Electrostatic Screening Effect Research Articles

Probing Single-Molecule Dynamics in Self-Assembling Viral Nucleocapsids.

All viruses on Earth rely on host cell machinery for replication, a process that involves a complex self-assembly mechanism. Our aim here is to scrutinize in real time the growth of icosahedral viral nucleocapsids with single-molecule precision. Using total internal reflection fluorescence microscopy, we probed the binding and unbinding dynamics of fluorescently labeled capsid subunits on hundreds of immobilized viral RNA molecules simultaneously at each time point. A step-detection algorithm combined with statistical analysis allowed us to estimate microscopic quantities such as the equilibrium binding rate and mean residence time, which are otherwise inaccessible through traditional ensemble-averaging techniques. Additionally, we could estimate a set of rate constants modeling the growth kinetics from nonequilibrium measurements, and we observed an acceleration in growth caused by the electrostatic screening effect of monovalent salts. Single-molecule fluorescence imaging will be crucial for elucidating virus self-assembly at the molecular level, particularly in crowded, cell-like environments.

Sodium Ion-Induced Structural Transition on the Surface of a DNA-Interacting Protein.

Protein surfaces have pivotal roles in interactions between proteins and other biological molecules. However, the structural dynamics of protein surfaces have rarely been explored and are poorly understood. Here, the surface of a single-stranded DNA (ssDNA) binding protein (SSB) with four DNA binding domains that bind ssDNA in binding site sizes of 35, 56, and 65 nucleotides per tetramer is investigated. Using oligonucleotides as probes to sense the charged surface, NaCl induces a two-state structural transition on the SSB surface even at moderate concentrations. Chelation of sodium ions with charged amino acids alters the network of hydrogen bonds and/or salt bridges on the surface. Such changes are associated with changes in the electrostatic potential landscape and interaction mode. These findings advance the understanding of the molecular mechanism underlying the enigmatic salt-induced transitions between different DNA binding site sizes of SSBs. This work demonstrates that monovalent salt is a key regulator of biomolecular interactions that not only play roles in non-specific electrostatic screening effects as usually assumed but also may configure the surface of proteins to contribute to the effective regulation of biomolecular recognition and other downstream events.

Linear and nonlinear interfacial rheology of responsive microgels at the oil-water interface

Microgelation can significantly enhance the interfacial activity of polysaccharide and the ability to stabilize emulsion, but the interfacial behaviour of microgels and the intrinsic mechanism of stabilizing emulsion is not fully understood. In this study, chitosan microgels (h-CSMs) with uniform size were successfully prepared by electrostatic crosslinking hydrophobically modified chitosan (h-CS) with sodium phytate (SP) using microfluidic technique. The microfluidic conditions for fabricating of h-CSM were optimized: the mass ratio of h-CS: SP = 5: 1 with h-CS concentration of 0.5 mg/ml, and the pressure ratio of Ph-CS (Pa):PSP (Pa) = 1600:1000. The prepared h-CSMs were pH-responsive, with a swollen state at pH 5 and a shrunken state at pH 3 and 7. Further, the interfacial adsorption kinetics, and the interfacial rheology particularly the nonlinear interfacial rheology were systematically studied. The instantaneous Si-factor was proposed to describe the nonlinear responses of the microgel interface during an individual dilatational oscillation cycle. The results showed that microgelation significantly improved the interfacial ability of chitosan molecules at the oil-water interface. The h-CSM interface exhibited strain-softening response during extension and strain-hardening response during compression. The interface formed by h-CSMs under the swollen state had higher viscoelastic modulus, lower degree of nonlinearity and higher emulsifying capacity compared to that formed under the shrinking state. Low ionic strength significantly increased the viscoelastic modulus and reduced the nonlinearity and enhanced emulsifying capacity of the h-CSM interface, whereas high ionic strength disrupted the interaction between the h-CSMs and increased the nonlinear of the h-CSM interface due to too strong electrostatic screening effect.

Phase Separation and Aggregation of α-Synuclein Diverge at Different Salt Conditions.

The coacervation of alpha-synuclein (αSyn) into cytotoxic oligomers and amyloid fibrils are considered pathological hallmarks of Parkinson's disease. While aggregation is central to amyloid diseases, liquid-liquid phase separation (LLPS) and its interplay with aggregation have gained increasing interest. Previous work shows that factors promoting or inhibiting aggregation have similar effects on LLPS. This study provides a detailed scanning of a wide range of parameters, including protein, salt and crowding concentrations at multiple pH values, revealing different salt dependencies of aggregation and LLPS. The influence of salt on aggregation under crowding conditions follows a non-monotonic pattern, showing increased effects at medium salt concentrations. This behavior can be elucidated through a combination of electrostatic screening and salting-out effects on the intramolecular interactions between the N-terminal and C-terminal regions of αSyn. By contrast, this study finds a monotonic salt dependence of LLPS due to intermolecular interactions. Furthermore, it observes time evolution of the two distinct assembly states, with macroscopic fibrillar-like bundles initially forming at medium salt concentration but subsequently converting into droplets after prolonged incubation. The droplet state is therefore capable of inhibiting aggregation or even dissolving aggregates through heterotypic interactions, thus preventing αSyn from its dynamically arrested state.

Solving the retention time repeatability problem of hydrophilic interaction liquid chromatography

Hydrophilic interaction (liquid) chromatography (HILIC) has become the first choice LC mode for the separation of hydrophilic analytes. Numerous studies reported the poor retention time repeatability of HILIC. The problem was often ascribed to slow equilibration and insufficient re-equilibration time to establish the sensitive semi-immobilized water layer at the interface of the polar stationary phase and the bulk mobile phase. In this study, we compare retention time repeatability in HILIC for borosilicate glass and PFA (co-polymer of tetrafluoroethylene and perfluoroalkoxyethylene) solvent bottles. During this study, we observed peak patterns shifting towards higher retention times (for metabolites and peptides) and lower retention times (oligonucleotide sample) with ongoing analysis time when standard borosilicate glass bottles were used as solvent reservoirs. It was hypothesized that release of ions (sodium, potassium, borate, etc.) from the borosilicate glass bottles leads to alterations (thickness and electrostatic screening effects) in the semi-immobilized water layer which is adsorbed to the polar stationary phase surface under acetonitrile-rich eluents in HILIC with concomitant shifts in retention. When PFA solvent bottles were employed instead of borosilicate glass, retention time repeatability was greatly improved and changed from average 8.4 % RSD for the tested metabolites with borosilicate glass bottles to 0.14 % RSD for the PFA solvent bottles (30 injections over 12 h). Similar improvements were observed for peptides and oligonucleotides. This simple solution to the retention time repeatability problem in HILIC might contribute to a better acceptance of HILIC, especially in fields like targeted and untargeted metabolomics, peptide and oligonucleotide analysis.

Synthesis of recyclable and light-weight graphene oxide/chitosan/genipin sponges for the adsorption of diclofenac, triclosan, and microplastics

Emerging micropollutants, such as pharmaceuticals and microplastics (MPs), have become a pressing water environmental concern. The aim of this study is to synthesize chitosan sponges using graphene oxide (GO) and genipin (GP) for the removal of pharmaceuticals (diclofenac (DCF) and triclosan (TCS)) and MPs, verify their adsorption mechanisms, evaluate the effects of temperature, pH, and salinity on their adsorption capacities, and determine their reusability. The GO5/CS/GP sponge exhibited a macroporous nature (porosity = 95%, density = 32.6 mg/cm3). GO and cross-linker GP enhanced the adsorption of DCF, TCS, and polystyrene (PS) MPs onto the CS sponges. The adsorption of DCF, TCS, and PS MPs involved multiple steps: surface diffusion and pore diffusion of the sponge. The adsorption isotherms demonstrated that Langmuir model was the most fitted well model to explain adsorption of TCS (qm = 7.08 mg/g) and PS MPs (qm = 7.42 mg/g) on GO5/CS/GP sponge, while Freundlich model suited for DCF adsorption (qm = 48.58 mg/g). DCF adsorption was thermodynamically spontaneous and endothermic; however, the adsorption of TCS and PS MPs was exothermic (283–313 K). The optimal pH was 5.5–7 due to the surface charge of the GO5/CS/GP sponge (pHzpc = 5.76) and ionization of DCF, TCS, and PS MPs. As the salinity increased, DCF removal efficiency drastically decreased due to the weakening of electrostatic interactions; however, TCS removal efficiency remained stable because TCS adsorption was mainly caused by hydrophobic and π–π interactions rather than electrostatic interaction. The removal of PS MPs was enhanced by the electrostatic screening effects of high Na+ ions. PS nanoplastics (average size = 26 nm) were removed by the GO5/CS/GP sponge at a rate of 73.0%, which was better than that of PS MPs (41.5%). In addition, the GO5/CS/GP sponge could be recycled over five adsorption–desorption cycles.

PSPICA Force Field Extended for Proteins and Peptides.

Many coarse-grained (CG) molecular dynamics (MD) studies have been performed to investigate biological processes involving proteins and lipids. CG force fields (FFs) in these MD studies often use implicit or nonpolar water models to reduce computational costs. CG-MD using water models cannot properly describe electrostatic screening effects owing to the hydration of ionic segments and thus cannot appropriately describe molecular events involving water channels and pores through lipid membranes. To overcome this issue, we developed a protein model in the pSPICA FF, in which a polar CG water model showing the proper dielectric response was adopted. The developed CG model greatly improved the transfer free energy profiles of charged side chain analogues across the lipid membrane. Application studies on melittin-induced membrane pores and mechanosensitive channels in lipid membranes demonstrated that CG-MDs using the pSPICA FF correctly reproduced the structure and stability of the pores and channels. Furthermore, the adsorption behavior of the highly charged nona-arginine peptides on lipid membranes changed with salt concentration, indicating the pSPICA FF is also useful for simulating protein adsorption on membrane surfaces.

Heavy oil separation and recovery by the self-assembly of polymers and silica particles in hypersaline water

Emulsification and separation are of great significance in oil recovery. Herein, we report a synergic system of polymers and silica particles, which can achieve the emulsification and separation of heavy oil through the alkaline/acidic solution. Since the high salinity of formation water is an inevitable issue for chemical waterflooding, the effects of salinity on the properties of heavy oil emulsions were investigated by the zeta potential, interfacial tension (IFT), separation efficiency, dynamic light scattering (DLS), and rheology in experiments. The results show that heavy oil emulsions at extreme salinity (up to 50 g/L) remain stable under alkaline conditions. But conversely, the separation process of heavy oil emulsions is expedited under acidic conditions. Furthermore, the interaction mechanism is also elucidated by molecular dynamics simulations to provide a well-researched interpretation of the experimental phenomena. The self-assembly between the polymer and silica particles is seriously affected by the salt ions through the electrostatic screening effect, with increasing zeta potential values from −52.5 mV to −18.1 mV, and the interfacial films are crippled, exhibiting more viscous properties, which induces the separation of heavy oil emulsions. However, it can be stable under alkaline conditions with separation efficiencies of less than 14.3% in 24 h. This novel reversible PS system is used in hypersalinity (30 g/L) to realize emulsification and separation without any demulsifiers, breaking through the current salinity limit of polymer waterflooding (EOR increased by 15.51%). The findings of this study can help for a better understanding of the molecular mechanism of switchable heavy oil emulsions and develop a potential solution for EOR in reservoirs with high salinity.

Co-encapsulation of curcumin and quercetin with zein/HP-β-CD conjugates to enhance environmental resistance and antioxidant activity

In this study, composite nanoparticles consisting of zein and hydroxypropyl beta-cyclodextrin were prepared using a combined antisolvent co-precipitation/electrostatic interaction method. The effects of calcium ion concentration on the stability of the composite nanoparticles containing both curcumin and quercetin were investigated. Moreover, the stability and bioactivity of the quercetin and curcumin were characterized before and after encapsulation. Fluorescence spectroscopy, Fourier Transform infrared spectroscopy, and X-ray diffraction analyses indicated that electrostatic interactions, hydrogen bonding, and hydrophobic interactions were the main driving forces for the formation of the composite nanoparticles. The addition of calcium ions promoted crosslinking of the proteins and affected the stability of the protein–cyclodextrin composite particles through electrostatic screening and binding effects. The addition of calcium ions to the composite particles improved the encapsulation efficiency, antioxidant activity, and stability of the curcumin and quercetin. However, there was an optimum calcium ion concentration (2.0 mM) that provided the best encapsulation and protective effects on the nutraceuticals. The calcium crosslinked composite particles were shown to maintain good stability under different pH and simulated gastrointestinal digestion conditions. These results suggest that zein–cyclodextrin composite nanoparticles may be useful plant-based colloidal delivery systems for hydrophobic bio-active agents.

Optimizing the Martini 3 Force Field Reveals the Effects of the Intricate Balance between Protein-Water Interaction Strength and Salt Concentration on Biomolecular Condensate Formation.

Condensation/dissolution has become a widely acknowledged biological macromolecular assembly phenomenon in subcellular compartmentalization. The MARTINI force field offers a coarse-grained protein model with a resolution that preserves molecular details with an explicit (CG) solvent. Despite its relatively higher resolution, it can still achieve condensate formation in a reasonable computing time with explicit solvent and ionic species. Therefore, it is highly desirable to tune this force field to be able to reproduce the experimentally observed properties of the condensate formation. In this work, we studied the condensate formation of the low-sequence complexity domain of fused in sarcoma protein using a MARTINI 3 force field by systematically modifying (increasing) the protein-water interaction strength and varying the salt concentration. We found that the condensate formation is sensitive both to the protein-water interaction strength and the presence of salt. While the unmodified MARTINI force field yields a complete collapse of proteins into one dense phase (i.e., no dilute phase), we reported a range of modified protein-water interaction strength that is capable of capturing the experimentally found transfer free energy between dense and dilute phases. We also found that the condensates lose their spherical shape upon the addition of salt, especially when the protein-water interactions are weak. Interchain amino acid contact map analysis showed one explanation for this observation: the protein-protein contact fraction reduces as salt is added to systems (when the protein-water interactions are weak), consistent with electrostatic screening effects. This reduction might be responsible for the condensates becoming nonspherical upon the addition of salt by reducing the need for minimizing the interfacial area. However, as the protein-water interactions become stronger to the extent that makes the transfer free energy agree well with experimentally observed transfer free energy, we found an increase in the protein-protein contact fraction upon the addition of salt, consistent with the salting-out effects. Therefore, we concluded that there is an intricate balance between screening effects and salting-out effects upon the addition of salt and this balance is highly sensitive to the strength of protein-water interactions.

Second Harmonic Generation in van der Waals Heterostructure of Centrosymmetric ReS2 and Graphene

AbstractVan der Waals (vdW) heterostructures of two‐dimensional (2D) materials promise exotic properties beyond the reach of existing material systems and open unprecedented opportunities for device applications. Here, it is demonstrated that vdW stacking of centrosymmetric ReS2 and graphene into heterostructure could induce strong second harmonic generation (SHG), though there is not any SHG from the individual ReS2 or graphene. It could be attributed to the interfacial charge transfer in the heterostructure. With the distorted 1T crystal structure of ReS2 and electrostatic screening effect, the charge transfer gives rise to non‐uniform charge distribution across the ReS2's atomic layers, resulting in the broken centrosymmetry for the second‐order hyperpolarizability. At the specific pump wavelength of 1550 nm, the strength of the induced SHG in a trilayer ReS2/graphene vdW heterostructure is approximately twice of that from a monolayer MoS2. This work reveals vdW stacking is a simple and efficient method for inducing SHG in 2D materials with centrosymmetry, which could be considered as another unique attribute of 2D materials. It also indicates that SHG spectroscopy is a valid technique for probing charge transfer and distribution in heterostructures of 2D materials.

The effect of sodium alginate on the nanomechanical properties and interaction between oil body droplets studied using atomic force microscopy

This study investigates the nanomechanical properties of different oil bodies (OBs), including soybean, peanut, sesame, and rapeseed, coated with sodium alginate (ALG), and the interaction between ALG-coated OBs using atomic force microscopy (AFM). Hooke's law, Reissner theory, and the Membrane model were respectively applied to analyze the nanomechanical properties of the linear and non-linear mechanics of the ALG-coated OBs. It was found that stiffness Kb and modulus ER from the linear deformation of ALG-coated OBs increased with the increase of the ALG layer thickness, while modulus Em from the non-linear deformation was larger than ER and correlated with the compression degree of the ALG layer. The interaction between pure OBs depended on the OB type. Electrostatic interaction which is related to the surface ζ-potential of the OBs occurs at a relatively long interaction distance, while at a relatively short distance, interfacial deformation of OBs occurs and the interaction force is affected by the structure and mechanics of OB interfacial membrane. After coating by ALGs, the electrostatic repulsion occurred from a longer distance than that between pure OBs, and both electrostatic repulsion and steric hindrance exist for a long interaction distance as the ALG-coated OBs continued to approach each other. ALG coating can also weaken the electrostatic screening effect of salt ions, avoiding aggregation of OBs and thus improving their stability. The present work demonstrates the feasibility of using AFM to study the mechanical properties and interaction of OB droplets at the molecular level, and reveals the mechanism of the influence of polysaccharide macromolecules on the stability of OB emulsions from the microscopic scale.

Electrical and Optoelectrical Dual-Modulation in Perovskite-Based Vertical Field-Effect Transistors

Organolead trihalide perovskites have drawn a great deal of interest for application in electronic and optoelectronic devices owing to their exceptional physical properties. However, the majority of reported perovskite field-effect transistors (FETs) demonstrates unsatisfactory performance, such as poor mobility, low on/off ratio, and low current density, which remains a significant obstacle for their potential applications. In this work, we report a vertical FET (VFET) composed of a single-crystalline MAPbBr3 perovskite Schottky junction, which effectively modulates the intrinsic carrier characteristics and enhances the performance of the device by reducing channel length and weakening the electrostatic screening effect. The device exhibits excellent performance with a high on/off ratio (104), high carrier mobility (23.4 cm2 V–1 s–1), and current density of 2.69 A cm–2 at room temperature. Importantly, the regulation of the drain voltage plays a similar role to that of the gate voltage in our device, which is attributed to the doping of perovskite with regulation of the source contact/perovskite Schottky junction. With the drain modulation, a superior photoresponse with enhanced responsivity of 16 A W1– and a low dark current are simultaneously obtained under light illumination, leading to a high detectivity of 1014 Jones. Our research may open up new possibilities for perovskite electronics, such as logic applications for various flexible, wearable, and disposable devices.

Effect of electrostatic screening on 2D diffusion of cytochrome c in the yeast III-IV respiratory supercomplex

Effect of electrostatic screening on 2D diffusion of cytochrome c in the yeast III-IV respiratory supercomplex

New insights into the NaCl impact on emulsifying properties of globular proteins

In the work, the emulsifying properties of three representative globular proteins (soy β-conglycinin, glycinin and bovine serum albumin; designated as SC, SG and BSA, respectively) with different structural characteristics, as affected by the addition of NaCl (0–1000 mM), were investigated and compared, using two emulsion systems at oil fractions (ø) of 0.2 and 0.8, respectively. The modulation of physicochemical properties and conformations of these three proteins by NaCl was first evaluated in terms of solubility, ζ-potential, surface hydrophobicity, particle size and intrinsic fluorescence profile. The electrostatic screening by the presence of appropriate concentrations (50–100 mM) of NaCl resulted in progressive increases in extent of protein aggregation and surface hydrophobicity of both SC and SG, but the addition of high concentrations (>300 mM) of NaCl was favorable for the ‘salting-in’ effects. At ø = 0.2, the presence of NaCl impaired the emulsification performance of SC, while in the SG case, the emulsification performance was slightly affected. At ø = 0.8, the presence of NaCl remarkably improved the emulsification performance of SC, and facilitated the droplet flocculation and gel network formation in the HIPEs, while in the SG case, the gel stiffness of the HIPEs was also improved. All the evidences indicated that at low ø values, the influence of NaCl on the emulsifying properties of oligomeric globulins was dominated by the electrostatic screening effect, while at high ø values (e.g., 0.8), the hydration repulsion between bound hydrated Na+ played a crucial role in the performance of these globulins as Pickering stabilizers. The findings are of importance for the understanding of the salt impact on the properties and stability of food protein emulsion formulations.

A green initiative for oiled sand cleanup using chitosan/rhamnolipid complex dispersion with pH-stimulus response

The released oil can affect the vulnerable shoreline environment if the oil spills happen in coastal waters. The stranded oil on shorelines is persistent, posing a long-term influence on the intertidal ecosystem after weathering. Therefore, shoreline cleanup techniques are required to remove the oil from the shoreline environment. In this study, a new shoreline cleanup initiative using chitosan/rhamnolipid (CS/RL) complex dispersion with pH-stimulus response was developed for oiled sand cleanup. The results of factorial and single-factor design revealed that the CS/RL complex dispersion maintained high removal efficiency for oiled sand with different levels of oil content in comparison to using rhamnolipid alone. However, the increase of salinity negatively affected the removal efficiency. The electrostatic screening effect of high ionic strength can hinder the formation of the CS/RL complex, and thus reduce removal efficiency. The pH-responsive characteristic of chitosan allows the easy separation of water and oil in washing effluent. The chitosan polyelectrolytes aggregated and precipitated due to the deprotonation of amino groups by adjusting the pH of the washing effluent to above 8. The microscope image demonstrated that the chitosan aggregates wrapped around the oil droplets and settled to the bottom together, thus achieving oil–water separation. Such pH-stimulus response may help achieve an easy oil-water separation after washing. These findings have important implications for developing the new strategies of oil spill response.

Investigation of phonon modes in 2H-TaX2 (X = S/Se) flakes with electrostatic doping

Electrostatic doping-assisted phonon softening has been intensively investigated in semiconducting transition metal dichalcogenides (TMDCs), in which strong electron–phonon interactions can be achieved in thin layers. Though electron–phonon coupling plays an important role in structure phase transitions for metallic 2H-TaX2 (X = S, Se), it has been rarely studied under electrostatic doping. Here, the effect of electrostatic doping on the vibrational phonon modes of 2H-TaSe2 and 2H-TaS2 thin films is studied with ionic liquid gating by the electric-double-layer gating technique. Under a gate bias (VG) of 1.5 V, 2H-TaSe2 has a blue shift of 7 cm−1 and a red shift of 3 cm−1 for the in-plane (E2g) and out-of-plane vibration (A1g) modes, respectively, indicating a strong electron–phonon interaction in both intralayer and interlayer. By varying the thickness of the flakes, it has been found that there exists a threshold VG value for the stiffening of the E2g mode and the softening of the A1g mode because of the strong electrostatic screening effect at lower doping density. As the intensity of the E2g mode decreases with VG, an anomalous enhancement of the A1g phonons can be achieved, which is further convinced in TaS2. The asymmetric phonon evolution behavior is very different with that in the semiconducting TMDCs, which may provide useful information for understanding electron–phonon interplay in metallic layer materials.

Crystallization of charged gold particles mediated by nonadsorbing like-charged polyelectrolyte.

We report that the aqueous dispersions of negatively charged submicron-sized colloidal Au particles formed non-close-packed colloidal crystals by the addition of a like-charged linear polyelectrolyte, sodium polyacrylate (NaPAA). Au particles often form irregular aggregates in dispersions because of a strong van der Waals force acting between them. To prevent aggregation, we introduced negative electric charges on particle surfaces. By the addition of NaPAA, colloidal crystals were formed on the bottom of a sample cell because of the supply of Au particles by sedimentation and 2D diffusion even under very dilute conditions. Interparticle potential calculations demonstrated that the addition of NaPAA caused depletion attraction between the particles as well as a significant reduction in the interparticle repulsion because of the electrostatic screening effect. However, the electrostatic repulsion was strong enough to prevent the direct contact of particles in the excluded region between Au particles. Large-area crystals could be obtained by tilting the sample cell. By drying the sample, the Au particles came into contact and the non-space-filling crystals changed into closest packed crystals. These closest packed crystals exhibited a significant enhancement of Raman scattering intensity because of high hot-spot density.

Effect of ionic strength on assembly behaviors and rheological properties of rice glutelin based fibrils

This study investigated the assembly behaviors and rheological properties of rice glutelin based fibrils with varying ionic strengths (0–150 mM). The addition of NaCl accelerated the growth rate of fibrils, likely due to the effect of electrostatic screening and specific ions-protein interactions. In the morphological studies, the lower ionic strength (50 mM) promoted the elongation of fibrils, whereas the average contour length reduced from 1005 to 470 nm at the ionic strength of 150 mM, since the chaotic, haphazard aggregation of building block at higher ionic strength was not beneficial to the elongation of fibrils. The increased ionic strength facilitated the polypeptides hydrolysis, leading to the increased content of released smaller peptides (<10 kDa). The released peptides assembled into fibrils with stacked β-sheet, and the addition of salt promoted the formation of ordered secondary structure. The rheological properties of fibrils were changed with the effect of ionic strength, attributing to the increased fibrils density and the formation of larger fibrillar aggregates. This work provides a new insight into the effect of ionic strength on the formation and rheological properties of rice glutelin based fibrils, which will offer a promising technology for development of the innovative and agriculturally-sustainable food ingredient.

Effects of protein concentration, pH, and NaCl concentration on the physicochemical, interfacial, and emulsifying properties of β-conglycinin

The physicochemical characteristics, interfacial, and emulsifying properties of β-conglycinin (7S) at various protein concentrations (c), pH values (pH), and NaCl concentrations (NaCl) were characterized. The increase in c did not change the z-average diameters, solubility, and hydrophobicity but remarkably increased the net charges of 7S. The interfacial properties and emulsifying efficiency of 7S exhibited a dramatic dependence on the increase in c. Thus, the increased electrostatic repulsions facilitating the structural rearrangement and enough protein adsorbing onto the oil droplets' interfaces were the requirements for good emulsifying efficiency. 7S at pH 3 and 8 exhibited smaller z-average diameters, higher net charges, and solubility than that at pH 5, positively affecting their adsorption and the formation of viscoelastic layers. Thus, 7S at pH 3 and 8 showed better emulsifying efficiency. The increased NaCl did not change the z-average diameters, solubility, and hydrophobicity but decreased Zeta potentials of 7S due to electrostatic screening effects. Also, the increased NaCl improved interfacial adsorption kinetics but less viscoelastic interfacial layers of 7S. It suggested that low net charges decreased the electrostatic barrier for adsorption but did not benefit the intermolecular interaction of 7S at the interface. The emulsions aggregation at a high ionic strength indicated a negative effect on emulsifying activity.