Heat-induced Formation Research Articles

Effect of electron irradiation on the gel properties of Collichthys lucidus surimi

This study evaluated the effect of electron irradiation on the gel properties of Collichthys lucidus surimi. The results showed that irradiation decreased the trichloroacetic acid-soluble peptide content of the surimi gel. At 5kGy, a more compact and ordered gel network structure was achieved, resulting in a higher gel strength, whiteness, and water-holding capacity than non-irradiated surimi gel. During heat-induced formation of the gel, the α-helix content decreased, whilst the β-sheet and β-turn content increased. Irradiation treatments also decreased the α-helix content and increased β-sheet content, and this transformation is beneficial for the protein denaturation and gel formation. Collectively, the results suggest that electron irradiation, at an optimal dose of 5kGy, could be an effective method for application in the surimi manufacturing industry

Influence of pH and ionic strength on heat-induced formation and rheological properties of cottonseed protein gels

The influence of pH and ionic strength on gel formation and gel properties of cottonseed protein isolation (CPI) was studied using dynamic oscillatory rheometer, differential scanning calorimeter (DSC), and scanning electron microscopy (SEM). The gelation temperature was influenced by ionic strength; salt had a stabilization effect, which inhibited CPI denaturation at higher salt concentrations resulting in higher gelling points. The strongest gel stiffness was made with 0.2M NaCl. The pH also altered the denaturation temperature of the CPI; higher pH values resulted in higher denaturation temperatures. Maximum gel stiffness occurred at pH 3.8 in 0.5M NaCl; higher or lower pH values resulted in reduced gel stiffness. The pH and NaCl also played a major role in the structure of gel networks formed by CPI. Lower pH and higher salt concentrations resulted in dense networks. These results are helpful to improve understanding of cottonseed protein, to control aggregation behavior, to improve the quality of cottonseed protein products, and to provide a theoretical base for its development and utilization.

アガロース・ポリアクリルアミド混合ゲルを用いたラクトフェリンの加熱変性に伴う構造変化の解析

アガロース・ポリアクリルアミド混合ゲルを用いたラクトフェリンの加熱変性に伴う構造変化の解析

Heat-induced formation of one-dimensional coordination polymers on Au(111): an STM study.

The formation of one-dimensional coordination polymers of cyano-substituted porphyrin derivatives on Au(111) induced by thermal annealing is demonstrated by means of scanning tunnelling microscopy. The polymer is stabilised by an unusual threefold coordination motif mediated between an Au atom and the cyano groups of the porphyrin derivatives.

Heat-induced formation of myosin oligomer-soluble filament complex in high-salt solution

Heat-induced aggregation of myosin into an elastic gel plays an important role in the water-holding capacity and texture of meat products. Here, we investigated thermal aggregation of porcine myosin in high-salt solution over a wide temperature range by dynamic light scattering experiments. The myosin samples were readily dissolved in 1.0M NaCl at 25°C followed by dilution into various salt concentrations. The diluted solutions consistently contained both myosin monomers and soluble filaments. The filament size decreased with increasing salt concentration and temperature. High temperatures above Tm led to at least partial dissociation of soluble filaments and thermal unfolding, resulting in the formation of soluble oligomers and binding to the persistently present soluble filaments. Such a complex formation between the oligomers and filaments has never been observed. Our results provide new insight into the heat-induced myosin gelation in high-salt solution.

Effect of heat-induced formation of rice bran protein fibrils on morphological structure and physicochemical properties in solutions and gels

The effects of heat-induced rice bran protein (RBP) fibrils on structure and properties of solutions and gels in a complex system were investigated using transmission electron microscopy (TEM), atomic force microscopy (AFM), Congo red spectral analysis, and circular dichroism (CD). Planar and 3-dimensional images of RBP fibrils all revealed structural details. A Congo red spectral shift indicated fibril formation. Fibril secondary structural components exhibited differences at pH 2.0 and pH 7.0. The β-type was decreased with an increased pH. Rheological results exhibited shear thinning behavior for all solutions. Addition of fibrils to RBP solutions, which made the system complex, resulted in an order of magnitude increase in viscosity and shear stress. Adding fibrils to RBP solutions accelerated the kinetics of gel formation, resulting in an increase in gel strength. Scanning electron microscopy (SEM) images showed gel network structural differences with and without fibrils at different pH values.

Heat-induced formation of porous and free-standing MoS2/GS hybrid electrodes for binder-free and ultralong-life lithium ion batteries

Flexible and free-standing MoS2/GS films are constructed for the first time based on a novel heat-induced formation process, during which self-generated gaseous species successfully trigger the formation of porous structure, without the assistance of any templates or spacers. Graphene forms an open porous network, with few-layered MoS2 uniformly grown on the surface of GS. The fascinating structure provides several attractive features as anode material, including efficient ion transport, high conductivity and good structure durability. When used as free-standing and binder-free electrodes for lithium-ion batteries, the optimized hybrid film with graphene content of 32% exhibits superior rate capability (994, 880, and 598mAhg−1 at 0.5, 1, and 5Ag−1, respectively) and outstanding cycling performance at high rates (retaining 100.6% of the initial capacity after 1000 cycles at 1000mAg−1). Importantly, the electrochemical reaction kinetics and interfacial behavior of the hybrid electrode are also in-depth investigated by EIS and morphological study. The work described here can be extended to prepare various porous graphene-based hybrid films, for the application in a broad range of LIBs, electrochemical capacitors, sensors, and catalysts.

Influence of sulphate, chloride, and thiocyanate salts on formation of β-lactoglobulin–pectin microgels

Effects of sulphate, chloride, and thiocyanate salts on the heat-induced formation of protein-based microgels from β-lactoglobulin–pectin complexes were determined as a function of pH and protein-to-polysaccharide ratio. Aggregation temperatures were initially decreased at low ionic strength due to shielding of electrostatic interactions between β-lactoglobulin and pectin but increased with further increases in ionic strength. Turbidity of heated mixtures and associated sizes of formed microgels were increased with up to 75mmolkg−1 ionic strength. Aggregation and microgel formation were relatively increased in the presence of thiocyanate salts compared to chloride salts and relatively decreased in the presence of sulphate salts, indicating that the inverse Hofmeister series was relevant in this system. Topographical analysis of dried microgels by atomic force microscopy verified that microgels were smallest in the presence of sulphate salts and showed that added ions, particularly thiocyanate, increased the deformability of microgels during drying.

5-Hydroxymethyl-2-Furfural (HMF) – Heat-Induced Formation, Occurrence in Food and Biotransformation - a Review

The chemical structure of 5-hydroxymethyl-2-furfural (HMF), its physicochemical properties and reactions that lead to the synthesis of HMF were discussed. Special attention was paid to HMF formation in food during processing. The potential applications of this compound in industry were described as well. Moreover, this review outlines the most important sources of HMF in human diet and estimates the potential daily intake of HMF by consumers. The known and suggested metabolic pathways, as well as the impact of HMF and its metabolites on human health are also discussed.

Heat-induced formation of nitrogen oxides in water

It was found by the fluorimetric method using 2,3-diaminonaphthalene that moderate heating of water (60-80°C, for up to 4h) leads to the fixation of atmospheric nitrogen with the formation of nitrite. The kinetic parameters of this process were determined. The energy of activation of [Formula: see text]formation was estimated to be 139kJ/mol. It was found that the amount of nitrite formed depends on the concentration of dissolved oxygen and nitrogen. It was shown by two independent methods (Griess reagent/VCl3 and 2,3-diaminonaphthalene/nitrate reductase) that heating of water (80°C, 1h) results in the formation of nitrate; with the use of the fluorescent probe dihydrorhodamine 123, the generation of nitrogen dioxide (peroxynitrite) was revealed. Nitrite, nitrate, and nitrogen dioxide are formed in water upon heating in approximately equal amounts. A scheme of reactions proceeding with bidistilled water by the action of heat with the formation of nitrogen oxides is proposed.

Assessment of leaching characteristics of heavy metals from industrial leach waste

Leaching of valuable metals from residues generated by pyrometallurgical or hydrometallurgical process usually results in a large amount of wastes. In the present study, the leaching behavior of the zinc leach waste was investigated by utilizing a regression model with dummy variables. The results of different leaching methods indicate that addition of fly ash and blast furnace slag to the zinc leach waste reduces the heavy metal content in the effluent and that fly ash performs better than blast furnace slag. The results of thermal treatment showed that the zinc leach waste cannot be disposed of in the present form. The metal release from the zinc leach waste decreased in relation to increasing treatment temperature. Metal releases for residues treated at 1000–1200°C decreased because of heat-induced formation of a glassy matrix. The levels of Zn, Pb and Mn released for 1200°C treatment temperature were 1.05, 0.08, 0.07mg/l, respectively. Therefore an immobilization treatment is necessary prior to disposal.

Impact of lipid oxidation-derived aldehydes and ascorbic acid on the antioxidant activity of model melanoidins

As the heat-induced formation of antioxidants throughout the Maillard reaction is known, this study was undertaken to evaluate the impact of lipid oxidation-derived aldehydes and ascorbic acid in Maillard model systems on the resulting antioxidant activity. For this purpose, various fractions of melanoidin-like polycondensation products were obtained from mixtures of amino acids (glycine, lysine, arginine) and lipid oxidation-derived aldehydes (hexanal, (E)-2-hexenal), in the presence or absence of glucose or ascorbic acid. All fractions showed a significant radical scavenging capacity (DPPH assay) and ferric reducing power (FRAP assay). The activity varied according to the composition of the model system tested, although some similar trends were discovered in both assays applied. The presence of lipid oxidation products in the browning products augmented the antioxidant activity in specific cases. For instance, the combined presence of arginine, hexanal and glucose in heated model systems resulted in a significantly higher antioxidant capacity. With an exception of ascorbic acid-containing model systems, melanoidin-like polycondensation products possessed significantly stronger antioxidant activities than the corresponding unheated initial reactant mixtures. Water-soluble high molecular weight (>12kDa) and nonsoluble fractions comprised the major part of the antioxidants derived from amino acid/lipid oxidation product model systems, with or without glucose or ascorbic acid.

Heat-Induced Formation of Single Giant Unilamellar Vesicles

Giant unilamellar vesicles (GUVs) are an excellent model system for the investigation of lipid membranes, the study of membrane proteins and ion channels in a biomimetic environment, and in the creation of artificial cells. Here, we describe a novel method for the preparation of GUVs from single multilamellar liposomes by means of directed infrared laser heating. Our method generates individual unilamellar vesicles at selected locations, not only from natural and artificial lipid mixtures containing negatively charged lipids, but also from preparations of single lipids, such as neutral phosphatidylethanolamine. The presented method provides a new efficient resource for giant vesicle research and offers an alternative to the electroformation and de/rehydration techniques.

Heat-induced formation of single giant unilamellar vesicles

Giant unilamellar vesicles (GUVs) are an excellent model system for the investigation of lipid membranes, the study of membrane proteins and ion channels in a biomimetic environment, and in the creation of artificial cells. Here, we describe a novel method for the preparation of GUVs from single multilamellar liposomes by means of directed infrared laser heating. Our method generates individual unilamellar vesicles at selected locations, not only from natural and artificial lipid mixtures containing negatively charged lipids, but also from preparations of single lipids, such as neutral phosphatidylethanolamine. The presented method provides a new efficient resource for giant vesicle research and offers an alternative to the electroformation and de/rehydration techniques.

Heat-Induced Formation of Monodisperse Gold Nanoparticles in Different Conditions

We investigate the preparation of nearly monodisperse gold nanoparticles by heat treatment in different conditions. The effects of various solvents, heating temperature, and heating time length on the monodispersity of gold nanoparticles were studied systematically and a general route to generate gold nanoparticles with uniform size was determined. The first step was to prepare gold nanoparticles with less than 3 nm and the following operation was to heat the gold nanoparticles in the present of thiolated solvents where monodispersed gold nanoparticles could be obtained easily. Our approach has enriched synthesis of monodisperse gold nanoparticles, and may provide some valuable experimental data about how the heating process affects the size evolution of gold nanoparticles.

Heat-induced darkening and spectral broadening in photodarkened ytterbium-doped fiber under thermal cycling

We study thermal bleaching of photodarkening-induced loss in a 20-microm core diameter, large-mode-area ytterbium-doped silica fiber. Pristine and photodarkened samples are subjected to thermal cycling pulses. Recovery of the photodarkened fiber absorption coefficient initiates at approximately 350 degrees C and complete recovery is reached at approximately 625 degrees C. However, prior to recovery, the photodarkened fiber exhibits further heat-induced increase of absorption loss. This increase of loss is attributed to both a permanent increase of loss-inducing color centers and a temperature-dependent broadening of the absorption spectrum. Post-irradiation heat-induced formation of color centers suggests the presence of an intermediate energy state in the near-infrared photochemical mechanism for photodarkening.

The heat-induced γ-H2AX response does not play a role in hyperthermic cell killing

Purpose: The goal of this study was to determine whether the heat-induced formation of γ-H2AX foci is involved in hyperthermic cell killing.Materials and methods: The heat-induced γ-H2AX response was determined in cells exhibiting various degrees of heat sensitivity. The panel of cells tested included cells that are transiently thermotolerant, permanently heat resistant, permanently heat sensitive, and permanently resistant to oxidative stress. Cells exposed to non-thermal environmental conditions that lead to protection from, or sensitization to, heat were also tested. The heat sensitivity of cells in which H2AX was knocked out was also ascertained.Results: The protein synthesis independent state of thermotolerance, but not the protein synthesis dependent state of thermotolerance, was found to be involved in the attenuation of the γ-H2AX response in thermotolerant cells. The initial magnitude of the γ-H2AX response was found to be the same in all cell lines with altered heat sensitivity. Furthermore, no differences in the resolution of γ-H2AX foci were found among the cell lines tested. We also found that H2AX knock-out cells were not more heat sensitive.Conclusions: We conclude that the heat-induced γ-H2AX response does not play a role in heat-induced cell killing, thereby adding further evidence that the heat-induced γ-H2AX foci are not due to DNA double strand breaks.

Selective Substrate Supply in the Regulation of Yeast de Novo Sphingolipid Synthesis

The heat stress response of Saccharomyces cerevisiae is characterized by transient cell cycle arrest, altered gene expression, degradation of nutrient permeases, trehalose accumulation, and translation initiation of heat shock proteins. Importantly heat stress also induces de novo sphingolipid synthesis upon which many of these subprograms of the heat stress response depend. Despite extensive data addressing the roles for sphingolipids in heat stress, the mechanism(s) by which heat induces sphingolipid synthesis remains unknown. This study was undertaken to determine the events and/or factors required for heat stress-induced sphingolipid synthesis. Data presented indicate that heat does not directly alter the in vitro activity of serine palmitoyltransferase (SPT), the enzyme responsible for initiating de novo sphingolipid synthesis. Moreover deletion of the small peptide Tsc3p, which is thought to maximize SPT activity, specifically reduced production of C(20) sphingolipid species by over 70% but did not significantly decrease overall sphingoid base production. In contrast, the fatty-acid synthase inhibitor cerulenin nearly completely blocked sphingoid base production after heat, indicating a requirement for endogenous fatty acids for heat-mediated sphingoid base synthesis. Consistent with this, genetic studies show that fatty acid import does not contribute to heat-induced de novo synthesis under normal conditions. Interestingly the absence of medium serine also ameliorated heat-induced sphingoid base production, indicating a requirement for exogenous serine for the response, and consistent with this finding, disruption of synthesis of endogenous serine did not affect heat-induced sphingolipid synthesis. Serine uptake assays indicated that heat increased serine uptake from medium by 100% during the first 10 min of heat stress. Moreover treatments that increase serine uptake in the absence of heat including acute medium acidification and glucose treatment also enhanced de novo sphingoid base synthesis equivalent to that induced by heat stress. These data agree with findings from mammalian systems that availability of substrates is a key determinant of flux through sphingolipid synthesis. Moreover data presented here indicate that SPT activity can be driven by several factors that increase serine uptake in the absence of heat. These findings may provide insights into the many systems in which de novo synthesis is increased in the absence of elevated in vitro SPT activity.

Heat-induced formation of ordered structures of ovalbumin at low ionic strength studied by small angle X-ray scattering

Small angle X-ray scattering (SAXS) has been performed on native ovalbumin solutions and heated ovalbumin systems at neutral pH and low ionic strength. In native ovalbumin solutions there is a partial ordering, where the interparticle distance ( d max) scales with the protein concentration ( C) as d max ∼ C −0.28. This exponent indicates that the ovalbumin monomers behave as a uniform distribution of charged spheres in solution. The q-dependent scattering intensity of ovalbumin aggregates can be well described by a form factor of rods. The dependence of d max for aggregates on the protein concentration was found to be d max ∼ C −0.51, this scaling behavior is in good agreement with that theoretically derived for the distribution of spaces in a random network of straight fibers. The existence of a well-defined interparticle distance between aggregates is confirmed by cryo-TEM. The scattering profiles of native and aggregated ovalbumin were successfully fitted including both form factor and structure factor, using the preferred distance ( L), a measure of disorder ( σ/ L), and the radius ( R or a) as fitting parameters.

Structural characterization of CdS nanoparticles grown in polystyrene matrix by thermolytic synthesis

Cadmium sulfide nanoparticles embedded in a polystyrene matrix (CdS/PS) were successfully prepared by in situ thermolysis of a cadmium thiolate precursor dispersed in the polymer. The heat-induced formation of cadmium sulfide was studied by thermogravimetric analysis and differential thermal analysis, while the chemistry of the reaction forming the CdS/PS compound was investigated by nuclear magnetic resonance and X-ray photoelectron spectroscopy. The structural characterization was performed by X-ray diffraction and transmission electron microscopy. The CdS nanocrystals are single crystals of cubic phase (zincblende structure) of spherical shape. The average diameter of the nanocrystals embedded in the polystyrene matrix achieved by our synthesis process is as small as 2.5±0.5 nm. Room temperature UV–VIS absorption spectra exhibit a shoulder at 412 nm that is consistent with the presence of CdS nanocrystals of ∅≈2 nm. The role of the polymer on the nanoparticle growth was also discussed.