嗜酸乳杆菌亚油酸异构酶的分离纯化研究

本实验对嗜酸乳杆菌亚油酸异构酶的分离纯化进行了研究。嗜酸乳杆菌的粗酶液经40%～80%饱和度的硫酸铵盐析、透析、SephadexG-100凝胶过滤层析等步骤进行分离纯化后,酶的纯化倍数达到3.10,比活力为475.75U/(mg蛋白质);纯化后的亚油酸异构酶在SDS-PAGE电泳中只呈现一条带,并测得分子量约为46.6kDa。     

不同反胶束体系提取大豆蛋白质的研究

反胶束技术是一种新的生物技术,是表面活性剂在非极性溶剂中形成的与正胶束结构相反的含水聚集体。本文对四种常用表面活性剂所形成的反胶束在提取大豆蛋白质方面进行了研究,首次对它们“水池”（ω0）大小、蛋白质提取率及通过SDS-PAGE电泳实验对蛋白质的亚基条带进行了比较。     

SDS-PAGE of salted anchovies (Engraulis encrasicholus L) during the ripening process

 Changes in the muscle proteins during the ripening of salted anchovies have been examined using sodium dodecyl sulphate polyacrylamide gel electrophoresis. The chemical changes occurring in the muscle proteins of anchovy during the ripening process were related to the degradation of the myofibrillar structure of the muscle. In spite of a considerable protein degradation the ripened salted anchovy maintained its structure and was easily cut into fillets. Hydrolysis of muscle proteins was significant during the first 6 weeks. Proteins of molecular weight higher than 35 kDa were more likely to be hydrolysed. Myosin heavy chains were the most sensitive myofibrillar protein. α-Actinin, actin and tropomyosin were more resistant to enzymatic degradation. Due to protein build-up of peptides resulting from the breakdown of the higher molecular proteins, it was difficult to measure changes in the myosin light chains and troponin sub-units. Received: 28 December 1999 / Revised version: 9 March 2000     

Sesame seed as an alternative plant protein source: A comprehensive physicochemical characterisation study for alkaline,salt and enzyme-assisted extracted samples

Sesame seed is mostly utilised for its oil but also the waste of the oil processing; the seed meal has also significant potential to be used as an alternative protein source. In this study, the goal is to produce sesame seed protein by using three different techniques; alkaline, salt and enzyme-assisted extraction. A comprehensive physicochemical characterisation of the extracts was performed. Total and soluble protein contents, emulsification activity & emulsion stability, FTIR spectroscopy, hydration behaviour and gelling ability experiments by TD-NMR were conducted for all extracted proteins. Also, SDS-PAGE experiments were performed to observe the effect of extraction conditions on protein folding. Overall, the aqueous phase of enzyme-assisted extracted proteins (E-ACP) had the highest protein content and solubility, which resulted in other improved physicochemical properties. Salt extracted samples were ‘salted-out’, therefore, had poor physicochemical properties. TD-NMR experiments further confirmed the solubility and gelling ability results by measuring the change in the T₂ spin relaxation times. Additionally, FTIR spectroscopy confirmed the most critical peaks for the proteins; Amide I (C=O stretching) and Amide II (N–H bending). In summary, depending on the physicochemical property of interest, different extraction methods yielded proteins with different properties.     

Purification and characterization of superoxide dismutase from garlic

An efficient and easily scaled up method to isolate superoxide dismutase from garlic is proposed. The separation and purification procedure consists of phosphate buffer extraction, heat treatment and a two-stage ultrafiltration process. The enzyme was purified 139-fold with a specific activity of 2867 U/mg protein and a yield of 91%. The native molecular mass of superoxide dismutase estimated by fast protein liquid chromatography on a Superose 6 column was 28 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed a single band near 14 kDa, suggesting that native enzyme was homo-dimeric. The optimal pH for enzyme activity was found to be 7.0, and at this pH the enzyme exhibited maximum activity at 50 °C in 50 mM sodium phosphate buffer. Among various metal ions examined, Cu²⁺ and Zn²⁺ exerted a positive effect on superoxide dismutase activity, whereas Hg²⁺ was found to be a strong inhibitor. The final purified enzyme had an isoelectric point of 5.1-5.4 and a sheet content of 46%, consistent with the literature values. This shows that the purified SOD folded with a reasonable secondary structure.     

大豆脂肪氧化酶凝胶电泳分析研究

本文介绍利用SDS电泳、簿层等电聚焦电泳技术及激光光密度计扫描分析大豆脂肪氧化酶的方法,其中薄层等电聚焦电泳技术具有准确、快速、分辨率高的特点,并应用于53份大豆资源LOX同功酶缺失体的鉴定以及激光扫描定量测定酶带峰值面积,为在我国开展大豆脂肪氧化酶研究提供了鉴定技术。     

Japanese barnyard millet (Echinochloa frumentacea): Protein content,quality and SDS–PAGE of protein fractions

Total protein from five varieties of Japanese barnyard millet (Echinochloa frumentacea,) was separated into albumin/globulin, prolamin and glutelin fractions. The protein fractions were examined by sodium dodecylsulphate polyacrylamide gel electrophoresis. Total protein of the varieties ranged from 110·5 to 139·3 mg g^?1 of which 11·3–17·2% was albumin/globulins, 6·8–9·3% prolamins, 7·5–11·6% prolamin–like, 5·9–9·1% glutelin-like and 39·3–54·4% true glutelins. Amino acid analyses of the total protein showed that the varieties had essentially the same ammo acid composition. With the exception of lysine the amino acid levels adequately matched the provisional FAO scoring pattern. The amino acid composition of the protein fractions was also very similar. Electrophoretic analysis showed that the albumin/globulin fraction contained three or four components; the prolamin and glutelin fractions each had five components. The glutelin fraction had higher molecular weight components than the other two fractions.     

利用蛋白质"指纹"技术鉴定澳大利亚、法国啤酒大麦的品种和纯度

采用操作简便、分辨率高的种子醇溶蛋白SDS-PAGE电泳技术对常用澳大利亚和法国啤酒大麦进行鉴定，利用Gel-Pro软件对电泳图谱进行条带分析和比较，建立了澳大利亚和法国啤酒大麦品种标准图谱库。利用Cross Checker 2．8和MEGA3软件对供试的啤麦品种进行遗传聚类分析，结果与传统分类相近。并成功进行了人工混种试验。     

Isolation and partial characterization of the surface protein of Lactobacillus acidophilus strains

A surface protein layer was found to be present in some Lactobacillus acidophilus strains. it could be visualized with electron microscopy and extracted with sodium dodecyl sulfate or guanidine hydrochloride. The protein was resistant to several proteolytic enzymes, but sensitive to pronase. Amino acid composition analysis revealed about 30% hydrophobic amino acids. Hydrophobicity study with a hexadecane partition assay demonstrated that the cells were hydrophobic and removal of the surface layer with pronase destroyed the hydrophobic nature of the cells. Several growth conditions studies were found to have little effect on synthesis of the surface protein.     

不同还原剂对大豆胰蛋白酶抑制剂的钝化研究

研究了二巯基苏糖醇(DTT)、亚硫酸钠(Na2SO3)和半胱氨酸(Cys)对大豆胰蛋白酶抑制剂活性的影响。实验在温度80℃,pH7.5条件下反应,并以BAPNA为底物,采用改进的方法测定DTT对大豆蛋白酶抑制剂的钝化作用,最后用SDS-PAGE方法和凝胶排阻色谱法研究其蛋白酶钝化敏感性。通过改进的BAPNA法得出还原剂钝化大豆胰蛋白酶抑制剂由大到小顺序依次为:DTT>Na2SO3>Cys,并通过SDS-PAGE进一步证实了比色法得出的结论。而凝胶排阻色谱法说明了还原剂对大豆胰蛋白酶抑制剂作用使得抑制剂中二硫键被打断,抑制剂结构发生改变,有新的物质生成。所以,得出大豆胰蛋白酶抑制剂的稳定性与二硫键的存在有关。