不同贮藏时间的莲子蛋白质提取及其理化特性研究

为研究莲子在陈化过程中蛋白质变化规律,本文首先通过正交实验对莲子蛋白质提取条件进行优化,再利用优化的条件,分别以不同贮藏时间的莲子为材料,提取获得莲子蛋白。采用SDS-PAGE电泳和氨基酸分析仪,研究提取蛋白质的相对分子量（Mr）组成及氨基酸组成。结果表明:莲子蛋白的优化提取条件为:p H11,料液比1∶30,提取时间2h,提取率达60.11%;随着贮藏时间的增加,莲子蛋白组成发生了一定变化,Mr在26⁴3ku的蛋白质含量逐渐变少;当年莲子蛋白的总氨基酸含量最高,但随着陈化过程的进行,含硫氨基酸中蛋氨酸含量下降。贮藏过程中莲子蛋白质结构等的变化是莲子陈化的主要原因之一。      

大豆粕蛋白酶酶解条件和产物分析研究

以水解度为衡量指标,通过正交试验设计,对木瓜蛋白酶、胰蛋白酶和As1.398蛋白酶酶解大豆粕的最佳水解条件进行了筛选.试验结果表明:木瓜蛋白酶水解大豆粕的最佳条件为pH7.0、温度60℃、时间5 h、酶浓度5%.胰蛋白酶水解大豆粕的最佳条件为pH7.0、温度50℃、时间7 h、酶浓度5%;As1.398蛋白酶水解大豆粕的最佳条件为pH6.5、温度50℃、时间7 h、酶浓度5%.对酶解产物进行超滤和SDS-PAGE电泳分析表明,因酶解条件不同,大豆粕酶解产物中蛋白质和肽的组成及其数量也不同;酶的种类不同,大豆粕酶解产物组成也不同;大豆粕水解度越高,其酶解产物中小分子肽数量越多.     

菊粉酶的分离纯化与鉴定

将无花果曲霉(Aspergillus ficuum)SK004菌株所产菊粉酶系进行分离纯化。通过活性炭脱色、硫酸铵分级沉淀、透析脱盐、DEAE-Sepharose CL-6B离子交换层析、Sephadex G-75凝胶色谱后,主要得到1种菊粉酶。经SDS-PAGE分析此菊粉酶为单一谱带,分子质量为53665u。     

大红袍花椒籽种仁蛋白的分类研究

对大红袍花椒种仁蛋白质进行了Osborne蛋白质分类,分离出花椒种仁清蛋白16.38%、球蛋白41.09%、醇溶蛋白2.53%、谷蛋白33.29%,然后将分类后的各种花椒种仁蛋白质进行SDS-PAGE电泳分析测定亚基大小.结果表明,蛋白质组分中含有大量盐溶性的球蛋白和碱溶性的谷蛋白,易采用盐溶法或稀碱提取;并且花椒种仁中各蛋白质组分的相对分子质量较小,有利于人体对蛋白质的消化吸收.     

Physicochemical Properties of Wheat Flour Dough Modified by Microbial Transglutaminase

ABSTRACT: In this study, microbial transglutaminase (MTGase) was employed to modify viscoelasticity of wheat flour dough. Three flours, namely In-, Mid-, and Out-flour derived from different parts of wheat kernel, were used. When adding 16 ppm MTGase, the maximum resistance to extension (R_max) of In-(58%), Mid-(56%), and Out-flour(52%) doughs, prepared at specific water levels indicated in parentheses, is increased by 51%, 35%, and 77%, respectively. The extensibility (E) of these 3 doughs is reduced by 16%, 11%, and 6%; the stickiness is also lowered by 12%, 5%, and 22%, respectively. SDS-PAGE analysis indicates that crosslinks occur within wheat gluten of MTGase-treated dough.     

人白细胞介素-2提纯样品中PHA残留量测定

应用SDS梯度聚丙烯酸胶凝胶电泳法、淋巴细胞增殖法和显微血凝法对三批提纯人IL-2样品中的残留PHA作了检测·结果表明我们提纯工艺对去除PHA效果较好，PHA残留浓度低于25μg／ml，PHA总量从提纯前的600mg降为0．75mg以下．去除率达99％以上，另外，我们还对三种检测方法进行了比较，认为显微血凝法是一种简便、特异、灵敏的方法。     

Detection of soybean antigenicity and reduction by twin-screw extrusion

Antiserum toward soybean meal was prepared by feeding a soybean meal diet containing large amounts of antigens to calves. The antiserum was used to develop a sensitive detection method for soybean meal antigens by competitive inhibition enzyme-linked immunosorbent assay. With this method, the effectiveness of twin-screw extrusion cooking in reducing antigenicity in soybean meal was examined. Antigenicity was reduced to 0.1% of the original activity by extrusion cooking with screws containing kneading-disc elements and die-end temperatures exceeding 66°C. Electrophoretic analysis of the cooked meal indicated that the reduction in antigenicity was due to degradation of protein structures, particularly those with molecular weights exceeding 40 kDa.     

Comparison of Electrophoretic Protein Profiles from Sheep and Goat Parotid Saliva

Saliva provides a medium for short-term adaptation to changes in diet composition, namely, the presence of plant secondary metabolites. Salivary proteins have biological functions that have particular influence on oral homeostasis, taste, and digestive function. Some salivary proteins, such as proline-rich proteins, are present in browsers but absent in grazers. Despite the significance of salivary proteins, their expression patterns in many herbivores are unknown. We investigated the sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile of parotid salivary proteins from two domesticated species, one a grazer, the sheep, Ovis aries, and the other a mixed feeder, the goat, Capra hircus, both fed on the same conventional diet. With 12.5% polyacrylamide linear gels, we observed uniform patterns of salivary proteins within the two species. In the goat profile, 21 major bands were observed, and 19 in the sheep profile. Each band was subjected to peptide mass fingerprinting for purposes of identification, allowing for 16 successful protein identifications. Marked differences were observed between the species in the region of 25–35 kDa molecular weights: one band was present in significantly different intensities; three bands were present only in goats; and one band was present only in sheep. This is the first report of a comparison of the protein salivary composition of sheep and goats and suggests that future research should be conducted to reveal a physiological function for salivary proteins related to the differences in feeding behavior of these species.     

Electrophoretic Characterization and Functional Properties of Rice Proteins from Indian Rice Cultivars

Rice protein isolates and extracts of protein fractions were prepared from Indian rice cultivars, namely, Jaya, HKR-120, P-44, Sharbati, Bas-370, and HBC-19. The protein extracts were characterized using SDS-PAGE. The total protein contents of rice cultivars ranged from 5.46 to 7.02 g/100 g sample with albumin and glutelin fractions showing the highest variability among rice cultivars. The electrophoretic patterns of protein fractions exhibited many varietal differences with glutelin fraction revealing the most heterogeneous (10–17 polypeptide units) and prolamin fraction revealing the most homogenous polypeptide composition (3 polypeptide units). The alkali extracted rice endosperm protein isolates showed favorable emulsifying and foaming capacities particularly at an alkaline pH of 11. The total protein content was significantly correlated positive with foaming capacity (r = 0.917, p < 0.01) and negative with oil absorption capacity (r =??0.914, p < 0.05). The total protein content was also correlated significantly positive with cooking time (r = 0.956, p < 0.01) and cooked grain hardness (r = 0.966, p < 0.01).     

Identification of an acidic α-amylase from Alicyclobacillus sp. A4 and assessment of its application in the starch industry

An acidic α-amylase was purified from thermoacidophilic Alicyclobacillus sp. A4 by ion exchange chromatography with 22% recovery, and showed a molecular mass of 64 kDa by SDS-PAGE. Its amino acid sequence was determined by sequencing three internal peptides and the complete genome of strain A4, and shared highest identity (64%) with Alicyclobacillusacidocaldarius α-amylase. Compared with other reported α-amylases, the purified enzyme had some distinct characteristics. The optimal activity was found to occur at 75 °C and pH 4.2, similar to the glucamylase widely used in the starch industry. The enzyme was Ca²⁺ independent, and had strong ability to digest raw starch (96.71%) with commercial glucamylase in one step. These properties of the purified enzyme make up the deficiency of the commercial α-amylases currently used and avoid repeated adjustment of pH and temperature in double-enzymatic sugar-making process. The purified enzyme will be commercially valuable in the starch industry.