mmol·L−1, applied to pre- and post-harvest fresh Ginkgo leaves. Parameters including reactive oxygen species, antioxidant enzymes, osmolytes, flavonoids, and ginkgolides were measured, and metabolomics and bioinformatics were conducted to analyze metabolites and fatty acid desaturase (FAD). As a result, superoxide radical, H2O2, and malondialdehyde significantly increased after treatment with exogenous H2O2, and antioxidant enzymes such as superoxide dismutase, catalase, and peroxidase, as well as osmolytes like proline, soluble protein, and soluble sugar, also notably increased. Concurrently, GbFAD was influenced, including stress-responsive elements, gene expression patterns, protein secondary structure, etc., leading to a significant upregulation of lipids and lipid-like molecules, which helped maintain cell membrane structure and function, facilitating secondary metabolism. Consequently, the secondary metabolites contents in post-harvest fresh Ginkgo leaves appreciably improved, particularly at 200 mmol·L−1, with quercetin, kaempferol, isorhamnetin, ginkgolide A, ginkgolide B, ginkgolide C, and bilobalide increasing by 68.01 %, 26.86 %, 42.99 %, 29.09 %, 39.60 %, 45.83 %, and 51.25 %, respectively. Exogenous H2O2 induces physiological responses in the post-harvest fresh Ginkgo leaves similar to those observed under pre-harvest stress, thereby improving flavonoids and ginkgolides contents. This groundbreaking discovery that exogenous H2O2 can induce stress in post-harvest fresh Ginkgo leaves to increase secondary metabolites contents on an industrial scale not only further advances the Ginkgo-related pharmaceutical industry but also provides a novel approach and perspective for improving secondary metabolites contents in other medicinal crops during post-harvest processing.

Enhancing functionality and bioactivity of walnut protein through limited enzyme digestion.

Walnut protein (WP) is recognized as a valuable plant protein. However, the poor solubility and functional properties limit its application in the food industry. It is a great requirement to improve the physicochemical properties of WP. Following a 90 min restricted enzymatic hydrolysis period, the solubility of WP significantly increased from 3.24% to 54.54%, with the majority of WP hydrolysates (WPHs) possessing a molecular weight exceeding 50 kDa. Circular dichroism spectra showed that post-hydrolysis, the structure of the protein became more flexible, while the hydrolysis time did not significantly alter the protein's secondary structure. After hydrolysis, WP's surface hydrophobicity significantly increased from 2279 to 6100. Furthermore, WPHs exhibited a strong capacity for icariin loading and micelle formation with critical micelle concentration values of 0.71, 0.99 and 1.09 mg mL-1, respectively. Moreover, similar immuno-enhancement activities were observed in WPHs. After exposure to WPHs, the pinocytosis of RAW264.7 macrophages was significantly improved. WPH treatment also increased the production of nitric oxide, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in macrophages. Up-regulation of mRNA expressions of IL-6, inducible nitric oxide synthase (iNOS) and TNF-α was observed in a dose-dependent manner. The enhancement of functionality and bioactivity in WP can be achieved through the application of limited enzyme digestion with trypsin. This process effectively augments the nutritional value and utility of the protein, making it a valuable component in various dietary applications. © 2024 Society of Chemical Industry.

Cryoprotective Activity of Different Characterized Fractions Isolated from Enzymatic Hydrolysates of Croceine Croaker (Pseudosciaena crocea).

In this study, ultrafiltration fractions (<3 k Da, LMH; >3 k Da, HMH) and solid-phase extraction fractions (hydrophilic hydrolysate, HIH; hydrophobic hydrolysate, HOH) from trypsin hydrolysate purified from croceine croaker (Pseudosciaena crocea) isolate were obtained to investigate the cryoprotective effects of the different fractions, achieved by means of maceration of turbot fish meat after three freeze-thaw cycles. Alterations in the texture, color, moisture loss, myofibrillar protein oxidation stability and conformation, and microstructure of the fish were analyzed after freezing and thawing. The results demonstrate that HIH maximized the retention of fish texture, reduced moisture loss, minimized the oxidation and aggregation of myofibrillar proteins, and stabilized the secondary and tertiary structures of myofibrillar proteins compared to the control group. In conclusion, the HIH component in the trypsin hydrolysates of croceine croaker significantly contributes to minimizing freeze damage in fish meat and acts as an anti-freezing agent with high industrial application potential.

Computational design of novel chimeric multiepitope vaccine against bacterial and viral disease in tilapia (Oreochromis sp.)

Regarding several infectious diseases in fish, multiple vaccinations are not favorable. The chimeric multiepitope vaccine (CMEV) harboring several antigens for multi-disease prevention would enhance vaccine efficiency in terms of multiple disease prevention. Herein, the immunogens of tilapia’s seven pathogens including E. tarda, F. columnare, F. noatunensis, S. iniae, S. agalactiae, A. hydrophila, and TiLV were used for CMEV design. After shuffling and annotating the B-cell epitopes, 5,040 CMEV primary protein structures were obtained. Secondary and tertiary protein structures were predicted by AlphaFold2 creating 25,200 CMEV. Proper amino acid alignment in the secondary structures was achieved by the Ramachandran plot. In silico determination of physiochemical and other properties including allergenicity, antigenicity, glycosylation, and conformational B-cell epitopes were determined. The selected CMEV (OSLM0467, OSLM2629, and OSLM4294) showed a predicted molecular weight (MW) of 70 kDa, with feasible sites of N- and O-glycosylation, and a number of potentially conformational B-cell epitope residues. Molecular docking, codon optimization, and in-silico cloning were tested to evaluate the possibility of protein expression. Those CMEVs will further elucidate in vitro and in vivo to evaluate the efficacy and specific immune response. This research will highlight the new era of vaccines designed based on in silico structural vaccine design.

Rational Approach toward COVID-19's Main Protease Inhibitors: A Hierarchical Biochemoinformatics Analysis.

This study investigated the potential of selected compounds as inhibitors of SARS-CoV-2 Mpro through pharmacokinetic and toxicological analyses, molecular docking, and molecular dynamics simulations. In silico molecular docking simulations revealed promising ligands with favorable binding affinities for Mpro, ranging from -6.2 to -9.5 kcal/mol. Moreover, molecular dynamics simulations demonstrated the stability of protein-ligand complexes over 200 ns, maintaining protein secondary structures. MM-PBSA analysis revealed favorable interactions between ligands and Mpro, with negative binding energy values. Hydrogen bond formation capacity during molecular dynamics was confirmed, indicating consistent interactions with Mpro catalytic residues. Based on these findings, selected ligands show promise for future studies in developing COVID-19 treatments.

Insights into the Binding Interactions between Microplastics and Human α-Synuclein Protein by Multispectroscopic Investigations and Amyloidogenic Oligomer Formation.

Aggregation of human α-synuclein protein is regarded to be a key stage in the etiology of Parkinson's disease and numerous other neurodegenerative illnesses. Microplastics pollution can be a potential agent to promote various neurodegenerative disorders. In this study, we have employed various multispectroscopic analytical methods to investigate the binding interactions between polyethylene (PE-MPs), polyvinyl chloride (PVC-MPs), polystyrene (PS-MPs) microplastics, and human α-synuclein protein. Spectroscopic investigations using UV-vis absorption, circular dichroism, and Fourier transform infrared have indicated different alterations in α-synuclein protein's secondary structures induced by the formation of the α-synuclein protein-MP binding complex. This study suggests that PS-MPs are found to be the most effective microplastic that promote amyloidogenic oligomer emergence because of their tiny size (100 nm).

Comparison of sea buckthorn fruit oil nanoemulsions stabilized by protein-polysaccharide conjugates prepared using β-glucan from various sources

To understand the influence of β-glucans structure on the emulsifying properties of protein-polysaccharide conjugates, sodium caseinate (NaCas) was utilized to form glycosylation conjugates with varying degrees of glycosylation (10.68–17.50%) using three β-glucans from bacteria, yeast, and oats. This process induced alterations in the secondary structure of protein. The nanoemulsions prepared with the glycosylated conjugates exhibited superior stability compared to those formulated solely with NaCas, particularly under conditions of drastic pH fluctuations and extended storage periods. The nanoemulsion prepared with the NaCas-Salecan conjugate demonstrated exceptional stability at pH 4 and 6, or storage for 20 days. Additionally, it significantly attenuated the oxidation of unsaturated fatty acids and exhibited the lowest levels of aggregation, flocculation, and free fatty acid release rate during in vitro digestion. This study suggested the potential of the NaCas-Salecan conjugates in enhancing the stability of nanoemulsions and facilitating the colorectal-targeted delivery of sea buckthorn fruit oil.

Rapid formation mechanism of SAD granular sludge: From flocculated activated sludge to granular sludge

The SAD (Simultaneous Anammox and Denitrification) process combines anammox with denitrification to achieve nitrogen removal and carbon reduction. In this study, the flocculent activated sludge in the secondary sedimentation tank of the traditional sewage treatment plant was used as the research object. Under the action of high NH4+, adding reflux, and adjusting HRT in the UASB reactor, the transformation from flocculent sludge to SAD granular sludge was quickly realized. The results showed that a relatively stable SAD granular sludge system could be formed after 250 days of operation, and the system with reflux was more resistant to changes in the external environment than the system without reflux. In the SAD system, TN Removal Rate (TNRE) ≈ 90 %, Carbon Removal Rate (CRR) ≈ 90 %. After 3D-EEM, FTIR, and analysis of protein secondary structure, it was found that the particle stability and aggregation of the SAD stage were significantly improved compared with the previous two stages. The bacterial community structure had obvious vertical heterogeneity, mainly AnAOB (Ca. Kuenenia≈30 %) and denitrifying bacteria (Comamonas≈20 %). When the temperature drops sharply, the performance of SAD can be effectively restored by adding reflux and reducing the carbon source.

Free radical-induced soybean protein isolate -curcumin conjugates: Characterization, antioxidant and in vitro digestion characteristics

Natural soybean protein isolate（SPI) is vulnerable to environmental factors that compromise its functionality. One effective method to improve this functionality is through free radical induction. In this study, SPI and curcumin (Cur) were utilized to prepare SPI-Cur conjugates using the free radical induction method. The formation mechanism, structure, and functional properties of these conjugates were subsequently. The results indicated that at pH 9, the SPI-Cur conjugate formed hydroxyquinone dimers, which exhibited higher inhibition of digestive enzymes and increased stability through free radical-induced reactions. Furthermore, the antioxidant properties of SPI-Cur conjugates increased significantly, with increases of 9.17-, 2.3-, and 7.70-fold in DPPH, ABTS, and reducing power, respectively (p < 0.05). Circular dichroism analysis revealed increases in the secondary structure of proteins in SPI-Cur conjugates α-helix from 0.40% to 1.47%, β-sheet from 28.70% to 98.38% (pH 3 to pH 9), β-turns from 70.83% to 0.15%, and Random coils from 0.00% to 81.21%. These results suggest a novel approach for creating SPI-Cur conjugates through free radical-induced reactions, which could aid in the development of a continuous delivery system for polyphenols based on SPI and improve the high-value utilization of SPI.

Mechanism Involved in Polyvinyl Chloride Nanoplastics Induced Anaerobic Granular Sludge Disintegration: Microbial Interaction Energy, EPS Molecular Structure, and Metabolism Functions.

Nanoplastics (NPs) are emerging pollutants and have been reported to cause the disintegration of anaerobic granular sludge (AnGS). However, the mechanism involved in AnGS disintegration was not clear. In this study, polyvinyl chloride nanoplastics (PVC-NPs) were chosen as target NPs and their long-term impact on AnGS structure was investigated. Results showed that increasing PVC-NPs concentration resulted in the inhibition of acetoclastic methanogens, syntrophic propionate, and butyrate degradation, as well as AnGS disintegration. At the presence of 50 μg·L-1 PVC-NPs, the hydrophobic interaction was weakened with a higher energy barrier due to the relatively higher hydrophilic functional groups in extracellular polymeric substances (EPS). PVC-NPs-induced ROS inhibited quorum sensing, significantly downregulated hydrophobic amino acid synthesis, whereas it highly upregulated the genes related to the synthesis of four hydrophilic amino acids (Cys, Glu, Gly, and Lys), resulting in a higher hydrophily degree of protein secondary structure in EPS. The differential expression of genes involved in EPS biosynthesis and the resulting protein secondary structure contributed to the greater hydrophilic interaction, reducing microbial aggregation ability. The findings provided new insight into the long-term impact of PVC-NPs on AnGS when treating wastewater containing NPs and filled the knowledge gap on the mechanism involved in AnGS disintegration by PVC-NPs.

Attenuated-total-reflection Fourier-transformed spectroscopy as a rapid tool to reveal the molecular structure of insect powders as ingredients for animal feeds

Abstract Unsustainable agriculture contributes to disastrous global effects – insect-based feed shows potential due to their sustainable, nutritional, and waste upcycling properties. Current EU legislation restricts insect-based meals to fish, pork, and poultry feed; but the near-future shows a great potential for wider acceptance in livestock feed. Black soldier fly larvae (BSFL), mealworm (MW), field cricket (FC), and banded cricket (BC) were sourced within three consecutive weeks – each batch was prepared, freeze-dried, then milled, and stored at −20 °C. Chemical composition of whole-insect meals was analysed for ether extract (EE), crude ash, and nitrogenic contents using standard wet chemistry protocols. Monogastric in vitro digestibility was determined through replicating gastric and full intestinal digestion; during this, R-amino acid content was determined through protein hydrolysis kinetics. Additionally, ATR-FTIR was used for molecular analysis, including identification of nutrient-associated functional spectral bands – structural differences were compared through principal component analysis. Insect-based ATR-FTIR analysis demonstrates notable differences in Amide regions, suggesting distinct protein secondary structures, but overall, FC and BC contain the highest crude protein (CP) levels. The lowest CP content was in BSFL; however, BSFL contained the highest ash content – likely consequence of high calcium. Dry matter (DM) yielded lowest in the crickets (FC-28.6; BC-26.9 g/100 g), and highest in MW-38.5 g/100 g; the sum of CP + EE in MW represented &gt;80% DM, but with higher EE contents-CP: EE = 2.45. Data shows greater chitin content in crickets than BSFL + MW. Crickets showed greater neutral detergent fibre (NDF) than BSFL + MW; however, acid-detergent fibre (ADF) was similar among all species, suggesting NDF may include amalgams of interlinked nutrients released by acid digestion. This first study shows for the first time evidence that rearing conditions and substrates influences molecular structure. Exponential solubilisation was observed during pepsin + pancreatin digestion for all, but BSFL exhibited the highest degree-of-hydrolysis during the pancreatin phase, surpassing others. Analysis indicates protein hydrolysis differences are linked to trypsin activity susceptibility.

Effect of casein genetic variants and glycosylation on bovine milk foaming properties

The effects of κ‐casein (κ‐CN) and β‐casein (β‐CN) genetic variant and κ‐CN glycosylation degree (GD, low or high) on interfacial and foaming properties of bovine skim milk were investigated. No significant effect was measured for milks with different ĸ‐CN and β‐CN genetic variants. However, milks of higher GD exhibited lower surface tension, enhanced foamability and differences in secondary protein structure compared to lower GD skim milks. Glycan attachment is believed to affect surface activity and the spread and packing of protein at the foam bubble liquid–air interface, leading to differences in foaming performance.

A novel homozygous FAM92A gene (CIBAR1) variant further confirms its association with non-syndromic postaxial polydactyly type A9 (PAPA9).

Polydactyly is a very common digit anomaly, having extra digits in hands and/or toes. Non-syndromic polydactyly in both autosomal dominant and autosomal recessive forms are caused by disease-causing variants in several genes, including GLI1, GLI3, ZNF141, FAM92A, IQCE, KIAA0825, MIPOL1, STKLD1, PITX1, and DACH1. Whole exome sequencing (WES) followed by bi-directional Sanger sequencing was performed for the single affected individual (II-1) of the family to reveal the disease causative variant/gene. 3D protein modeling and structural molecular docking was performed to determine the effect of the identified mutation on the overall protein structure. WES revealed a novel biallelic missense variant (c.472G>C; p.Ala158Pro) in exon 6 of the FAM92A gene. The identified variant segregated perfectly with the disease phenotype using Sanger sequencing. Furthermore, Insilco analysis revealed that the variant significantly changes the protein secondary structure, and substantially impact the stability of FAM92A. We report the second FAM92A disease-causing mutation associated with recessive non-syndromic postaxial polydactyly. The data further confirms the contribution of FAM92A in limb development and patterning.

Effects of Alkaline Extraction pH on Amino Acid Compositions, Protein Secondary Structures, Thermal Stability, and Functionalities of Brewer's Spent Grain Proteins.

A high alkaline pH was previously demonstrated to enhance the extraction yield of brewer's spent grains (BSG) proteins. The effects of extraction pH beyond the extraction yield, however, has not been investigated before. The present work examined the effects of extraction pH (pH 8-12) on BSG proteins' (1) amino acid compositions, (2) secondary structures, (3) thermal stability, and (4) functionalities (i.e., water/oil holding capacity, emulsifying, and foaming properties). The ideal extraction temperature (60 °C) and BSG-to-solvent ratio (1:20 w/v) for maximizing the extraction yield were first determined to set the conditions for the pH effect study. The results showed that a higher extraction pH led to more balanced compositions between hydrophilic and hydrophobic amino acids and higher proportions of random coils structures indicating increased protein unfolding. This led to superior emulsifying properties of the extracted proteins with more than twofold improvement between pH 8 and a pH larger than 10. The extraction pH, nevertheless, had minimal impact on the water/oil holding capacity, foaming properties, and thermal denaturation propensity of the proteins. The present work demonstrated that a high alkaline pH at pH 11-12 was indeed ideal for both maximizing the extraction yield (37-46 wt.%) and proteins' functionalities.

Determining Protein Secondary Structures in Heterogeneous Medium-Resolution Cryo-EM Images Using CryoSSESeg.

While the acquisition of cryo-electron microscopy (cryo-EM) at near-atomic resolution is becoming more prevalent, a considerable number of density maps are still resolved only at intermediate resolutions (5-10 Å). Due to the large variation in quality among these medium-resolution density maps, extracting structural information from them remains a challenging task. This study introduces a convolutional neural network (CNN)-based framework, cryoSSESeg, to determine the organization of protein secondary structure elements in medium-resolution cryo-EM images. CryoSSESeg is trained on approximately 1300 protein chains derived from around 500 experimental cryo-EM density maps of varied quality. It demonstrates strong performance with residue-level F 1 scores of 0.76 for helix detection and 0.60 for β-sheet detection on average across a set of testing chains. In comparison to traditional image processing tools like SSETracer, which demand significant manual intervention and preprocessing steps, cryoSSESeg demonstrates comparable or superior performance. Additionally, it demonstrates competitive performance alongside another deep learning-based model, Emap2sec. Furthermore, this study underscores the importance of secondary structure quality, particularly adherence to expected shapes, in detection performance, emphasizing the necessity for careful evaluation of the data quality.

Fermi Resonance of the N-D Stretching Mode Probing the Local Hydrogen-Bonding Environment in Proteins.

Local H-bonding interactions are crucial for proteins to undergo various structural transitions and form different secondary structures. However, identifying slight distinctions in the local H-bonding of proteins is rather challenging. Here, we demonstrate that the Fermi resonance of the N-D stretching mode can provide an effective probe for the localized H-bonding environment of proteins both at the surface/interface and in the bulk. Using sum frequency generation vibrational spectroscopy and infrared spectroscopy, we established a correlation between the Fermi resonance of the N-D mode and protein secondary structures. The H-bond of N-D···C═O splits the N-D modes into two peaks (∼2410 and ∼2470 cm-1). The relative strength ratio (R) between the ∼2410 cm-1 peak and the ∼2470 cm-1 peak is very sensitive to H-bond strength and protein secondary structure. R is less than 1 for α-helical peptides, while R is greater than 1 for β-sheet peptides. For R < 2.5, both α-helical/loop structures and β-sheet structures exhibit almost identical Fermi coupling strengths (W = 28 cm-1). For R > 2.5, W decreases from 28 to 14 cm-1 and depends on the aggregation degree of the β-sheet oligomers or fibrils. The initial local H-bonding status impacts the misfolding dynamics of proteins at the lipid bilayer interface.

Performance and microbial community evolution of toluene degradation in the presence of acetone vapors using hybrid membrane-aerated biofilm reactors (HMABRs)

Biological treatment methodologies offer cost-effective and eco-friendly solutions for volatile organic compounds (VOCs) removal, but they face limitations in effectively treating hydrophobic VOCs. Herein, this study introduces the Hybrid Membrane Aerated Biofilm Reactor (HMABR) for VOC treatment. The HMABR integrates a bio-trickling filter-like spraying function with MABR technology to construct a non-submerge system. What’s more, introducing hydrophilic gases enhances the degradation of hydrophobic VOCs in pollutant biotreatment. While hydrophilic VOCs are readily degraded by microorganisms, the mechanisms of their co-degradation remain understudied. Toluene and acetone, common industrial VOCs, were examined in the HMABR system. HMABR exhibits outstanding toluene removal, reaching a maximum capacity of 142.04 gm−3h−1. The addition of acetone boosts this capacity by 70.1 gm−3h−1, altering EPS composition, and notably increasing the PN/PS ratio from 0.35 to 2.76. It can be inferred that acetone’s presence enhances biofilm EPS hydrophobicity, aiding toluene breakdown. Besides, when adding acetone, the biofilm EPS sample exhibited a more compact secondary protein structure. Analysis of the microbial community in the HMABR system identified a dominance of Pseudomonadota, with an increased abundance of Rhodanobacter, which correlated strongly with toluene degradation in the presence of acetone. Gene analysis revealed an increase in toluene degradation genes in Rhodanobacter when acetone was added. Furthermore, acetone activation was found to enhance metabolic pathways related to xylene degradation and the tricarboxylic acid (TCA) cycle, thereby improving toluene removal efficiency. These findings provide insights into co-metabolism in treating hydrophobic pollutants in HMABR and contribute to designing more effective treatment systems for VOCs.

Insight into quality, microstructure, and protein physicochemical properties of Monopterus albus frozen with liquid nitrogen

Monopterus albus is highly susceptible to spoilage due to high protein and moisture contents while frozen storage can effectively prolong the shelf-life. To study the effect of liquid nitrogen freezing (LNF) on quality, microstructure of ice crystal and muscle fiber, and physicochemical properties of proteins, Monopterus albus was frozen at -20 °C by refrigerator (RF, control), -50 °C, -80 °C, and -110 °C by LNF, respectively. The -110 °C LNF exhibited the highest freezing rate among four groups, contributing to the formation of small ice crystals with more uniform distribution and alleviating the damage to muscle fiber. In -110 °C LNF group, protein secondary structure changed relatively subtle, resulting in high protein solubility, Ca2+-ATPase activity, and total sulfhydryl content, as well as low surface hydrophobicity and disulfide bond content. LNF retarded the rise of TVB-N value, prevented the loss of immobilized and free water, and maintained water holding capacity and shear force. In conclusion, -110 °C LNF was recommended a promising freezing process for frozen Monopterus albus due to less alteration of quality and alleviation of protein denaturation.

Effect of Dry and Wet Fractionation on Nutritional and Physicochemical Properties of Faba Bean and Yellow Pea Protein

ABSTRACTPlant‐based proteins continue to gain popularity as a sustainable alternative to animal proteins due to their nutritional, functional and health benefits. Dry and wet fractionation methods are increasingly being used for the production of value‐added pulse protein ingredients. The objective of this study was to compare the nutritional properties, protein quality, physicochemical properties and secondary structure of Australian faba bean and yellow pea protein concentrates and protein isolates obtained by dry and wet fractionation. Amino acid scores highlighted that faba bean and yellow pea protein isolates and concentrates were deficient in the sulphur‐containing amino acids, methionine and cysteine and tryptophan. Faba bean (63.7%) and yellow pea protein (63.0%) isolates had higher in vitro protein digestibility‐corrected amino acid scores compared to the protein concentrates, being 50.7% and 54.4%, respectively. Fourier‐transform infrared spectroscopy revealed different secondary structures between protein concentrates and isolates, especially for the amide I region. Faba bean and yellow pea protein concentrates had higher protein solubility (46.2% and 50.1%, respectively) and higher foaming capacity (65% and 59%, respectively) compared to the protein isolates. Water‐holding capacity was higher for faba bean and yellow pea protein isolates, being 4.3% and 4.0 g/g, respectively. These findings demonstrate that faba bean and yellow pea protein concentrates and isolates have unique functional properties that can be exploited for use in a diverse range of new and existing food applications.