非洲山毛豆种子蛋白质组分分析

以山毛豆种子为原料,对其蛋白质进行分级分离,测定了各组分蛋白含量、等电点和溶解度。结果表明,脱脂山毛豆粉的总蛋白含量为47.11%(m/m)。其中,清蛋白、球蛋白、醇溶蛋白和谷蛋白的相对百分含量分别为64.04%、8.83%、11.06%和14.50%,另外含有1.57%难溶的复合蛋白。清蛋白、球蛋白和醇溶蛋白的等电点为pH4.3、pH5.1和pH4.7,谷蛋白的等电点为3.5～3.8。它们在等电点附近溶解度较小,偏离等电点之后即pH>5或pH<4清蛋白和球蛋白的溶解度增大,而醇溶蛋白和谷蛋白的溶解度增加较小。SDS-PAGE电泳表明,非洲山毛豆种子总蛋白的相对分子量差异较大,在20.1～97.2kDa及小于20.1kDa的均有分布,但其谱带分布不明显。清蛋白谱带变化范围为主要有6条,变化区域集中在20.1～66.4kDa及小于20.1kDa的范围。球蛋白在20.1～66.4kDa大约出现了10条谱带。醇溶蛋白在20.1、29.0、44.3kDa分别有3条明显的谱带。谷蛋白在20.1～97.2kDa大约有10条以上的谱带,说明非洲山毛豆种子总蛋白及各组分蛋白均有不同的分子组成。     

花生蛋白酶解液特性的研究

本文研究了碱性蛋白酶、中性蛋白酶与木瓜蛋白酶对花生蛋白的酶解效果。结果表明,在0～6h时,随着酶解时间的延长,酶解产物的氮溶解指数不断增大,酶解6h时碱性蛋白酶、中性蛋白酶与木瓜蛋白酶酶解产物的氮溶解指数分别为33.84%,29.40%和26.06%,其中碱性蛋白酶酶解产物的氮溶解指数最高。SDS-PAGE图谱显示,与碱性蛋白酶与中性蛋白酶酶解液相比,木瓜蛋白酶酶解液中相对分子质量为20,000～31,000之间的条带缺失,三种酶解液中的未被酶解的蛋白质其相对分子质量都集中在14,000～43,000之间,开发利用时应予以注意。     

硫酸亚铁钝化大豆胰蛋白酶抑制剂的研究

大豆胰蛋白酶抑制剂（STI）可以抑制一些来源于动物或植物的蛋白酶的活力,使之降低水解蛋白质的效力。在食品加工的过程中,长时间及高温的热处理虽可破坏大豆胰蛋白酶抑制剂,但也破坏了其它的蛋白质,大大减低了食品的营养价值。文章的目的在于研究硫酸亚铁对大豆胰蛋白酶抑制剂的钝化作用。实验在温度70℃,pH7．5条件下进行反应,并以BAPNA为底物采用改进的方法溯定硫酸亚铁对大豆胰蛋白酶抑制剂的钝化作用。通过改进的BAPNA方法得出的结果显示：硫酸亚铁可钝化大豆胰蛋臼酶抑制剂;通过SDS—PAGE方法也证实了硫酸亚铁对STI的钝化作用。通过SDS．PAGE方法还得出,STI在经硫酸亚铁钝化后由于谷氨酰胺转氨酶的加入而聚合产生了一些高分子化合物,该结果从GPC图中也可以得出相同的结论。所以,得出STI的稳定性与二硫键的存在有关。     

SDS-PAGE法检测动物肌肉蛋白质加热终点温度的研究

为了探索检测动物组织蛋白质热变性程度的方法,分别对猪、牛、羊、鸡、鱼五种新鲜动物肌肉组织进行不同温度的热处理（新鲜未加热、50、60、70、80、90、100℃）,对处理后的样品提取蛋白质进行十二烷基磺酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）分析。结果显示,同种动物组织经不同温度热处理,所得电泳图谱具有较大差异,电泳条带的数量随温度的升高逐渐减少,猪、牛、羊三种动物肌肉组织加热到80℃后,电泳图谱不再变化,达到加热终点温度;鸡和鱼的肌肉组织加热到70℃后,电泳图谱不再变化,达到加热终点温度。不同种动物组织经相同温度热处理所得电泳图谱显示：猪、牛、羊三种动物组织蛋白质的电泳图谱相似,与鸡和鱼组织蛋白质的电泳图谱差异显著。     

白果过敏蛋白及其过敏原性研究

对白果的主要过敏蛋白进行鉴定,并对其过敏原性进行分析。以SDS-PAGE和Western-Blotting分析鉴定白果蛋白提取液中的蛋白质组分和过敏蛋白,通过间接ELISA法检测过敏小鼠血清中sIgE的效价。白果的蛋白质条带主要有13条,其中以21kD和32kD含量最多。Western-Blotting分析结果表明,白果蛋白中存在3条过敏原蛋白,分子质量分别为21、32、36kD。当酶标二抗稀释度为1:1000,白果蛋白包被质量浓度为50μg/mL,间接ELISA测得过敏小鼠血清中sIgE的效价为1:6400。对白果蛋白进行分析鉴定,明确了白果中存在的过敏原蛋白。     

Evaluating the profile of myofibrillar proteins and its relationship with tenderness among five styles of dry-cured hams

In order to investigate the relationship between profile of myofibrillar proteins and tenderness among 2 kinds of Chinese hams (Jinhua and Xuanwei) and 3 kinds of European hams (Iberian, Serrano and Parma), shear force, myofibril fragmentation index (MFI), SDS-PAGE, carbonyls content and Raman spectroscopy were investigated. The shear force and salt content of Chinese hams were significantly higher than that of European hams, while moisture content was lower than that of European hams (p < 0.05). MFI values and SDS-PAGE profile revealed that the degradation of myofibrillar proteins in Chinese hams was lower than in European hams. In addition, Chinese hams showed significantly higher carbonyls content and β-sheet content compared with European hams, indicated that proteins aggregation intensively inhibited the degradation of myofibrillar proteins in Chinese hams. These results indicated that the higher shear force in Chinese style hams could be attributed to the lower moisture content and limited proteolysis.     

Antibacterial mechanism of lactic acid on physiological and morphological properties of Salmonella Enteritidis,Escherichia coli and Listeria monocytogenes

Lactic acid is widely used to inhibit the growth of important microbial pathogens, but its antibacterial mechanism is not yet fully understood. The objective of this study was to investigate the antibacterial mechanism of lactic acid on Salmonella Enteritidis, Escherichia coli and Listeria monocytogenes by size measurement, TEM, and SDS-PAGE analysis. The results indicated that 0.5% lactic acid could completely inhibit the growth of Salmonella Enteritidis, E. coli and L. monocytogenes cells. Meanwhile, lactic acid resulted in leakage of proteins of Salmonella, E. coli and Listeria cells, and the amount of leakage after 6 h exposure were up to 11.36, 11.76 and 16.29 μg/mL, respectively. Measurements of the release of proteins and SDS-PAGE confirmed the disruptive action of lactic acid on cytoplasmic membrane, as well as the content and activity of bacterial proteins. The Z-Average sizes of three pathogens were changed to smaller after lactic acid treatment. The damaged membrane structure and intracellular structure induced by lactic acid could be observed from TEM images. The results suggested that the antimicrobial effect was probably caused by physiological and morphological changes in bacterial cells.     

Molecular profiling of Jatropha curcas L. collected from different geographical locations of India

The present study surveys the morphological, biochemical and molecular diversity in 30 accessions of Jatropha collected from different states of India by using random amplified polymorphic DNA (RAPD), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and isozyme analysis. The genotyping data were used to understand the relationships among accessions and to identify genetic diversity as a means for genetic improvement of Jatropha. Out of 37 decamer primers used, 18 yielded polymorphic banding pattern. In total, 126 different DNA bands were reproducibly obtained, out of which 81 were polymorphic. SDS-PAGE of seed, leaf and callus resolved into 18, 12 and 7 bands, while no biotype-specific band was found in leaf and callus protein profile. Cluster analysis of both RAPD and SDS-PAGE data produced two major clusters.     

生姜蛋白酶和猕猴桃蛋白酶对干腌羊火腿蛋白质降解的影响

为了促进干腌羊火腿肌肉蛋白质降解,加快其风干成熟进程,缩短加工周期,提高羊火腿的品质,在干腌羊火腿中添加生姜蛋白酶和猕猴桃蛋白酶。以带骨鲜羊后腿肉为试验材料,分别设计一个对照组和两个试验组;对照组不采取处理,而试验组分别添加0.05%的生姜蛋白酶和猕猴桃蛋白酶,并在相应条件下进行风干成熟,检测干腌羊火腿的总氮(Total nitrogen,TN)含量、非蛋白氮(Non-protein nitrogen,NPN)含量和蛋白质降解指数(Proteolysis index,PI)等蛋白质降解指标,并通过SDS-PAGE(聚丙烯酰氨凝胶电泳)分析了干腌羊火腿肌肉蛋白质的降解情况。结果表明,与对照组相比,猕猴桃蛋白酶处理组和生姜蛋白酶处理组的TN含量风干成熟后分别增加了1.2倍和1.3倍、NPN含量分别增加1.5倍和1.7倍、PI分别上升1.2倍和1.3倍;SDS-PAGE分析结果表明,生姜蛋白酶降解肌肉蛋白的效率较猕猴桃蛋白酶强。通过蛋白质将指数和SDS-PAGE电泳结果可知,生姜蛋白酶对肌肉蛋白的降解程度比猕猴桃蛋白酶大。     

麦汁蛋白在麦汁煮沸过程中的变化研究

采用凝胶过滤色谱、电泳以及圆二色谱等方法研究了煮沸过程中麦汁蛋白结构的变化。结果表明,麦汁煮沸导致蛋白和氨基酸含量略有下降;通过SE-HPLC和SDS-PAGE分析发现,ProteinZ(-40ku)是2种麦汁蛋白的主要组成,并能够抵挡住高温变性;而SDS-PAGE和CD以及DSC分析证实了麦汁煮沸导致了蛋白结构的部分展开和发生部分变性,且在煮沸过程中仅有少量的沉淀通过疏水作用而形成;实验表明.2个品种的麦汁蛋白在煮沸过程中组成和结构的差异不大。