SDS-PAGE方法测定宠物食品蛋白热变性程度

将干性宠物食品样品先用双蒸水处理,然后对加热处理和未加热处理的相同样品,采用SDS-PAGE(十二烷基硫酸钠-聚丙烯酰胺凝胶电泳)方法测定宠物干性食品蛋白热变性程度,以确保加工出厂的宠物干性食品中心温度达到规定的加热温度及加热时间.     

Functional properties of microwave-treated wheat gluten

In this study, the effects of microwave treatments on solubility, foaming and emulsifying properties of gluten were investigated. The solubility of microwave-heated gluten proteins gradually decreased as the treatment time increased, at all power levels applied. The highest solubility values were obtained for gluten samples microwave treated at 50% power level. The lowest emulsifying capacity values were obtained with the samples heated at 100% power level at all treatment times. The emulsifying stability values of microwave-heated gluten samples were found to be slightly higher than those of the control sample. However, there were no significant differences among the microwave power levels at all treatment times in terms of the emulsifying stability values. The foam volumes of the samples treated at 80 and 100% energy levels were slightly higher than those of the control gluten. The foam stability values of microwave-heated gluten samples gradually increased with treatment time at all power levels, which were more pronounced at 100% power level. Generally, microwave treatment did not cause major changes on the protein electrophoretic patterns of gluten samples at the power levels used.     

白果蛋白质提取及SDS-PAGE分析

以白果为原料,采用不同的原料处理及蛋白质提取方法,运用单因素和正交设计的方法,以料液比、提取时间、提取液浓度、提取液pH 值为考察因素,研究白果蛋白质提取的最佳工艺条件,并对提取的白果蛋白进行SDS-PAGE 凝胶电泳分析。结果表明：经过冷冻干燥处理的白果采用Tris-HCl 提取法获得的白果蛋白含量较高;Tris-HCl 法提取白果蛋白的最佳工艺为pH8.5、0.15mol/L Tris-HCl 溶液、料液比1:20(g/mL)、提取时间4h,白果蛋白质的提取率达到75.01%。白果蛋白SDS-PAGE 分析表明,白果蛋白中约含13 条亚基,主要为21kD 和32kD 的两种亚基,白果蛋白的亚基主要集中在31～100kD,占亚基总数的77%。     

Effect of Chemical Modification, pH Change, and Freezing on the Rheological, Solubility, and Electrophoretic Pattern of Wheat Flour Proteins

ABSTRACT: In this study the effect of chemical modification and freezing of dough on the characteristics of wheat proteins and the rheological properties of dough was investigated. A slight increase in the protein solubility and disappearance of protein bands in the range of 55 to 70 KDa was observed when samples were frozen for 6 to 8 weeks. Ascorbic acid decreased and cysteine and bisulfite increased solubility of wheat proteins. Dough stability increased as pH was raised above 6.5. Two protein bands in the range of 55 to 60 KDa appeared in ascorbic acid treated doughs and the intensity of bands of less than 6.5 KDa increased in cysteine or bisulfite treated doughs. Several protein bands in the range of 30, 50, and 90 KDa appeared when the pH was raised to 7.0 and above. The results of this study suggest that high- molecular-weight proteins of wheat flour have a major influence on the properties of dough and that these proteins are affected by chemical treatment, pH change, and freezing.     

Characterisation of thermostable trypsin and determination of trypsin isozymes from intestine of Nile tilapia (Oreochromis niloticus L.)

Trypsin from intestinal extracts of Nile tilapia (Oreochromis niloticus L.) was characterised. Three-step purification – by ammonium sulphate precipitation, Sephadex G-100, and Q Sepharose – was applied to isolate trypsin, and resulted in 3.77% recovery with a 5.34-fold increase in specific activity. At least 6 isoforms of trypsin were found in different ages. Only one major trypsin isozyme was isolated with high purity, as assessed by SDS-PAGE and native-PAGE zymogram, appearing as a single band of approximately 22.39 kDa protein. The purified trypsin was stable, with activity over a wide pH range of 6.0–11.0 and an optimal temperature of approximately 55–60 °C. The relative activity of the purified enzyme was dramatically increased in the presence of commercially used detergents, alkylbenzene sulphonate or alcohol ethoxylate, at 1% (v/v). The observed Michaelis–Menten constant (K_m) and catalytic constant (K_cat) of the purified trypsin for BAPNA were 0.16 mM and 23.8 s⁻¹, respectively. The catalytic efficiency (K_cat/K_m) was 238 s⁻¹ mM⁻¹.     

波纹巴非蛤蛋白分离及其性质研究

为了充分利用波纹巴非蛤蛋白质资源,对波纹巴非蛤蛋白质组成进行了分离,得到肌浆蛋白、肌原纤维蛋白、基质蛋白3种蛋白组分,并对其分子量分布和功能特性进行检测和分析。研究结果表明:肌浆蛋白组分占原料粗蛋白的31.2%,肌原纤维蛋白组分占45.42%,基质蛋白占20.69%,非蛋白氮占1.67%。SDS-PAGE电泳分析显示:肌浆蛋白组分亚基分子质量分布比较广泛,在200～29.0 kDa;肌原纤维蛋白组分分子质量大多介于66.4～200 kDa和29.0～38.0 kDa之间;基质蛋白组分在190 kDa、97 kDa、44 kDa、29 kDa附近有明显的条带。相同浓度下,温度升高肌浆蛋白和肌原纤维蛋白溶液浊度都上升,溶解度下降,变化趋势相似;pH对肌浆蛋白的浊度和溶解度影响不显著,在pH3.5～9.5,其溶解度均在71%以上,但肌原纤维蛋白浊度和溶解度受pH影响较大,当pH为4.5时,肌原纤维蛋白的溶解度降到最低,浊度达到最大;离子强度下降,肌原纤维蛋白溶液的浊度上升,溶解度下降。     

玉米胚芽蛋白的分离及物化特性研究

采用碱溶酸沉法提取玉米胚芽分离蛋白,利用氨基酸分析和电泳分析胚芽蛋白的氨基酸组成和有效亚基组成。凝胶层析分离玉米胚芽蛋白组分,并对各组分进行热变性温度及圆二色谱分析。氨基酸分析结果表明,玉米胚芽蛋白中谷氨酸和赖氨酸含量较高,其它氨基酸含量较均衡。还原的十二烷基硫酸钠-聚丙烯酰胺电泳(SDS-PAGE)图主要有九条谱带,其分子量依次为87.988、76.320、69.650、53.649、48.546、38.164、34.337、32.294和24.483 kDa。凝胶层析分离获得两个蛋白组分。差示扫描量热仪(DSC)分析表明分离所得两个组分的干粉变性温度分别为97.37℃和98.95℃,圆二色谱(CD)分析表明两个蛋白组分的二级结构主要为β-折叠和无规卷曲。     

乌珠穆沁羊生长过程中肌纤维类型的变化

采用不同月龄的乌珠穆沁羊骨骼肌中的股二头肌,采取组织化学染色法对肌纤维类型的变化进行研究,了解肉羊生长过程中肌纤维类型的变化规律.骨骼肌用多聚甲醛固定液固定、切薄片.在酸性和碱性孵育液中孵育后,巴比妥钠溶液中冲洗后硫化铵液中孵育.用乙醇脱水,中性树胶封片,显微镜下观察.结果表明,随着月龄的增加,股二头肌中Ⅱa型肌纤维百分含量在3、6月龄及12、18月龄之间差异不显著(P＞0.05),百分含量在12月龄时最高.Ⅱb型肌纤维的百分比在18月龄最高.Ⅰ型纤维在18月龄时含量最低.     

二系杂交小麦HMW-GS组合与品质关系的研究

高分子质量麦谷蛋白亚基(HMW-GS)的组成及含量是影响小麦加工品质的主要因素之一。以小麦光温敏雄性不育系BS20、BS210和BS366与17个恢复系配制的86个正反交组合为试材,研究二系杂交小麦正反交组合HMW-GS组成与蛋白质含量、沉淀值、揉混仪曲线的和面时间、八分钟带宽和衰弱角斜率等品质性状的关系。采用SDS-PAGE方法分析了杂交种的HMW-GS的组成,结果表明,正反交组合HMW-GS组成相同,在所有参试材料中普遍存在劣质亚基N和2+12,其频率分别是44.2%、67.4%,而优质亚基5+10所占比例仅为20.9%。HMW-GS对正交和反交组合的F1代品质性状的影响研究结果表明,Glu-D1位点对正反交品质性状的贡献最大;正交和反交组合的亚基及组合对大多数品质性状的影响无显著差异,因此正交和反交组合间的品质性状不具有明显的母体效应;正交和反交的亚基及亚基组合对品质性状的影响趋势一致,其对小麦品质参数的影响力大小分别为:在Glu-A1位点,1/1>N/1>N/N;Glu-B1位点,7+8/7+8>7+8/7+9≥7+9/7+9;Glu-D1位点,对蛋白质含量、八分钟带宽的影响力为2+12/5+10>2+12/2+12>2+12/4+12,对SDS沉降值、和面时间和衰弱角斜率的影响力为2+12/5+10>2+12/4+12>2+12/2+12;在所有参试的杂交组合中,组合1/1,7+8/7+8,2+12/5+10的品质最好。     

花生球蛋白和伴花生球蛋白在酸性条件下亚基结构的变化规律

本文通过Zeta电位、内源荧光光谱、粒度、SDS-PAGE凝胶电泳及溶解性,探讨花生球蛋白和伴花生球蛋白在酸性条件下亚基结构的变化规律。电泳分析表明,花生球蛋白40.5、37.5、35.5和27 ku亚基在常温p H 2.0~3.0的条件下被酸解,产生32.86±0.10ku的新亚基,同时22和15 ku这两条亚基增多;当p H2.0时,花生球蛋白的亚基酸解受静电屏蔽抑制。当p H为1.0~3.0,伴花生球蛋白Ⅱ61 ku亚基被酸解产生36.95±0.50、25.14±1.86、18.98±0.78和17.37±1.17 ku这四个条带。进一步研究表明,花生球蛋白和伴花生球蛋白在酸性条件下结构伸展,粒径增大,在p H 2.0-3.0时的Zeta电位及溶解度较高。在p H 2.0~3.0内,花生球蛋白荧光扫描最大发射波长相对中性条件下发生红移,红移幅度大于伴球蛋白,说明伴球蛋白展开程度较球蛋白小。伴花生球蛋白的酸解及结构变化程度都小于球蛋白,说明伴花生球蛋白亚基对酸的敏感性低于球蛋白。