高分子量大豆蛋白的溶液制备及组份分离

商品化的大豆分离蛋白(SPI)主要由7S和11S两种球蛋白组成,两者较难分离.同时,由于球蛋白的紧密结构使SPI难以直接溶解于水中.采用盐酸胍和二硫苏糖醇在溶解过程中对SPI进行处理,从而获得了较高浓度,并且蛋白质分子链未发生降解的SPI水溶液.此外,通过采用盐酸胍溶解和透析的方法,获得以7S球蛋白为主的溶液和以11S球蛋白为主的沉淀,比较简单地实现SPI中两种主要组份的初步分离.     

伴大豆球蛋白亚基色谱分离和制备及结构表征

研究了色谱方法对伴大豆球蛋白组成3个亚基的分离纯化工艺条件,并利用圆二色光谱对纯化得到的3个亚基的二级结构和三级结构进行了表征.结果显示:利用离子交换色谱(DEAE-sepharose fast flow, DEAE为二乙氨乙基)和金属螯合层析(Immobilized metal affinity column, IMAC)相结合的方法,能将3个亚基组分完全分开,得到了能制备相对大量的3个亚基α′, α和β的稳定工艺,纯度为95%,回收率达75%.远紫外CD结果显示,在3个亚基的二级结构中, α螺旋较少,但都具有较高含量的β折叠和无规卷曲; 近紫外CD结果显示, 3个亚基在制备过程中因为尿素的变性作用,都已经散失了三级结构.     

纤维素超细纤维增强大豆分离蛋白透光复合膜性能研究

以醋酸纤维素为原料, 由静电纺丝方法得到平均直径为430 nm的纤维素超细纤维, 将该纤维与大豆分离蛋白复合制备了一种新型的超细纤维增强透光复合膜. 采用扫描电镜、拉伸、三点弯曲和透光率试验等对其结构、力学和透光性进行了分析和表征. 结果表明: 超细纤维与大豆分离蛋白基体具有良好的界面相互作用; 超细纤维对复合材料起到了增强增韧的效果. 而且, 复合膜具有良好的透光率. 即使超细纤维质量分数达到13%, 该膜在700 nm波长处的透光率仍然可以达到77%.     

大豆分离蛋白的酶水解

大豆分离蛋白的酶水解;大豆分离蛋白;水解作用;光散射     

大豆分离蛋白改性的研究进展

首先介绍了大豆分离蛋白的基本组成与结构,然后分别从化学改性、酶改性和物理改性三个方面对大豆分离蛋白改性进行了综述.其中,在化学改性方面,针对大豆分离蛋白中含有的氨基、羧基、巯基等不同活性基团的改性原理及研究现状进行了介绍.在酶改性方面,主要介绍了谷胺酰胺转胺酶、木瓜蛋白酶等对大豆分离蛋白的改性作用.在物理改性方面,介绍了共混、加热改性等目前研究较多的方法.通过化学、物理和酶等方法等来引起分子结构的微变化,可使人们获得各种符合预期的性能优良的产品,开发其在医药、化工等领域的应用潜力.     

正交轴逆流色谱法对标准蛋白及中等分子量大豆肽的分离

本文报道分别以12．5％PEG8000-25％磷酸氢二钾(质量比1：1)的溶剂系统，以及正丁醇：三氟乙酸：水(120：1：160，V／V)的溶剂系统，用下相作流动相，上相作固定相，采用500r／min的转速和1mL／min流动相流速对标准蛋白质及大豆肽进行分离。在分离度损失不大的基础上提高了进样量，证明了正交轴逆流色谱法用于制备的有效性。为采用正交轴逆流色谱法分离制备天然生物肽提供了可选择的方法。     

大豆分离蛋白接枝改性与应用研究进展

随着人们对环保问题和新材料发展的日益重视,大豆分离蛋白由于其生物可降解性、营养价值高、对人体与环境无害、来源广泛等特点而倍受关注.本文介绍了大豆分离蛋白的接枝改性方法及在食品添加剂、包装膜和医用外敷膜材料的基料以及化妆品中的应用,并综述了国内外在改善膜的应用特性方面取得的研究进展.     

大豆分离蛋白与壳聚糖复合材料的制备

蛋白质与多糖的静电作用是生物体内一个基本医学-化学现象,是实现自组装的主要驱动力,可利用这种非共价作用设计和构筑理想的微结构。 以大豆分离蛋白(Soybean Protein Isolates,SPI)和壳聚糖(Chitosan,CS)为原料,采用浊度法考察了配比、溶液pH值、离子强度和温度对SPI与CS在溶液中相互作用的影响。 结果显示,由于pH值影响静电作用强度,从而成为影响SPI与CS相互作用的主要因素,其中,当pH值为5.5~6.6时,SPI与CS可以实现有效结合。在较低的离子强度下,有利于形成具有紧凑结构的CS/SPI聚集体,较高离子强度下聚集体发生解离。 蛋白质受热发生变性,多肽链上的疏水氨基酸残基暴露在溶液中,导致与壳聚糖链的疏水作用增强。 DLS结果显示,CS与SPI自组装形成了分布均一的纳米粒子,变性后的SPI与CS形成的纳米粒子粒径有所增大,分布均一;经戊二醛交联,粒径有所减小。 SEM显示,壳聚糖单层膜表面存在龟裂现象,与SPI形成双层膜后龟裂消失;同时,单层膜厚度约为300 nm,双层膜厚度约为500 nm。     

大豆分离蛋白甲基丙烯酸接枝共聚物的合成与表征

以过硫酸铵为引发剂、2-巯基乙醇为蛋白质变性剂,在浓度为8mol／L尿素溶液中进行了大豆分离蛋白与甲基丙烯酸的接枝共聚反应;傅里叶红外光谱和核磁共振谱证明,甲基丙烯酸成功地接枝到了大豆分离蛋白上;相关影响因素的单因数实验研究表明,各因数的最佳值分别为：引发剂浓度16mmol／L,单体浓度2．4mol／L,反应温度80℃,反应时间4h,巯基乙醇浓度0．05mol／L。     

利用免疫荧光法研究大豆种子发育过程中11S和7S蛋白的积累

本文利用免疫荧光法研究了种子发育过程中11S和7S两种球蛋白的积累过程。7S蛋白在子叶的沉积始于开花后15天,11S蛋白的沉积稍迟一些。开花后20—30天,这两种球蛋白增加非常迅速。观察到这两种蛋白或它们的类似物从珠被向子叶转运的趋势。还发现有的品种某些子叶细胞不积累11S蛋白,而在高蛋白品种和高蛋白野生大豆所有子叶细胞都充满11S蛋白和其它贮存物质。     

铁蛋白纳米蛋白壳结构与功能研究新进展

铁蛋白是广泛存在于生物体内的储存铁的蛋白质,它参与生物体内的铁代谢.本文从铁蛋白的亚基结构、血红素-电子隧道、铁氧化酶位点和捕获重金属离子角度,综述铁蛋白纳米蛋白壳的结构与功能研究的新进展.     

Sol-Gel Processing of Functional and Structural Ceramic Oxide Fibers

Structural ceramic oxide fibers like α-Al₂O₃, MgAl₂O₄ (spinel), Y₃Al₅O₁₂ (YAG) and eutectic Al₂O₃−Y₃Al₅O₁₂ as well as the functional Pb(Zr_1−xTi_x)O₃ (PZT) fibers were successfully prepared by sol-gel processing. All precursors are based on metal oxohydroxopropionates. A comparative study of sol-gel routes leading to spinnable sols demonstrates the key role of propionic acid as an excellent agent for controlling hydrolysis and condensation reactions.     

Interactions between Mannosylerythritol Lipid-A and Heat-Induced Soy Glycinin Aggregates: Physical and Chemical Characteristics,Functional Properties,and Structural Effects

Protein-surfactant interactions have a significant influence on food functionality, which has attracted increasing attention. Herein, the effect of glycolipid mannosylerythritol lipid-A (MEL-A) on the heat-induced soy glycinin (11S) aggregates was investigated by measuring the structure, binding properties, interfacial behaviors, and emulsification characteristics of the aggregates. The results showed that MEL-A led to a decrease in the surface tension, viscoelasticity, and foaming ability of the 11S aggregates. In addition, MEL-A with a concentration above critical micelle concentration (CMC) reduced the random aggregation of 11S protein after heat treatment, thus facilitating the formation of self-assembling core-shell particles composed of a core of 11S aggregates covered by MEL-A shells. Infrared spectroscopy, circular dichroism spectroscopy, fluorescence spectroscopy, and isothermal titration calorimetry also confirmed that the interaction forces between MEL-A and 11S were driven by hydrophobic interactions between the exposed hydrophobic groups of the protein and the fatty acid chains or acetyl groups of MEL-A, as well as the hydrogen bonding between mannosyl-D-erythritol groups of MEL-A and amino acids of 11S. The findings of this study indicated that such molecular interactions are responsible for the change in surface behavior and the enhancement of foaming stability and emulsifying property of 11S aggregates upon heat treatment.     

Influence of the Degree of Hydrolysis on Functional Properties and Antioxidant Activity of Enzymatic Soybean Protein Hydrolysates

Soybean protein hydrolysates were prepared using two proteolytic enzymes (Alcalase and Protamex) and the degree of hydrolysis (DH) and their functional and antioxidant properties were evaluated. The highest DH value was 20%, with a yield of 19.77% and protein content of 51.64%. The total amino acid content was more than 41% for all protein hydrolysates. The protein hydrolysates from Protamex at pH 2.0 had excellent solubility, emulsifying activity, and foaming capacity, at 83.83%, 95.03 m²/g, and 93.84%, respectively. The water-holding capacity was 4.52 g/g for Alcalase, and the oil-holding capacity was 4.91 g/g for Protamex. The antioxidant activity (62.07%), as measured by the samples’ reaction with DPPH (2,2-diphenyl-1-picrylhydrazyl) and the reducing power (0.27) were the strongest for Protamex. An ABTS activity rate of 70.21% was recorded for Alcalase. These findings indicated a strong potential for the utilization of soybean protein hydrolysates to improve the functional properties and antioxidant activity of soybeans as well as their nutritional values.     

Identification of Protein Functional Regions

Protein sequence stores the information relative to both functionality and stability, thus making it difficult to disentangle the two contributions. However, the identification of critical residues for function and stability has important implications for the mapping of the proteome interactions, as well as for many pharmaceutical applications, e. g. the identification of ligand binding regions for targeted pharmaceutical protein design. In this work, we propose a computational method to identify critical residues for protein functionality and stability and to further categorise them in strictly functional, structural and intermediate. We evaluate single site conservation and use Direct Coupling Analysis (DCA) to identify co-evolved residues both in natural and artificial evolution processes. We reproduce artificial evolution using protein design and base our approach on the hypothesis that artificial evolution in the absence of any functional constraint would exclusively lead to site conservation and co-evolution events of the structural type. Conversely, natural evolution intrinsically embeds both functional and structural information. By comparing the lists of conserved and co-evolved residues, outcomes of the analysis on natural and artificial evolution, we identify the functional residues without the need of any a priori knowledge of the biological role of the analysed protein.     

Structural and Functional Analysis of the Pyridoxal Phosphate Homeostasis Protein YggS from Fusobacterium nucleatum

Pyridoxal 5′-phosphate (PLP) is the active form of vitamin B6, but it is highly reactive and poisonous in its free form. YggS is a PLP-binding protein found in bacteria and humans that mediates PLP homeostasis by delivering PLP to target enzymes or by performing a protective function. Several biochemical and structural studies of YggS have been reported, but the mechanism by which YggS recognizes PLP has not been fully elucidated. Here, we report a functional and structural analysis of YggS from Fusobacterium nucleatum (FnYggS). The PLP molecule could bind to native FnYggS, but no PLP binding was observed for selenomethionine (SeMet)-derivatized FnYggS. The crystal structure of FnYggS showed a type III TIM barrel fold, exhibiting structural homology with several other PLP-dependent enzymes. Although FnYggS exhibited low (<35%) amino acid sequence similarity with previously studied YggS proteins, its overall structure and PLP-binding site were highly conserved. In the PLP-binding site of FnYggS, the sulfate ion was coordinated by the conserved residues Ser201, Gly218, and Thr219, which were positioned to provide the binding moiety for the phosphate group of PLP. The mutagenesis study showed that the conserved Ser201 residue in FnYggS was the key residue for PLP binding. These results will expand the knowledge of the molecular properties and function of the YggS family.     

Aβ蛋白分泌酶抑制剂研究进展

Aβ蛋白是淀粉样前体蛋白的代谢产物,它在脑组织中含量的异常增加可能是诱发AD的主要因素.应用分泌酶抑制剂可有效减少Aβ的生成,缓解患者症状.本文综述了其中的β分泌酶抑制剂的研究进展.     

大豆分离蛋白-十二烷基硫酸钠微胶囊的制备与表征

以大豆分离蛋白(SPI)和十二烷基硫酸钠(SDS)为壁材, 以十六烷为芯材, 通过复凝聚法制备了微胶囊. 首先确定了SPI和SDS发生复凝聚的适宜pH、SPI/SDS配比、壁材浓度等. 在确定的实验条件下进行复凝聚, 凝聚物产率可达85%. 改变搅拌转速和芯壁比, 考察它们对微胶囊性能的影响. 用光学显微镜观察了微胶囊形貌. 用气相色谱测定了微胶囊的载药量和包覆率. 芯壁比为2、搅拌转速为400 r/min时所制备微胶囊的载药量可达61%. 随着芯壁比的增大, 微胶囊粒径及载药量都逐渐增大.