Determination of Molecular Parameters of Linear and Circular Scleroglucan Coexisting in Ternary Mixtures Using Light Scattering

Soy protein particles with enhanced anti-aggregation behaviors under various heating temperatures, pH, and ionic strengths

Protein-containing food products are frequently heated during processing to passivate anti-nutritional components. However, heating also contributes to protein aggregation and gelation, which limits its application in protein-based aqueous systems. In this study, heat-stable soy protein particles (SPPs) were fabricated by preheating at 120 °C for 30 min and at 0.5% (w/v) protein concentration. Compared to untreated soy proteins (SPs), SPPs exhibited a higher denaturation ratio, stronger conformational rigidity, compacter colloidal structure, and higher surface charge. The aggregation state of SPs and SPPs at various heating conditions (temperatures, pH, ionic strength, and types) was analyzed by dynamic light scattering, atomic force microscopy, and cryo-scanning electron microscopy. SPPs showed less increase in particle size and greater anti-aggregation ability than SPs. When heated in the presence of salt ions (Na⁺, Ca²⁺) or at acidic conditions, both SPs and SPPs formed larger spherical particles, but the size increase rate of SPPs was significantly lower than SPs. These findings provide theoretical information for preparing heat-stable SPPs. Furthermore, the development of SPPs is conducive to designing protein-enriched ingredients for producing innovative foods.

Effect of cationic monomer structure on the aggregation behavior of amphoteric acrylic polymer around isoelectric point

Amphoteric polymer can be used as retanning agent in leather manufacture. It is particularly useful in chrome-free tanning systems since it can regulate the charge properties of chrome-free leather and enhance the fixation of anionic post-tanning chemicals in leather. However, the aggregation and precipitation of amphoteric polymer retanning agents around the isoelectric point (pI) hinder their wide application. Herein, we synthesized five amphoteric acrylic polymers (AAPs) by free radical copolymerization with acrylic acid and five different cationic acrylic monomers. The effect of cationic monomer structure on the aggregation behavior of AAPs was investigated. The aggregation of AAPs in aqueous solution showed pH and concentration dependence. Light scattering analysis showed that Poly (AA-co-MAPTAC) and Poly (AA-co-DMAPMA) were in the shape of coiled linear flexible chains with small particle size (Rg 7.6 nm and 14.8 nm, respectively) near the pI. However, Poly (AA-co-DAC), Poly (AA-co-DMC) and Poly (AA-co-DMAEMA) were in the shape of hollow spheres and exhibited serious aggregation. Quantum chemical calculations suggested that the amide groups in the cationic monomers MAPTAC and DMAPMA enhanced the nucleophilicity of AAPs. Thus the corresponding AAPs could carry a large number of cationic charges to slow their aggregation when the pH just climbed over the pI. The results are expected to provide theoretical reference for the synthesis and widespread application of AAPs.

Reduced Adhesive Force Leading to Enhanced Thermal Stability of Soy Protein Particles by Combined Preheating and Ultrasonic Treatment

Developing liquid systems with high protein contents is drawing intensive attention; however, this is challenged by heat-induced aggregation and gelation of proteins. Herein, we described a facile but robust approach of combined preheating and ultrasonic treatment (CPUT) to fabricate soy protein particles (SPPs) with enhanced heat stability. Results showed that these heat-stable particles, upon reheating at 1% (w/v), showed antiaggregation property evidenced from no obvious changes of the particle size distributions of suspensions. Besides, no gelation was found in the reheated test for SPPs suspended even at a concentration of 10% (w/v). In contrast, the control formed sol-gel after heating. The rearrangements of soy protein molecules by CPUT led to the formation of SPPs with reduced surface energy, which was primarily responsible for their heat stability. These findings highlighted that the CPUT could prepare thermally stable soy proteins, providing insights into the application of soy proteins in protein-enriched beverages.

Rice proteins and cod proteins forming shared microstructures with enhanced functional and nutritional properties

Low water solubility strictly limits the potential applications of plant or animal proteins such as rice proteins (RPs) and cod proteins (CPs). In this study, nanoscale hydrophilic colloidal co-assemblies (80 ~ 150 nm) with excellent water solubility were prepared by hydrating RPs and CPs at pH 12 combined with neutralization. The solubility of RPs was boosted to over 90% (w/v), while most of the subunits in CPs became fully soluble. Structural analysis revealed that RPs and CPs non-covalently reacted, which triggered sheet-helix transitions and formed a compact core of RPs coated by a layer of CPs. Both proteins exposed significant hydrophilic motifs and buried hydrophobic moieties, contributing to the high water-dispersibility of their co-assemblies. Moreover, the co-assembled proteins acquired leveraged amino acid compositions between RPs and CPs. This study will enrich the processing technology of protein components, customizing their structural and nutritional characteristics.

Fabrication of hydrophilic composites by bridging the secondary structures between rice proteins and pea proteins toward enhanced nutritional properties

Protein structures combining designable nutritional and functional properties are attracting great attention in the food industry. In this study, novel protein composites with shared internal structures were fabricated by co-dissolving rice proteins (RPs) and pea proteins (PPs) at pH 12 prior to a one-step neutralization. Structural and morphological characterization revealed that both unfolded protein molecules reacted at pH 12 via their secondary structures, driven by hydrophobic forces. The co-assembled structures therefore obtained considerable resistance against acid-induced refolding, affording the formation of nanoscale (∼100 nm), water-dispersible composites at pH 7. Eventually, the drawbacks of either proteins, such as the insolubility of RPs or slow digestion of PPs, were overcome due to structural alterations. Moreover, the strategy raised the level of Lys which was limiting in RPs in the same way as the level of those that were limiting in PPs such as Met and Cys-s. Based on the above results, the study would enrich the techniques of processing protein ingredients toward tailored structures and on-demand nutritional properties.

Preheat-induced soy protein particles with tunable heat stability

Recently, there is a growing interest in developing protein-enriched beverages with improved nutritional and functional properties. However, this is challenged by heat-induced aggregation and gelation of edible proteins, which limits their practical applications in high protein systems. In this study, soy protein particles (SPPs) with tunable heat stability were prepared by simply preheating soy proteins suspensions (pH 6.4 and 1% (w/v) concentration) at different temperatures and times. Results showed that heat-stabled SPPs were successfully obtained at high preheating temperatures with prolonged time. The SPPs structures were found to be highly unfolded, denatured, and compact. In addition, these particles exhibited lower viscosities and higher flow behavior index without gelation, whereas those prepared at lower preheating temperatures were found to readily gel after reheating. These results provide useful insights on how heat stable SPPs can be prepared, which extends their further application in protein-enriched beverages and relevant products.

Inducing secondary structural interplays between scallop muscle proteins and soy proteins to form soluble composites

Developing food protein structures with the freedom to tune their internal molecular arrangements is a fascinating aspect for serving the demands of multifunctional food components. However, a protein's conformation is highly submissive to its amino acid sequences, posing a great limitation on controlling its structural rearrangements. In this study, based on simply co-dissolving scallop muscle proteins (SMPs, water-insoluble) and soya proteins (SPs) at pH 12 prior to neutralization, the unfolding-folding pathways of both proteins were altered. Structural characterizations evidenced the complexation of SMPs and SPs using their secondary structures as the building blocks. Due to hydrophobic coalition between the α-helix (from SMPs) and β-sheet (from SPs), the co-assembled structures obtained considerable resistance against folding triggered by the hydrophobic effect. In addition, the kinetics by which the SMPs and SPs folded together was tailor-made by the compositional differences of the two proteins, resulting in the formation of well-defined, water-dispersible nanospheres with a tunable size and internal arrangements of the backbones. This study would enrich our choice of manipulated protein structures and enlarge the available protein sources with tailorable functions when applied in specific scenarios.

Recent Advances in Chain Conformation and Bioactivities of Triple-Helix Polysaccharides

Natural polysaccharides derived from renewable biomass sources are regarded as environmentally friendly and sustainable polymers. As the third most abundant biomacromolecule in nature, after proteins and nucleic acids, polysaccharides are also closely related with many different life activities. In particular, β-glucans are one of the most widely reported bioactive polysaccharides and are usually considered as biological response modifiers. Among them, β-glucans with triple-helix conformation have been the hottest and most well-researched polysaccharides at present, especially lentinan and schizophyllan, which are clinically used as cancer therapies in some Asian countries. Thus, creation of these active triple-helix polysaccharides is beneficial to the research and development of sustainable "green" biopolymers in the fields of food and life sciences. Therefore, full fundamental research of triple-helix polysaccharides is essential to discover more applications for polysaccharides. In this Review, the recent research progress of chain conformations, bioactivities, and structure-function relationships of triple-helix β-glucans is summarized. The main contents include the characterization methods of the macromolecular conformation, proof of triple helices, bioactivities, and structure-function relationships. We believe that the governments, enterprises, universities, and institutes dealing with the survival and health of human beings can expect the development of natural bioproducts in the future. Hence, a deep understanding of β-glucans with triple-helix chain conformation is necessary for application of natural medicines and biologics for a sustainable world.

Tile-based self-assembly of a triple-helical polysaccharide into cell wall-like mesoporous nanocapsules

Tile-based self-assembly is a robust system in the construction of three-dimensional DNA nanostructures but it has been rarely applied to other helical biopolymers. β-Glucan is an immunoactive natural polymer which exists in a triple helical conformation. Herein, we report that β-glucan, after modification using two types of short chain acyl groups, can self-assemble into tiles with inactivated sticky ends at the interface of two solvents. These tiles consist of a single layer of helices laterally aligned, and the sticky ends can be activated when a few acyl groups at the ends are removed; these tiles can further pack into mesoporous nanocapsules, in a similar process as the sticky DNA tiles pack into complex polyhedral nano-objects. These nanocapsules were found to have targeted effects to antigen presenting cells in a RAW264.7 cell model. Our study suggests that tile-based self-assembly can be a general strategy for helical biopolymers, and on fully exploiting this strategy, various new functional nanostructures will become accessible in the future.

Generation of Recombinant Antibodies against the beta-(1,6)-Branched beta-(1,3)-D-Glucan Schizophyllan from Immunized Mice via Phage Display

beta-(1,6)-Branched beta-(1,3)-D-glucans like schizophyllan from the basidiomycete Schizophyllum commune excite various immunostimulatory effects and have been clinically tested as adjuvants. Some of the glucans are also applicable in food or petrol industry due to their viscosity and temperature stability in aqueous solution. Antibodies against these glucans could be used as tool for analysis of glucan preparations or for further research of its bioactivity. Therefore, an immune phage display library was constructed from mice immunized with schizophyllan. Three recombinant monoclonal antibodies were isolated from this library by affinity selection (panning) on schizophyllan. The half-maximal effective concentration (EC50) values for those antibodies varied between 16.4 ng mL⁻¹ and 21.3 ng mL⁻¹. The clones showed binding specificity not only for schizophyllan but also for other beta-(1,6)-branched beta-(1,3)-D-glucans of similar macromolecular structure. Denaturation of the secondary structure led to a reduced antibody binding, indicating an epitope requiring the correct conformation of the triple helical structure of the glucans.

Extended chain conformation of β-glucan and its effect on antitumor activity

Extended chain conformation of β-glucan visualized by AFM, and its molecular weight- and chain conformation-dependent antitumor activity.

Anti-hepatoma activity of the stiff branched β-d-glucan and effects of molecular weight

The water soluble β-d-glucan AF1 with short branches isolated from Auricularia auricula-judae exhibited significant anti-hepatoma activities, and it was confirmed that AF1 had stiff chains and could induce cancer cell apoptosis and anti-angiogenesis through activating immune responses.