Influence of a hydrothermal treatment on protein fractions of wheat

Influence of different temperature modes of a hydrothermal treatment on the protein fractions of wheat, grown in Uzbekistan, has been studied within a temperature range from 40 to 80°C. Using inversed phase and exclusion chromatography, we have revealed that hydrothermal treatment reduces the extract content and causes some changes in the ratio between high- and low-molecular components. If the treatment temperature exceeded 60°C, then, in all cases, except the glutenin fraction, the content of high-molecular components decreased, whereas the content of low-molecular components increased. The glutenin fraction was more subjected to heat influence and demonstrated a higher ability to aggregation, occurring mainly due to the component whose molecular weight was 113.42 kDa. Reduction of the number of free sulfhydryl groups in wheat gluten and its fractions in the case of a temperature increase indicates the oxidation of these groups with formation of new intermolecular disulphide bonds, which, in turn, results in the aggregation of proteins and strengthening of gluten. The obtained results agree with data of our earlier studies of gluten microstructure and fractioning during a hydrothermal treatment.     

Thermal behavior of native and hydrophobized wheat gluten, gliadin and glutenin-rich fractions by modulated DSC

The glass transition temperature (T(g)) of hydrophobized and native wheat gluten and its protein fractions, with water mass fraction from 0 to 0.2, was studied using modulated differential scanning calorimetry. The T(g) values of unplasticized products were approximately 175 degrees C whatever the treatment (hydrophobization) or the fraction tested, except for the gliadin-rich fraction (162 degrees C). Experimental change in heat capacity at the glass transition (DeltaC(p)) ranged from 0.32 to 0. 50 J/g/ degrees C depending on the gluten fractions. The Gordon-Taylor fit of T(g) evolution as a function of water content showed that glutenin-rich fractions were more sensitive to water plasticization than the gliadin-rich fraction. The Kwei equation gave better fit to experimental data and demonstrated that the water plasticization of gluten and its fractions is influenced by secondary interactions. However, the application of the Couchman-Karasz equation without fitting predicts satisfactorily the plasticization of gluten proteins by water.     

Relation between Aggregation Behavior of Glutenin and Its Polypeptide Composition

It was found in the previous studies that the quality of flour is closely related to the aggregation behavior of gluten separated from it, and that difference of aggregation behavior of gluten was mainly due to the nature of glutenin contained in it. In the present paper, aggregation behaviors of glutenins were investigated in relation to their polypeptide compositions with ten kinds of flours. Component polypeptides of glutenin were fractionated into three fractions, FI, FII and FIII, by gel filtration, and their polypeptide compositions and aggregation behaviors were investigated. The ratio of the three fractions was different among the ten glutenins, and a correlation was found between τ₁₀/C values, a parameter for aggregation reaction, of glutenins and their FI and FII contents. τ₁₀/C decreased with increasing content of FI and with decreasing content of FII. Therefore, the aggregation behavior of gluten depends at least partly on the contents of FI and FII in glutenin.     

Physicochemical properties of proteins from wheat grown under high-contrast climatic conditions

Studies using electrophoresis, gel chromatography, viscometry, and calorimetry revealed an interrelation of several physicochemical properties of proteins of soft wheat grown under conditions of cool and wet weather with rheological characteristics of gluten and dough and bread quality. The ratio of gliadin and albumin-globulin polypeptides in flour with short-tearing gluten was much lower compared to that in flour with normal gluten. Proteins from flour with short-tearing gluten, including the water-soluble and salt-soluble fraction, had a loose spatial structure. Gluten fractions of this gluten (gliadin and glutenin) were characterized by a more compact and elongated structure compared to normal gluten. As distinct from normal gluten, the conformation of protein particles in short-tearing gluten depended little on hydrophobic interactions. The results suggest that the main components of grain determine the rheological properties of short-tearing gluten.     

Physicochemical properties of proteins from wheat grown under high-contrast climatic conditions

Studies using electrophoresis, gel chromatography, viscometry, and calorimetry revealed an interrelation of several physicochemical properties of proteins of soft wheat grown under conditions of cool and wet weather with rheological characteristics of gluten and dough and bread quality. The ratio of gliadin and albumin-globulin polypeptides in flour with short-tearing gluten was much lower compared to that in flour with normal gluten. Proteins from flour with short-tearing gluten, including the water-soluble and salt-soluble fraction, had a loose spatial structure. Gluten fractions of this gluten (gliadin and glutenin) were characterized by a more compact and elongated structure compared to normal gluten. As distinct from normal gluten, the conformation of protein particles in short-tearing gluten depended little on hydrophobic interactions. The results suggest that the main components of grain determine the rheological properties of short-tearing gluten.     

Compositional Difference of Wheat Flour Glutens in Relation to Their Aggregation Behaviors

Comparison of the aggregation behavior of gluten was made by following the turbidity change of gluten suspension with four kinds of glutens prepared from flours different in flour quality. The four kinds of glutens showed different behaviors suggesting a relation to the flour quality. From the observation of the aggregation behavior of separated glutensis and gliadins and also of reconstituted glutens, it was concluded that the aggregation behavior of gluten is determined mainly by the nature of glutenin it contains. To investigate the difference of compositions of glutenins, component polypeptides of glutenin were fractionated by gel filtration into three fractions FI, FII and FIII after reduction and cyanoethylation of glutenin The glutenin from a strong flour was rich in FII, while the glutenin from a weak flour in FI. The observation of the aggregation behaviors of FI, FII and FIII suggested that the aggregation behavior of glutenin depends on the contents of these fractions.     

强筋与弱筋小麦籽粒蛋白质组分与加工品质对灌浆期弱光的响应

选用强筋小麦品种济麦20和弱筋小麦品种山农1391,在大田试验条件下,分别于籽粒灌浆前期(花后6—9 d)、中期(花后16—19 d)和后期(花后26—29 d)对小麦进行弱光照处理,研究了籽粒产量、蛋白质组分及加工品质的变化。灌浆期弱光显著降低小麦籽粒产量,灌浆中期对济麦20和灌浆后期对山农1391的产量降幅最大。弱光处理后,籽粒氮素积累量及氮素收获指数减少。但弱光使籽粒蛋白质含量显著升高,其中灌浆中期弱光升幅最大,原因可能是由于其粒重降低造成的。弱光对可溶性谷蛋白无显著影响,但增加不溶性谷蛋白含量,使谷蛋白聚合指数显著升高,面团形成时间和稳定时间亦升高,籽粒灌浆中、后期弱光对上述指标的影响较前期大。灌浆期短暂的弱光照对改善强筋小麦粉质仪参数有利,但使弱筋小麦变劣;并均伴随籽粒产量的显著降低这一不利影响。     

基因型与生态环境对小麦籽粒品质与蛋白质组分的影响

通过2年3点试验,研究了40个小麦(Triticum aestivum)品种(品系)籽粒品质性状和蛋白质组分含量的变异。结果表明,籽粒品质和蛋白质组分在基因型间存在较大的差异;根据小麦籽粒品质的综合性状,可将40个小麦品种(品系)分为6组不同的品质类型,在本试验点的生态环境条件下。基本以中筋及弱筋小麦为主;生态环境对小麦籽粒的容重、沉降值、湿面筋含量、蛋白质含量、赖氨酸含量与蛋白质组分含量均有极显著的影响,而面筋指数、淀粉含量和直链淀粉含量对环境反应不敏感,适宜的生态环境条件有利于形成合理的谷蛋白／醇溶蛋白比。面粉面筋质量好,基因型与生态环境的互作对小麦籽粒品质。谷蛋白与醇溶蛋白及两者的比值有显著影响,对球蛋白影响不大,而面粉蛋白质含量、面筋含量、沉降值及千粒重主要受基因的表达和环境的独立影响,蛋白质组分含量在基因型间和环境间的变化与小麦籽粒烘烤品质密切相关。     

Modification of the Low Molecular Weight (LMW) Glutenin Composition of Transgenic Durum Wheat: Effects on Glutenin Polymer Size and Gluten Functionality

The low-molecular weight (LMW) glutenin subunits are major determinants of the viscoelasticity of durum wheat gluten, and therefore of its technological quality, with both quantitative effects and qualitative effects. We have modified the LMW glutenin subunit composition of the durum wheat cultivar Ofanto by expression of a transgene encoding a B-type LMW glutenin subunit and have carried out detailed analyses of two independent transformed lines in order to assess the effect of the transgene on the size distribution of the glutenin polymers and on their functional properties. In one line the expression of the transgene led to an increase in the amount of large glutenin polymers resulting in stronger and more stable dough. In the second line, however, the expression of the transgenic subunit was accompanied by decreased expression of endogenous LMW subunits with consequent detrimental effects on glutenin polymers and dough viscoelasticity. These results demonstrate that the LMW glutenin subunits contribute to the functional properties of wheat by influencing the amount and the distribution of glutenin polymers and indicate that either plant breeding or GM technology can be used to 'fine tune' the properties of durum wheat for different end uses by manipulating the amount and structures of individual LMW subunit proteins.     

Aggregation Behaviors of Glutens,Glutenins and Gliadins from Various Wheats

The aggregation behavior was investigated by the method presented in the previous paper, with the glutens separated from ten kinds of wheat flours different in the mixing property. It was shown that the rate constant of aggregation, k, increased in the order of the weak, medium and strong flour. This is an additional evidence for the correlation between the aggregation behavior of the separated gluten and the mixing property of the flour, which was suggested in the previous paper with four kinds of flours. The aggregation behaviors of glutenin and gliadin were also investigated after fractionation of gluten. A good correlation was observed between the τ₁₀/C values of gluten and glutenin separated from it, showing that the difference of the aggregation behavior of gluten is mainly due to the nature of glutenin.     

Enlarged processing window of plasticized wheat gluten using salicylic acid

The temperature window for the extrusion of glycerol-plasticized wheat gluten was increased by the use of salicylic acid, a known scorch retarder and radical scavenger. It was possible to extrude 30 wt % glycerol-wheat gluten films with a die-head temperature as high as 135 degrees C, rather than 95 degrees C, by incorporating only 1 wt % salicylic acid. Small effects of shear-induced heating during extrusion at the higher temperatures suggested that the acid acted as a lubricant and viscosity reducer. The latter was suggested to originate primarily from the salicylic-acid-induced reduction in the degree of protein aggregation/cross-linking, as indicated by size-exclusion high-performance liquid chromatography and chemiluminescence. Electron paramagnetic resonance spectroscopy on extruded films indicated that the beneficial effect of salicylic acid was due to its radical scavenging effect. Tensile tests on extrudates revealed that the materials produced at the substantially higher processing temperature were still ductile. The complex shear modulus increased more slowly with increasing salicylic acid content above 110-120 degrees C, indicating that the aggregation/cross-linking rate was slower with salicylic acid, that is, that it did have a scorch-retarding effect, besides yielding a lower final degree/complexity of aggregation.     

山东强筋和中筋小麦品质形成的气象条件及区划

1999—2003年选用4个强筋小麦品种和12个中筋小麦品种在山东省的31个县进行试验,以各试验点当地气象站观测的小麦开花至成熟期的气象资料为依据,采用逐步回归和一元非线性回归模型进行分析.结果表明:平均气温分别为20.0℃和20.5℃时,有利于强筋和中筋小麦面团稳定时间的延长;气温日较差分别为12.7℃和11.7℃时,有利于强筋和中筋小麦籽粒蛋白质含量的提高;降水量分别为48.6mm和52.1mm,日照时数分别为297h和299h时,有利于强筋和中筋小麦沉降值的提高;降水量分别为53.5mm和53.9mm,日照时数分别为295h和298h时,有利于强筋和中筋小麦面团稳定时间的延长.单一气象因子对小麦籽粒蛋白质含量、沉降值和面团稳定时间的影响不完全同步.依据对各地气象条件进行综合评价的结果,将山东省划分为胶东与鲁中强筋、中筋小麦适宜区,鲁西北和鲁西南强筋、中筋小麦次适宜区,鲁南强筋小麦次适宜、中筋小麦适宜区.     

A proteomic approach to verify in vivo expression of a novel gamma-gliadin containing an extra cysteine residue

Gliadins and glutenins are the main protein fractions present in wheat gluten. They are responsible for technological and nutritional quality of wheat based products. In particular, glutenins are mainly responsible for dough visco-elastic properties, whereas gliadins confer extensibility to dough and are the most important factor triggering celiac disease, the major human intolerance to gluten. Gliadins are monomeric proteins, whereas glutenins are polymers stabilized by disulfide bonds. Although they have distinctive structural characteristics, it is possible that some gliadins become part of the glutenin fraction because of mutations that affect cysteine number and distribution. Here, we provide evidence that a naturally mutated gamma-gliadin with an extra cysteine residue is incorporated into the polymeric fraction. This goal was achieved using an integrated approach involving heterologous expression, 2-DE, RP-HPLC and MS.     

花后灌水次数对强筋小麦籽粒产量和品质的影响

在防雨池栽培条件下,以2个优质强筋小麦品种（济麦20和藁城8901）为试验材料,研究了花后不同水分供应状况对籽粒产量、籽粒品质（粉质仪参数和面包体积）及其蛋白质组分的影响.结果表明：2个品种的籽粒产量、面粉的面团形成时间、面团稳定时间和制成面包体积均随花后灌水次数的增加呈先升高后降低的趋势;其中,花后灌1水（花后7 d）时藁城8901的籽粒产量最高,花后灌2水（花后7 d+花后14 d）时济麦20的籽粒产量最高;2个品种面粉的面团形成时间、面团稳定时间和制成面包体积均以花后灌1水时最优.单体蛋白含量、不溶性谷蛋白含量、谷蛋白总含量、蛋白质含量以及湿面筋含量也呈现类似的变化趋势.逐步回归分析表明,花后不同水分供应状况下,不溶性谷蛋白含量是影响面团稳定时间的关键因素,谷蛋白总含量与面包体积的变化密切相关.因此,为了保持优质强筋小麦品质的稳定性,水分管理应以改善籽粒蛋白质特别是谷蛋白组分的构成为目标.     

Production and characterization of a transgenic bread wheat line over-expressing a low-molecular-weight glutenin subunit gene

The end-use properties, and thus the value, of wheat flours are determined to a large extent by the proteins that make up the polymeric network called gluten. Low molecular weight glutenin subunits (LMW-GS) are important components of gluten structure. Their relative amounts and/or the presence of specific components can influence dough visco-elasticity, a property that is correlated with the end-use properties of wheat flour. For these reasons, manipulation of gluten dough strength and elasticity is important. We are pursuing this goal by transforming the bread wheat cultivar Bobwhite with a LMW-GS gene driven by its own promoter. Particle bombardment of immature embryos produced several transgenic lines, one of which over-expressed the LMW-GS transgene. Southern blots confirmed that the transgene was integrated into the wheat genome, although segregation analyses showed that its expression was sometimes poorly transmitted to progeny. We have determined that the transgene-encoded LMW-GS accumulates to very high levels in seeds of this line, and that it is incorporated into the glutenin polymer, nearly doubling its overall amount. However, SDS sedimentation test values were lower from the transgenic material compared to a non transgenic flour. These results suggest that the widely accepted correlation between the amount of the glutenin polymers and flour technological properties might not be valid, depending on the components of the polymer.     

Gliadins polymerized with cysteine: effects on the physical and water barrier properties of derived films

To study the effects of disulfide bonds on certain functional properties of films made from the wheat gluten proteins gliadin and glutenin, cysteine was used to promote the formation of interchain disulfide bridges between gliadins in 70% ethanolic solution. Disulfide-mediated polymerization of gliadins was confirmed by means of SDS-PAGE analysis. After chemical treatment of gliadins, films were solution cast and the effects of both glycerol (used as a plasticizer) and relative humidity were studied on water vapor permeability, moisture sorption isotherms at 23 degrees C, and the optical properties of the films. The results were compared with those obtained from analogous films made from untreated glutenin macromolecules. Cysteine-mediated polymerization of gliadins improved the water vapor resistance of films achieving values close to those obtained for glutenin films. Development of intra- and interchain disulfide bonds did not change the moisture sorption capacity of the films but transparency was slightly diminished.     

播期和种植密度对强、中筋冬小麦蛋白质组分及品质性状的影响

采取裂裂区试验设计,研究了播期和种植密度对强筋小麦临优145和中筋小麦临优2018蛋白质组分和品质性状的影响.结果表明：适期播种的小麦籽粒蛋白质含量和蛋白质产量均最高;推迟播期,强筋品种的醇溶蛋白和谷蛋白含量明显增加,而中筋品种变化不明显;强筋品种的品质性状受播期影响程度高于中筋品种.适期播种,小麦籽粒蛋白质、麦谷蛋白与湿面筋、沉降值、稳定时间、软化度和评价值呈显著或极显著正相关;推迟播期,醇溶蛋白与湿面筋含量呈显著正相关.播期变化引起的蛋白质各组分所占比例的改变是改善小麦品质性状的重要原因.在试验种植密度范围内（225万株·hm-2、300万株·hm^-2和375万株·hm^-2）,小麦籽粒蛋白质含量变化不明显,密度对强筋品种的品质性状有一定调节作用;在低密度条件下（225万株·hm^-2）中筋品种的品质性状最佳.     

Characterization and quantification of low molecular weight glutenins in durum wheats

Durum wheat proteins have been considered as a model because of the very clear-cut relationship previously evidenced between the electrophoretic type '42' or '45' of the components that are coded by the Gli-B1 chromosome locus and the intrinsic quality (gluten viscoelasticity) of cultivars. The proteins from 4 cultivars were subjected to sequential extraction and separated into five groups, respectively, in: NaCl, EtOH (gliadins-I), EtOH + mercaptoethanol (ME) (gliadins-II), AcOH + ME (glutenins-I) and SDS + ME (glutenins-II) and characterized using polyacrylamide gel electrophoresis (PAGE), SDS-PAGE and 2-dimensional (NEPHGE X SDS - PAGE) electrophoretic systems. EtOH-soluble fractions were also separated by ion-exchange chromatography, each fraction being characterized in PAGE and SDS-PAGE and its composition in major bands determined by densitometry. From the ratio of each chromatographic fraction and of each solubility group, an estimation of the major bands or electrophoretic zones was also made in respect to the whole proteins. In 'type 45' cultivars, it was shown that only 67% of the EtOH-soluble fraction (although considered as classical gliadins) had a monomeric character, giving rise to discrete bands in PAGE systems. The remainder (33%) were aggregated fractions, essentially those referred to as low molecular weight glutenins (LMWG), that migrate, upon reduction only, in SDS-PAGE systems. LMWG make up 27% of total proteins and are revealed as a strong triplet in the 44,500-51,500 MW region, in gliadin-I and especially in gliadin-II groups. In type '42' cultivars, the LMWG ratio is reduced about by half (18% of EtOH soluble fraction, 14% of total proteins). This difference, coupled with their aggregative behavior, leads to their consideration as the major functional markers of gluten quality, gliadins 42/45 being genetic markers only. Without excluding possible physicochemical differences between different LMWG allelic types, it is hypothesized that quantitative differences could explain by themselves the quality differences between the two durum wheat genetic types. Concerning the other aggregative fractions, like high molecular weight glutenin (HMWG) subunits in glutenin-I and II groups, they do not show (unlike bread wheats) quantitative or qualitative differences large enough to play a major role in explaining genetic differences in durum wheat gluten characteristics. It is recommended, especially for physicochemical studies of wheat quality, to rely on a protein classification based on monomeric or aggregative characteristics, instead of Osborne's scheme based only on fractionation by solubility.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effect of hypothermia on subcellular distribution and various physico-chemical properties of cathepsin D in rat brain

The total cooling ef rats down to the rectal temperature 30 degrees and 20 degrees C does not change significantly the ratio of the relative specific activity of cathepsin D in subcellular fractions of the rat brain. The gel chromatographic analysis of heterogeneity of cathepsin D molecular forms in subcellular fractions established the presence of a high-molecular (in the fractions of lysosome and microsome mitochondria) and a low-molecular (in the fractions of lysosome and cytosol mitochondria) enzyme forms. Under hypothermia (20 degrees C) in the brain cytosol fraction there arises a minor zone of the cathepsin D activity corresponding to the high-molecular enzyme form.     

小麦高分子量麦谷蛋白亚基的遗传变异与小麦加工品质改良

高分子量麦谷蛋白亚基（HMW-GS）是小麦胚乳中一种具有多态性的蛋白质组分,在面团中它们可以通过相互之间或与低分子量麦谷蛋白亚基（LMw-Gs）之间形成二硫键来组成麦谷蛋白多聚体。由于其在小麦面粉加工所需的粘性和弹力方面具有极其重要的作用,过去几十年间在小麦加工品质相关蛋白研究方面的工作大多数集中在高分子量麦谷蛋白亚基上。近几年在高分子量麦谷蛋白亚基及其编码基因的鉴定、基因的遗传变异以及不同变异在小麦加工品质中的作用方面进行了大量研究。本文对近几年在HMW-GS领域的研究进展进行综述并且重点讨论HMW-GS的变异及其对小麦品质育种的重要意义。