Functional Properties Of Proteins Research Articles

Proteomic and N-glycoproteomic analyses of total subchondral bone protein in patients with primary knee osteoarthritis

N-glycosylation is an important post-translational modification necessary to maintain the structural and functional properties of proteins. Impaired N-glycosylation has been observed in several diseases. It is significantly modified by the state of cells and is used as a diagnostic or prognostic indicator for multiple human diseases, including cancer and osteoarthritis (OA). Aim of the study was to explore the N-glycosylation levels of subchondral bone proteins in patients with primary knee OA (KOA) and screen for potential biological markers for the diagnosis and treatment of primary KOA. A comparative analysis of total protein N-glycosylation under the cartilage was performed in medial subchondral bone (MSB, N = 5) and lateral subchondral bone (LSB, N = 5) specimens from female patients with primary KOA. To analyse the N-glycosylation sites of the proteins, non-labelled quantitative proteomic and N-glycoproteomic analyses were performed based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) data. Parallel reaction monitoring (PRM) validation experiments were carried out on differential N-glycosylation sites of proteins in selected specimens, including MSB (N = 5) and LSB (N = 5), from patients with primary KOA. In total, 1149 proteins with 1369 unique N-chain glycopeptides were detected, and 1215 N-glycosylation sites were found, in which ptmRS scores for 1163 N-glycosylation sites were ≥ 0.9. In addition, N-glycosylation of the total protein in MSB compared to that in LSB was identified, in which 295 N-glycosylation sites were significantly different, including 75 upregulated and 220 downregulated N-glycosylation sites in MSB samples. Importantly, Gene Ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment analyses of proteins with differential N-glycosylation sites showed that they were primarily associated with metabolic pathways including ECM-receptor interactions, focal adhesion, protein digestion and absorption, amoebiasis, and complement and coagulation cascades. Finally, PRM experiments confirmed the N-glycosylation sites of collagen type VI, alpha 3 (COL6A3, VAVVQHAPSESVDN[+3]ASMPPVK), aggrecan core protein (ACAN, FTFQEAAN[+3]EC[+57]R, TVYVHAN[+3]QTGYPDPSSR), laminin subunit gamma-1 (LAMC1, IPAIN[+3]QTITEANEK), matrix-remodelling-associated protein 5 (MXRA5, ITLHEN[+3]R), cDNA, FLJ92775, highly similar to Homo sapiens melanoma cell adhesion molecule (MCAM), mRNA(B2R642, C[+57]VASVPSIPGLN[+3]R), and aminopeptidase fragment (Q59E93, AEFN[+3]ITLIHPK) in the array data of the top 20 N-glycosylation sites. These abnormal N-glycosylation patterns provide reliable insights for the development of diagnostic and therapeutic methods for primary KOA.

Sulfur in determining seed protein composition: present status on its interaction with abiotic stresses and future directions.

Improving and stabilizing the quality of seed proteins are of growing interest in the current food and agroecological transitions. Sulfur is a key determinant of this quality since it is essential for the synthesis of sulfur-rich proteins in seeds. A lack of sulfur provokes drastic changes in seed protein composition, negatively impacting the nutritional and functional properties of proteins, and leading in some cases to diseases or health problems in humans. Sulfur also plays a crucial role in stress tolerance through the synthesis of antioxidant or protective molecules. In the context of climate change, questions arise regarding the trade-off between seed yield and seed quality with respect to sulfur availability and use by crops that represent important sources of proteins for human nutrition. Here, we review recent work obtained in legumes, cereals, as well as in Arabidopsis, that present major advances on: (i) the interaction between sulfur nutrition and environmental or nutritional stresses with regard to seed yield and protein composition; (ii) metabolic pathways that merit to be targeted to mitigate negative impacts of environmental stresses on seed protein quality; (iii) the importance of sulfur homeostasis for the regulation of seed protein composition and its interplay with seed redox homeostasis.

Changes of structure and functional properties of rice protein in the fresh edible rice during the seed development

It has been reported that fresh edible rice has more bioactive compounds and its protein is easier to digest and has lower hypoallergenic than mature rice. In this paper, the changes in structure and functional properties of proteins at five different stages, including early milky stage (EMS), middle milky stage (MMS), late milky stage (LMS), waxy ripe stage (WS) and ripening stage (RS), during the seed development were investigated. It was found that with the seed developing, the molecular weight of fresh rice protein gradually become larger while the secondary structure changed from the highest content of disordered structure at MMS to the highest content of ordered structure at RS, which affect the surface hydrophobicity and then the functional properties of proteins, including foaming properties, emulsifying properties and oil holding capacity. Fresh rice protein at MMS has the strongest surface hydrophobicity while fresh edible rice protein at RS has the strongest oil holding capability. The results of our study can provide a theoretical basis for the application of fresh rice protein in the food industry and help to develop new fresh edible rice food.

Ultrasound-assisted alkaline extraction of protein from Tenebrio molitor larvae: Extraction kinetics, physiochemical, and functional traits

Currently, as a promising alternative protein source, the interest of edible insect protein has been continuously increased. However, the extraction processing had distinct effects on the physicochemical properties and functionalities of this novel and sustainable protein. In this study, Tenebrio molitor larvae protein (TMLP) was extracted via ultrasound (US)-assisted alkaline extraction. The changes of extraction kinetics, physicochemical characteristics, and functional properties of TMLP as a function of US time (10, 20, 30, 40, 50 min) were investigated. The results showed that 30 min US treatment rendered the maximum protein yield (60.04 %) (P < 0.05). Meanwhile, Peleg's model was considered a suitable model to represent the extraction kinetics of TMLP, with a correlation coefficient of 0.9942. Moreover, the protein secondary structure, particle size, and amino acid profiles of TMLP were changed under the US-assisted alkaline extraction process. Additionally, a significant improvement of the functional properties of TMLP extracted with this method was observed compared to traditional alkaline extraction. In conclusion, the present work suggests that US-assisted alkaline extraction could be considered as a potential method to improve the protein yield, quality profiles, and functional properties of TMLP.

Food protein glycation: A review focusing on stability and in vitro digestive characteristics of oil/water emulsions.

Recently, increasing studies have shown that the functional properties of proteins, including emulsifying properties, antioxidant properties, solubility, and thermal stability, can be improved through glycation reaction under controlled reaction conditions. The use of glycated proteins to stabilize hydrophobic active substances and to explore the gastrointestinal fate of the stabilized hydrophobic substances has also become the hot spot. Therefore, in this review, the effects of glycation on the structure and function of food proteins and the physical stability and oxidative stability of protein-stabilized oil/water emulsions were comprehensively summarized and discussed. Also, this review sheds lights on the in vitro digestion characteristics and edible safety of emulsion stabilized by glycated protein. It can further serve as a research basis for understanding the role of structural features in the emulsification and stabilization of glycated proteins, as well as their utilization as emulsifiers in the food industry.

An overview of protein powders and their use in food formulations

AbstractProtein quality, as well as quantity, must be taken into account when designing healthy and sustainable diets and food systems. This is particularly crucial for protein powders since there is a wide range of sources and production methods affecting powder and particle properties, and protein functionality and quality. Proteins can be derived from numerous raw materials and converted into powder or particulate form for several reasons, such as ease of transportation and storage stability. Therefore, it is key to understanding the sources, processing methods, powder, and particle properties of protein powders to provide high‐quality products. This study reviews the origins of proteins, extraction techniques, and drying methods employed to produce protein powders. In addition, functional and powder properties, their use in foods, and regulatory issues are highlighted.Practical applicationsProteins are found in different foods and in food processing side streams such as de‐oiled oilseed meals. Most seeds are typically discarded as food waste worldwide, even though they have high protein content. This review provides an insight into protein sources, extraction methods, powder production techniques, and use in food formulations. It also assessed the effect of powder properties on the functional properties of proteins. To our knowledge, no reviews have been conducted on protein powders. By providing information and insights, this article should contribute to better understanding the protein powders and their use in the production of functional foods.

Effect of Enzymatic Pre-Treatment on Oat Flakes Protein Recovery and Properties

Oats are considered an exceptional source of high-quality protein. Protein isolation methods define their nutritional value and further applicability in food systems. The aim of this study was to recover the oat protein using a wet-fractioning method and investigate the protein functional properties and nutritional values among the processing streams. The oat protein was concentrated through enzymatic extraction, eliminating starch and non-starch polysaccharides (NSP), treating oat flakes with hydrolases, and reaching protein concentrations of up to about 86% in dry matter. The increased ionic strength from adding sodium chloride (NaCl) improved protein aggregation and resulted in increased protein recovery. Ionic changes improved protein recovery in provided methods by up to 24.8 % by weight. Amino acid (AA) profiles were determined in the obtained samples, and protein quality was compared with the required pattern of indispensable amino acids. Furthermore, functional properties of the oat protein, such as solubility, foamability, and liquid holding capacity, were investigated. The solubility of the oat protein was below 7 %; foamability averaged below 8%. The water and oil-holding reached a ratio of up to 3.0 and 2.1 for water and oil, respectively. Our findings suggest that oat protein could be a potential ingredient for food industries requiring a protein of high purity and nutritional value.

Addition of NaCl or Sucrose on the Protein Content, and Functional and Physicochemical Properties of Egg Whites Liquid under Heat Treatment.

In this study, differences in the protein content and functional and physicochemical properties of four varieties of egg white (EW) were studied by adding 4-10% sucrose or NaCl and then heating them at 70 °C for 3 min. According to a high-performance liquid chromatography (HPLC) analysis, the percentages of ovalbumin, lysozyme and ovotransferrin rose with an increase in the NaCl or sucrose concentration; however, the percentages of ovomucin and ovomucoid decreased. Furthermore, the foaming properties, gel properties, particle size, α-helixes, β-sheets, sulfhydryl groups and disulfide bond content also increased, whereas the content of β-turns and random coils decreased. In addition, the total soluble protein content and functional and physicochemical properties of black bone (BB) chicken and Gu-shi (GS) EWs were higher than those of Hy-Line brown (HY-LINE) and Harbin White (HW) Ews (p < 0.05). Subsequently, transmission electron microscopy (TEM) confirmed the changes in the EW protein structure in the four varieties of Ews. As the aggregations increased, the functional and physicochemical properties decreased. The protein content and functional and physicochemical properties of Ews after heating were correlated with the concentration of NaCl and sucrose and the EW varieties.

Lentil and Mungbean protein isolates: Processing, functional properties, and potential food applications

Among the wide range of plant-based protein sources, pulse proteins stand out for their nutritional values and functional properties, together with sustainability. The global attention on soy and pea proteins, however, has overlooked other pulses. This review has explored underutilized and under-researched pulses, lentils and mungbean, by considering their comparable protein contents but different protein composition to that of soy and pea proteins. The traditional subsistence farming of lentils and mungbean has evolved with their emergence in the global agriculture sector. Research on lentil and mungbean protein extraction, however, has not been as extensive as for soy and pea. The novel dry fractionation methods benefiting protein native structure are in the early stage of optimizing protein yield. The milder wet extraction techniques-ultrafiltration or salt extraction-dilutive precipitations-have been investigated to a lesser extent. The harsh conventional wet extraction, i.e. alkaline extraction-isoelectric precipitation, is widely employed for lentils and mungbean. Apart from extraction method, drying process, pH condition, and genetic makeup of the plants directly influence protein functional properties. Protein functional properties, including gelation, emulsification, water holding (WHC) and oil absorption capacities (OAC), and foaming of lentils and mungbean, are discussed to understand their potentiality in the development of meat analogs. Lentil protein exhibited comparable gelling, emulsifying, and superior foaming properties to pea and soy protein. Meanwhile, the gelling, WHC and OAC of mungbean proteins are comparable to soy. This review highlights the promising application of lentil and mungbean proteins as sustainable plant-based protein sources for human food applications.

Improved gelling and emulsifying properties of myofibrillar protein from frozen shrimp (Litopenaeus vannamei) by high-intensity ultrasound

The deterioration of shrimp protein functionality during chilling and frozen storage has recently attracted wide attention due to its adverse effects on shrimp quality. The high-intensity ultrasound (20 kHz, 400 W) was applied to improve the protein structure and functional properties of frozen shrimp ( Litopenaeus vannamei ) in this study. Fourier transform infrared (FTIR) spectroscopy showed that the cavitation effect of ultrasound could change the secondary structure of myofibrillar protein (MP) by turning the α-helix and random coil to β-sheet and β-turn. The unfolding of MP conformation increased the reactive sulfhydryl content and surface hydrophobicity accordingly. The structure changes eventually led to the significant improvement of protein functionality. Gel properties analysis showed after ultrasonic treatment, the gel strength and water holding capacity of protein gels were increased gradually. Scanning electron microscopy (SEM) images also demonstrated that ultrasound treatment contributed to the formation of stable network structures in protein gels. In addition, ultrasonic homogenization could increase the emulsifying ability (45.54 m 2 /g to 78.82 m 2 /g) and stability of protein in a short time, which might be related to the decrease of particle size. Confocal laser scanning microscope (CLSM) analysis further illustrated that ultrasound treatment made the emulsion distribution more uniform. The application of these findings will improve the deep processing ability and expand the commercialization of frozen shrimp products. • Ultrasonic treatment led to the unfolding of shrimp MP conformation. • Conformational change led to the increase of SH groups and surface hydrophobicity. • Ultrasound increased gel strength and water holding capacity of shrimp MP gel. • Ultrasound increased the emulsifying capacity and stability of frozen shrimp MP. • CLSM analysis illustrated ultrasound made emulsion distribution more uniform.

Composition and functional properties of hemp seed protein isolates from various hemp cultivars.

Hemp seed protein isolates (HPI) were extracted from seven commercial hemp cultivars, a Cornell breeding line, and a commercial hemp heart product, and their composition and functional properties were investigated. HPI contained different ratios of edestin, vicilin, and albumin proteins, which affected protein solubility and functionality. Higher protein solubility was associated with cultivars that contained more vicilin and albumin, which influenced the subsequent functional properties of HPI. Significant differences in water holding capacity (0.83-1.05g water/g protein isolate), oil holding capacity (1.28-1.81g oil/g protein isolate), foam capacity (52.9%-84.9%), and foam stability (68.1%-89.4%) were observed across HPI. The Cornell hemp breeding line exhibited the highest protein solubility at pH 7.0 and was uniquely capable of forming an emulsion. The relationship identified between hemp seed protein composition and functionality, in conjunction with the demonstration of an on-going hemp breeding line, suggest that continued, targeted development of hemp cultivars can improve its seed protein functional properties for ingredient utilization in plant-based foods.

Plant Protein versus Dairy Proteins: A pH-Dependency Investigation on Their Structure and Functional Properties.

Plant proteins are constantly gaining attention as potential substitutes for dairy proteins, due to their suitable functionality and nutritional value. This study was designed to compare the structural and functional responses of different plant protein isolates (soy, pea, lentil, and chickpea) with two commonly used dairy protein (whey protein isolates and sodium caseinate) under different pH treatments (pH 3.0, 5.0, 7.0, and 9.0). The results showed that pH had a different alteration on the structural, surface properties and functional properties of plant and dairy proteins. Plant protein generally possessed a darker color, lower solubility, emulsifying properties, and foaming capacity, whereas their foaming stability and water holding capacity were higher than those of dairy proteins. Soy protein isolates were characterized by its comparable proportion of β-turn and random coils, zeta-potential, emulsifying (30.37 m2/g), and water-holding capacity (9.03 g/g) at alkaline conditions and chickpea protein isolates showed good oil-holding capacity (3.33 g/g at pH 9) among plant proteins. Further analysis confirmed that pH had a greater influence on the structural and functional properties of proteins as compared to protein sources, particularly at acidic conditions. Overall, this study might help processors select the appropriate plant protein as dairy alternatives for their target application in plant-based food products.

Recovery of proteins from soybean oil-body wastewater at various pH levels and their structural and functional characterization

Soybean oil-body extraction produces large amounts of protein-containing wastewater, which wastes proteins and pollutes the environment. Herein, we investigated protein recovery from the wastewater generated during soybean oil-body production using the alkaline-extraction–isoelectric-point-precipitation method at various alkaline pH levels. We also investigated the effects of varying alkaline-extraction pH on the basic composition and physicochemical, rheological, and thermal properties of the recovered proteins. The basic composition showed that protein recovery increased with increasing pH, with a 58.88% recovery at pH 11, and that protein purity decreased above pH 10. Structural analysis using FT-IR spectroscopy showed that the α-helix predominance decreased with increasing pH, while β-sheet predominance exhibited the opposite trend. Proteins recovered at pH 8 and 9 were more soluble than those recovered at pH 10 and 11. Proteins recovered at pH 9 exhibited the highest emulsification (p < 0.05) while those recovered at pH 11 afforded the best gelation. The extraction pH has an essential effect on the structural and functional properties of proteins; maximizing value and minimizing waste during soybean processing by recovering functional proteins from wastewater are industrially applicable.

Systems-Wide Site-Specific Analysis of Glycoproteins.

Glycosylation is one of the most common and complex post-translation modifications that influence the structural and functional properties of proteins. Glycoproteins are highly heterogeneous and exhibit site- and protein-specific expression differences. Mass spectrometry in combination with liquid chromatography has emerged as the most powerful tool for the comprehensive characterization of glycosylation. The analysis of intact glycopeptides has emerged as a promising strategy to analyze glycoproteins for their glycan heterogeneity at both protein- and site-specific levels. Nevertheless, intact glycopeptide characterization is challenging as elucidation of the glycan and peptide moieties requires specific sample preparation workflows that, combined with the tandem mass spectrometry approach, enable the identification of single glycopeptide species. In this chapter, we provide a detailed description of the methods that include procedures for (i) proteolytic digestion using specific proteases, (ii) optional glycopeptide enrichment using hydrophilic interaction liquid chromatography, (iii) nano-LC-MS/MS analysis of glycopeptides, and (iv) data analysis for identification of glycopeptides. Together, our workflow provides a framework for the system-wide site-specific analysis of N- and O-glycopeptides derived from complex biological or clinical samples.

Effects of ultrasound assisted cell wall disruption on physicochemical properties of camellia bee pollen protein isolates.

Camellia bee pollen protein isolates were extracted by cell wall disruption using ultrasonication, freeze-thawing, enzymatic hydrolysis, and their combinations. The effects of these methods on microstructure of cell wall, protein release, protein yield, physiochemical properties and structure of proteins were investigated. As compared with physical treatments (ultrasonication, freeze-thawing and their combination), the enzymatic hydrolysis significantly improved the yield of proteins, because it not only promoted the release of proteins from the inside of pollen, but also released proteins in pollen wall. The proteins extracted by enzymatic hydrolysis method also exhibited better solubility, emulsifying and gelation properties due to the partial hydrolysis of proteins by protease. In addition, when ultrasound was combined with freeze-thawing or enzymatic hydrolysis, it could further improve the yield of proteins and the functional properties of proteins, which was mainly related to the changes of protein structure induced by cavitation effect of ultrasound.

Effects of polyphenols on the gel and digestive properties of Penaeus vannamei myosin after freezing.

Polyphenols could inhibit the freezing-induced denaturation of myosin, and affect its nutritional and functional properties, which have rarely been studied to date. Therefore, the effects of interactions between polyphenols and myosin after freezing on myosin gel and digestive properties were investigated using low field NMR, a texture analyzer, a dynamic rheometer, ultraviolet-visible spectra, scanning electron microscopy, LC-MS/MS, an automatic amino acid analyzer, etc. Hesperetin (HE), dihydroquercetin (DI), salidroside (SA), and mangiferin (MA) increased the water-holding capacity, non-flowable water content, gel strength, texture, storage modulus, and fractal dimensions of the myosin gel, while modifying its leading force. The results of scanning electron microscopy revealed that the surfaces of polyphenol groups were relatively smoother than those of the control group. Meanwhile, the four types of polyphenols under study significantly improved the gastric and gastrointestinal digestibility of myosin. Furthermore, they significantly increased the contents of essential, flavor, and total free amino acids, as well as the unique peptide numbers in myosin digestion products. This work provides reliable guidance for polyphenols to improve protein function and nutritional properties.

Structural evolution of an amphibian-specific globin: A computational evolutionary biochemistry approach

Studies on the globin family are continuously revealing insights into the mechanisms of gene and protein evolution. The rise of a new globin gene type in Pelobatoidea and Neobatrachia (Amphibia:Anura) from an α-globin precursor provides the opportunity to investigate the genetic and physical mechanisms underlying the origin of new protein structural and functional properties. This amphibian-specific globin (globin A/GbA) discovered in the heart of Rana catesbeiana is a monomer. As the ancestral oligomeric state of α-globins is a homodimer, we inferred that the ancestral state was lost somewhere in the GbA lineage. Here, we combined computational molecular evolution with structural bioinformatics to determine the extent to which the loss of the homodimeric state is pervasive in the GbA clade. We also characterized the loci of GbA genes in Bufo bufo. We found two GbA clades in Neobatrachia. One was deleted in Ranidae, but retained and expanded to yield a new globin cluster in Bufonidae species. Loss of the ancestral oligomeric state seems to be pervasive in the GbA clade. However, a taxonomic sampling that includes more Pelobatoidea, as well as early Neobatrachia, lineages would be necessary to determine the oligomeric state of the last common ancestor of all GbA. The evidence presented here points out a possible loss of oligomerization in Pelobatoidea GbA as a result of amino acid substitutions that weaken the homodimeric state. In contrast, the loss of oligomerization in both Neobatrachia GbA clades was linked to independent deletions that disrupted many packing contacts at the homodimer interface.

DisCanVis: Visualizing integrated structural and functional annotations to better understand the effect of cancer mutations located within disordered proteins.

Intrinsically disordered proteins (IDPs) play important roles in a wide range of biological processes and have been associated with various diseases, including cancer. In the last few years, cancer genome projects have systematically collected genetic variations underlying multiple cancer types. In parallel, the number and different types of disordered proteins characterized by experimental methods have also significantly increased. Nevertheless, the role of IDPs in various types of cancer is still not well understood. In this work, we present DisCanVis, a novel visualization tool for cancer mutations with a special focus on IDPs. In order to aid the interpretation of observed mutations, genome level information is combined with information about the structural and functional properties of proteins. The web server enables users to inspect individual proteins, collect examples with existing annotations of protein disorder and associated function or to discover currently uncharacterized examples with likely disease relevance. Through a REST API interface and precompiled tables the analysis can be extended to a group of proteins.

Foaming properties of the complex of chitooligosaccharides and bovine serum albumin and its application in angel cake

The complex of chitooligosaccharides (COS) and protein is worthy of investigation, as COS is an important functional ingredient and the functional properties of protein might be improved after complexation. Using bovine serum albumin (BSA) as the model protein, this work explored the foaming properties and interfacial behavior of COS-BSA complex, as well as its application as a substitute for egg whites in angel cake. The effects of pH and mixing ratio ( r ) on the foam properties and interfacial behavior of COS-BSA complex were studied using dilute solution. And the effects of the COS-BSA substitution rate on the physical properties and microbial storability of the cake were studied. Compared with BSA, the foaming capacity and foam stability of COS-BSA complexes were significantly improved in the pH range of 3.0–10.0, and both the foaming capacity and foam stability of COS-BSA complexes at pH 7.0 were in the order of r 0.5 ≥ r 0.25 ≥ r 1.0 > r 2.0 > BSA > COS. Angel cake with the COS-BSA substitution rate of 25% had the best physical properties, in which COS and BSA had a synergistic effect on the specific volume and texture of the cake. The substitute of COS-BSA complex for egg white in angel cake significantly inhibited microbial growth during storage. This work provided COS-BSA complex as a substitute for egg white in cake making, and COS-BSA complex improved the physical properties of cake and inhibited microbial growth. • Chitooligosaccharides improved foaming properties of bovine serum albumin. • Good foaming of complexes was related with their surface dilatational rheology. • Cake with complex substitution rate of 25% exhibited the best physical properties. • Complex addition in cake significantly inhibited microbial growth during storage.

Characteristics of the Protein Coating and Functional Properties of Cadmium Sulfide Nanoparticles Obtained by Microbial Synthesis

Characteristics of the Protein Coating and Functional Properties of Cadmium Sulfide Nanoparticles Obtained by Microbial Synthesis