Comparison of Alternative Protein Hydrogels for Delivering Myricetin: Interaction Mechanism and Stability Evaluation.

Food protein carriers from different sources might have distinct stabilizing and enhancing effects on the same small molecule. To elucidate the molecular mechanism, five different sourced proteins including soy protein isolates (SPIs), whey protein isolates (WPIs), edible dock protein (EDP), Tenebrio molitor protein (TMP), and yeast protein (YP) were used to prepare protein hydrogels for delivering myricetin (Myr). The results suggested that the loading capacity order of Myr in different protein hydrogels was EDP (11.5%) > WPI (9.3%) > TMP (8.9%) > YP (8.0%) > SPI (7.6%), which was consistent with the sequence of binding affinity between Myr and different proteins. Among five protein hydrogels, EDP had an optimum loading ability since it possessed the highest hydrophobic amino acid content (45.52%) and thus provided a broad hydrophobic cavity for loading Myr. In addition, these protein-Myr composite hydrogels displayed the core-shell structure, wherein hydrogen bonding and hydrophobic interaction were the primary binding forces between proteins and Myr. Moreover, the thermal stability, storage stability, and sustained-release properties of Myr were significantly enhanced via these protein delivery systems. These findings can provide scientific guidance for deeper utilization of food alternative protein sources.

Fabrication and characterization of novel prolamin nanoparticle-filled starch gels incorporating resveratrol.

This study aimed to improve the mechanical properties of wheat starch gels (WSG) and the stability and bioaccessibility of resveratrol (Res) in prolamin nanoparticles. Res-loaded gliadin (Gli), zein, deamidated gliadin (DG) and deamidated zein (DZ) nanoparticles were filled in WSG. The hardness, G' and G'' of WSG were notably increased. It can be attributed to the more ordered and stable structure induced by the interaction of prolamin nanoparticles and starch. The Res retention of nanoparticles and nanoparticle-filled starch gels was at least 24.6 % and 36.0 % higher than free Res upon heating. When exposed to ultraviolet, the Res retention was enhanced by over 6.1 % and 37.5 %. The in-vitro digestion demonstrated that the Res releasing percentage for nanoparticle-filled starch gels was 25.8 %-38.7 % lower than nanoparticles in the simulated stomach, and more Res was released in the simulated intestine. This resulted in a higher bioaccessibility of 82.1 %-93.2 %. The bioaccessibility of Res in Gli/Res/WSG and DG/Res/WSG was greater than that of Zein/Res/WSG and DZ/Res/WSG. More hydrophobic interactions occurred between Res and Gli, DG. The interactions between Res and zein, DZ were mainly hydrogen bonding. The microstructure showed that nanoparticles exhibited dense spherical structures and were uniformly embedded in the pores of starch gels.

Effects of two celery fibers on the structural properties and digestibility of glutinous rice starch: A comparative study.

The present study focused on the extraction of water-soluble dietary fiber (CSDF) and water-insoluble dietary fiber (CIDF) from celery. It investigated their effects on glutinous rice starch's (GRS) physicochemical, structural, and digestive properties. The results showed that as the addition of the two dietary fibers increased, they compounded with GRS to varying degrees, with the complexing index reaching 69.41 % and 60.81 %, respectively. The rheological results indicated that the two dietary fibers reduced the viscosity of GRS during pasting and inhibited the short-term regrowth of starch. The FTIR and XRD results revealed that the two fibers interacted with GRS through hydrogen bonding, effectively inhibiting starch retrogradation. Furthermore, both fibers increased the pasting temperature of GRS, thus delaying its pasting and exhibiting better thermal stability. Regarding digestibility, the starch gels containing dietary fibers exhibited significantly reduced digestibility, with RS significantly increased by 8.15 % and 8.95 %, respectively. This study provides insights into the interaction between two dietary fibers and GRS during processing. It enriches the theoretical model of dietary fiber-starch interaction and provides a reference for the application development of starch-based functional foods.

Insight into the solubilization mechanism of wheat gluten by protease modification from conformational change and molecular interaction perspective.

The low solubility limits the utilization of other functional characteristics of wheat gluten (WG). This study effectively improved the solubility of WG through protease modification and explored the potential mechanism of protease modification to enhance the solubility of WG, further stimulating the potential application of WG in the food industry. Solubility of WG modified with alkaline protease, complex protease, and neutral protease was enhanced by 98.99%, 54.59%, and 51.68%, respectively. Notably, the content of ß-sheet was reduced while the combined effect of hydrogen bond and ionic bond were increased after protease modification. Meanwhile, the reduced molecular size and viscoelasticity as well as the elevated surface hydrophobicity, thermostability, water absorption capacity, and crystallinity were observed in modified WG. Moreover, molecular docking indicated that protease was specifically bound to the amino acid residues of WG through hydrogen bonding, hydrophobic interaction, and salt bridge.

Preparation of the black rice starch-gallic acid complexes by ultrasound treatment: Physicochemical properties, multiscale structure, and in vitro digestibility.

This study aimed to investigate the multiscale structure, physicochemical properties, and in vitro digestibility of black rice starch (BRS) and gallic acid (GA) complexes prepared using varying ultrasound powers. The findings revealed that ultrasonic treatment disrupted BRS granules while enhancing the composite degree with GA. The starch granules enlarged and aggregated into complexes with uneven surfaces. Moreover, the crystallinity of the BRS-GA complexes increased to 22.73 % and formed V6-I-type complexes through non-covalent bonds. The increased short-range ordering of the complexes and nuclear magnetic resonance hydrogen (1H NMR) further indicated that the BRS and GA molecules interacted mainly through non-covalent bonds such as hydrogen bonds. Additionally, ultrasound reduced the viscoelasticity of the complexes while minimizing the mass loss of the complexes at the same temperature. In vitro digestion results demonstrated an increase in resistant starch content up to 37.60 % for the BRS-GA complexes. Therefore, ultrasound contributes to the formation of V-typed complexes of BRS and GA, which proves the feasibility of using ultrasound alone for the preparation of starch and polyphenol complexes while providing a basis for the multiscale structure and digestibility of polyphenol and starch complexes.

Mechanism of interaction between L-theanine and maize starch in ultrasonic field based on DFT calculations: Rheological properties, multi-scale structure and in vitro digestibility.

The digestibility of starch-based foods is receiving increased attention. To date, the full understanding of how including L-theanine (THE) can modify the structural and digestive properties of starch has not been fully achieved. Here, we investigated the multi-scale structure and digestibility of maize starch (MS) regulated by THE in ultrasound field and the molecular interactions. Ultrasound disrupted the structure of starch granules and opened the molecular chains of starch, promoting increased THE binding and producing more low-order or disordered crystal structures. In this case, the aggregation of starch molecules, especially amylose, was reduced, leading to increased mobility of the systems. As a result, the apparent viscosity, G', and G" were significantly decreased, which retarded the starch regeneration. Density functional theory calculations indicated that there were mainly non-covalent interactions between THE and MS, such as hydrogen bonding and van der Waals forces. These interactions were the main factors contributing to the decrease in the short-range ordering, the helical structure, and the enthalpy change (ΔH) of MS. Interestingly, the rapidly digestible starch (RDS) content of THE modified MS (MS-THE-30) decreased by 17.89 %, while the resistant starch increased to 26.65 %. These results provide new strategies for the safe production of resistant starch.

Influence of the structure and physicochemical properties of OSA modified highland barley starch based on ball milling assisted treatment.

This study aimed to investigate the influence of ball milling assisted treatment on the degree of substitution of octenyl succinic anhydride (OSA) modified highland barley starch (HBS) and on the physicochemical properties and structure of HBS. Scanning electron microscopy (SEM) findings showed that with the increasing of ball milling time, the surface morphology of OSA modified HBS became rougher and rougher and the particle morphology and crystal structure were damaged. When the pretreatment time of ball milling was 40 min, the degree of substitution of OSA modified HBS was 1.32 times higher than that of the conventional modification method. In addition, the longer the ball milling assistant, the longer the short-range ordering of the OSA modified HBS significantly decreased, and the relative crystallinity decreased (from 16.68 % to 7.93 %), leading to a decrease in thermal stability too. However, it greatly enhanced the aging resistance and flowability. In terms of emulsification properties, the emulsification properties of OSA modified HBS increased from 60.67 % to 75.67 %. Therefore, the HBS with better freeze-thaw stability and higher degree of substitution can be prepared by ball milling pretreatment and OSA modification, which provides technical support for further development of starch resources.

Molecular mechanism governing RNA-binding property of mammalian TRIM71 protein.

TRIM71 is an RNA-binding protein with ubiquitin ligase activity. Numerous functions of mammalian TRIM71, including cell cycle regulation, embryonic stem cell (ESC) self-renewal, and reprogramming of pluripotent stem cells, are related to its RNA-binding property. We previously reported that a long noncoding RNA (lncRNA) Trincr1 interacts with mouse TRIM71 (mTRIM71) to repress FGF/ERK pathway in mouse ESCs (mESCs). Herein, we identify an RNA motif specifically recognized by mTRIM71 from Trincr1 RNA, and solve the crystal structure of the NHL domain of mTRIM71 complexed with the RNA motif. Similar to the zebrafish TRIM71, mTRIM71 binds to a stem-loop structured RNA fragment of Trincr1, and an adenosine base at the loop region is crucial for the mTRIM71 interaction. We map similar hairpin RNAs preferably bound by TRIM71 in the mRNA UTRs of the cell-cycle related genes regulated by TRIM71. Furthermore, we identify key residues of mTRIM71, conserved among mammalian TRIM71 proteins, required for the RNA-binding property. Single-site mutations of these residues significantly impair the binding of TRIM71 to hairpin RNAs in vitro and to mRNAs of Cdkn1a/p21 and Rbl2/p130 in mESCs. Furthermore, congenital hydrocephalus (CH) specific mutation of mTRIM71 impair its binding to the RNA targets as well. These results reveal molecular mechanism behind the recognition of RNA by mammalian TRIM71 and provide insights into TRIM71 related diseases.

Exploring the formation mechanism of resistant starch (RS3) prepared from high amylose maize starch by hydrothermal-alkali combined with ultrasonic treatment.

In this study, type III resistant starch (RS3) was prepared from high amylose maize starch (HAMS) using hydrothermal (RS-H), hydrothermal combined ultrasonication (RS-HU), hydrothermal-alkali (RS-HA), and hydrothermal-alkali combined ultrasonication (RS-HAU). The role of the preparation methods and the mechanism of RS3 formation were analyzed by studying the multiscale structure and digestibility of the starch. The SEM, NMR, and GPC results showed that hydrothermal-alkali combined with ultrasonication could destroy the granule structure and α-1,6 glycosidic bond of HAMS and reduce the molecular weight of HAMS from 195.306 kDa to 157.115 kDa. The other methods had a weaker degree of effect on the structure of HAMS, especially hydrothermal and hydrothermal combined ultrasonication. The multiscale structural results showed that the relative crystallinity, short-range orderliness, and thermal stability of RS-HAU were significantly higher compared with native HAMS. In terms of digestion, RS-HAU had the highest RS content of 69.40 %. In summary, HAMS can generate many short-chain amylose due to structural damage, which rearrange to form digestion-resistant crystals. With correlation analysis, we revealed the relationship between the multiscale structure and the RS content, which can be used to guide the preparation of RS3.

Regulation Mechanism of Phenolic Hydroxyl Number on Self-Assembly and Interaction between Edible Dock Protein and Hydrophobic Flavonoids.

In this study, galangin (Gal), kaempferol (Kae), quercetin (Que), and myricetin (Myr) were chosen as the representative flavonoids with different phenolic hydroxyl numbers in the B-ring. The edible dock protein (EDP) was chosen as the new plant protein. Based on this, the regulation mechanism of the phenolic hydroxyl number on the self-assembly behavior and molecular interaction between EDP and flavonoid components were investigated. Results indicated that the loading capacity order of flavonoids within the EDP nanomicelles was Myr (10.92%) > Que (9.56%) > Kae (6.63%) > Gal (5.55%). Moreover, this order was consistent with the order of the hydroxyl number in the flavonoid's B ring: Myr (3) > Que (2) > Kae (1) > Gal (0). The micro morphology exhibited that four flavonoid-EDP nanomicelles had a core-shell structure. In the meantime, the EDP encapsulation remarkably improved the flavonoids' water solubility, storage stability, and sustained release characteristics. During the interaction of EDP and flavonoids, the noncovalent interactions including van der Waals forces, hydrophobic interaction, and hydrogen bonding were the main binding forces. All of the results demonstrated that the hydroxyl number of bioactive compounds is a critical factor for developing a delivery system with high loading ability and stability.

Angiotensin-(1-7) suppresses airway inflammation and airway remodeling via inhibiting ATG5 in allergic asthma.

BACKGROUND: Angiotensin (Ang)-(1-7) can reduce airway inflammation and airway remodeling in allergic asthma. Autophagy-related 5 (ATG5) has attracted wide attentions in asthma. However, the effects of Ang-(1-7) on ATG5-mediated autophagy in allergic asthma are unclear. METHODS: In this study, human bronchial epithelial cell (BEAS-2B) and human bronchial smooth muscle cell (HBSMC) were treated with different dose of Ang-(1-7) to observe changes of cell viability. Changes of ATG5 protein expression were measured in 10 ng/mL of interleukin (IL)-13-treated cells. Transfection of ATG5 small interference RNA (siRNA) or ATG5 cDNA in cells was used to analyze the effects of ATG5 on secretion of cytokines in the IL-13-treated cells. The effects of Ang-(1-7) were compared to the effects of ATG5 siRNA transfection or ATG5 cDNA transfection in the IL-13-treated cells. In wild-type (WT) mice and ATG5 knockout (ATG5-/-) mice, ovalbumin (OVA)-induced airway inflammation, fibrosis and autophagy were observed. In the OVA-induced WT mice, Ang-(1-7) treatment was performed to observe its effects on airway inflammation, fibrosis and autophagy. RESULTS: The results showed that ATG5 protein level was decreased with Ang-(1-7) dose administration in the IL-13-treated BEAS-2B and IL13-treated HBSMC. Ang-(1-7) played similar results to ATG5 siRNA that it suppressed the secretion of IL-25 and IL-13 in the IL-13-treated BEAS-2B cells, and inhibited the expression of transforming growth factor (TGF)-ß1 and α-smooth muscle actin (α-SMA) protein in the IL-13-treated HBSMC cells. ATG5 cDNA treatment significantly increased the secretion of IL-25 and IL-13 and expression of TGF-ß1 and α-SMA protein in IL-13-treated cells. Ang-(1-7) treatment suppressed the effects of ATG5 cDNA in the IL-13-treated cells. In OVA-induced WT mice, Ang-(1-7) treatment suppressed airway inflammation, remodeling and autophagy. ATG5 knockout also suppressed the airway inflammation, remodeling and autophagy. CONCLUSIONS: Ang-(1-7) treatment suppressed airway inflammation and remodeling in allergic asthma through inhibiting ATG5, providing an underlying mechanism of Ang-(1-7) for allergic asthma treatment.

Effects of starch multiscale structure on the physicochemical properties and digestibility of Radix Cynanchi bungei starch.

Radix Cynanchi bungei (RCb) contains 40-70 % starch, yet little is known about the structure and properties of RCb starch. In this study, the multiscale structure of two cultivars of RCb starch (YW201501 and BW201001) were characterized, and the effects of starch structure on its physicochemical properties were investigated. The differences in physicochemical properties of RCb starch were influenced by its multiscale structure. The starch granules were round and irregular polygon, with sizes ranging between 2 and 14 µm. YW201501 had a higher amylose (21.81 %) and lipid (0.96 %) content, molecular weight (59.5 × 106 g/mol), and A chain proportion (27.5 %), and a lower average granule size (6.14 µm), amylopectin average chain length (19.7), and B3 chain proportion (10.3 %). Both starches were B-type crystalline, with higher crystallinity (26.3 %) and R1047/1022 (0.74) for YW201501, resulting in large gelatinization enthalpy. In addition, the higher peak viscosity and larger retrogradation degree of YW201501 were correlated to its higher amylose content. In vitro digestibility revealed that the low rapidly digestible starch and high resistant starch of BW201001 were related to the fine structure of starch. YW201501 and BW201001 had a medium glycemic index (62.6-66.0) with potential for processing into healthy starchy foods.

Structural insights into histone binding and nucleosome assembly by chromatin assembly factor-1.

Chromatin inheritance entails de novo nucleosome assembly after DNA replication by chromatin assembly factor-1 (CAF-1). Yet direct knowledge about CAF-1's histone binding mode and nucleosome assembly process is lacking. In this work, we report the crystal structure of human CAF-1 in the absence of histones and the cryo-electron microscopy structure of CAF-1 in complex with histones H3 and H4. One histone H3-H4 heterodimer is bound by one CAF-1 complex mainly through the p60 subunit and the acidic domain of the p150 subunit. We also observed a dimeric CAF-1-H3-H4 supercomplex in which two H3-H4 heterodimers are poised for tetramer assembly and discovered that CAF-1 facilitates right-handed DNA wrapping of H3-H4 tetramers. These findings signify the involvement of DNA in H3-H4 tetramer formation and suggest a right-handed nucleosome precursor in chromatin replication.

Impact of climate change on SARS-CoV-2 epidemic in China.

The outbreak and prevalence of SARS-CoV-2 have severely affected social security. Physical isolation is an effective control that affects the short-term human-to-human transmission of the epidemic, although weather presents a long-term effect. Understanding the effect of weather on the outbreak allow it to be contained at the earliest possible. China is selected as the study area, and six weather factors that receive the most attention from January 20, 2020 to April 30, 2020 are selected to investigate the correlation between weather and SARS-CoV-2 to provide a theoretical basis for long-term epidemic prevention and control. The results show that (1) the average growth rate (GR) of SARS-CoV-2 in each province is logarithmically distributed with a mean value of 5.15%. The GR of the southeastern region is higher than that of the northwestern region, which is consistent with the Hu Line. (2) The specific humidity, 2-m temperature (T), ultraviolet (UV) radiation, and wind speed (WS) adversely affect the GR. By contrast, the total precipitation (TP) and surface pressure (SP) promote the GR. (3) For every 1 unit increase in UV radiation, the GR decreases by 0.30% in 11 days, and the UV radiation in China is higher than that worldwide (0.92% higher per day). Higher population aggregation and urbanization directly affect the epidemic, and weather is an indirect factor.

Development of antioxidant and smart NH3 -sensing packaging film by incorporating bilirubin into κ-carrageenan matrix.

BACKGROUND: Active and smart food packaging based on natural polymers and pH-sensitive dyes as indicators has attracted widespread attention. In the present study, an antioxidant and amine-response color indicator film was developed by incorporating bilirubin (BIL) into the κ-carrageenan (Carr) matrix. RESULTS: It was found that the introduction of BIL had no effect on the crystal/chemical structure, water sensitivity and mechanical performance of the Carr-based films. However, the barrier properties to light and the thermal stability were significantly improved after the addition BIL. The Carr/BIL composite films exhibited excellent 1,1-diphenyl-2-picryl-hydrazyl (i.e. DPPH)/2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (i.e. ABTS) free radical scavenging abilities and color responsiveness to different concentrations of ammonia. The application assay reflected that the Carr/BIL0.0075 film was effective in delaying the oxidative deterioration of shrimp during storage and realizing the color response of its freshness through the change of b* value. CONCLUSION: Active and smart packaging films were successfully prepared by incorporating different contents of BIL into the Carr matrix. The present study helps to further encourage the design and development of a multi-functional packaging material. © 2023 Society of Chemical Industry.

Changes in morphological and structural characteristics of high amylose maize starch in alkaline solution at different temperatures.

In this study, high amylose maize starch(HAMS)was treated by Hydrothermal-alkali. SEM, SAXS, XRD, FTIR, LC-Raman, 13C CP/MAS NMR, GPC and TGA were used to study the changes in the granules and structure of HAMS. The results show that the granule morphology, lamellar structure, and birefringence of HAMS remained intact at 30 °C and 45 °C. With increasing temperature, the starch granules are fragmented, and the crystallinity, DD, FWHM values, molecular weight, and thermal stability of HAMS decrease. The double helical structure dissociated, and the content of amorphous regions increased, indicating the from order to the disorder of the HAMS structure. A similar annealing behavior occurred in HAMS at 45 °C, with the rearrangement of amylose and amylopectin occurring. At 75 °C and 90 °C, the short-chain starch produced by chain breakage regroups to form an ordered double helix structure. In general, the granule structure level of HAMS was damaged to different degrees at varying temperatures. HAMS showed gelatinization behavior in alkaline solutions when the temperature is 60 °C. This study expects to provide a model for the gelatinization theory of HAMS systems.

Influence pathways of nanocrystalline cellulose on the digestibility of corn starch: Gelatinization, structural properties, and α-amylase activity perspective.

This work focused on the pathways by which NCC regulated the digestibility of corn starch. The addition of NCC changed the viscosity of the starch during pasting, improved the rheological properties and short-range order of the starch gel, and finally formed a compact, ordered, and stable gel structure. In this respect, NCC affected the digestion process by changing the properties of the substrate, which reduced the degree and rate of starch digestion. Moreover, NCC induced changes in the intrinsic fluorescence, secondary conformation, and hydrophobicity of α-amylase, which lowered its activity. Molecular simulation analyses suggested that NCC bonded with amino acid residues (Trp 58, Trp 59, and Tyr 62) at the active site entrance via hydrogen bonding and van der Waals forces. In conclusion, NCC decreased CS digestibility by modifying the gelatinization and structural properties of starch and inhibiting α-amylase activity. This study provides new insights into the mechanisms by which NCC regulates starch digestibility, which could be beneficial for the development of functional foods to tackle type 2 diabetes.

Self-assembly and interaction mechanisms of edible dock protein and flavonoids regulated by the phenolic hydroxyl position.

In this study, chrysin (Chr), baicalein (Bai), apigenin (Api) and galangin (Gal) were selected as the representative flavonoids with different position of phenolic hydroxyl groups, and edible dock protein (EDP) was used as a material to construct delivery system. Subsequently, the molecular interactions and functional properties of flavonoids-loaded EDP nanomicelles were investigated. Results exhibited that hydrogen bond, hydrophobic interaction and van der Waals force were the main driving forces for self-assembly of flavonoids and EDP molecules. Meanwhile, this self-assembly remarkably enhance the storage and digestion stability of flavonoid compounds. Among four flavonoids, the order of loading ability was: Api > Gal > Bai > Chr. Herein, Api had a largest loading capacity (6.74%) because of its active phenolic hydroxyl group in ring B. These results suggested that the position of phenolic hydroxyl groups in flavonoids is a key factor to regulate its self-assembly with protein molecules.

Multiscale structure and precipitation mechanism of debranched starch precipitated by different alcohols.

Alcohol solution is a cheap, simple, and effective precipitating solvent frequently used for separating debranched starch (DBS), yet little is known about the precipitation mechanism of DBS by different alcohols. This study precipitated DBS from pullulanase-hydrolyzed starch using ethanol, n-butanol, and isopentanol. The multiscale structures of DBS were characterized, including chain length, single/double helix, and crystalline. The chain conformation and precipitation mechanism of DBS in different alcohols was investigated using molecular dynamics (MD) simulation. DBS precipitated by n-butanol contained the largest proportion of short chain (DP6-24, 83.2 %), the highest V-type crystallinity (21.1 %), and the largest single-helix content (24.7 %). A single helix conformation of DBS chain was determined in alcohols, where alcohol molecules entered the helix cavity. Intra/inter-molecular hydrogen bonds stabilized the helix, with a large number of hydrogen bonds leading to strong molecular interaction and stable helical structure. The solvent accessible surface area of DBS chain decreased by 7.88-19.32 % in alcohols, and the radial distribution function revealed that the first solvent layer of DBS chain at 0.29 nm was closely related to hydrogen bonding. This study provides a basis for the choice of precipitation solvent for preparing DBS with different chain lengths and physicochemical properties.