Rheological properties of Uzbekistan wheat gluten as a function of disulfide and h-bond contents during conditioning

Rheological properties of wheat gluten as a function of the presence of free sulfhydryls and disulfide bonds in addition to their ratio during various conditioning regimes were studied. It was shown that coagulation of the gluten as the temperature increased was accompanied by a decrease in the number of free sulfhydryls and an increase in the number of rheologically active disulfide bonds. Changes occurring in the gliadin and glutenin fractions during various conditioning regimes were seen using IR spectroscopy. It was found that the relative strength of absorption bands due to H-bonds increased as the treatment temperature was raised above 60°C. Significant changes in the protein molecule structure that caused substantial changes in its rheological properties because of thiol–disulfide exchange reactions and H-bond strength occurred during the conditioning.     

Edible wheat gluten (WG) protein films

Commercial wheat gluten (WG) films, hard wheat gluten films and soft wheat gluten films, plasticized with glycerol have been cast from water–ethanol solutions. The effect of aging on various film properties has been investigated. The films were aged for about 6 months at 50% relative humidity and ~25 °C, and the mechanical (tensile strength and the percentage of elongation at break (E _b)), thermal (TG and DSC) and Attenuated Total Reflectance (ATR)-FTIR spectral properties have been studied. Changes in the protein structure were determined by ATR-FTIR spectroscopy. Films from soft WG exhibited the highest E _b (508%) and the highest TS (6.33 MPa). The TG analysis results show that the moisture content in all three kinds of WG protein films is about 5%. The absence of the glycerol phase transition in DSC curves implies that there is no separate phase containing glycerol in the WG protein-glycerol films with 40% glycerol.     

Preparation of nano-sized LiCoO2 powder by the combination of sonication and modified Pechini process

A sonication (ultrasonic processing) and modified Pechini process were combined to fabricate nano-sized LiCoO₂ powder. A composition of precursor solution for fabricating LiCoO₂ was modulated by controlling the molar ratios of lithium acetate to cobalt acetate and ethylene glycol to citric acid, respectively. The sonication was applied on the precursor solution to get highly dispersed transition-metal oxide powder. The sonicated precursor gels pre-dried were calcined in the range of 400 to 800 °C for 10 h. Effect of sonication on the particle size and the morphology of LiCoO₂ prepared by the modified Pechini process was elucidated. After calcination, the unsonicated LiCoO₂ powder had an aggregated-like morphology, as combined loosely and/or firmly, while the sonicated LiCoO₂ was more ultra-finely particulated and presented more mono-dispersed morphology without severe aggregation. The nano-sized LiCoO₂ with high crystallinity and homogeneity could be prepared by the combination of sonication and modified Pechini process.     

PDI-Regulated Disulfide Bond Formation in Protein Folding and Biomolecular Assembly

Disulfide bonds play a pivotal role in maintaining the natural structures of proteins to ensure their performance of normal biological functions. Moreover, biological molecular assembly, such as the gluten network, is also largely dependent on the intermolecular crosslinking via disulfide bonds. In eukaryotes, the formation and rearrangement of most intra- and intermolecular disulfide bonds in the endoplasmic reticulum (ER) are mediated by protein disulfide isomerases (PDIs), which consist of multiple thioredoxin-like domains. These domains assist correct folding of proteins, as well as effectively prevent the aggregation of misfolded ones. Protein misfolding often leads to the formation of pathological protein aggregations that cause many diseases. On the other hand, glutenin aggregation and subsequent crosslinking are required for the formation of a rheologically dominating gluten network. Herein, the mechanism of PDI-regulated disulfide bond formation is important for understanding not only protein folding and associated diseases, but also the formation of functional biomolecular assembly. This review systematically illustrated the process of human protein disulfide isomerase (hPDI) mediated disulfide bond formation and complemented this with the current mechanism of wheat protein disulfide isomerase (wPDI) catalyzed formation of gluten networks.     

Preparation and properties of wheat gluten/silica composites

Wheat gluten (WG)/silica (SiO₂) hybrids were prepared through in-situ synthesis of SiO₂ in WG dispersion of aqueous ammonia. The hybrids with different SiO₂ contents were mixed with glycerol plasticizer to form cohesive dough and the dough was compressively molded to form cross-linked sheets. Morphology, moisture absorption, protein solubility in water, tensile mechanical properties and dynamic rheological behavior of the WG/SiO₂ composites were investigated in relation to SiO₂ contents. Supported by the National Natural Science Foundation of China (Grant No. 50773068) and Natural Science Foundation of Zhejiang Province (Grant No. Y407011)     

Bulk plastic materials obtained from processing raw powders of renewable natural polymers via back pressure equal channel angular consolidation (BP-ECAC)

Renewable natural polymers wheat starch (WS) and wheat gluten (WG) were successfully processed into plastic bulk materials using back pressure equal channel angular consolidation (BP-ECAC) without using any additional plasticizers at relatively low temperatures. The strong shear deformation occurred during the process caused an effective deformation of WS or WG granular structures and resulted in an efficient gelatinization of starch or plasticization of gluten with the natural moisture content. Sufficient chain entanglement was formed in both WS and WG materials for achieving strong cohesion among the macromolecule matrixes. The mechanical strength of the obtained plastic materials was comparable to that of conventional polymers but stronger than the strength of thermoplastic WS or plasticized WG. The processing temperature played an important role in determination of morphologies and properties of the plastic materials. Increasing processing temperature would cause more effective gelatinization or plasticization of the natural polymers, enhance the interactions among different components in the systems, and form materials with improved mechanical properties. Thermal cross-linking might play a positive role in the improvement of mechanical properties when processing temperature was increased. However, thermal decomposition could also occur under such severe shearing especially at high temperatures. The optimum temperature for conducting such process was around 100-120 °C for WS and WG. The BP-ECAC method provides a potential to manufacture natural polymer based plastic materials efficiently on an industrial scale for various applications.     

Effect of different preparation methods on mechanical behaviors of carbon fiber-reinforced PEEK-Titanium hybrid laminates

This paper aims to investigate the mechanical behaviors of carbon fiber-reinforced PEEK-Titanium hybrid laminates (TiGr) prepared by different surface treatment conditions using silane coupling agent. In order to improve the bonding performance between the titanium sheets and PEEK, the titanium layers were subjected to sandblasting roughening and silanization treatment, the curing process was explored by setting different concentrations of silane coupling agent, curing temperatures and curing times. The optimum parameters of the process were determined by analyzing the mechanical properties of the laminates, which are 10% of SCA concentration, 130 °C of curing temperature and 1 h of curing time, and the corresponding tensile, bending and inter-laminar shearing strengths are 837, 1071 and 75 MPa, respectively. The surface composition, structures and chemical bonding of the modified titanium sheet were analyzed through Scanning Electronic Microscope (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). It was evidenced that the optimal process could produce a relatively complete and uniformed silane film compared to other cases. In addition, the results show that the Si–O–Ti covalent bonds were formed, which demonstrated that the preparation of the laminates through silane coupling agent is reliable.     

Preparation and properties of wheat gluten/rice protein composites plasticized with glycerol

Environment friendly thermosetting composites were prepared by blending wheat gluten(WG) and rice protein (RP) at different weight ratios with glycerol as plasticizer followed by compression molding the mixture at 120℃to crosslink the proteins.Reducing agent of sodium bisulfate and sodium sulfite and crosslinking agent formaldehyde were used to adjust the properties of the composites.Morphology,moisture absorption and tensile properties were evaluated.The results showed that formaldehyde could increase t...     

Secreted fungal sulfhydryl oxidases: sequence analysis and characterisation of a representative flavin-dependent enzyme from <Emphasis Type="Italic">Aspergillus oryzae</Emphasis>

Background  

Sulfhydryl oxidases are flavin-dependent enzymes that catalyse the formation of de novo disulfide bonds from free thiol groups, with the reduction of molecular oxygen to hydrogen peroxide. Sulfhydryl oxidases have been investigated in the food industry to remove the burnt flavour of ultraheat-treated milk and are currently studied as potential crosslinking enzymes, aiming at strengthening wheat dough and improving the overall bread quality.     

The colloidal stability of raw bentonite deformed mechanically by ultrasound

The present study examined the effect of sonication time on the particle–size and the colloidal stability (i.e. point of zero charge, PZC and zeta potential, ζ) of raw bentonite (RB) from Saudi Arabia. In this study, bentonite suspensions were sonicated for various time intervals (30, 60 and 120 min). The effect of sonication time on specific surface area and the colloidal stability behavior of bentonite at various pH and in presence of different NaCl concentration were investigated. The increased in lightness and brightness of bentonite suspension was observed during sonication experiment which could be attributed to the reduction in the particles size.With increasing sonication time the specific surface area increased and consequently the zeta potential of bentonite suspension increased. Also a shifting in the PZC from pH 3 for raw bentonite to pH 2 after 120 min of sonication.The zeta potential of sonicated bentonite suspension in presence of different concentration of NaCl shows unusual trend compared to the unsonicated bentonite. In conclusion, the stability of raw bentonite suspension was significantly modified due the application of ultrasound with rending the particle-size of the bentonite.     

A novel electrochemical method for efficient reduction of disulfide bonds in peptides and proteins prior to MS detection

A novel electrochemical (EC) method for fast and efficient reduction of the disulfide bonds in proteins and peptides is presented. The method does not use any chemical agents and is purely instrumental. To demonstrate the performance of the EC reactor cell online with electrospray mass spectrometry, insulin and somatostatin were used as model compounds. Efficient reduction is achieved in continuous infusion mode using an EC reactor cell with a titanium-based working electrode. Under optimized conditions, the presented method shows almost complete reduction of insulin and somatostatin. The method does not require any special sample preparation, and the EC reactor cell makes it suitable for automation. Online EC reduction followed by collision-induced dissociation fragmentation of somatostatin showed more backbone cleavages and improved sequence coverage. By adjusting the settings, the EC reaction efficiency was gradually changed from partial to full disulfide bonds reduction in α-lactalbumin, and the expected shift in charge state distribution has been demonstrated. The reduction can be controlled by adjusting the square-wave pulse, flow rate or mobile phase composition. We have shown the successful use of an EC reactor cell for fast and efficient reduction of disulfide bonds for online mass spectrometry of proteins and peptides. The possibility of online and gradual disulfide bond reduction adds a unique dimension to characterization of disulfide bonds in mid- and top-down proteomics applications.

PP/PP-g-MAH与铝板粘接界面相的XPS研究

用X射线光电子能谱(XPS)研究铝板/聚丙烯层状复合材料的粘接界面相，提出了粘接界面的化学反应机制.研究发现,聚丙烯(PP)中加入马来酸酐接枝聚丙烯(PP-g-MAH)时，铝板面上Al 2p、O 1s谱线明显向高结合能端移动，表明PP-g-MAH与铝板表面发生了化学反应，形成Al－O－C配位键.配位键的形成使界面粘接强度明显提高. PP中不含PP-g-MAH时，铝板面上Al 2p、O 1s谱线处于低结合能端，聚丙烯未与铝板表面形成化学配位作用.     

聚甲基丙烯酸甲酯/石墨薄片纳米复合及其导电性能研究

在聚合物绝缘材料基体中添加入足够数量的导电填料 ,聚合物便具有导电性或半导体性能 .石墨材料 ,由于资源丰富、价廉、性质稳定 ,被广泛用作导电聚合物复合材料的填料 .一般 ,填料含量越高 ,复合材料的导电性能越好 ,但是材料的力学性能也随之劣化 ,特别是材料脆性增加 .将石墨加工成纳米级粒子 ,再与聚合物纳米复合 ,有望用较少的石墨填充量使复合材料具有良好的电传导性能 ,从而保持材料的力学性能 .最近报道的利用膨胀石墨与聚合物实现纳米复合的研究引起了人们的兴趣 ,如所报道的尼龙 6 膨胀石墨[1] 、PS PMMA 膨胀石墨[2 ] 、PP …     

Influence of Glycerol Content on Properties of Wheat Gluten/Hydroxyethyl Cellulose Biocomposites

Environmentally friendly biocomposites were prepared by blending wheat gluten（WG）as a matrix, hydroxyethyl cellulose（HEC）as a filler,and glycerol as a plasticizer,followed by thermo-molding of the mixture at 120°C for crosslinking the matrix.Moisture absorption,tensile properties,dynamic mechanical analysis,and dynamic rheology were evaluated in relation to the glycerol content.Tensile strength and modulus drop dramatically with increasing glycerol content,which is accompanied by significant depression in the glass transition temperature and improvement in the extensibility of the biocomposites.     

Structure and properties of composites compression‐molded from silk fibroin powder and waterborne polyurethane

The degummed silk filament was pulverized with a home‐made machine to obtain the silk fibroin (SF) powder with the diameter of around 3 µm. The resulting SF powder was blended with waterborne polyurethane (WPU) aqueous dispersion, and then was dried and compression‐molded to prepare novel blended materials with improved miscibility and mechanical properties. WPU acted as a plasticizer and one of the components for the blends during the compression‐molded process. The structure, morphology, and properties of the blended films were investigated. The results indicated that β‐sheet of SF existed in the blended films. The SEM images showed that the cross‐section of the blended films exhibited an overall homogeneous morphology. Furthermore, the transmission electron microscope observation exhibited that some sphere‐like SF particles were well dispersed in the WPU matrix. The hydrogen bond interaction between SF and WPU in the blended films led to an increase of the glass transition temperature for the soft segment of WPU in the blended films. The blended films showed an improved Young's modulus and tensile strength from 1.2 to 288.9 MPa and 0.3 to 16.5 MPa, respectively, with the increasing of SF up to a content of 70 wt%. The hydrogen‐bonding interactions existing in SF and WPU and compression molding method played the important role in improving the miscibility and mechanical properties of the blended films. Copyright © 2011 John Wiley & Sons, Ltd.     

Self‐healing polyurethane based on disulfide bond and hydrogen bond

Tough and transparent polyurethane networks with self‐healing capability at mild temperature conditions were successfully prepared in a 1‐pot procedure. The self‐healing ability of synthesized polyurethane comes from the covalent disulfide metathesis and non‐covalent H‐bonding. The mechanical testing indicates that disulfide metathesis reforms the covalent bonds on a longer time scale, while H‐bonding gives rise to a healing efficiency of around 46% in the early healing processing. The compromise between mechanical performance and healing capability is reached by tailoring the concentration of disulfide. The tensile strength of the sample with 100% self‐heal efficiency can get to 5.01 MPa, which can be explained by higher mobility of polymer chain under ambient temperature from creep testing.     

Preparation and properties of gluten/calcium carbonate composites

Environment friendly thermosetting composites were prepared by blending wheat gluten （WG） as matrix, calcium carbonate （CaCO3） as filler and glycerol as plasticizer followed by compression molding the mixture at 120 ℃ to crosslink the WG matrix. Morphology observation showed that the CaCO3 particles were finely dispersed in matrix. Incorporation of CaCO3 up to 10 wt% into the composites caused Young＇s modulus and tensile strength to increase markedly. On the other hand, the moisture absorption and elongation at break decreased slightly.     

A new bio-based nanocomposite: fibrillated TEMPO-oxidized celluloses in hydroxypropylcellulose matrix

Utilization of TEMPO-oxidized celluloses in bio-based nanocomposites is reported for the first time. TEMPO-oxidized wood pulps (net carboxylate content 1.1 mmol/g cellulose) were fibrillated to varying degrees using a high intensity ultrasonic processor. The degree of fibrillation was controlled by varying sonication time from 1 to 20 min. The sonication products were then characterized independently and as fillers (5 wt% loading) in hydroxypropyl cellulose nanocomposite films. Nanofibril yields ranging from 11 to 98 wt% (on fiber weight basis) were obtained over the range of sonication times used. Suspension viscosities increased initially with sonication time, peaked with gel-like behavior at 10 min of sonication and then decreased with further sonication. The thermal degradation temperature of unfibrillated oxidized pulps was only minimally affected (6 °C decrease) by the fibrillation process. Dynamic mechanical analysis of the nanocomposites revealed strong fibril-matrix interactions as evidenced by remarkable storage modulus retention at high temperatures and a suppression of matrix glass transition at “high” (~5 wt%) nanofibril loadings. Creep properties likewise exhibited significant (order of magnitude) suppression of matrix flow at high temperatures. It was also believed, based on morphologies of freeze-fracture surfaces that the nanocomposites may be characterized by high fracture toughness. Direct fracture testing will however be necessary to verify this suspicion.     

An ultrasound assisted cyclocondensation reaction for the efficient synthesis of [1]benzopyranopyrido[d]pyrimidines using porous graphene/MoO3

In this paper, we report a feasible protocol for the preparation of [1]benzopyranopyrido[d]pyrimidines via expeditious sonochemical route. The reaction efficiency was evaluated by influence of several parameters including sonication power, sonication time, different solvents, and using porous graphene/MoO₃ nanocomposite as catalyst, for the first time. The effect of the ultrasonication comparing with the conventional heating on the synthesis of the titled compounds shows that the ultrasonic irradiation is required to rich the cyclized products. The structural properties of porous graphene/MoO₃ nanocomposite were determined by Fourier transform infrared spectroscopy (FT‐IR), powder X‐ray diffractometry (XRD), scanning electron microscope (SEM), Raman spectroscopy, and also by TGA analysis. Confirmation of the structures of compounds 4a – 4h were also established with IR, ¹H NMR, and ¹³C NMR spectroscopic data and also by elemental analyses.     

Characterization of disulfide linkages and disulfide bond scrambling in recombinant human macrophage colony stimulating factor by fast-atom bombardment mass spectrometry of enzymatic digests

Fast-atom bombardment mass spectrometry was used to study disulfide bonding patterns in heat-denatured human recombinant macrophage colony stimulating factor (rhM-CSF). The heat-denaturated protein was studied by analysis of the pattern of peptides in the proteolytic digests. Native rhM-CSF is a homodimer with intramolecular disulfide linkages between Cys7–Cys90, Cys48–Cys139, and Cys102–Cys146 and intermolecular linkages between Cys31-Cys31, and the pairs Cys157 and Cys159. Brief heating for 1 min leads to partial disulfide bond scrambling. In addition to the native disulfide bonds between Cys7–Cys90, Cys48–Cys139, and Cys31-Cys31, nonnative disulfide bonds were detected between Cys48–Cys90 and Cys48–Cys102. When heated for 5 min the disulfide bonds of rhM-CSF are completely scrambled and lead to nonnative intramolecular disulfide bonds between Cys48–Cys102 and Cys90–Cys102 and one intermolecular disulfide bond between Cys102–Cys102.