The complete amino-acid sequence of hen ovalbumin

A Versatile, Low-Cost Modular Microfluidic System to Prepare Poly(Lactic-co-Glycolic Acid) Nanoparticles With Encapsulated Protein

OBJECTIVE

Microfluidics has emerged as a promising technique to prepare nanoparticles. However, the current microfluidic devices are mainly chip-based and are often integrated into expensive systems that lack on-the-spot versatility. The aim of this study was to set up a modular microfluidic system based on low-cost capillaries and reusable, easy-to-clean building blocks that can prepare poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles with and without incorporated water-soluble biomacromolecules.

METHODS

A two-syringe system variant of the microfluidic system was set up to prepare PLGA particles and to investigate how the flow rates, solvents, and PLGA concentrations impacted the PLGA nanoparticle formation. A three-syringe system was designed to examine the incorporation of proteins into the PLGA particles.

RESULTS

The formation of the nanoparticles was affected by the PLGA concentration in the organic solvent, where an increasing concentration led to larger particle diameters (33-180 nm), and by the total flow rate, where an increase in the total flow rate led to smaller nanoparticles (197-77 nm). Using ultrapure water as the aqueous solvent resulted in precipitation at the outlet at higher PLGA concentrations. Aqueous poly(vinyl alcohol) created neutral particles in contrast to the negatively charged particles obtained with ultrapure water or an ethanol-water mixture. Incorporation of the proteins ovalbumin or lysozyme with a three-syringe system resulted in encapsulation efficiencies above 40%.

CONCLUSION

A cheap and easily adjustable modular microfluidic system was developed to prepare PLGA nanoparticles with highly reproducible particle diameters that can effectively be loaded with proteins for drug and vaccine delivery.

Identifying the potential of ovalbumin and its' hydrolysates to be used in a liquid food system to develop functional beverages

Ready-to-drink protein beverages have gained attention in the functional beverage market. This study examined the possibility of using ovalbumin and its hydrolysates to develop functional protein beverages. Lyophilized ovalbumin (5%, w/v) was dissolved in distilled water (pH 10) with sugar, salt, and vanilla and pasteurized at 56.7°C for 3.5 min to prepare a basal ovalbumin beverage (OVA). The beverages were sequentially hydrolyzed using pepsin (pH 2.5, 37°C for 3 h) first, then with protease (pH 6.5, 37°C for 3 h), or protease (pH 6.5, 37°C for 3 h) followed by trypsin (pH 7.8, 37°C for 3 h) combinations. Three beverages (OVA, PrTr, and PePr) were tested for physical, functional, and quality characteristics. Complete hydrolysis by enzyme combinations was ensured using 15% SDS-PAGE. Enzymatic hydrolysis caused an increase in the solubility of ovalbumin in water. The beverages showed antioxidant activity, and hydrolyzed drinks showed antimicrobial activity. No significant difference in acidity, but a reduction in pH, an increase in TSS, and alterations in viscosity were observed among the drinks with storage. A significant difference (p < 0.05) in titratable acidity was identified between the two hydrolyzed drinks, but no difference (p > 0.05) within a treatment was observed until Day 14. In conclusion, ovalbumin and its hydrolysates have the potential for preparing functional protein beverages with a shelf-life of up to 7 days.

The Role of Ovalbumin in Manganese Homeostasis during Chick Embryogenesis: An EPR Spectroscopic Study

Ovalbumin (OVA), a protein vital for chick embryo nutrition, hydration, and antimicrobial protection, together with other egg-white proteins, migrates to the amniotic fluid and is orally absorbed by the embryo during embryogenesis. Recently, it has been shown that for optimal eggshell quality, the hen diet can be supplemented with manganese. Although essential for embryonic development, manganese in excess causes neurotoxicity. This study investigates whether OVA may be involved in the regulation of manganese levels. The binding of Mn(II) to OVA was investigated using electron paramagnetic resonance (EPR) spectroscopy. The results show that OVA binds a maximum of two Mn(II) ions, one with slightly weaker affinity, even in a 10-fold excess, suggesting it may have a protective role from Mn(II) overload. It seems that the binding of Mn(II), or the presence of excess Mn(II), does not affect OVA's tertiary structure, as evidenced from fluorescence and UV/vis measurements. Comparative analysis with bovine and human serum albumins revealed that they exhibit higher affinities for Mn(II) than OVA, most likely due to their essentially different physiological roles. These findings suggest that OVA does not play a role in the transport and storage of manganese; however, it may be involved in embryo protection from manganese-induced toxicity.

Animal-free production of hen egg ovalbumin in engineered Saccharomyces cerevisiae via precision fermentation

To enable the sustainable production of ovalbumin (OVA) without relying on animal sources, the generally recognized as safe (GRAS) host Saccharomyces cerevisiae was used for the precision fermentation-based production of recombinant OVA. For this purpose, a signal peptide derived from EPX1, the most abundant extracellular protein produced by Pichia pastoris, was identified as a novel signal peptide for the efficient secretion of OVA in S. cerevisiae. To improve OVA secretion and cell growth, three helper proteins (PDI1, KAR2, and HAC1) present in the endoplasmic reticulum were expressed individually or in combination. Notably, the +P1/K2 strain coexpressing PDI1 and KAR2 with OVA produced 2 mg/L of OVA in the medium fraction; this value was 2.6-fold higher than the corresponding value for the control strain without helper proteins. Finally, a glucose-limited fed-batch fermentation process using the +P1/K2 strain yielded 132 mg/L of total OVA with 8 mg/L of extracellular OVA.

Dry-heat-induced phosphoserine-specific fragmentation of ovalbumin

When subjected to dry-heating, egg white ovalbumin, a phosphoglycoprotein, undergoes fragmentation and forms soluble aggregates. We investigated the mechanisms of dry-heat-induced fragmentation of ovalbumin. SDS-PAGE analysis showed that ovalbumin fragmented into five polypeptides, and their amount increased over 6 h of dry-heat treatment at 120 °C. The fragments contained fewer or no phosphoserine, compared with that in crude ovalbumin. Liquid chromatography-tandem mass spectrometry analysis of tryptic digests revealed that the fragmentation sites were located on phosphoserine residues, S68 and S344. During fragmentation, the phosphoserine residues underwent conversion into dehydroalanine residues, which were subsequently hydrolyzed. The nitrogen from the dehydroalanine became a newly formed terminal amide group on the N-terminal fragment, while the remaining molecule predominantly formed a new terminal pyruvoyl group. Furthermore, the fragments were incorporated into monomers or soluble aggregates of ovalbumin via covalent and non-covalent bonds. This study demonstrated a novel mechanism for dry-heat-induced fragmentation of phosphoproteins.

Selective Hydrolysis of Ovalbumin by Zr-Based Lacunary Polyoxotungstate in Surfactant Solutions

This study aims to design an artificial metalloprotease based on a Zr-containing polyoxometalate Na8[Zr(W5O18)2] [Zr(W5)2] for the hydrolysis of ovalbumin (OVA) in the presence of different surfactants, which can be used in many areas of the biological and medical sciences, particularly for targeted proteolytic drug design. For this reason, parameters, including the free energy of binding, the chemical nature of amino acid residues, secondary structures, and electrostatic potentials, of Zr(W5)2-OVA and Zr(W5)2-OVA-surfactant were analyzed by molecular docking simulations. The investigations showed that the presence of surfactants decreases the binding affinity of Zr(W5)2 for OVA amino acids, and hydrogen bonds and van der Waals interactions are formed between Zr(W5)2 and OVA amino acids. Additionally, GROMACS further illustrated the significance of SDS and CTAB surfactants in influencing the conformational changes of the OVA that lead to selective protein hydrolysis. In agreement with molecular dynamics simulation results, the experimental analysis showed more protein hydrolysis for the Zr(W5)2-OVA-surfactant systems. For instance, circular dichroism spectroscopy indicated that Zr(W5)2-OVA-CTAB and Zr(W5)2-OVA-TX-100 were more hydrolytically efficient due to the increased level of β-structures rather than α-chains, which showed that surfactants can facilitate the accessibility of Zr(W5)2 to the cleavage sites by inducing partial unfolding of the OVA structure.

Modularized viromimetic polymer nanoparticle vaccines (VPNVaxs) to elicit durable and effective humoral immune responses

Virus-like particle (VLP) vaccines had shown great potential during the COVID-19 pandemic, and was thought to be the next generation of antiviral vaccine technology due to viromimetic structures. However, the time-consuming and complicated processes in establishing a current recombinant-protein-based VLP vaccine has limited its quick launch to the out-bursting pandemic. To simplify and optimize VLP vaccine design, we herein report a kind of viromimetic polymer nanoparticle vaccine (VPNVax), with subunit receptor-binding domain (RBD) proteins conjugated to the surface of polyethylene glycol-b-polylactic acid (PEG-b-PLA) nanoparticles for vaccination against SARS-CoV-2. The preparation of VPNVax based on synthetic polymer particle and chemical post-conjugation makes it possible to rapidly replace the antigens and construct matched vaccines at the emergence of different viruses. Using this modular preparation system, we identified that VPNVax with surface protein coverage of 20%-25% had the best immunostimulatory activity, which could keep high levels of specific antibody titers over 5 months and induce virus neutralizing activity when combined with an aluminum adjuvant. Moreover, the polymer nano-vectors could be armed with more immune-adjuvant functions by loading immunostimulant agents or chemical chirality design. This VPNVax platform provides a novel kind of rapidly producing and efficient vaccine against different variants of SARS-CoV-2 as well as other viral pandemics.

Effective interactions and phase behavior of protein solutions in the presence of hexamine cobalt(III) chloride

It is well established that deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) exhibit a reentrant condensation (RC) phase behavior in the presence of the trivalent hexamine cobalt(III) cations (Hac) which can be important for their packing and folding. A similar behavior can be observed for negatively charged globular proteins in the presence of trivalent metal cations, such as Y3+ or La3+. This phase behavior is mainly driven by charge inversion upon an increasing salt concentration for a fixed protein concentration (cp). However, as Hac exhibits structural differences compared to other multivalent metal cations, with six ammonia ligands (NH3) covalently bonded to the central cobalt atom, it is not clear that Hac can induce a similar phase behavior for proteins. In this work, we systematically investigate whether negatively charged globular proteins β-lactoglobulin (BLG), bovine serum albumin (BSA), human serum albumin (HSA) and ovalbumin (OVA) feature Hac-induced RC. Effective protein-protein interactions were investigated by small-angle X-ray scattering. The reduced second virial coefficient (B2/B2HS) was obtained as a function of salt concentration. The virial coefficient analysis performed confirms the reentrant interaction (RI) behavior for BLG without actually inducing RC, given the insufficient strengths of the interactions for the latter to occur. In contrast, the strength of attraction for BSA, HSA and OVA are too weak to show RC. Model free analysis of the inverse intensity [Formula: see text] also supports this finding. Looking at different q-range by employing static (SLS) and dynamic light scattering experiments, the presence of RI behavior can be confirmed. The results are further discussed in view of metal cation binding sites in nucleic acids (DNA and RNA), where Hac induced RC phase behavior.

X-ray driven and intrinsic dynamics in protein gels

We use X-ray photon correlation spectroscopy to investigate how structure and dynamics of egg white protein gels are affected by X-ray dose and dose rate. We find that both, changes in structure and beam-induced dynamics, depend on the viscoelastic properties of the gels with soft gels prepared at low temperatures being more sensitive to beam-induced effects. Soft gels can be fluidized by X-ray doses of a few kGy with a crossover from stress relaxation dynamics (Kohlrausch-Williams-Watts exponents [Formula: see text] to 2) to typical dynamical heterogeneous behavior ([Formula: see text]1) while the high temperature egg white gels are radiation-stable up to doses of 15 kGy with [Formula: see text]. For all gel samples we observe a crossover from equilibrium dynamics to beam induced motion upon increasing X-ray fluence and determine the resulting fluence threshold values [Formula: see text]. Surprisingly small threshold values of [Formula: see text] s[Formula: see text] nm[Formula: see text] can drive the dynamics in the soft gels while for stronger gels this threshold is increased to [Formula: see text] s[Formula: see text] nm[Formula: see text]. We explain our observations with the viscoelastic properties of the materials and can connect the threshold dose for structural beam damage with the dynamic properties of beam-induced motion. Our results suggest that soft viscoelastic materials can display pronounced X-ray driven motion even for low X-ray fluences. This induced motion is not detectable by static scattering as it appears at dose values well below the static damage threshold. We show that intrinsic sample dynamics can be separated from X-ray driven motion by measuring the fluence dependence of the dynamical properties.

Experimental animal models of chronic inflammation

Inflammation is a general term for a wide variety of both physiological and pathophysiological processes in the body which primarily prevents the body from diseases and helps to remove dead tissues. It has a crucial part in the body immune system. Tissue damage can recruit inflammatory cells and cytokines and induce inflammation. Inflammation can be classified as acute, sub-acute, and chronic. If it remained unresolved and lasted for prolonged periods, it would be considered as chronic inflammation (CI), which consequently exacerbates tissue damage in different organs. CI is the main pathophysiological cause of many disorders such as obesity, diabetes, arthritis, myocardial infarction, and cancer. Thus, it is critical to investigate different mechanisms involved in CI to understand its processes and to find proper anti-inflammatory therapeutic approaches for it. Animal models are one of the most useful tools for study about different diseases and mechanisms in the body, and are important in pharmacological studies to find proper treatments. In this study, we discussed the various experimental animal models that have been used to recreate CI which can help us to enhance the understanding of CI mechanisms in human and contribute to the development of potent new therapies.

Improvement of enzymatic cross-linking of ovalbumin and ovotransferrin induced by transglutaminase with heat and reducing agent pretreatment

The effects of transglutaminase (TGase, 1.0 unit/mL) with heat (95 °C, 5 min), 2-mercaptoethanol (2-ME, 0.83 %), and l-cysteine (l-Cys, 50 mM) pretreatment on the cross-linking of ovalbumin (OVA) and ovotransferrin (OVT) were investigated. SDS-PAGE revealed that although the polymerization of OVA and OVT did not occur after 3 h of incubation at 40 °C with TGase, OVA polymerized into high molecular weight polymers following TGase with 2-ME and heat pretreatment after 3 h of incubation. The surface hydrophobicity and reactive sulfhydryl (SH) groups of OVA samples significantly increased from 4065.7 ± 136.7 and 89.3 ± 1.2 SH groups (μmol/g) to 31483.6 ± 342.7 and 119.5 ± 3.7 SH groups (μmol/g), respectively. Similar results were obtained for OVT with TGase and l-Cys pretreatment and a 3-h incubation at 40 °C. The use of TGase, a reducing agent, and/or heat pretreatment can be used for the polymerization of OVA and OVT.

Lateral force separation of biopolymers using an atomic force microscope

The lateral force separation of long chain biomolecules is demonstrated using an atomic force microscope (AFM). This is achieved by using an AFM tip to pull molecules away from the edge of a nanofluidic solution. By monitoring the torsion on the AFM cantilever, a characteristic force-distance signal is produced when long chain molecules separate and detach from the solvent edge. This lateral force separation using AFM (LFS-AFM) is demonstrated on egg albumin proteins and synthetic DNA strands. The detected length of the protein and nucleotide biopolymers was consistent with their calculated molecular contour length. LFS AFM provides separation and detection of single polymer strands that has potential applications in biochemical analysis, paleontology, and life detection.

Deciphering the interactions of phytochemicals with ovalbumin, the major food allergen from egg white: spectroscopic and computational studies

Ovalbumin (OVA), the major component of egg white, has been used as a model carrier protein to study the interaction of four bioactive phytochemicals 6-hydroxyflavone, chrysin, naringin, and naringenin. A static quenching mechanism was primarily associated with the complexation of the flavonoids with OVA. Hydrophobic forces play a major part in the stability of the complexes. The structural changes within the protein in response to flavonoid binding revealed a decrease in OVA's α-helical content. The hypothesized binding site for flavonoids in OVA overlaps with one or more immunoglobulin E-binding epitopes that may have some effect in the immunoglobulin E response pathway. The flavonoids remain in the same binding site throughout the simulation time and impart protein stability by forming different noncovalent interactions. This study presents comprehensive information about the interaction of the flavonoids with OVA and the associated structural variations after the binding, which might help researchers better comprehend similar medication pharmacodynamics and provide critical information for future therapeutic development.

Egg white protein-based delivery system for bioactive substances: a review

Some bioactive substances in food have problems such as poor solubility, unstable chemical properties and low bioavailability, which limits their application in functional food. Recently, many egg white protein-based delivery carriers have been developed to improve the chemical stability, biological activity and bioavailability of bioactive substances. This article reviewed the structure and properties of several major egg white proteins commonly used to construct bioactive substance delivery systems. Several common carrier types based on egg white proteins, including hydrogels, emulsions, micro/nanoparticles, aerogels and electrospinning were then introduced. The biological functions of common bioactive substances, the limitations, and the role of egg white protein-based delivery systems were also discussed. At present, whole egg white protein, ovalbumin and lysozyme are most widely used in delivery systems, while ovotransferrin, ovomucoid and ovomucin are less developed and applied. Egg white protein-based nanoparticles are currently the most commonly used delivery carriers. Egg white protein-based hydrogels, emulsions, and microparticles are also widely used. Future research on the application of various egg white proteins in developed new delivery systems will provide more choices for the delivery of various bioactive substances.

Advances in dietary proteins binding with co-existed anthocyanins in foods: Driving forces, structure-affinity relationship, and functional and nutritional properties

Anthocyanins, which are the labile flavonoid pigments widely distributed in many fruits, vegetables, cereal grains, and flowers, are receiving intensive interest for their potential health benefits. Proteins are important food components from abundant sources and present high binding affinity for small dietary compounds, e.g., anthocyanins. Protein-anthocyanin interactions might occur during food processing, ingestion, digestion, and bioutilization, leading to significant changes in the structure and properties of proteins and anthocyanins. Current knowledge of protein-anthocyanin interactions and their contributions to functions and bioactivities of anthocyanin-containing foods were reviewed. Binding characterization of dietary protein-anthocyanins complexes is outlined. Advances in understanding the structure-affinity relationship of dietary protein-anthocyanin interaction are critically discussed. The associated properties of protein-anthocyanin complexes are considered in an evaluation of functional and nutritional values.

Effect of glycation degree on the structure and digestion properties of ovalbumin: A study of amino acids and peptides release after in vitro gastrointestinal simulated digestion

Glycation can improve the functional properties of protein. However, in vitro and animal studies have shown that glycation induced lysine blockage and impaired protein digestibility. This study aimed to explore the effects of different glycation degree on the structure and digestive characteristics of ovalbumin. The results showed that glycation decreased the turbidity and hydrophobicity of the protein and changed the protein structure. Moreover, the results of in vitro simulated digestion revealed that glycation reduced the contents of essential amino acids and total amino acids after digestion. Glycation changed the amino acids and peptides release from the protein by resisting the digestion of digestive enzymes, especially trypsin. In conclusion, this work links glycation, protein digestibility, and the release of amino acids and peptides. This emphasizes the importance of the balance between improving properties and ensuring the digestibility of proteins during food processing.

A systematic assessment of structural heterogeneity and IgG/IgE-binding of ovalbumin

Ovalbumin (OVA), one of the major allergens in hen egg, exhibits extensive structural heterogeneity due to a range of post-translational modifications (PTMs). However, analyzing the structural heterogeneity of native OVA is challenging, and the relationship between heterogeneity and IgG/IgE-binding of OVA remains unclear. In this work, ion exchange chromatography (IXC) with salt gradient elution and on-line detection by native electrospray ionization mass spectrometry (ESI MS) was used to assess the structural heterogeneity of OVA, while inhibition-ELISA was used to assess the IgG/IgE binding characteristics of OVA. Over 130 different OVA proteoforms (including glycan-free species and 32 pairs of isobaric species) were identified. Proteoforms with acetylation, phosphorylation, oxidation and succinimide modifications had reduced IgG/IgE binding capacities, whereas those with few structural modifications had higher IgG/IgE binding capacities. OVA isoforms with a sialic acid-containing glycan modification had the highest IgG/IgE binding capacity. Our results demonstrate that on-line native IXC/MS with salt gradient elution can be used for rapid assessment of the structural heterogeneity of proteins. An improved understanding of the relationship between IgG/IgE binding capacity and OVA structure provides a basis for developing biotechnology or food processing methods for reducing protein allergenicity reduction.

Polymerization-induced proteinosome formation

In recent years, the fabrication of well-organized proteinosomes has been a popular topic due to the potential applications of the structures in materials science and nanotechnology. A big challenge in the fabrication of proteinosomes is to maintain the structures and the functionalities of proteins on the proteinosomes. In this research, a new concept of polymerization-induced formation of proteinosomes is proposed. In thermal dispersion polymerization of N-isopropyl acrylamide (NIPAM) in the presence of bovine serum albumin (BSA), the growing PNIPAM chains experience phase transition from hydrated coils to dehydrated globules, and the dehydrated PNIPAM chains have hydrophobic interaction with BSA, leading to the formation of hollow proteinosomes. Kinetics studies indicate that there is a transition from the homogeneous polymerization of NIPAM in solution to the heterogeneous polymerization in the proteinosomes. Transmission electron microscopy, atomic force microscopy, confocal laser scanning microscopy and dynamic light scattering all demonstrate the formation of hollow structures. The results of circular dichroism spectroscopy indicate that the secondary structure of BSA remains unchanged in the polymerization process. The formation of proteinosomes is reversible. Upon cooling of the solution to a temperature below the phase transition temperature of PNIPAM, the proteinosomes are dissociated due to the absence of the hydrophobic interaction. The proteinosomes can be used in the encapsulation of hydrophilic compounds in aqueous solution. In this research, not only BSA but also ovalbumin (OVA) is used as a model protein for the fabrication of proteinosomes by the polymerization-induced approach.

An insight on egg white: From most common functional food to biomaterial application

Natural egg white tis widely used as an ingredient in nutritional foods and for food processing. Due to its characteristic foaming, emulsification, adhesion, and gelation, and its heat setting, biocompatibility, and low cost, research into the application and development of egg white in biomaterials, especially medical biomaterials, have been receiving attention. The composition and characteristics of egg white protein, and the physical mixing and chemically cross-linking of egg white with other materials used to make degradable packaging films, bioceramics, bioplastics, biomimetic films, hydrogels, 3D scaffolds, bone regeneration, biopatterning, biosensors, and so forth, are reviewed in detail in this report. The novel egg white-based biomaterials in various forms and applications could be constructed mostly through physical treatments such as ultrasonic wave, ultraviolet, laser and other radiation or high-temperature calcination. Furthermore, the application and prospects for the use of egg white in biomaterials is also discussed.

A comparative study of CE-SDS, SDS-PAGE, and Simple Western: Influences of sample preparation on molecular weight determination of proteins

The development of capillary electrophoresis, especially CE-SDS devices, has led CE-SDS to become an established tool in a wide range of applications in the analysis of biopharmaceuticals and is increasingly replacing its method of origin, SDS-PAGE. The goal of this study was to evaluate the comparability of molecular weight (MW) determination especially by CE-SDS and SDS-PAGE. For ensuring comparability, model proteins that have little or no posttranslational modifications and an IgG antibody were used. Only a minor influence of sample preparation conditions, including sample buffer, temperature conditions, and different reducing agents on the MW determination were found. In contrast, the selection of the MW marker plays a decisive role in determining the accurate apparent MW of a protein. When using different MW markers, the deviation in MW determination can exceed 10%. Interestingly, CE-SDS and 10% SDS-PAGE hardly differ in their trueness of MW determination. The trueness in relation to the reference MW for each protein was calculated. Although the trueness values for the model proteins considered range between 1.00 and 1.11 using CE-SDS, they range between 0.93 and 1.03 on SDS-PAGE, depending on the experimental conditions chosen.

Integrated proteomic, phosphoproteomic and N-glycoproteomic analyses of chicken eggshell matrix

Eggshell matrix (EM) proteins play an important biological role in eggshell mineralization and embryo development. Many studies have demonstrated that some matrix proteins undergo posttranslational modifications, including phosphorylation and glycosylation, which have important regulatory effects on the functional properties of the proteins. Systematic analysis of the proteome, the phosphorylated modified proteome and the glycosylated modified proteome of the chicken EM was performed using a proteomics strategy. A total of 112 phosphorylation sites from 69 phosphoproteins and 297 N-glycosylation sites from 182 N-glycoproteins were identified in the chicken EM. Among all these identified modified proteins, 129 were not identified in the proteome (547 proteins). Therefore, a total of 676 EM proteins were identified in this study. Gene ontology (GO) enrichment analysis indicated that EM proteins and phosphoproteins were mainly enriched in regulation of enzyme activity, while EM N-glycoproteins were enriched in immune response regulation.

Phosphoproteomic analysis of duck egg white and insight into the biological functions of identified phosphoproteins

Phosphorylation of proteins is one of the most important and pleiotropic modifications. It plays a vital role in controlling protein functions. However, the phosphoproteome of duck egg white (DEW) has not been studied yet. To investigate the role of phosphorylation on DEW proteins, a detailed phosphoproteome analysis of DEW was performed using an immobilized metal affinity chromatography enrichment strategy. A total of 92 phosphosites representing 36 phosphoproteins were identified. [S-x-E] and [T-x-E] were found to be the most overrepresented motifs in DEW. The identified phosphoproteins in DEW were mainly involved in the binding, transport activity, biological regulation, and metabolic processes. Gene ontology analysis was used to elucidate the biological functions of DEW phosphoproteins and compare them with those of chicken egg white (CEW), which showed the differences mostly involved molecular functions and biological processes. PRACTICAL APPLICATIONS: These findings provide fundamental insight into the biological functions of identified phosphoproteins of DEW to better understand the roles of phosphorylated DEW proteins for food industries and human health. Phosphoproteomic study of DEW would be valuable for the food and nutrition industry to exploit the potential of this avian proteins in the processing of health benefit products.

Omics analysis of holoproteins and modified proteins of quail egg

Confirmed to be a new type of food resource, quail egg can provide humans with high-quality protein and offer various nutrients that can promote growth and development. Post-translational modification of proteins can regulate their molecular structures and physiological functions. However, the understanding and related research of quail egg holoproteins and post-translationally modified proteins is not yet sufficient. This study provides an in-depth analysis of quail egg proteins using an omics strategy. A total of 175 proteins, 109 N-glycoproteins (293 N-glycosylation sites) and 23 phosphoproteins (84 phosphorylation sites) were identified. Motif analysis showed that N-glycosylation sites of quail eggs were classical sites. The main characteristic sequence of the phosphorylation site is "S-X-E" (77%). Functional analysis indicated that quail egg proteins, modified proteins were enriched in the regulation of enzyme activity. These results have significant reference value for understanding the structure, function of quail eggs, explaining the physicochemical reaction during the storage.

Plant virus particles with various shapes as potential adjuvants

Plant viruses are biologically safe for mammals and can be successfully used as a carrier/platform to present foreign epitopes in the course of creating novel putative vaccines. However, there is mounting evidence that plant viruses, their virus-like and structurally modified particles may also have an immunopotentiating effect on antigens not bound with their surface covalently. Here, we present data on the adjuvant properties of plant viruses with various shapes (Tobacco mosaic virus, TMV; Potato virus X, PVX; Cauliflower mosaic virus, CaMV; Bean mild mosaic virus, BMMV) and structurally modified TMV spherical particles (SPs). We have analysed the effectiveness of immune response to individual model antigens (ovalbumin, OVA/hen egg lysozyme, HEL) and to OVA/HEL in compositions with plant viruses/SPs, and have shown that CaMV, TMV and SPs can effectively induce total IgG titers to model antigen. Some intriguing data were obtained when analysing the immune response to the plant viruses/SPs themselves. Strong immunity was induced to CaMV, BMMV and PVX, whereas TMV and SPs stimulated considerably lower self-IgG titers. Our results provide new insights into the immunopotentiating properties of plant viruses and can be useful in devising adjuvants based on plant viruses.

Retardation of some drugs in thin-layer chromatographic systems with impregnated silica gel plates with hen's egg white and bovine serum albumin

The influence of impregnation the chromatographic plate adsorbent layer, silica, with hen's egg white albumin (OVA) or bovine serum albumin (BSA) on the retention of some popular medicines (paracetamol, aminophenazone, theophylline, caffeine, acetanilide, ciprofloxacin, tramadol, acetylsalicylic acid, acebutolol) is investigated. The effect of composition and buffer pH of the mobile phase on solute separation selectivity is also studied. The chromatographic systems with and without above mentioned albumins and their influence on investigated drug retention are compared. In general, it has been turned out that retention of tested medicines in systems with the sorbent impregnated with albumin significantly increase relative to those with non-impregnated.

Impacts of Proteins on Dissolution and Sulfidation of Silver Nanowires in an Aquatic Environment: Importance of Surface Charges

With increasing utilization of silver nanomaterials, growing concerns are raised on their deleterious effects to the environment. Once discharged in an aquatic environment, the interactions between silver nanowires (AgNWs) and proteins may significantly affect the environmental behaviors, fate, and toxicities of AgNWs. In the present study, three representative model proteins, including ovalbumin (OVA), bovine serum albumin (BSA), and lysozyme (LYZ), were applied to investigate the impacts of the interactions between proteins and AgNWs on the transformations (oxidative dissolution and sulfidation) of AgNWs in an aquatic environment. Fluorescence spectroscopy and isothermal titration calorimetry analyses indicated that there was very weak interaction between OVA or BSA and AgNWs, but there was a strong interaction between the positively charged LYZ and the negatively charged AgNWs. The presence of LYZ not only reversed the surface charge of AgNWs but also resulted in the breakup of the nanowire structure and increased the reactive surface area. The positively charged surface of AgNWs in the presence of LYZ favored the access of sulfide ions. As a consequence, the kinetics of oxidative dissolution and sulfidation of AgNWs were not affected by OVA and BSA but were significantly facilitated by LYZ. The results shed light on the important roles of electrostatic interactions between AgNWs and proteins, which may have important implications for evaluating the fate and effects of silver nanomaterials in complicated environments.

Kinetic trapping in protein folding

The founding principles of protein folding introduced by Christian Anfinsen, together with the numerous mechanistic investigations that followed, assume that protein folding is a thermodynamically controlled process. On the other hand, this review underscores the fact that thermodynamic control is far from being the norm in protein folding, as long as one considers an extended chemical-potential landscape encompassing aggregates, in addition to native, unfolded and intermediate states. Here, we highlight the key role of kinetic trapping of the protein native state relative to unfolded, intermediate and, most importantly, aggregated states. We propose that kinetic trapping serves an important role in biology by protecting the bioactive states of a large number of proteins from deleterious aggregation. In the event that undesired aggregates were somehow formed, specialized intracellular disaggregation machines have evolved to convert any aberrant populations back to the native state, thus restoring a fully bioactive and aggregation-protected protein cohort.

Molecular interaction of sulfonamides and ovalbumin, an allergenic egg protein, exploring biophysical, theoretical and biological studies

Biophysical, theoretical and biological in vitro studies were carried out to evaluate the interaction of the main allergen protein of egg white (ovalbumin, OVA) with sulphonamides (SA): sulphathiazole (S1), sulfaquinoxaline (S2), sulfadimethoxine (S3) and sulfamethazine (S4). The binding constants for the OVA-SA supramolecular complexes ranged from 1.20 to 30.66 × 10⁵ M^-1, observing the following order of affinity: S1 > S2 > S4 > S3. The preferential forces in the stabilization of the OVA complexes with S2 and S3 were hydrogen bonds and Van der Waals forces, whereas for OVA-S1 and OVAS4, were electrostatic interactions. Interaction process led to a change in the native structure of the protein, which may potentiate its natural allergenicity. Cations Ca(II), Mg(II) and Fe(III) favor the interaction of OVA with S1 and S2. The theoretical studies performed were consistent with the spectroscopic data. Finally, it was found that the interaction process for sulfonamides evaluated with OVA change the inhibition activity profile these antibiotics against strains of Escherichia coli ATCC 25922 and Bacillus megaterium APFSG3isox, but not the minimal inhibitory concentration values.

Quantitative Comparative Integrated Proteomic and Phosphoproteomic Analysis of Chicken Egg Yolk Proteins under Diverse Storage Temperatures

To investigate the alterations of egg yolk protein abundances and their phosphorylation status at different storage temperatures, a comparative quantitative study of unfertilized chicken egg yolk after 15 days of storage at 4 and 37 °C was performed. Altogether, 445 proteins were identified in our study, of which the abundances of 154 proteins were significantly changed when comparing high-temperature storage with low-temperature storage, including 42 up-regulated and 112 down-regulated proteins. In the phosphoproteome, we identified a total of 137 phosphorylated sites on 326 peptides corresponding to 51 proteins. The results showed that the degree of phosphorylation for most egg yolk proteins was enhanced during high-temperature storage. Furthermore, GO analysis indicated that these phosphoproteins of egg yolk may be closely related to the binding, catalysis, and transport functions. The results provide further insights into the effect of storage temperature on egg proteome changes and their phosphorylation level. Moreover, this study can provide a theoretical basis for the improvement of egg quality during storage by phosphorylation modification in the food industry.

Adjuvant-free immunization with infective filarial larvae as lymphatic homing antigen carriers

Controlled infection with intestinal nematodes has therapeutic potential for preventing the symptoms of allergic and autoimmune diseases. Here, we engineered larvae of the filarial nematode Litomosoides sigmodontis as a vaccine strategy to induce adaptive immunity against a foreign, crosslinked protein, chicken egg ovalbumin (OVA), in the absence of an external adjuvant. The acylation of filarial proteins with fluorescent probes or biotin was not immediately detrimental to larval movement and survival, which died 3 to 5 days later. At least some of the labeled and skin-inoculated filariae migrated through lymphatic vessels to draining lymph nodes. The immunization potential of OVA-biotin-filariae was compared to that of an OVA-bound nanoparticulate carrier co-delivered with a CpG adjuvant in a typical vaccination scheme. Production of IFNγ and TNFα by restimulated CD4+ cells but not CD8+ confirmed the specific ability of filariae to stimulate CD4+ T cells. This alternative method of immunization exploits the intrinsic adjuvancy of the attenuated nematode carrier and has the potential to shift the vaccination immune response towards cellular immunity.

Sonochemically modified ovalbumin enhances enantioenrichment of some amino acids

As part of our efforts to develop a new method for chiral resolution of amino acids with sonochemically modified proteins, we present result that indicates how ovalbumin microspheres (OAMS) interact specifically with l-amino acids from a racemate in solution, leaving an excess of d-enantiomer in the permeate solution. Among different amino acids that interacted with the OAMS, tryptophan (Trp) was the most successfully resolved with 65% enantiomeric excess. A control experiment with native ovalbumin in solution did not show any chiral resolution of amino acids. Interestingly, when the OAMS were pretreated with racemic lysine (Lys) solution and then used for resolution of tryptophan the enantiomeric enrichment of d-tryptophan was raised to 98%. This unanticipated positive effect is discussed in terms of the structural correlation between Trp and Lys, which is less apparent in other amino acids such as phenylalanine.

Reutilization of Food Waste: One-Step Extration, Purification and Characterization of Ovalbumin from Salted Egg White by Aqueous Two-Phase Flotation

For the purpose of reducing pollution and the reutilization of salted egg whites, which are byproducts of the manufacturing process of salted egg yolks and normally treated as waste, an aqueous two-phase flotation (ATPF) composed of polyethylene glycols (PEG 1000) and (NH4)2SO4 was applied to develop a simple, inexpensive and efficient process for the separation of ovalbumin (OVA) from salted egg whites. The effects of the concentration of PEG, the concentration of (NH4)2SO4, the flow rate and the flotation time on the flotation efficiency (Y) and purity (P) of OVA were investigated. A response surface method (RSM) experiment was carried out on the basis of a single-factor experiment. An efficient separation was achieved using ATPF containing 5 mL of 80% PEG 1000 (w/w), 28 mL of 28% (NH4)2SO4 (w/w), 35 mL/min of the flow rate and 30 min of the flotation time, while 2 mL of the salted egg white solution (salted eggs white (v): water (v) = 1:4) was loaded. Under the optimal conditions, Y and P of OVA could reach 82.15 ± 0.24% and 92.98 ± 0.68%, respectively. The purified OVA was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), reverse phase high-performance liquid chromatography (RP-HPLC), liquid chromatography-nano electrospray ionisation mass spectrometry (Nano LC-ESI-MS/MS), ultraviolet spectrum (UV), fluorescence spectrum (FL) and fourier transform infrared spectroscopy (FT-IR). The results indicated that the purity of OVA obtained by ATPF was satisfactory and there was no obvious difference in the structure of the OVA separated by ATPF and the standard. The results of the functional properties revealed no significant differences between OVA obtained by ATPF and the standard in oil binding capacity, viscosity, emulsibility and foam capacity.

Patterning Nanoparticles with DNA Molds

We report a nanopatterning strategy in which self-assembled DNA nanostructures serve as structural templates. In previous work, ordering of NPs primarily relied on specific recognition, e.g., DNA-DNA hybridization. Only a few cases have been reported on nonspecific adsorption. Unfortunately, these studies were limited by the integrity and homogeneity of templates and the variety of patterned nanoparticles (NPs). Herein, we have developed a general method to pattern various NPs. The NPs adsorb onto substrate via NP-substrate direct interactions and the substrates are patterned into large arrays (>4 × 4 μm) of tiny, accessible cavities by self-assembled DNA arrays. As a demonstration, DNA templates include tetragonal and hexagonal arrays and the NPs include individual DNA nanomotifs, gold nanoparticles (AuNPs), and proteins. All nanostructures have been confirmed by atomic force microscopy and corresponding fast Fourier transform (FFT) analysis.

Investigation of the Mechanism of Conformational Alteration in Ovalbumin as Induced by Glycation with Different Monoses through Conventional Spectrometry and Liquid Chromatography High-Resolution Mass Spectrometry

Glycation between ovalbumin (OVA) and different monoses under mild dry heating at 37 °C was studied. The content of free amino groups decreased dramatically, and the conformational changes based on fluorescence and circular dichroism spectra were evident in glycated OVA. The glycated sites and the average degree of substitution per peptide molecule per site were determined using liquid chromatography high-resolution mass spectrometry. Lysine and arginine were the predominant glyaction sites, in which Lys207 was a relatively reactive site for glycation in all of the conjugates. In general, the extent of glycation of aldose was higher, and its alterations on the steric layouts of protein were more drastic than those of ketose. The configuration of hydroxyl groups at C-4 in sugar epimers might be important for the glycation reactivity and conformational modification in the glycated proteins. These insights would have important implications for the creation of sweetened food products with desirable structures and excellent quality control.