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Ovalbumin (OVA) is the primary allergenic protein, associated with T helper 2 (Th2)-mediated allergy reactions. Here, we studied OVA’s conformational structure, digestibility, and allergenic potency upon galactomannan (Man) conjugation along with transglutaminase-catalyzed crosslinking (TG-Man/OVA) and tyrosinase/caffeic acid-catalyzed crosslinking (Tyr-Man/OVA). Enzymatic glycosylation altered OVA’s conformation and enhanced the gastrointestinal digestibility. Stimulation of bone marrow-derived dendritic cells (BMDCs) with enzymatically glycosylated OVA reduced the expression of CD40, CD80, CD86 and MHC class II molecules. Furthermore, glycosylated OVA increased IL-10 production while suppressing proinflammatory cytokine production in BMDCs. In an OVA-induced mouse asthma model, TG-Man/OVA and Tyr-Man/OVA upregulated IFN-γ and IL-10 expression and downregulated IL-4, IL-5, and IL-13 in lungs. Crosslinked OVA diminished infiltrated cells in bronchoalveolar lavage fluid and lung and attenuated eosinophilic airway inflammation. These findings offer valuable insights into the development of a novel product with improved hypoallergenic and immunomodulatory properties and hold promise in attenuating allergic diseases.

Poly(ethylene terephthalate) (PET) is the most common plastics produced for applications in food and drinking containers. It is degraded to valuable product by several methods. Glycolysis of PET gains bis(2-hydroxyethylene) terephthalate (BHET) as the main product utilized as plasticizer. Calcium catalysts, Ca2+ and Ca(OH)2∙2H2O were explored to study the mechanism of PET cleavage by DFT calculations at B3LYP/6-311++G** level. Two possible pathways, coordination, and non-coordination of ethylene glycol on the calcium in glycolysis reaction, have been investigated. In addition, poly(ethylene furanoate) (PEF), considered as a sustainable polymer with the similar functional properties, was chose for the comparison of conformational structures with PET. The understanding of the relationship between PET (and PEF) structures and calcium catalysts is useful for the future development of linear sustainable polyesters.

Conformational rearrangements of polyampholytic polypeptides adsorbed on the surface of a charged prolate gold nanospheroid with a periodic change in time of its polarity along the rotation axis have been studied using molecular dynamics simulation. The radial distributions of the density of polypeptide atoms in the equatorial region of the nanospheroid have been calculated, as well as the distributions of the linear density of polypeptide atoms along the major axis of the nanospheroid. At a low simulation temperature, a girdle polyampholytic fringe was formed in the central region of the nanospheroid and its ordering by layers, depending on the type of units, occurred with an increase in the charge of the nanospheroid with a simultaneous increase in the width of the macromolecular fringe along the rotation axis. The thickness of such a fringe along the cross section depends on the distance between the oppositely charged units in the polyampholyte. At high temperatures and high absolute values of the total charge of the spheroidal nanoparticle, there were periodic displacements of the polyampholytic fringe toward the poles of the nanospheroid, being in antiphase for oppositely charged metallic nanospheroids. A mathematical model is presented for describing the conformational structure of a polyampholyte macromolecule on a prolate nanospheroid in an alternating electric field with the approximation of a prolate spheroid by a spherical cylinder. [ABSTRACT FROM AUTHOR]

The rearrangement of the conformational structure of polyampholytic polypeptides on the surface of a charged spherical gold nanoparticle with its polarity intermittently changing over time was studied using molecular dynamics modeling. The angular distributions of the polypeptide atoms, as well as the radial distributions of the macrochain atomic density in the equatorial region of the nanoparticle with differentiation according to the types of links, were calculated. The polyampholyte shell acquired an annular shape, and the resulting macromolecular ring was located around the charged nanoparticle perpendicularly to the vector of the external electric field strength. With an increase in the charge of the nanoparticle, the ring belt was ordered according to the types of macrochain links, forming concentric annular layers. The diameter of the macromolecular ring depended on the law of distribution of charged units in the macrochain. At elevated temperatures the annular macromolecular ring was deformed at the moments of the highest polarization of the nanoparticle. [ABSTRACT FROM AUTHOR]

Background: The aim of the present study was to investigate the effect of substrate conformational structure changes on the laccase-induced protein cross-linking. The effects of laccase amount, pH, and ferulic acid (FA) on the enzymatic cross-linking of substrate, Cyt C, were determined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. High-performance size exclusion chromatography, laser particle size analysis and isothermal titration calorimetry (ITC) were also applied to investigate the cross-linking product and enthalpy changes. Structural changes of Cyt C at different pH values were analyzed by ultraviolet–visible (UV–vis), fluorescence, and circular dichroism (CD) measurements. Results: Complete cross-linking, partial cross-linking, minute cross-linking, and no cross-linking occurred at pH 2.0, 4.0, 6.0, and 8.0, respectively. ITC analysis demonstrated that the enzymatic cross-linking of Cyt C was an endothermic process. The UV–vis, fluorescence, and CD measurements exhibited that the tertiary structure of Cyt C was disrupted, and part of the α-helical polypeptide region unfolded at pH 2.0. The structural flexibilities decreased, and the tertiary structure of Cyt C became increasingly compact with the increase in pH values from 4.0 to 8.0. The gradual changes in the structure of Cyt C at different pH values were in accordance with the cross-linking results of Cyt C catalyzed by laccase. Conclusions: The results demonstrated that minute structure changes of substrate had a remarkable effect on the laccase-induced cross-linking. The findings promote the understanding of the substrate requirement of laccase in protein cross-linking and are instructive for the modulation of laccase-induced protein cross-linking.How to cite: Li D-X, Qi Z-Y, Liu J-Y, et al. Effect of pH on the conformational structure of cytochrome c and subsequent enzymatic cross-linking catalyzed by laccase. Electron J Biotechnol 2022;60. https://doi.org/10.1016/j.ejbt.2022.07.002.

Food allergies are a global food safety problem. Peanut allergies are common due, in part, to their popular utilization in the food industry. Peanut allergy is typically an immunoglobulin E‐mediated reaction, and peanuts contain 17 allergens belonging to different families in peanut. In this review, we first introduce the mechanisms and management of peanut allergy, followed by the basic structures of associated allergens. Subsequently, we summarize methods of epitope localization for peanut allergens. These methods can be instrumental in speeding up the discovery of allergenicity‐dependent structures. Many attempts have been made to decrease the allergenicity of peanuts. The structures of hypoallergens, which are manufactured during processing, were analyzed to strengthen the desensitization process and allergen immunotherapy. The identification of conformational epitopes is the bottleneck in both peanut and food allergies. Further, the identification and modification of such epitopes will lead to improved strategies for managing and preventing peanut allergy. Combining traditional wet chemistry research with structure simulation studies will help in the epitopes' localization. [ABSTRACT FROM AUTHOR]

This study evaluated the impact of proanthocyanidins on immunoglobulin E (IgE) binding capacity, antioxidant, foaming and emulsifying properties in soy 11S protein following alkali treatment at 80 °C for 20 min. The formation of >180 kDa polymer was observed in the combined heating and proanthocyanidins-conjugation treatment sample (11S-80PC) rather than in the heating treated sample (11S-80) using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The structural analyzes demonstrated that 11S-80PC exhibited more protein unfolding than 11S-80. Heatmap analysis revealed that 11S-80PC had more alteration of peptide and epitope profiles in 11S than in 11S-80. Molecular docking showed that PC could well react with soy protein 11S. Liquid chromatography tandem MS analysis (LC/MS-MS) demonstrated that there was a 35.6 % increase in 11S-80, but a 14.5 % decrease in 11S-80PC for the abundance of total linear epitopes. As a result, 11S-80PC exhibited more reduction in IgE binding capacities than 11S-80 owing to more obscuring and disruption of linear and conformational epitopes induced by structural changes. Moreover, 11S-80PC exhibited higher antioxidant capacities, foaming properties and emulsifying activity than 11S-80. Therefore, the addition of proanthocyanidins could decrease allergenic activity and enhance the functional properties of the heated soy 11S protein. • 11S-80PC showed more reduction in IgE binding capacity than 11S-80. • 11S-80PC had higher antioxidant, EAI and foaming properties than 11S-80. • 11S-80PC exhibited more protein-unfolding than 11S-80. • 11S-80PC showed more changes in peptide and epitope profiles than 11S-80. • Proanthocyanidins alleviate the allergenicity and functionality in heated samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • TG and Tyr/CA crosslinking plus Man coupling altered OVA's structural properties. • TG-Man/OVA and Tyr-Man/OVA showed enhanced gastrointestinal digestibility. • Enzymatically glycosylated OVA modulated the function and maturation of BMDCs. • Moreover, this method effectively alleviated the allergic response in mice model. • Enzyme-crosslinked Man-conjugated OVA possesses improved hypoallergenic properties. Ovalbumin (OVA) is the primary allergenic protein, associated with T helper 2 (Th2)-mediated allergy reactions. Here, we studied OVA's conformational structure, digestibility, and allergenic potency upon galactomannan (Man) conjugation along with transglutaminase-catalyzed crosslinking (TG-Man/OVA) and tyrosinase/caffeic acid-catalyzed crosslinking (Tyr-Man/OVA). Enzymatic glycosylation altered OVA's conformation and enhanced the gastrointestinal digestibility. Stimulation of bone marrow-derived dendritic cells (BMDCs) with enzymatically glycosylated OVA reduced the expression of CD40, CD80, CD86 and MHC class II molecules. Furthermore, glycosylated OVA increased IL-10 production while suppressing proinflammatory cytokine production in BMDCs. In an OVA-induced mouse asthma model, TG-Man/OVA and Tyr-Man/OVA upregulated IFN-γ and IL-10 expression and downregulated IL-4, IL-5, and IL-13 in lungs. Crosslinked OVA diminished infiltrated cells in bronchoalveolar lavage fluid and lung and attenuated eosinophilic airway inflammation. These findings offer valuable insights into the development of a novel product with improved hypoallergenic and immunomodulatory properties and hold promise in attenuating allergic diseases. [ABSTRACT FROM AUTHOR]

Summary: The influence of pH (3.0, 5.0, 7.0 and 9.0) on the conformation, physico‐chemical properties, interfacial properties and emulsion stability of golden pompano protein (GPP) was investigated. The conformation structures of GPP were characterised by Fourier transform‐infrared spectroscopy and intrinsic emission fluorescence spectroscopy. The particle size, zeta‐potential and solubility of GPP were also investigated. The interfacial properties were characterised by the interfacial tension and the percentage of absorbed protein at the oil/water interface. GPP under pH 3.0 displayed a lowest interfacial tension, the highest emulsifying stability index value. Creaming stability, viscosity and microstructure of the emulsion stabilised by GPP under different oil/water ratios (2:8, 3:7, 4:6 and 5:5) (v/v) were also investigated. The increase of the oil/water ratio increased the viscosity of the continuous phase, thereby improving the emulsion stability. The conformational changes of GPP significantly affected their physico‐chemical and interfacial properties, thus improving GPP‐stabilised emulsion stability. [ABSTRACT FROM AUTHOR]

• The conformational behavior of glecaprevir in both protic and aprotic solvents was investigated. • Molecular docking has disclosed the potential of glecaprevir in targeting tumor-associated proteins. • Glecaprevir exhibited conformational adaptation mechanisms upon binding to diverse protein targets. The realm of drug development and supramolecular chemistry has been revolutionized by the emergence of macrocyclic compounds, which have emerged as formidable contenders. Glecaprevir is an 18-membered macrocycle used for the treatment of chronic hepatitis C virus infection. The inherent structural flexibility of glecaprevir's side chain enables it to adopt diverse solution conformations, thereby influencing its binding modes with biological proteins and unlocking new potentials for the treatment of other diseases. The present study delved into the solution structural characteristics of glecaprevir through a combination of experimental UV–Vis and electronic circular dichroism spectra, complemented by theoretical calculations. Our findings reveal that glecaprevir consistently exhibits spectral characteristics in both protic and aprotic solvents due to its stable conformational distribution. DFT-assisted structural analyses were conducted to explore the weak noncovalent interactions within the stable conformations of glecaprevir. The molecular docking analysis conducted on a diverse range of conformers of glecaprevir revealed its exceptional selectivity against proteins associated with breast cancer, colorectal cancer, lung cancer, and lymphoma. These remarkable findings suggest that glecaprevir holds immense potential as a lead compound for drug design targeting these specific types of cancers. Furthermore, the conformationally adapted mechanism is indicated by the alteration of intramolecular hydrogen bonds subsequent to molecular docking. [Display omitted] [ABSTRACT FROM AUTHOR]

• The urease-GO and GO NH 2 interaction was thoroughly studied through multispectroscopic techniques, microscopy, and in-silico modeling. • GO interacted with urease mainly through hydrophobic forces, causing static and dynamic quenching of its intrinsic fluorescence, greatly affecting the protein's Trp microenvironment. • The GO NH 2 interaction with urease involved static quenching via Van der Waals interactions and hydrogen bonding. • GO induced a structural transition in urease from α-helical to a β-sheet configuration. In contrast, GO NH 2 exhibited a minimal effect on the protein's helical structure. • While GO NH 2 augmented urease activity without affecting its V max or K m values, GO hindered urease activity in a non-competitive manner. The increasing use of graphene-based nanomaterials raises concerns about their potential environmental impact as ecotoxicants. This article examines the interaction and effects of graphene oxide (GO) and its amine-derived (GO NH 2) 2-D nanosheets on urease dynamics, a crucial enzyme in soil nutrient cycling, through spectroscopic, microscopic, and computational analyses. The findings reveal the distinct interaction mechanisms: GO formed ground - and excited-state complexes with urease; thus, fluorescence quenching was static and dynamic via hydrophobic interaction. In contrast, GO NH 2 nanosheets formed a ground-state complex by static quenching involving Van der Waals and hydrogen bonding. These interactions were energetically favored and altered tryptophan (Trp) residues' microenvironment more than tyrosine (Tyr). The average exciton lifetime of urease in the presence of GO have decreased from 4.34 ns to 3.647 ns at the mere concentration of 7.11 µM, while for GO NH 2 , no discernable change (4.16 ns) was observed even at the concentration of 16.75 µM. Primarily, the strong interaction of GO leads to the rearrangement of polypeptide structure, reduced α-helices to 12 %, and increased β-sheets by six times. In contrast, with GO NH 2 , α-helices were reduced to 79 %, and β-sheets were increased by 1.8 times at the similar concentration. Molecular docking revealed that neither GO nor GO NH 2 interacted with the active site of urease, and binding was primarily via hydrophobic, Van der Waals, and hydrogen bonding, concurrent with in-vitro incubation results. Positive total energy (3.85 kJ mol−1) during molecular docking analysis of urease-GO interaction and inhibition in enzyme activity to 62 %, altered V max value (0.04606 ± 0.001 mM/s), without affecting the K m (4.78045 ± 0.12 mM) suggested that inhibition was noncompetitive and steric clashes due to disruptive binding might drove the inhibition. Meanwhile, negative total internal energy (-3.97 kJ mol−1) during urease + GO NH 2 binding and enhanced enzymatic activity by 32 % in-vitro without altering V max (0.063091 ± 0.003 mM/s) and K m (4.953943 ± 0.2 mM) values suggested that urease's binding site was well-complemented by GO NH 2 nanosheets, serving as a redox-mediator and radical-quencher. [Display omitted] [ABSTRACT FROM AUTHOR]

In recent years, the exceptional biocatalytic properties of glucose oxidase (GOx) have spurred the development of various GOx-functionalized nanocatalysts for cancer diagnosis and treatment. Carbon dots, renowned for their excellent biocompatibility and distinctive fluorescence properties, effectively incorporate GOx. Given the paramount importance of GOx's enzymatic activity in therapeutic efficacy, this study conducts a thorough exploration of the molecular-level binding dynamics between GOx and near-infrared carbon dots (NIR-CDs). Utilizing various spectrometric and molecular simulation techniques, we reveal that NIR-CDs form a ground-state complex with GOx primarily via hydrogen bonds and van der Waals forces, interacting directly with amino acid residues in GOx's active site. This binding leads to conformational change and reduces thermal stability of GOx, slightly inhibiting its enzymatic activity and demonstrating a competitive inhibition effect. In vitro experiments demonstrate that NIR-CDs attenuate the GOx's capacity to produce H 2 O 2 in HeLa cells, mitigating enzyme-induced cytotoxicity and cellular damage. This comprehensive elucidation of the intricate binding mechanisms between NIR-CDs and GOx provides critical insights for the design of NIR-CD-based nanotherapeutic platforms to augment cancer therapy. Such advancements lay the groundwork for innovative and efficacious cancer treatment strategies. • This study delves into the molecular binding mechanism between GOx and NIR-CDs. • NIR-CDs form a ground-state complex with GOx under hydrogen bonds and van der Waals forces. • NIR-CDs induces a conformational change in GOx and further reduces its thermal stability. • NIR-CDs slightly inhibit the catalytic activity of GOx via competitive inhibition mode. • NIR-CDs suppress H 2 O 2 production catalyzed by GOx, regulating cells from enzyme-induced damage. [ABSTRACT FROM AUTHOR]

In this study, the physicochemical properties, functional properties and N-glycoproteome of tilapia myofibrillar protein (TMP), golden pompano myofibrillar protein (GPMP) and skipjack tuna myofibrillar protein (STMP) were assessed. The microstructures and protein compositions of the three MPs were similar. TMP and GPMP had higher solubility, sulfhydryl content and endogenous fluorescence intensity, lower surface hydrophobicity and β-sheet contents than STMP. The results showed that the protein structures of TMP and GPMP were more folded and stable. Due to its low solubility and high surface hydrophobicity, STMP had low emulsifying activity and high foaming activity. By N-glycoproteomics analysis, 23, 85 and 22 glycoproteins that contained 28, 129 and 35 N-glycosylation sites, were identified in TMP, GPMP and STMP, respectively. GPMP had more N-glycoproteins and N-glycosylation sites than STMP, which was possibly the reason for GPMP's higher solubility and EAI. These results provide useful information for the effective utilization of various fish products. [ABSTRACT FROM AUTHOR]

The paper presents quantum chemical calculations of the conformational structure in the ground and excited states of tetraaryltetracyanoporphyrazine (H2–Pz(Ph)4(CN)4) and its derivatives, which are considered promising photodynamic photosensitizers with the function of fluorescent control of the degree of destruction of cancer cells. It was shown that, in the absence of specific interactions with the solvent, these compounds are characterized by a planar macrocycle structure both in the ground and the excited S1 states. Among the low-lying excited states, there are no those whose population can lead to fluorescence quenching due to a noticeable change in the position of the phenyl rings relative to the macrocycle in the torsion coordinate. This suggests that these compounds cannot be classified as fluorescent rotors, as was previously assumed. It has been found that H2–Pz(Ph)4(CN)4 and its derivatives in the solution form solvate complexes with oxygen-containing solvent molecules (water, methanol, ethanol, glycerol, tetrahydrofuran) with the participation of the H and N atoms of the pyrrole and pyrrolenine rings, respectively. These complexes are characterized by out-of-plane distortion of the macrocycle, which increases significantly in the S1 state and leads to large displacements of peripheral substituents perpendicularly to the macrocycle. The conformational dynamics in the S1 state is accompanied by a reduction in the energy gap ΔЕ(S0 – S1), an increase in the spin–orbit interaction between the excited states, and anharmonicity of NH stretching vibrations. All these factors lead to a decrease in the fluorescence lifetime (τF) of H2–Pz(Ph)4(CN)4 and their derivatives in the solution and contribute to the dependence of τF on the viscosity of the medium. [ABSTRACT FROM AUTHOR]

Poly(ethylene terephthalate) (PET) is the most common plastics produced for applications in food and drinking containers. It is degraded to valuable product by several methods. Glycolysis of PET gains bis (2-hydroxyethylene) terephthalate (BHET) as the main product utilized as plasticizer. Calcium catalysts, Ca 2+ and Ca(OH) 2 ∙2H 2 O were explored to study the mechanism of PET cleavage by DFT calculations at B3LYP/6-311++G** level. Two possible pathways, coordination, and non-coordination of ethylene glycol on the calcium in glycolysis reaction, have been investigated. In addition, poly(ethylene furanoate) (PEF), considered as a sustainable polymer with the similar functional properties, was chose for the comparison of conformational structures with PET. The understanding of the relationship between PET (and PEF) structures and calcium catalysts is useful for the future development of linear sustainable polyesters., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ekasith Somsook reports financial support was provided by 10.13039/501100004156Mahidol University. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

In this work, binding interaction between molybdenum disulfide quantum dots (MoS 2 QDs) and human serum albumin (HSA) was researched deeply to dissect the conformational variation and fibrillation of HSA affected by MoS 2 QDs. The results revealed that MoS 2 QDs bound strongly with HSA with molar ratio of 1:1 under the joint actions of hydrogen bond and van der Waals force, leading to the static fluorescence quenching of HSA. MoS 2 QDs caused the secondary structure transition of HSA from α -helix stepwise to β -turn, β -sheet, and random coil gradually. MoS 2 QDs reduced both the molar enthalpy change and the melting temperature of HSA, reducing the thermal stability of HSA significantly. It is worth noting that MoS 2 QDs inhibited the fibrillation process of HSA according to the reduced hydrophobic environment and the disturbance of disulfide bonds in HSA network structure. These results reveal the precise binding mechanism of MoS 2 QDs with HSA at molecular level, providing indispensable information for the potential application of MoS 2 QDs in biological fields. • Binding interaction between MoS 2 QDs and HSA was systematically investigated. • MoS 2 QDs bound with HSA and statically quenched its inherent fluorescence. • MoS 2 QDs caused structure transform of HSA changing to be more incompact. • MoS 2 QDs efficiently inhibited the formation of HSA fibrils. • MoS 2 QDs possessed potentials in the prevention of serious amyloid-related diseases. [ABSTRACT FROM AUTHOR]

There is a need to understand the ultrasound-induced changes in the interactions between proteins and phenolic compounds at different pH. This study systematically explored the role of high-intensity ultrasound pre-treatment on the binding mechanisms of β-lactoglobulin (β-LG) to two common phenolic compounds, i.e., (−)-epigallocatechin-3-gallate (EGCG) and chlorogenic acid (CA) at neutral and acidic pH (pH 7.2 and 2.4). Tryptophan fluorescence revealed that compared to proteins sonicated at 20% and 50% amplitudes, 35%-amplitude ultrasound pre-treatment (ULG-35) strengthened the binding affinities of EGCG/CA to β-LG without altering the main interaction force. After phenolic addition, ULG-35 displayed a similar but a greater extent of protein secondary and tertiary structural changes than the native protein, ascribed to the ultrasound-driven hydrophobic stacking among interacted molecules. The dominant form of β-LG (dimer/monomer) played a crucial role in the conformational and interfacial properties of complexes, which can be explained by the distinct binding sites at different pH as unveiled by molecular docking. Combining pre-ultrasound with EGCG interaction notably increased the foaming and emulsifying properties of β-LG, providing a feasible way for the modification of bovine whey proteins. These results shed light on the understanding of protein–phenolic non-covalent binding under ultrasound and help to develop complex systems with desired functionality and delivery.

Glycosylation induces covalent grafting, resulting in conformational shifts that modulate the functional properties of proteins. This study examines the effect of conformational changes on the foaming and gelation properties of d -xylose glycosylated egg white protein (G-EWP) under different pH, ionic strength, and temperature conditions. Glycosylation end-products content increases initially, then reduces with increasing temperature while negatively correlating with pH and NaCl concentration. Treatment with NaCl induces electrostatic shielding on the G-EWP surface, decreasing the absolute value of ζ-potential from 19.63 mV to 14.9 mV. Temperature promotes thermal denaturation and macromolecular aggregation of G-EWP, increasing the particle size significantly from 523.9 nm to 4458.92 nm. Spectroscopic and protein structure analyses show that different environmental stresses alter the conformational structure of G-EWP, causing the rearrangement of amino acid residues. High temperature exerts a more pronounced effect on the secondary structure of G-EWP compared to variations in pH and NaCl, where the α-helices decline from 40.37% to 7.83% and the β-turns content increases from 19.30% to 39.57%. Reheating at 60 °C and acid treatment significantly increase the gel hardness, and the foaming capacity of G-EWP declines gradually with increasing pH and NaCl concentration, but improves with increasing temperature. Correlation analysis reveals that the molecular flexibility, β-sheet and β-turns effectiveness regulate the foaming capacity, and the charge variation positively modulates the gel properties of G-EWP.This study provides insight into regulating the functional properties of G-EWP effectively in industrial applications. [Display omitted] • The AGEs content of G-EWP was more evidently affected by temperature. • Environmental-stress mainly affected tyrosine rearrangements and random structure. • Heating exposed the covalent rigid structure to enhance foaming ability and stability. • Gel strength declined with pH, NaCl, and temperature increasement as charge blocking. • Molecular flexibility, β-turn and β-sheet were attributed to foaming capacity of G-EWP. [ABSTRACT FROM AUTHOR]

The aim of this study is to enhance the efficiency of enzymes, reduce operational costs, and increase production output. Experimental research shows that ultrasound positively impacted the activity of α-amylase and glucoamylase, with the peak α-amylase activity observed at 30 W for 5 min and the highest glucoamylase activity at 60 W for 3 min. Ultrasonication extended the optimal temperature of both enzymes, but had no effect on the optimal pH. According to the kinetic experiments, ultrasonic treatment could improve the catalytic efficiency of α-amylase and glucoamylase. Furthermore, the SDS-PAGE results revealed that ultrasound treatment did not alter the molecular weights of the enzymes and their primary structures; The circular dichroism and fluorescence spectroscopy analysis indicated the secondary structural components, especially the α-sheet and the tryptophan fluorescence intensity, were notably affected by ultrasound. The changes in the secondary and tertiary structure of α-amylase and glucoamylase suggest that ultrasonic treatment may enhance their activities. Our findings provide a theoretical basis for the efficient utilization of α-amylase and glucoamylase through understanding the enzyme structure changes after ultrasound. [Display omitted] • Ultrasound widen the reaction temperature and pH range of α-amylase and glucoamylase. • Ultrasound increase Vmax compared to the untreated α-amylase and glucoamylase. • Ultrasound alter the secondary and tertiary structure of α-amylase and glucoamylase. • The cavitation and thermal effects induced conformational changes of enzyme molecule. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ratio of iron to protein influences the iron binding capacity of WPI and the valence state of the iron on the surface of the WPI-Fe complexes. • Fe2+ and WPI can undergo spontaneous enthalpy-driven exothermic reactions. • When Fe: WPI = 1:10, the protein has a high amount of bound iron and the highest (Fe2+) content from a high-quality iron source. Whey protein isolates (WPI) are known to have mineral-binding capacity to promote iron absorption. The aim of this study was to investigate the effect of iron ratio on the conformational structure of iron-bound whey protein isolate (WPI-Fe) and its thermodynamic stability. It was shown that the iron to protein ratio affects both the iron binding capacity of WPI and the iron valence state on the surface of WPI-Fe complexes. As the iron content increases, aggregation between protein molecules occurs. In addition, WPI-Fe nanoparticles have thermodynamic stability and Fe2+ has a high affinity with WPI for spontaneous exothermic reactions. This study demonstrates that WPI-Fe complexes can be used to efficiently deliver high-quality iron source (Fe2+) for future iron supplements. [ABSTRACT FROM AUTHOR]

When nanoparticles were introduced into the biological media, the protein corona would be formed, which endowed the nanoparticles with new bio-identities. Thus, controlling protein corona formation is critical to in vivo therapeutic effect. Controlling the particle size is the most feasible method during design, and the influence of media pH which varies with disease condition is quite important. The impact of particle size and pH on bovine serum albumin (BSA) corona formation of solid lipid nanoparticles (SLNs) was studied here. The BSA corona formation of SLNs with increasing particle size (120–480 nm) in pH 6.0 and 7.4 was investigated. Multiple techniques were employed for visualization study, conformational structure study and mechanism study, etc. "BSA corona-caused aggregation" of SLN2‒3 was revealed in pH 6.0 while the dispersed state of SLNs was maintained in pH 7.4, which significantly affected the secondary structure of BSA and cell uptake of SLNs. The main interaction was driven by van der Waals force plus hydrogen bonding in pH 7.4, while by electrostatic attraction in pH 6.0, and size-dependent adsorption was confirmed. This study provides a systematic insight to the understanding of protein corona formation of SLNs. Different protein corona formation phenomena were shown in solid lipid nanoparticles (SLNS) with the various size and medium pH. The biological effect and the underlying interaction mechanisms were studied to provide a systematic perspective. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the physicochemical properties, functional properties and N-glycoproteome of tilapia myofibrillar protein (TMP), golden pompano myofibrillar protein (GPMP) and skipjack tuna myofibrillar protein (STMP) were assessed. The microstructures and protein compositions of the three MPs were similar. TMP and GPMP had higher solubility, sulfhydryl content and endogenous fluorescence intensity, lower surface hydrophobicity and β-sheet contents than STMP. The results showed that the protein structures of TMP and GPMP were more folded and stable. Due to its low solubility and high surface hydrophobicity, STMP had low emulsifying activity and high foaming activity. By N-glycoproteomics analysis, 23, 85 and 22 glycoproteins that contained 28, 129 and 35 N-glycosylation sites, were identified in TMP, GPMP and STMP, respectively. GPMP had more N-glycoproteins and N-glycosylation sites than STMP, which was possibly the reason for GPMP’s higher solubility and EAI. These results provide useful information for the effective utilization of various fish products.

Organometallic rhodium(III) complexes with curcuminoid ligands attracted considerable attention in biological‐related fields and the variation of curcuminoid ligands may regulate the biological activity of these organometallic rhodium(III) complexes. To deeply evaluate the biological influences of these complexes, the binding interactions between three rhodium(III) complexes with curcuminoid ligands and human serum albumin (HSA) were comparably investigated by spectroscopic and electrochemical techniques. The results suggested that the intrinsic fluorescence of HSA was quenched by three complexes through static fluorescence quenching mode. Three complexes bonded with Sudlow's site I of HSA to form ground‐state compounds under the binding forces of van der Waals interactions, hydrogen bonds formation, and protonation. Finally, the native conformational structure and the thermal stability of HSA were all changed. Space steric hindrance of complexes took part in the differences of the fluorescence quenching processes, and the chemical polarity of the complexes played a vital role in the variations of the structure and biological activity of HSA. These results illustrated the molecular interactions between protein and organometallic rhodium(III) complexes with curcuminoid ligands, offering new insight about the prospective applications of analogical rhodium(III) complexes in biomedicine areas. [ABSTRACT FROM AUTHOR]

Currently, there has been a surge of interest in revealing the interactions between plasma and food matrices. In this study, we investigated the impacts of atmospheric cold plasma (ACP) treatment on the structural, physicochemical and allergenic characteristics of soybean protein isolate (SPI). SPI dispersions were subjected to ACP treatments at different frequencies (80 to 100 Hz) and durations (1 to 10 min) to investigate the effects of exposing conditions. Results showed that ACP induced reactive oxygen species‐mediated oxidation of soy proteins, resulting in modifications in the secondary and ternary structures of SPI. As a consequence, functional properties of SPI, such as emulsifying (56 to 168%, compared with control) and foaming properties (60 to 194%) were influenced by varying degrees. In addition, under certain circumstance (120 Hz, 5 min), the IgE‐binding level of SPI was decreased by up to 75%, when compared to the control. Moderate treatment yielded products with improved functionality and reduced allergenicity, while extensive exposure induced a loss of vendibility due to protein aggregation. Practical Application: In this study, we demonstrated for the first time, that plasma species reacted with soybean proteins, resulting in spatial structural changes which are closely related with protein functionality and allergenicity. ACP interacts with macromolecules in aqueous systems and thus can be an alternative and promising nonthermal approach in modifying soybean proteins, whereas the exact role of different processing parameters needs to be well‐elaborated. [ABSTRACT FROM AUTHOR]

Highlights • Ultrastructure of fish was more effectively disrupted by chopping than blending. • Comminution method influenced proteins' structural and biochemical properties. • Myofibrillar proteins unfolded and then aggregated as chopping extended. • Under blending myofibrillar proteins continuously unfolded without aggregating. Abstract Effects of two typical comminution methods (shearing and blending) on structural and biochemical properties of silver carp surimi were comparatively investigated. Surimi myofibrils in striated appearance were progressively disrupted within 15 min of blending. The myofibrils were completely disintegrated after shearing for 5 min. Surface hydrophobicity of surimi increased and then gradually decreased (p < 0.05) under shearing, while it continuously increased (p < 0.05) under blending. As shearing time was extended, α-helical structure decreased and β-sheet structure increased simultaneously; surface active sulfhydryl content (SH) increased and then decreased (p < 0.05); and intensity of myosin heavy chain (MHC) was gradually reduced. However, secondary structure, MHC intensity and SH were slightly changed as blending time extended. Ca2+-ATPase activities increased and then declined (p < 0.05) with transition times at 1 min and 5 min under shearing and blending, respectively. Results indicated that shearing disrupted the ultrastructure and changed biochemical properties of surimi more pronouncedly than blending. [ABSTRACT FROM AUTHOR]

Highlights • High intensity ultrasound treatments on quinoa proteins. • Conformational changes in protein quinoa caused by ultrasound treatments. • Ultrasound produce formation/dissociation of trimeric/hexameric structure. • Conformational/physicochemical size and solubility increase by ultrasound. Abstract Quinoa proteins (QP) have promise as a potential source of novel food ingredients, and it is of great interest to know how high-intensity ultrasound (HIUS) treatments affect the properties of QP. This work aimed to study the impact of on-off time-pulses of HIUS treatments on the structural and physicochemical properties of QP; samples were treated at 5, 10, 20, and 30 min with on-off pulses of 10 s/10 s, 5 s/1 s, and 1 s/5 s). Structural changes were evaluated using PAGE-SDS, circular dichroism, fluorescence spectroscopy, and differential scanning calorimetry. Meanwhile, physicochemical properties were also examined, including solubility, Z-average, polydispersity index PDI, and Z-potential. PAGE-SDS showed the appearance of polypeptides over 190 kDa in HIUS samples-treated. All samples presented 15.6% α-helices, 31.3% β-sheets, 21.8% β-rotations, and 31.4% random coils independent of the HIUS treatment. β-Turn structures and "random coils" were not affected by HIUS. When US 10 s/10 s and 1 s/5 s were applied, an increase in the % α-helix and a decrease in β-fold were observed, which could indicate a small conversion of β-folds to α-helices. Fluorescence spectra for all HIUS showed a significant increase (23%) of average fluorescence intensity and a decrease of λmax in relation to that of the control (346 dnm and 340 nm average HIUS treatment). DSC showed one endotherm in all cases (81.6–99.8 °C), and an increase in Td was observed due to the effect of the HIUS treatment. HIUS caused a 48% increase in solubility. The Z-average of the HIUS samples compared to that of the controls showed an increase from 37.8 to 47.3 nm. PDI and Z-potential values from the QP controls and the HIUS samples did not show significance differences and presented average values of 0.466 ± 0.021 (PDI) and −16.63 ± 0.89 (Z-potential). It is possible to conclude that HIUS treatments affect the secondary and tertiary structure of quinoa proteins, and these changes resulted in an increase of solubility and particle size. HIUS treatment as a new and promising technology that can improve the QP solubility properties and in that way allow its use as an ingredient with a good source of protein to develop different types of beverages/protein sauces. [ABSTRACT FROM AUTHOR]

• Binding interactions between three iridium(III) complexes and HSA was comparatively investigated. • Three complexes bound with HSA tightly at its Sudlow's site I and quenched its intrinsic fluorescence. • Three complexes reduced the α -helical content and the thermal stability of HSA efficiently. • Both steric-hindrance effect and chemical polarity play vital roles during their binding interactions. Organometallic iridium(III) complexes, as high-efficient phototherapic drugs for cancer therapy and tumor treatment, have attracted widespread interest in diverse areas. To further clarify the biological functions of iridium(III) complexes, the interaction mechanism and native conformation of human serum albumin (HSA) affected by three organometallic iridium(III) complexes containing curcuminoid ligands were systematically and comparably investigated via various spectroscopic and electrochemical approaches. The results revealed that three iridium(III) complexes reacted with HSA tightly at its Sudlow's site I under the binding forces of van der Waals interaction, protonation, and hydrogen bond, leading to the hypochromic effect in the absorption spectrum of HSA and the static quenching in the intrinsic fluorescence of HSA. Three iridium(III) complexes disturbed the native conformation of HSA by reducing its α -helical content, finally reducing the melting temperature and the thermal stability of HSA. In comparison, the iridium(III) complex containing curcuminoid ligand with bigger spatial steric-hindrance effect and stronger chemical polarity was prone to binding with HSA more tightly and subsequently affecting its native conformation and biological function more prominently. This research finding reveals the interaction mechanisms of organometallic iridium(III) complexes with HSA and evaluates the function of curcuminoid ligands during their binding interactions, which pays the way for the targeted design and the potential application of novel iridium(III) complexes in biological fields. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract In this work, the interactions between bovine serum albumin (BSA) and five sweeteners including aspartame (APM), acesulfame (AK), sucralose (TGS), sodium cyclamate (SC), and rebaudioside-A (REB-A) have been studied by multispectroscopic techniques, and molecular simulation in order to provide much useful information for the application of new and safer artificial sweeteners. Fluorescence quenching assays indicated that the formation of complexes between sweeteners and BSA mainly induced the fluorescence quenching of protein and the binding site number were about 1 indicting that there is one mainly binding site of APM, AK, TGS, SC, or REB-A in domain of BSA with relatively weak interactions. Molecular modeling results indicated that hydrogen bonding interactions were the mainly binding forces of sweeteners with BSA. Circular dichroism spectra indicated that APM and REB-A obviously induced the secondary structure changes of BSA. The presence of APM increased the fraction of α–Helix of BSA from 65.4% to 73.8%, while the presence of REB-A resulted in decreasing the fraction of α–helix of BSA from 65.4% to 51.2%. The melting temperature studies showed that these five sweeteners except REB-A act as stabilizers to increase the thermal stability of BSA during the thermal denaturation process. In addition, AK, TGS, and SC obviously increased the esterase-like activity of BSA, and such loss of activity of BSA induced by APM and REB-A. Graphical Abstract Unlabelled Image Highlights • The binding abilities of sweeteners with BSA were studied. • APM and REB-A obviously induced the secondary structure changes of BSA. • AK, TGS, and SC obviously increased the esterase-like activity of BSA. • APM, AK, TGS, and SC act as a stabilizer to increase the secondary structure stability of BSA during the thermal process. [ABSTRACT FROM AUTHOR]

Nervous necrosis virus (NNV) belongs to genus Betanodavirus within family of Nodaviridae . It is highly pathogenic to various marine fishes. In this study, we determined conformational structures of NNV epitopes for generating NNV-neutralizing antibodies using several rabbit antisera and mouse monoclonal antibodies (MAbs). Rabbit antiserum against naïve NNV particles (anti-NNV serum) with high NNV-neutralization activity reacted with naïve NNV particles, but not with heat-denatured NNV particles, suggesting that NNV-neutralizing antibodies in the anti-NNV serum could not react with heat-denatured NNV antigens. In contrast, rabbit antiserum against heat-denatured NNV particles (anti-HD-NNV serum) reacted with both naïve and heat-denatured NNV particles. However, no NNV-neutralization activity was observed in this anti-HD-NNV serum, suggesting that heat-denatured NNV particles had no epitope for generating NNV-neutralizing antibodies. Mouse MAbs with NNV-neutralization activity also reacted with naïve NNV particles, but not react with heat-denatured NNV particles. Therefore, epitopes of NNV particles for generating NNV-neutralizing antibodies had conformational structures sensitive to heat-denaturation. NNV-neutralizing antibodies were also generated by immunization with SDS-denatured NNV antigens after dialysis and ultrafiltration, suggesting that epitopes for generating NNV-neutralizing antibodies might have relatively simple conformational structures. [ABSTRACT FROM AUTHOR]

Comprehending the interactions between graphene oxide (GO) and enzymes is critical for understanding the toxicities of GO. In this study, the inherent interactions of GO with α-amylase as a typical enzyme, and the impacts of GO on the conformation and biological activities of α-amylase were systematically investigated. The results reveal that GO formed ground-state complex with α-amylase primarily via hydrogen bonding and van der Waals interactions, thus quenching the intrinsic fluorescence of the protein statically. Particularly, the strong interactions altered the microenvironment of tyrosine and tryptophan residues, caused rearrangement of polypeptide structure, and reduced the contents of α-helices and β-sheets, thus changing the conformational structure of α-amylase. According to molecular docking results, GO binds with the amino acid residues (i.e., His299, Asp300, and His305) of α-amylase mainly through hydrogen bonding, which is in accordance with in vitro incubation experiments. As a consequence, the ability of α-amylase to catalyze starch hydrolysis into glucose was depressed by GO, suggesting that GO might cause dysfunction of α-amylase. This study discloses the intrinsic binding mechanisms of GO with α-amylase and provides novel insights into the adverse effects of GO as it enters organisms. [Display omitted] • Binding interaction between GO and α-amylase was firstly investigated. • GO strongly binds with α-amylase in a spontaneous and exothermic manner. • GO binds with α-amylase mainly via hydrogen bonding and van der Waals force. • GO quenches intrinsic fluorescence of α-amylase by changing secondary conformation. • GO reduces the ability of α-amylase to catalyze digestion of starch into glucose. [ABSTRACT FROM AUTHOR]

Succinylation can improve the thermal stability of various proteins. In this study, succinylated egg white protein (SEWP) samples with different succinylation degrees were prepared by adding various succinic anhydride additives to egg white protein (EWP). The thermal stability of SEWP and the conformational structure under various succinylation degrees were investigated. With the increase in succinylation degree, the turbidity of heated SEWP solution (90 °C for 30 min) markedly declined. The heated SEWP solution with high succinylation degree (37.63%, 66.57%, and 72.37%) was transparent. Moreover, the result of differential scanning calorimetry confirmed that the thermal stability of succinylated EWP increased. The results of intrinsic fluorescence spectra and Fourier-transform infrared spectroscopy illustrate that succinylation changed the conformational structure of EWP. Succinylation increased the electrostatic repulsion and decreased the surface hydrophobicity, and it changed the aggregation morphology of EWP. Cross-linked spherical aggregates of low succinylation degree transformed to thready aggregates of a high succinylation degree. Thus, succinylation improved the thermal stability of EWP.

In this study, the immunogenic and structural properties of ovalbumin (OVA) induced by pulsed electric fields (PEF) treatment were investigated. The immunogenic properties were estimated by the IgG and IgE binding abilities, which were determined by enzyme-linked immunosorbent assay (ELISA) using rabbit polyclonal antibodies and egg-allergy patients’ sera, respectively. The structural changes were monitored by circular dichroism (CD), ultraviolet absorption, and fluorescence spectroscopy. When the OVA samples were treated at low electric field intensity (below 25 kV/cm, for 180 μs) or for short time (less than 60 μs, at 35 kV/cm), the IgG and IgE binding capacities gradually increased due to the partial unfolding of OVA. This was reflected in the increase in free SH content, surface hydrophobicity, and UV absorption. However, when the OVA samples were treated at high electric field intensity (exceeding 25 kV/cm, for 180 μs) or for long time (more than 60 μs, at 35 kV/cm), the IgG and IgE binding abilities significantly reduced due to the aggregation of OVA. This was also reflected in the decrease in free SH content, surface hydrophobicity, and UV absorption. Moreover, high-intensity PEF treatment caused a loss of the α-helix structure. The results showed that the largest decrease in the immunogenic properties was observed at 35 kV/cm for 180 μs. Therefore, PEF processing has the potential for utilization as a method for egg desensitization. [ABSTRACT FROM AUTHOR]

The circumsporozoite protein (CSP) of the malaria parasite Plasmodium vivax is a major pre-erythrocyte vaccine candidate. The protein has a central repeat region that belongs to one of repeat families (VK210, VK247, and the P. vivax -like). In the present study, computer modelling was employed to select chimeric proteins, comprising the conserved regions and different arrangements of the repeat elements (VK210 and VK247), whose structure is similar to that of the native counterparts. DNA encoding the selected chimeras (named CS127 and CS712) were synthetically constructed based on E. coli codons, then cloned and expressed. Mouse monoclonal antibodies (mAbs; anti-Pv-210-CDC and −Pv-247-CDC), recognized the chimeric antigens in ELISA, indicating correct conformation and accessibility of the B-cell epitopes. ELISA using IgG from plasma samples collected from 221 Iranian patients with acute P. vivax showed that only 49.32% of the samples reacted to both CS127 and CS712 proteins. The dominant subclass for the two chimeras was IgG1 (48% of the positive responders, OD 492 = 0.777 ± 0.420 for CS127; 48.41% of the positive responders, OD 492 = 0.862 ± 0.423 for CS712, with no statistically significant difference P > 0.05; Wilcoxon signed ranks test). Binding assays showed that both chimeric proteins bound to immobilized heparan sulphate and HepG2 hepatocyte cells in a concentration-dependent manner, saturable at 80 μg/mL. Additionally, anti-CS127 and −CS712 antibodies raised in mice recognized the native protein on the surface of P. vivax sporozoite with high intensity, confirming the presence of common epitopes between the recombinant forms and the native proteins. In summary, despite structural differences at the molecular level, the expression levels of both chimeras were satisfactory, and their conformational structure retained biological function, thus supporting their potential for use in the development of vivax-based vaccine. [ABSTRACT FROM AUTHOR]

In the present study, we have investigated the thermal stability of bovine serum albumin (BSA) in the presence of TiO 2 nanoparticles (TiO 2 NPs). The effects of TiO 2 NPs on the transportation function of BSA were also studied by fluorescence spectral method. The circular dichroism (CD) study revealed that addition of TiO 2 NPs moderately decreased the α-Helix content of the protein with the abruptly changing its tertiary structure by hydrogen bonding, van der Waals or electrostatic forces. It has been found that TiO 2 NPs acted as a structure destabilizer for BSA during the thermal denaturation process. The fluorescence quenching and molecular modeling data indicated the existence of strong interaction between BSA and the TiO 2 NPs surface that changed the binding affinities of some ligands for BSA, implying that TiO 2 NPs in blood will affect the transporting ability of serum albumin. [ABSTRACT FROM AUTHOR]

Pectinase is commercially important in the fruit processing and fiber degumming industries. Emerging technologies that improve its stability and activity could have potential in improving its commercial value further. The effects of pulsed electric field (PEF) treatment on the enzymatic activity, kinetics and conformational structure of pectinase were evaluated. Maximum activity was obtained at 12 kV/cm and a flow velocity of 80 mL/min, and was 21.89 ± 1.67% higher than the untreated enzyme. This enhancing effect could be maintained for 19 h when the treated enzyme was stored at 4 °C. PEF treatment increased the enzyme kinetic constants V max , k cat , t 1/2 , ΔG , and decreased K m , k , Ea , ΔH , and ΔS , indicating improved affinity between enzyme and substrate and enhanced catalytic efficiency. PEF treatment did not alter the polypeptide composition of the pectinase molecules, but induced the transfer of the tryptophan micro-environment from the polar surface to the hydrophobic interior, with a 10.28% increase in α-helices and a 17.80% reduction in random coils. [ABSTRACT FROM AUTHOR]

In this study, the effect of ball-milling (BM, Mixer Mill MM 400) treatments on the physicochemical properties of soybean protein isolate (SPI) and its cold-set gels induced by glucono-δ-lactone was studied. BM of SPI increased the gel strength and water holding capacity of cold-set gels significantly after 4 min of BM treatments. BM treatments did not alter the primary structure of SPI, but caused minor changes of the secondary structure. Furthermore, surface hydrophobicity of SPI increased gradually from 2058 to 5051 after 10 min of BM, while free SH groups reduced from 3.92 to 2.65 μmol/g protein. Moreover, near-UV CD spectra indicated that the tertiary conformation stability was increased and the hydrophobic groups might shift to a more hydrophobic microenvironment. In conclusion, appropriate BM treatments could change the physicochemical properties of SPI and increased the gelation properties of SPI cold-set gels. [ABSTRACT FROM AUTHOR]

This study assessed the alteration of IgE-reactivity and functional attribute in soy protein 7S-proanthocyanidins conjugates (7S-80PC) formed by alkali-heating treatment (pH 9.0, 80 °C, 20 min). SDS-PAGE demonstrated that 7S-80PC exhibited the formation of >180 kDa polymers, although the heated 7S (7S-80) had no changes. Multispectral experiments revealed more protein unfolding in 7S-80PC than in 7S-80. Heatmap analysis showed that 7S-80PC showed more alteration of protein, peptide and epitope profiles than 7S-80. LC/MS-MS demonstrated that the content of total dominant linear epitopes was increased by 11.4 % in 7S-80, but decreased by 47.4 % in 7S-80PC. As a result, Western-blot and ELISA showed that 7S-80PC exhibited lower IgE-reactivity than 7S-80, probably because 7S-80PC exhibited more protein-unfolding to increase the accessibility of proanthocyanidins to mask and destroy the exposed conformational epitopes and dominant linear epitopes induced by heating treatment. Furthermore, the successful attachment of PC to soy 7S protein significantly increased antioxidant activity in 7S-80PC. 7S-80PC also showed higher emulsion activity than 7S-80 owing to its high protein flexibility and protein unfolding. However, 7S-80PC exhibited lower foaming properties than 7S-80. Therefore, the addition of proanthocyanidins could decrease IgE-reactivity and alter the functional attribute of the heated soy 7S protein. • 7S-80PC had a 37.3 % reduction in IgE-reactivity compared to 7S-80. • 7S-80PC showed higher antioxidant and emulsion activity than 7S-80. • 7S-80PC exhibited more protein-unfolding than 7S-80. • 7S-80PC showed more changes in peptide and epitope profiles than 7S-80. • Proanthocyanidins alleviate IgE-reactivity and functionality in heated samples. [ABSTRACT FROM AUTHOR]

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 m2/g to 78.82 m2/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. [Display omitted] • 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. [ABSTRACT FROM AUTHOR]

In order to explore the effects of high intensity ultrasound (HIU) on the gelation properties of glucono-δ-lactone (GDL) induced cold-set soy protein isolate (SPI), this study used HIU-heat pre-treated SPI to form GDL induced cold-set SPI gels. Texture analyzer, circular dichroism (CD) spectrum, fluorescence chromatography, scanning electron microscope (SEM), sodium dodecyl sulphate - polyacrylamide gel electrophoresis (SDS-PAGE) and particle sizer were used in this study. Compared with heat pretreatment, HIU-heat pretreatments increased the gel strength and water holding capacity (WHC) of cold SPI gels significantly (P<0.05). HIU-heat pretreatment of SPI could not change the primary structure of SPI. However, the secondary structure, tertiary structure, intermolecular forces, protein solubility and particle size of SPI were changed after HIU-heat pretreatments. For instance, HIU-heat pretreatments increased the α-helix amount but decreased the β-sheet amount as demonstrated by far-CD spectra. Moreover, HIU-heat pretreatments of SPI increased the surface hydrophobicity, free or total sulfhydryl groups of SPI. The near-CD spectra and fluorescence spectra indicated that HIU-heat treatments reduced the tertiary structure and increased the hydrophobic environments of SPI. The protein solubility in different solvents (DW, deionized water at pH value of 8.0; Buffer B, Tris-glycine buffer (0.086 mol/L Tris, 0.09 mol/L glycine, and 4 mmol/L Na2EDTA, pH value of 8.0); Buffer BSU, Buffer B containing 0.5% sodium dodecyl sulphate and 6 mol/L urea) suggested that HIU-heat treatments increased the electrostatic interactions but reduced or did not change non-covalent interactions among SPI molecules. SEM showed that the three-dimensional (3D) structure of HIU-heat pretreated SPI gels became denser and more uniform. However, different HIU-heat pretreatments influenced the gelation properties of SPI gels diversely. The gel strength and WHC of gels prepared by Method 1 (M1, HIU for 2, 4 or 10 min then heating at 95 ℃ for 20 min) increased gradually with the increasing of HIU time (gel strength: from (5.83±0.31) to (46.37±1.15) g, WHC: from 42.03%±1.59% to 81.74%±6.22%), while those of gels prepared by Method 2 (M2, heating at 95 ℃ for 20 min then HIU for 2, 4 or 10 min) increased rapidly within 4 min under HIU (gel strength: from (5.83±0.31) to (37.57±2.57) g, WHC: from 42.03%±1.85% to 79.31% ± 3.00%). This means that M2 can shorten the total producing time and reduce the energy, which might have more potential in soy bean protein industry. The mechanism for the above differences between M1 and M2 may be due to that the heating pretreatment could facilitate the unfolding of SPI, causing the following HIU treatments to modify SPI more easily. Therefore, M2 could change the conformational structures of SPI within a short time of HIU (within 4 min), resulting in the improvement of exposing hydrophobic groups, the increase of hydrophobic environment, the increase of surface hydrophobicity and the increase of protein solubility in DW, as demonstrated by CD, fluorescence and spectrophotometer data. Moreover, the intermolecular electronic interactions also increased as demonstrated by the protein solubility changes in DW, Buffer B and Buffer BSU. Therefore, a more uniform and denser micro-structure was formed to increase the gel strength and WHC as demonstrated by SEM. The results of this study can facilitate the application of HIU-heat technology in soy protein industry. [ABSTRACT FROM AUTHOR]

A wide consensus based on robust experimental evidence indicates pyroglutamylated amyloid-β isoform (AβpE3-42) as one of the most neurotoxic peptides involved in the onset of Alzheimer’s disease. Furthermore, AβpE3-42 co-oligomerized with excess of Aβ1-42, produces oligomers and aggregates that are structurally distinct and far more cytotoxic than those made from Aβ1-42 alone. Here, we investigate quantitatively the influence of AβpE3-42 on biophysical properties and biological activity of Aβ1-42. We tested different ratios of AβpE3-42/Aβ1-42 mixtures finding a correlation between the biological activity and the structural conformation and morphology of the analyzed mixtures. We find that a mixture containing 5% AβpE3-42, induces the highest disruption of intracellular calcium homeostasis and the highest neuronal toxicity. These data correlate to an high content of relaxed antiparallel β-sheet structure and the coexistence of a population of big spheroidal aggregates together with short fibrils. Our experiments provide also evidence that AβpE3-42 causes template-induced misfolding of Aβ1-42 at ratios below 33%. This means that there exists a critical concentration required to have seeding on Aβ1-42 aggregation, above this threshold, the seed effect is not possible anymore and AβpE3-42 controls the total aggregation kinetics. [ABSTRACT FROM AUTHOR]

For the first time, the effects of picoplatin on the structure and esterase-like catalytic activity of human serum albumin (HSA) have been investigated by spectroscopic approaches and molecular modeling. The circular dichroism (CD) spectral examinations indicated that the binding of picoplatin with HSA induced a slight decrease of a-helix content of protein and unfolded the constituent polypeptides of the protein. The synchronous fluorescence and three-dimensional fluorescence spectral methods were used to estimate the effect of picoplatin on the micro-environmental changes of the Trp and Tyr residues of HSA, indicating that the micro-environment around the Tyr and Trp residue is partly disturbed by picoplatin. UV–vis absorption spectral result indicated the formation of the ground state complex between picoplatin with HSA. The ANS binding assay indicated the existence of competitive combination of picoplatin and ANS with HSA. The studies on the effects of picoplatin on the binding of HSA with bilirubin and heme showed that picoplatin binding caused a change of angle between two chromophores of bound bilirubin and the binding site of picoplatin does not locate in subdomain IB in HSA that bound with heme. The molecular modeling results showed that picoplatin binds to the connection between domain I and domain II by hydrophobic, hydrogen bonds, and van der Waals forces. In addition, HSA maintains most of its esterase activity in the presence of picoplatin. The investigations on how picoplatin interacts with HSA are important for the understanding of the anticancer mechanism and toxicity of platinum-based anticancer drug. [ABSTRACT FROM AUTHOR]

This work aimed at investigating the effects of Pulsed Light (PL) processing at different fluences (from 4 to 16 J/cm 2 ) on the structure and functional properties of Whey Protein Isolate (WPI) solution. The determination of the free and total sulfhydryl (SH) groups was used to detect the variation of WPI tertiary and quaternary structure. Additionally, PL-induced changes in secondary structure were determined by FT-IR spectroscopy and the differential scanning calorimetry (DSC), and primary structure by carbonyl content. The experimental data demonstrated that PL treatments increased the concentration of total and free sulfhydryl groups and protein carbonyls. A decrease of the denaturation temperature and enthalpy ratio with increasing the intensity of PL treatments was observed in DSC measurements. Small but significant changes in the secondary structure of PL treated WPI solution were also taking place and detected. The extent of whey protein structure modifications was fluence dependent. The results of this investigation demonstrated the potential of PL treatments to induce dissociation and partial unfolding of WPI, thus improving some of their functional properties, such as solubility and foaming ability. [ABSTRACT FROM AUTHOR]

This work is concerned with the study of the conformational structure and crystallinity of sericin from silk cocoon ( Bombyx mori ) and the role these play in the physical and chemical properties of the final materials. Silk sericin (SS) powders were prepared by degumming processes with different storage temperatures before drying into the final powders; defined as RT-SS (room, 25 °C), C-SS (10 °C) and F-SS (freezing, 0 °C), and then fabricated into films and scaffolds by reacting with poly(vinyl alcohol) (PVA) in the presence of a new cross-linker (dimethylolurea; DMU). RT-SS and C-SS structures favour random coil structuring as witnessed by Amide I (C O stretching), II (N H bending) and III (in phase combination of N H in plane-bending and C N stretching vibrations) being observed at 1661, 1538, and 1232 cm −1 , respectively. Whereas, F-SS favours β-sheets structure proved by the amide bands shifting to a lower frequency. The N H stretching (3200–2400 cm −1 ) of F-SS is also observed at a lower frequency with a broader band than RT-SS and C-SS due to the hydrogen bonding in the β-sheets. The differences in the X-ray peaks between RT- and C-SS ( d spacing = 1.9–5.2 Å) and F-SS ( d spacing = 3.0 Å and 5.2–8.2 Å) were also measured. Films of PVA/RT-SS/DMU showed better properties than that of PVA/F-SS/DMU films in terms of the interactions (hydrogen bonding) between the components that formed the network. Therefore, RT-SS was chosen for the preparation of 3D porous scaffolds with different concentrations of DMU. All scaffolds showed good support for skin fibroblast cells, as well as promoted cell proliferation. However, a minimal amount of cross-linker, 10% DMU PVA/RT-SS scaffold with average pore diameter between 20 and 30 μm, was the best composition for cell viability and cell adhesion. In this work, therefore, a novel scaffold based on biomaterials was explored for tissue engineering scaffolds with the potential to be a new technology platform for skin tissue regeneration. [ABSTRACT FROM AUTHOR]

Cystathionine γ-lyase (CGL) is a key enzyme in the methionine–cysteine cycle in all living organisms forming cysteine, α-ketobutyrate and ammonia via homocysteine and cystathionine intermediates. Although, human and plant CGLs have been extensively studied at the molecular and mechanistic levels, there has been little work on the molecular and catalytic properties of fungal CGL. Herein, we studied in detail for the first time the molecular and catalytic stability of Aspergillus fumigatus CGL, since conformational instability, inactivation and structural antigenicity are the main limitations of the PLP-dependent enzymes on various therapeutic uses. We examined these properties in response to buffer compositions, stabilizing and destabilizing agents using Differential Scanning Fluorometery (DSF), steady state and gel-based fluorescence of the intrinsic hydrophobic core, stability of internal aldimine linkage and catalytic properties. The activity of the recombinant A. fumigatus CGL was 13.8 U/mg. The melting temperature ( T m ) of CGL in potassium phosphate buffer (pH 7.0–8.0) was 73.3 °C, with ∼3 °C upshifting in MES and sodium phosphate buffers (pH 7.0). The conformational thermal stability was increased in potassium phosphate, sodium phosphate and MES buffers, in contrast to Tris–HCl, HEPES (pH 7.0) and CAPS (pH 9.0–10.0). The thermal stability and activity of CGL was slightly increased in the presence of trehalose and glycerol that might be due to hydration of the enzyme backbone, unlike the denaturing effect of GdmCl and urea. Modification of surface CGL glutamic and aspartic acids had no significant effect on the enzyme conformational and catalytic stability. Molecular modeling and dynamics simulations unveil the high conformational stability of the overall scaffold of CGL with high flexibility at the non-structural regions. CGL structure has eight buried Trp residues, which are reoriented to the enzyme surface and get exposed to the solvent under perturbation of destabilizers. Furthermore, electrostatic calculations of selected snapshots of CGL 3D structure under different experimental conditions showed a remarkable differences on the polarity of the enzyme surface. [ABSTRACT FROM AUTHOR]

The binding interaction of anticancer drug (using 5-fluorouracil (FU) as an example) with the model protein human serum albumin (HSA), and the FU-binding-induced microenvironment alterations in subdomain IIA of HSA molecule were studied by a combination of spectroscopic techniques and molecular docking method. The results indicated that the nature of forces involved in binding interaction between HSA and FU molecule were mainly van der Waal’s forces and hydrogen bonding interactions. These interactions resulted in the formation of FU–HSA complex, making the local microenvironment in subdomain IIA of the protein more hydrophobic than its native state. Moreover, the interaction caused the large conformation changes of HSA, leading to the increase of the compact α-helix structures at low concentration of FU (less than 150 μM). However, the high concentration of FU (higher than 150 μM) made the compact α-helix structure decreasing, probably due to the protein undergoing some sort of distortion. Molecular docking study revealed that FU could enter the inside a hydrophobic cavity of subdomain IIA (Sudlow’s site I) in proximity of Trp214 residue with the formation of specific hydrogen bonding with Trp214 and Lys199 residues, causing the fluorescence quenching of Trp214 through a static quenching mechanism. The study essentially provides an effective way for investigating the microenvironment alterations of protein induced by the drug molecules, and this approach can further be used in development of biomedicines and assessment of the safety-engineered drug delivery. [ABSTRACT FROM AUTHOR]