Increased Surface Hydrophobicity Research Articles

Structural properties and antioxidant activities of soybean protein hydrolysates produced by Lactobacillus delbrueckii subsp. bulgaricus cell envelope proteinase

In this work, we investigated the structural and biological properties of soybean protein isolate (SPI) after 0–8 h hydrolyzation with cell envelope proteinase (CEP) extracted from Lactobacillus delbrueckii subsp. bulgaricus. CEP hydrolysis increased the β-sheet and red-shifted the fluorescence peak, while decreasing the α-helix, indicating the unfolding of soybean proteins. Increased surface hydrophobicity and fluorescence of the soybean protein hydrolysates were correlated with the increased hydrophobic amino acid (from 209.67 to 217.6 mg/100 g). CEP tended to hydrolyze the N- and C-terminal regions of sequences dominated by Gly and Leu, which enhanced the antioxidant activity of the SPHs (lowest IC50s value of ABTS•+ and hydroxyl radical scavenging activity were 0.324 ± 0.006 mg/mL and 0.365 ± 0.001 mg/mL after 4 h hydrolysis). Comparison with the database of bioactive peptides suggested various potential biological activities, including antioxidant activity, angiotensin-converting enzyme inhibitory activity and dipeptidyl peptidase-IV inhibitory activity. The study findings have theoretical significance for the development of CEP hydrolysis and novel bioactive soybean peptides.

Nucleation of water vapor on nanodimpled surfaces: Effects of curvature radius and surface wettability

• The effects of dimple curvature radius and wettability on nucleation are studied. • Surface potential energy analysis confirms nucleation sites. • Increasing dimple curvature radius worsens nucleation. • More dimples increase vapor nucleation probability at lower surface subcooling. • The coupling effect of the surface structure affects the nucleation. The mechanisms of vapor nucleation on nanostructured surfaces, whose geometrical characteristic sizes are comparable to those of nuclei, remain unsatisfactorily explored. This study investigates the correlations among the wettability, dimple curvature radius, and nucleation characteristics of vapor molecules on nanodimpled surfaces through molecular dynamics simulations. The surface potential energy analysis demonstrates that nucleation sites are located in the interior of dimples. With an increase in surface hydrophobicity or dimple curvature radius, a higher nucleation energy barrier would render nucleation more difficult. The critical sizes of nuclei obtained from MD simulation are larger than the results estimated by the classical nucleation theory. The discrepancy is attributed to the fact that the formed nucleus in simulations deviates from the spherical cap assumption. The formation of nuclei is not observed at all dimples, indicating that the coupling effects of surface structure would affect nucleation. Additionally, the comparisons of coalescence phenomena noted for different dimple numbers reveal the benefits of increasing the dimple number, which can be attributed to the fact that more high-energy nucleation sites increase the nucleation probability of vapor molecules at reduced surface subcooling. Therefore, an enhanced condensation performance can be achieved by artificially controlling the dimple number.

Structure relationship of non-covalent interactions between lotus seedpod oligomeric procyanidins and glycated casein hydrolysate during digestion.

Procyanidin-amino acid interactions during transmembrane transport cause changes in the structural and physical properties of peptides, which limits further absorption of oligopeptide-advanced glycation end products (AGEs). In this study, glycated casein hydrolysates (GCSHs) were employed to investigate the structure and interaction mechanism of GCSH with lotus seedpod oligomeric procyanidin (LSOPC) complexes in an intestinal environment. LSOPC can interact with GCSH under certain conditions to form hydrogen bonds and hydrophobic interactions to form GCSH-LSOPC complexes. Results showed that procyanidin further leads to the transformation of a GCSH secondary structure and the increase of surface hydrophobicity (H0). The strongest non-covalent interaction between GCSH and (-)-epigallocatechin gallate (EGCG) was due to the polyhydroxy structure of EGCG. Binding site analysis showed that EGCG binds to the internal cavity of P1 to maintain the relative stability of the binding conformation. The antioxidant capacity of GCSH was remarkably elevated by GCSH-LSOPC. This study will provide a new reference for the accurate control of oligopeptide-AGEs absorption by LSOPC in vivo.

Effect on myofibrillar protein gelation induced by eugenol modification under oxidative stress

This study aimed to investigate the effects of eugenol (Eu) at different concentrations (0, 10, 50, 100, 200, and 300 μM/g protein) on the gel properties and chemical structure changes of porcine myofibrillar protein (MP). The results showed that Eu inhibited the increase of surface hydrophobicity and carbonyl content but did not prevent the oxidation-induced loss of thiol groups. Moreover, Eu intensified the loss of the α-helical conformation as well as the tertiary structure of MP under oxidative stress. The physicochemical changes at 10 and 50 μM/g Eu resulted in a significant enhancement of the gelling ability of MP and enhanced the positive role of oxidation in building elastic gel networks. Conversely, Eu at the concentrations of 100, 200, and 300 μM/g was not conducive to gelling ability, especially at 300 μM/g, and these concentrations were associated with Eu-induced protein conformational changes.

Epidermal Patch with Biomimetic Multistructural Microfluidic Channels for Timeliness Monitoring of Sweat

Wearable sweat sensors have been developed rapidly in recent years due to the great potential in health monitoring. Developing a convenient manufacturing process and a novel structure to realize timeliness and continuous monitoring of sweat is crucial for the practical application of sweat sensors. Herein, inspired by the striped grooves and granular structures of bamboo leaves, we realized an epidermal patch with biomimetic multilevel structural microfluidic channels for timeliness monitoring of sweat via 3D printing and femtosecond laser processing. The striped grooves and ridges are alternately arranged at the bottom of the microfluidic channels, and the surface of the ridges has rough granular structures. The striped grooves improve the capillary effect in the microchannels by dividing the microchannels, and the granular structures enhance the slip effect of sweat by increasing surface hydrophobicity. The experimental results show that compared with the conventional microfluidic channels, the water collecting rate of the biomimetic microchannels increased by about 60%, which is consistent with the theoretical analysis. The superior sweat-collecting efficiency in the epidermal patch with the biomimetic multistructure enables sensitive, continuous, and stable monitoring of sweat physiological signals. Besides, this work provides new design and manufacturing approaches for other microfluidic applications.

Impact of Different Enzymatic Processes on Antioxidant, Nutritional and Functional Properties of Soy Protein Hydrolysates Incorporated into Novel Cookies.

Soy protein concentrate (SPC) was hydrolyzed using several commercial food-grade proteases (Alcalase, Neutrase, papain, Everlase, Umamizyme, Flavourzyme) and their combination to obtain promising ingredients in the manufacture of functional bakery products. In all cases, the hydrolysis caused nutritional, sensory, and rheological changes in SPC, as well as protein structural changes like increased surface hydrophobicity and content of exposed SH groups with the magnitude of these changes depending on enzyme specificity. The hydrolysis with the combination of Neutrase and Flavourzyme (NeuFlav) increased essential amino acid content by 9.8% and that of Lys by 32.6% compared to SPC. This hydrolysate showed also significant antioxidant activities including ABTS and superoxide anion scavenging activity and metal-chelating ability. The addition of all hydrolysates in wheat flour decreased water adsorption and increased development time to some extent due to gluten network weakening, but also decreased the rate of starch retrogradation, contributing to the increase of the shelf-life of bakery products. The NeuFlav tasted less bitter than other hydrolysates, while E-nose provided a discrimination index of 93 between control and hydrolysates. It appeared that the addition of the NeuFlav hydrolysate in a cookie formulation improved protein content and nutritional quality and directed to its higher general consumer acceptability than cookies formulated with only wheat flour.

Investigation of novel cold atmospheric plasma sources and their impact on the structural and functional characteristics of pea protein

The impact of three cold atmospheric plasma (CAP) sources, atmospheric pressure plasma jet (APPJ), two- dimension dielectric barrier discharge (2D-DBD), and nanosecond pulsed discharge (ns-pulsed) on the structure, functionality, and amino acid composition of pea protein was evaluated. Different plasma sources and associated reactive species resulted in protein denaturation, increased surface hydrophobicity, formation of soluble aggregates mostly by disulfide linkages, and changes in secondary structures. Enhancement in surface properties, presence of soluble aggregates, and increase in β-sheet contributed to significant improvement in gelation and emulsification. Enhanced emulsion stability was attributed to relatively small droplet sizes and high surface-charge. Differences among CAP-treated samples were attributed to differences in fluence and composition of plasma-produced reactive species. While all three plasma treatments could be appreciable functionalization approaches, 2D-DBD (Ar + O2) treatment for 30 min had insignificant effect on the amino acid composition.

Improve stability and application of rice oil bodies via surface modification with ferulic acid, (-)-epicatechin, and phytic acid

Rice bran oil bodies (RBOBs) are one of the most exploited functional components from rice bran by-products and are predominantly based on oleosin stabilization. In this study, we explored the effects of different concentrations of added (-)-epicatechin, ferulic acid, and phytic acid on the RBOBs stability. The results revealed that the incorporation of all three natural phytoconstituents could reduce the RBOBs particle size and increase emulsifying properties, demonstrating increasing surface hydrophobicity (p < 0.05), and a good antioxidant effect, which was especially obvious with (-)-epicatechin incorporation. Fourier transform infrared (FT-IR) spectroscopy data demonstrated that these three small molecule substance classes can modify with oleosin on RBOBs surface by covalent and noncovalent effects. Raman spectroscopic analysis illustrated that the vibrational modes of disulphide bonds in oleosin were modified by these three plant natural ingredients. The interactions between the three phytoconstituents and the model protein were investigated by molecular docking experiments.

Structural Transitions of Alpha-Amylase Treated with Pulsed Electric Fields: Effect of Coexisting Carrageenan.

Pulsed electric field (PEF) is an effective way to modulate the structure and activity of enzymes; however, the dynamic changes in enzyme structure during this process, especially the intermediate state, remain unclear. In this study, the molten globule (MG) state of α-amylase under PEF processing was investigated using intrinsic fluorescence, surface hydrophobicity, circular dichroism, etc. Meanwhile, the influence of coexisting carrageenan on the structural transition of α-amylase during PEF processing was evaluated. When the electric field strength was 20 kV/cm, α-amylase showed the unique characteristics of an MG state, which retained the secondary structure, changed the tertiary structure, and increased surface hydrophobicity (from 240 to 640). The addition of carrageenan effectively protected the enzyme activity of α-amylase during PEF treatment. When the mixed ratio of α-amylase to carrageenan was 10:1, they formed electrostatic complexes with a size of ~20 nm, and carrageenan inhibited the increase in surface hydrophobicity (&lt;600) and aggregation (&lt;40 nm) of α-amylase after five cycles of PEF treatment. This work clarifies the influence of co-existing polysaccharides on the intermediate state of proteins during PEF treatment and provides a strategy to modulate protein structure by adding polysaccharides during food processing.

Nano-assemblies enhance chaperone activity, stability, and delivery of alpha B-crystallin-D3 (αB-D3).

Crystallins, small heat shock chaperone proteins that prevent protein aggregation, are of potential value in treating protein aggregation disorders. However, their therapeutic use is limited by their low potency and poor intracellular delivery. One approach to facilitate the development of crystallins is to improve their activity, stability, and delivery. In this study, zinc addition to αB-crystallin-D3 (αB-D3) formed supramolecular nano- and micro- assemblies, induced dose-dependent changes in structure (beta-sheet to alpha-helix) and increased surface hydrophobicity and chemical stability. Further, crystallin assemblies exhibited a size-dependent chaperone activity, with the nano-assemblies being superior to micro-assemblies and 4.3-fold more effective than the native protein in preventing β-mercaptoethanol induced aggregation of insulin. Insulin rescued by crystallin assemblies retained the activity as evidenced by glucose uptake in 3T3-L1 cells. The most active nano-assemblies enhanced protein stability, in the presence of urea, by 1.6-fold, whereas intracellular delivery was enhanced by 3.0-fold. The αB-D3 crystallin nano-assemblies exhibit uniquely enhanced stability, activity, and delivery compared to the native protein.

Fabrication of icariin-soymilk nanoparticles with ultrasound-assisted treatment.

Ultrasound is effective to fabricate nanocomplex. Soymilk is a natural nanocarrier with good compatibility. However, information about soymilk-nutraceuticals nanocomplex is limited. In this work, soymilk was used to encapsulate icariin, a well known nutraceutical with poor bioavailability. The effect of ultrasound on the quality of icariin-soymilk nanocomplexes (ISNCs) was investigated. Ultrasound could reduce the particle size, improve the surface hydrophobicity and change the microstructure of soymilk. With increasing ultrasound treatment time, an increased surface hydrophobicity was observed. The highest encapsulation efficiency (89.67%) and loading capacity (28.92µg/mg) were found for USI-20, whereas the smallest particle size (132.47nm) was observed for USI-120. USI-60 showed the lowest ζ-potential (-31.33mV) and the highest bioaccessibility (76.08%). Ultrasound could enhance the storage stability of ISNCs. The data of NMR and fluorescence indicated that ISNCs were mainly stabilized by hydrophobic interaction.

Improved in vitro bioaccessibility of quercetin by nanocomplexation with high-intensity ultrasound treated soy protein isolate

The health benefits of quercetin are limited by its low bioaccessibility. This could be improved by developing plant-based protein delivery systems. Encapsulating quercetin using untreated and high-intensity ultrasound treated (20 kHz at 139 W for 10, 15 and 20 min) soy protein isolate (SPI) produced composite nanoparticles at around 127–136 nm. Ultrasound treatments on SPI caused structural changes of proteins (e.g. around 6-fold increase of surface hydrophobicity and protein solubility) favorable to encapsulation. The encapsulation efficiency for quercetin complexed with 15 min ultrasound treated SPI (76.5 %) was around 10-fold of that with the native SPI (7.2 %). Quercetin was significantly more in vitro bioaccessible when complexed with the treated SPI (61.1 %–64.5 %), as compared to the free quercetin (10.5 %–13.0 %). Ultrasound treated SPI seems to be a promising nanocarrier to encapsulate hydrophobic bioactive ingredients with higher solubility, stability, and bioaccessibility.

Enhanced hydrophobic paper-sheet derived from Miscanthus × giganteus cellulose fibers coated with esterified lignin and cellulose acetate blend

Biobased packaging materials derived from carbon-neutral feedstocks are sustainable alternatives to conventional fossil-based polymers. In this study, a method was developed to prepare paper-sheets derived from Miscanthus × giganteus cellulose fibers for potential food contact applications. The papers were hydrophobized with modified lignin from Miscanthus × giganteus biomass and commercial Kraft alkali lignin through hydroxyethylation with ethylene carbonate, followed by esterification with propionic acid. The esterified lignin (10 % w/w) and cellulose acetate (5 % w/w, based on lignin content) were dissolved in acetone and applied as a coating on the miscanthus paper sheets. The esterified lignins were characterized using FTIR, NMR, DSC, TGA, and elemental analyses. The uncoated and coated paper-sheets had contact angle values 52.4° and >130°, respectively, indicating an increased surface hydrophobicity of the coated paper samples. The water vapor transmission rate decreased significantly from 213.7 (uncoated paper-sheet) to 63.3 g/m2.d (coated paper-sheet). The tensile strength of the coated paper (64.6 MPa) was higher than the uncoated counterpart (57.1 MPa). Results from this study suggest that the esterified lignin coated miscanthus paper is a promising hydrophobic food packaging material alternative to conventional fossil-based thermoplastics.

Which Surface Is More Scaling Resistant? A Closer Look at Nucleation Theories for Heterogeneous Gypsum Nucleation in Aqueous Solutions.

Developing engineered surfaces with scaling resistance is an effective means to inhibit surface-mediated mineral scaling in various industries including desalination. However, contrasting results have been reported on the relationship between scaling potential and surface hydrophilicity. In this study, we combine a theoretical analysis with experimental investigation to clarify the effect of surface wetting property on heterogeneous gypsum (CaSO4·2H2O) formation on surfaces immersed in aqueous solutions. Theoretical prediction derived from classical nucleation theory (CNT) indicates that an increase of surface hydrophobicity reduces scaling potential, which contrasts our experimental results that more hydrophilic surfaces are less prone to gypsum scaling. We further consider the possibility of nonclassical pathway of gypsum nucleation, which proceeds by the aggregation of precursor clusters of CaSO4. Accordingly, we investigate the affinity of CaSO4 to substrate surfaces of varied wetting properties via calculating the total free energy of interaction, with the results perfectly predicting experimental observations of surface scaling propensity. This indicates that the interactions between precursor clusters of CaSO4 and substrate surfaces might play an important role in regulating heterogeneous gypsum formation. Our findings provide evidence that CNT might not be applicable to describing gypsum scaling in aqueous solutions. The fundamental insights we reveal on gypsum scaling mechanisms have the potential to guide rational design of scaling-resistant engineered surfaces.

Hydrophobic Magnetite Nanoparticles for Bioseparation: Green Synthesis, Functionalization, and Characterization

In this study, three types of hydrophobized alkyl-modified magnetic nanoparticles (MNPs) comprising direct alkylated-MNPs (A-MNPs), silica-mediated alkyl MNPs (A-SiMNPs), and arginine (Arg)-mediated alkyl MNPs (A-RMNPs) were synthesized successfully. For this purpose, the co-precipitation method was used to synthesize, and octadecyl trimethoxy silane (OTMS) was used as a functionalizing agent. Accordingly, the hydrophobic octadecyl moieties were connected to MNPs. The nanoparticles (NPs) were characterized by XRD, SEM, FTIR, CHN, DLS, and zeta potential analyses. The synthesized coated MNPs represented a decrease in surface charge and magnetization alongside increased surface hydrophobicity and size. It was revealed that the alkylation process was successfully performed to all three MNPs, but A-SiMNPs showed the highest hydrophobicity. Additionally, the novel A-RMNPs, as the most biocompatible type, and A-MNPs showed the highest magnetization among the synthesized MNPs. The results indicate that synthesized NPs can play an important role in bio applications. However, it was revealed that alkyl chains are easily connected to all three MNPs, and that A-MNPs contained the highest alkyl chains and could affect the re-folding and denaturation process of recombinant proteins.

Physicochemical and gel properties of pumpkin seed protein: a comparative study

SummaryThe physicochemical properties and heat‐induced gel properties of pumpkin seed protein isolates (PSPI) were explored and compared with soybean protein isolate (SPI) and pea protein isolates (PPI). These plant proteins were subjected to ultrasound, acid or alkaline treatment (pH 3 or 11). The content of amino acids and subunit composition were different in PSPI compared with SPI and PPI. Rheological and textural experiments showed that native PSPI had the highest gel strength among the three proteins. This was due to the high hydrophobicity of PSPI and the filling effect of insoluble particles in the protein solution. PSPI had a more pronounced improvement in gel properties after ultrasound or alkaline treatment compared with SPI and PPI, which was due to the increased surface hydrophobicity, increased solubility and reduced particle size of the proteins. The acid treatment induced insoluble aggregates increased the protein particle size, and decreased the protein solubility, resulting in a negative effect on the PSPI protein gel. Therefore, it can be concluded that PSPI has better heat‐induced gelation than SPI and PPI and can be used as a substitute for SPI and PPI in the food industry.

Unraveling pH Effects on Ultrafiltration Membrane Fouling by Extracellular Polymeric Substances: Adsorption and Conformation Analyzed with Localized Surface Plasmon Resonance.

Extracellular polymeric substances (EPSs) can conform and orient on the surface according to the applied aquatic conditions. While pH elevation usually removes EPSs from membranes, small changes in pH can change the adsorbed EPS conformation and orientation, resulting in a decrease in membrane permeability. Accordingly, EPS layers were tested with localized surface plasmon resonance (LSPR) sensing and quartz crystal microbalance with dissipation monitoring (QCM-D) using a hybrid sensor. A novel membrane-mimetic hybrid QCM-D-LSPR sensor was designed to indicate both "dry" mass and mechanical load ("wet" mass) of the adsorbed EPS. The effect of pH on the EPS layer's viscoelastic properties and hydrated thickness analyzed by QCM-D corroborates with the shift in EPS areal concentration, ΓS, and the associated EPS conformation, analyzed by LSPR. As pH elevates, the processes of (i) elevation in EPS layer's thickness (QCM-D) and (ii) decrease in the EPS areal density, ΓS (LSPR), provide a clear indication for changes in EPS conformation, which decrease the effective ultrafiltration (UF) membrane pore diameter. This decrease in the pore diameter together with the increase in surface hydrophobicity elevates UF membrane hydraulic resistance.

Effective role of konjac oligosaccharide against oxidative changes in silver carp proteins during fluctuated frozen storage

The aim of this research was to perform a comparative analysis of konjac oligosaccharides (KOG) and conventional cryoprotectant (4% sucrose + 4% sorbitol) mixture (positive control, PC) as an effective antioxidant during fluctuated (FLUC) frozen storage of silver carp proteins. The surimi proteins were added with PC, KOG (1%) and KOG (3%) and antioxidative abilities were analyzed during FLUC frozen storage. The Ca2+-ATPase, total and reactive sulfhydryl groups (SH) groups were significantly reduced in all samples due to denaturation of myosin globular head. The control (C) samples also showed increase in carbonyls from 29.36 to 49.11 nmol/mg during FLUC-I and from 29.81 to 46.09 nmol/mg during FLUC-II. Meanwhile, the PC sample and KOG (1 and 3%) significantly (P < 0.05) reduced the carbonyls and surface hydrophobicity by inhibiting the formation of disulfide bindings. The addition of KOG (3%) restricted the increase in surface hydrophobicity, decline in SH groups and Ca2+-ATPase than the PC and KOG (1%) added samples due to better and strong intermolecular interactions with protein molecules. Furthermore, KOG (3%) enhanced the gel strength of surimi by forming well-established and dense gel network of protein. Overall, KOG (3%) was found to be a potential substitute of PC for seafood frozen preservation and commercial benefits.

Changes in partial properties of glycosylated egg white powder during storage.

Glycosylation is an effective method to modify protein. However, there is a lack of research on the property changes of glycosylated protein during storage. In the present study, the changes in the physicochemical, functional, and structural properties of xylo-oligosaccharide (XOS) glycosylated egg white powder (EWP) (XOS-EWP conjugates) prepared with different glycosylation conditions (XOS/EWP ratio and reaction time) were investigated when stored at 25 °C and 60% relative humidity. In the 12 weeks of storage, the degree of grafting, browning, and the formation of Maillard reaction products of XOS-EWP conjugates increased. The increase in XOS/EWP ratio and reaction time led to an increase in protein aggregation, though a decrease in solubility, due to increased degree of glycosylation and structural changes. Furthermore, improved gel hardness of XOS-EWP conjugates deteriorated, while improved emulsification ability was kept stable during storage. For the sample with a lower XOS/EWP ratio and reaction time, the gel hardness and emulsifying properties underwent little or no deterioration even improving during storage. The results could be attributed to the limited degree of glycosylation, further unfolding of the protein structure, increased surface hydrophobicity of protein, and improved thermal characteristics. During storage, the Maillard reaction would continue to occur in the glycosylated EWP, further affecting the performance of modified EWP. Modified EWP prepared under different glycosylation conditions performed differently during storage. Modified EWP with a larger XOS/EWP ratio and reaction time meant it was harder to maintain good performance. Modified EWP with a smaller XOS/EWP ratio and reaction time changed significantly to better performances. © 2022 Society of Chemical Industry.

Physical and emulsifying properties of pea protein: influence of combined physical modification by flaxseed gum and ultrasonic treatment

This study characterized and compared the physical and emulsifying properties of pea protein (PP) and its modified proteins (ultrasound treated- PP (PPU), flaxseed gum (FG) treated PP (PPFG) and ultrasound treated- PPFG (PPFGU)). The results showed FG triggered the formation of loosely attached complex with PP via physical modification under gentle magnetic stirring at pH 7.0, while ultrasound played an important role in reducing protein size, increasing surface hydrophobicity and molecular fluidity onto oil-water interface. So ultrasound further enhanced the interaction of PP with FG, and produced the PPFGU complex with smaller droplet size, higher ζ-potential and lower turbidity. Further, combination of FG and ultrasound improved the physical properties of PP with higher viscosity, stiffer gels (defined as higher elastic modulus), stronger hydrophobic properties, better thermal stability, and fast protein absorption rate. Therefore, the PPFGU coarse emulsion performed highest emulsifying activity index (EAI) and emulsion stability index (ESI) that the stabilized nanoemulsion obtained smallest droplet size, higher ζ-potential, and longest storage stability. The combination of FG and ultrasonic treatment will be an effective approach to improving the emulsifying property and thermal stability of PP, which can be considered as a potential plant-based emulsifier applied in the food industry.