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Protein–polysaccharide complexes have received increasing attention as delivery systems to improve the stability and bioavailability of multiple bioactive compounds. However, deep and comprehensive understanding of the interactions between proteins and polysaccharides is still required for enhancing their loading efficiency and facilitating targeted delivery. In this study, we fabricated a type of protein–polysaccharide complexes using food-grade materials of β-lactoglobulin (β-Lg) and gum arabic (GA). The formation and characteristics of β-Lg–GA complexes were investigated by determining the influence of pH and other factors on their turbidity, zeta-potential, particle size and rheology. Results demonstrated that the β-Lg and GA suspension experienced four regimes including co-soluble polymers, soluble complexes, insoluble complexes and co-soluble polymers when the pH ranged from 1.2 to 7 and that β-Lg–GA complexes formed in large quantities at pH 4.2. An increased ratio of β-Lg in the mixtures was found to promote the formation of β-Lg and GA complexes, and the optimal β-Lg/GA ratio was found to be 2:1. The electrostatic interactions between the NH3+ group in β-Lg and the COO− group in GA were confirmed to be the main driving forces for the formation of β-Lg/GA complexes. The formed structure also resulted in enhanced thermal stability and viscosity. These findings provide critical implications for the application of β-lactoglobulin and gum arabic complexes in food research and industry.

Lipases are among the most applied biocatalysts in organic synthesis to catalyze the kinetic resolution of a wide range of racemic substrates to yield optically pure compounds. Due to the rapidly increased demands for optically pure compounds, deep understanding of the molecular basis for lipase stereoselectivity and how to obtain lipases with excellent asymmetric selectivity have become one of primary research goals in this field. This review is focused on the molecular factors that have impacts on the stereoselectivity of lipases including the steric complementarity between the lipase topological structure and its substrate, the regional structural flexibility, the hydrogen bonds between the residues around the catalytic site and the tetrahedral intermediates, and the electrostatic interactions between surface residues. Moreover, the synergistic effects of these structural factors on the catalytic properties including stereoselectivity, activity, and stability are also discussed.

In this paper, Eichhornia Crassipes stems were used as biomass feedstock, and Fe 2+ was used as the precursor solution to prepare Fe 3 O 4 -modified magnetic mesoporous biochar (Fe 3 O 4 @BC). By using Box-Behnken design (BBD) response surface methodology, the influences of three preparation parameters (X 1  = Fe 2+ concentration, X 2  = pyrolysis temperature and X 3  = pyrolysis time) on the adsorption of methyl orange (MO) by Fe 3 O 4 @BC were investigated, and a reliable response surface model was constructed. The results show that X 1 X 2 and X 1 X 3 have a significant influence on the adsorption of MO by Fe 3 O 4 @BC. The surface area and pore volume of Fe 3 O 4 @BC are controlled by all preparation parameters. The increase of pyrolysis time will significantly reduce the -OH on the surface of Fe 3 O 4 @BC and weaken its MO adsorption capacity. Through the numerical optimization of the constructed model, the optimal preparation parameters of Fe 3 O 4 @BC can be obtained as follows: Fe 2+ concentration = 0.27 mol/L, pyrolysis temperature = 405 °C, and pyrolysis time = 3.2 h. The adsorption experiment shows that the adsorption of Fe 3 O 4 @BC to MO is a spontaneous exothermic process, and the adsorption capacity is maximum when pH = 4. The adsorption kinetics and adsorption isotherms of Fe 3 O 4 @BC to MO conform to the pseudo-second-order kinetics and Sips model, respectively. Mechanism analysis shows that electrostatic interaction and H bond formation are the main forces for Fe 3 O 4 @BC to adsorb MO. This research not only realizes a new way of resource utilization of Eichhornia Crassipes biomass but also enriches the preparation research of magnetic biochar.

To study an effective removal method of residual cephalosporin antibiotics in water, taking the ceftriaxone sodium (CFS) as a research object, the adsorption effects of the resins with different characteristic parameters for CFS were investigated in the pH range of 2.0–5.0. MTS9570, a sorbent containing sulfonic-phosphoric acid bi-functional group, was optimally selected and further to study the adsorption removal behavior to CFS in depth for the first time. Owning to the highest fitness of the pseudo-second-order and intra-particle diffusion (R2 > 0.99), two models can better describe the process of CFS onto MTS9570, indicating that the process is controlled by the chemi-sorption and intra-particle diffusion together. Compared with Freundlich and Temkin isotherm, Langmuir isotherm is the best fitness with highest R2 and lowest AIC values, indicating that there exists a monolayer adsorption on the surface of MTS9570 sorbent to CFS. ∆H < 0, ∆S > 0 and ∆G < 0, imply that the adsorption is an exothermic spontaneous process with increased randomness at the solid–liquid interface. The adsorption ability of MTS9570 after six adsorption–desorption cycles can still reach 90.13% of the initial adsorption capacity, indicating that the adsorbent has good reusability. Combining the above results with the bi-functional group of the adsorbent as well as the molecular structure of CFS, we speculate that the potential adsorption mechanism of MTS9570 to CFS may be mainly controlled by electrostatic interaction and supplemented by hydrogen bonding.

Here, an efficient in vitro fluorescence biosensor for bovine serum albumin (BSA) based on the aggregation and release of CdS quantum dots (QDs) within carboxymethyl cellulose (CMC) was investigated and discussed. The aggregation of CdS QDs within CMC was prepared by electrostatic interaction. The release of CdS QDs was due to strong covalent linking between BSA and CMC, thus leading to the more favorable combination of BSA and CMC in the system with the presence of BSA. The detection of BSA was based on the quenching and recovery of fluorescence intensity in the system, which was caused by the aggregation and release of CdS QDs. An excellent linear relationship (R2 = 0.99286) was obtained between fluorescence intensity and BSA concentration (0.05–2.00 μM) with a detection limit of 10−8 M. In addition, the detection method showed high selectivity towards BSA and good stability. These results suggest that the method can be utilized as an efficient and highly selective reagent for quantification of BSA for in vitro biological science.

In this study, carnosine (0‒0.20%, w/v) was introduced to improve the dispersibility of myosin under a low-salt condition (0.1 M NaCl). The underlying dispersion mechanism was investigated. Carnosine has positive effects on the dispersibility of myosin, as evidenced by the significantly improved solubility and turbidity. After the addition of carnosine, the average particle size in each sample remarkably decreased, and the mole mass of the aggregates decreased from 6.74 × 107 g/mol to 4.00 × 107 g/mol as the carnosine increased from 0.10 to 0.20%. Changes in protein secondary structure, ζ-potential, and ITC (Isothermal titration calorimetry) results indicated that electrostatic interaction is the main force between myosin and carnosine. Moreover, carnosine may hinder the formation of large aggregates by affecting the structure and charge distribution of the myosin tail when carnosine was ≤ 0.10%. However, excess carnosine (˃ 0.10%) had a negative effect on the long-term stability of the protein solution. Turbiscan stability index, visual appearance, and hydrophobicity analyses showed that the instability of the system was possibly due to increase in the hydrophobicity of myosin head after excess carnosine was applied. Our research may contribute to the improvement of the functional properties of myosin under low-salt condition and regulation of protein behavior.

The poor solubility and sensitive photosensitivity of resveratrol (RES) greatly limit its application in functional aqueous food systems. Herein, the composite particles with gliadin (GLI) as the core and type B gelatin (GEL) as the shell were designed to load resveratrol to enhance its ability to resist ultraviolet radiation and bioavailability. The core-shell structure and size (650 nm) of the composite particles were confirmed by dynamic light scattering, isothermal titration calorimetry (ITC) and transmission electron microscopy (TEM), and the binding between gliadin and gelatin was mainly driven by spontaneous electrostatic force (∆H=-3.080*107, ∆G=-9.055*104). The encapsulation efficiency (EE) and loading capacity (LC) of resveratrol by the particles were 7f8.9% and 35.9 µg/mg, and the particles were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimeter (DSC). Furthermore, compared with free resveratrol, the anti-ultraviolet radiation ability of resveratrol protected by core-shell particles was significantly enhanced (P < 0.05), and the release percentage was increased from 55.1 to 79.5%. These findings indicate that the composite particles have good application potential for the protection and delivery of hydrophobic active substances.

  At present, studies on biochar transport have focused on biochar obtained by oxygen-limited pyrolysis, which may differ from conventional biochar produced by incineration in nature. This work investigated the transport and retention mechanisms of three types of oxygen-limited pyrolytic biochar and three types of traditional biochar in saturated porous media. The results showed that the specific surface area of the three oxygen-limited pyrolysis biochar (180–200 m 2 ·g −1 ) was higher than that of the traditional biochar (50–60 m 2 ·g −1 ). Therefore, the retention capacity of pyrolytic biochar is strong and the permeability is less than 0.1. The absolute value of the zeta potential of traditional biochar is greater than 30 mV, and the electrostatic repulsion generated is stronger, with a peak penetration rate of 0.16. Moreover, the zeta potential of biochar and traditional biochar is regulated by pH value and ionic strength. In acidic conditions or solutions with high ionic strength, the zeta potentials of the six types of biochar changed to about − 15 mV, and the second minimum value was less than 0, indicating that there was a tendency for sedimentation. This study provides a new perspective for assessing the transport and environmental risks of biochar in the environment.

Liposomes have been widely applied in bioanalytical assays. Most liposomes used bare negative charges to prevent non-specific binding and increase colloidal stability. Here, in contrast, highly stable, positively charged liposomes entrapping the fluorescent dye sulforhodamine B (SRB) were developed to serve as a secondary, non-specific label‚ and signal amplification tool in bioanalytical systems by exploiting their electrostatic interaction with negatively charged vesicles, surfaces, and microorganisms. The cationic liposomes were optimized for long-term stability (> 5 months) and high dye entrapment yield. Their capability as secondary, non-specific labels was first successfully proven through electrostatic interactions of cationic and anionic liposomes using dynamic light scattering, and then in a bioassay with fluorescence detection leading to an enhancement factor of 8.5 without any additional surface blocking steps. Moreover, the cationic liposomes bound efficiently to anionic magnetic beads were stable throughout magnetic separation procedures and could hence serve directly as labels in magnetic separation and purification strategies. Finally, the electrostatic interaction was exploited for the direct, simple, non-specific labeling of gram-negative bacteria. Isolated Escherichia coli cells were chosen as models and direct detection was demonstrated via fluorescent and chemiluminescent liposomes. Thus, these cationic liposomes can be used as generic labels for the development of ultrasensitive bioassays based on electrostatic interaction without the need for additional expensive recognition units like antibodies, where desired specificity is already afforded through other strategies.

Phage therapy has significant potential in specifically targeting bacterial pathogens in food and medicine. There is a significant interest to combine phages with materials to enhance and broaden potential applications of phages. This study compares non-specific adsorption, protein–ligand binding, and electrostatic interactions on cellulose microfibers without any chemical or genetic modification of phages. Success in immobilization of phages on biomaterials without genetic and chemical modification can enable effective translation of naturally occurring phages and their cocktails for antimicrobial applications. The immobilization approaches were characterized by phage loading efficiency, phage distribution, and phage release from fibers. The results indicated that non-specific adsorption and protein–ligand binding had insignificant phage loading while electrostatic interactions yielded approximately 15–25% phage loading normalized to the initial titer of the phage loading solution. Confocal imaging of the electrostatically immobilized phage fibers revealed a random phage distribution on the fiber surface. Phage release from the electrostatically immobilized phage fibers indicated a slow release over a period of 24 h. Overall, the electrostatic immobilization approach bound more active phages than non-specific adsorption and protein–ligand binding and thus may be considered the optimal approach to immobilizing phages onto biomaterial surfaces.