DETECTION OF PROTEOLYSIS BY SODIUM DODECYL SULFATE POLYACRYLAMIDE GEL ELECTROPHORESIS: A DEMONSTRATION OF PROTEIN HYDROLYSIS AND ELECTROPHORESIS FUNDAMENTALS

A laboratory exercise is presented for evaluating the action of proteolytic enzymes on the proteins BSA and two types of catalase. The proteins are incubated with papain and bromelain-based meat tenderizers and the digestion products are analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The exercise demonstrates both electrophoresis fundamentals and the manner by which proteases function.     

DISC GEL ELECTROPHORESIS OF PROTEINS IN NATIVE AND HEAT-TREATED ALBUMEN, YOLK, AND CENTRIFUGED WHOLE EGG

SUMMARY– Polyacrylamide disc gel electrophoresis was an effective technique for resolving the proteins of albumen, yolk, and centrifuged whole egg into distinct bands. Albumen proteins including ovalbumins, conalbumins, and globulins were separated into 12 bands. Ovomucoid could not be detected and lysozyme did not migrate into the gel. With yolk, 19 bands including livetins and lipovitellins but not low-density lipoproteins were formed. When centrifuged whole egg was subjected to electrophoresis, livetin and albumen protein bands were detected, but no evidence was obtained for the formation of new protein complexes. Alterations of gel patterns were observed when albumen, yolk, and centrifuged whole egg were heated to pasteurization temperatures of 61.7°C and above.     

PERTURBATION OF THE STRUCTURE OF CLOSTRIDIUM PERFRINGENS ENTEROTOXIN BY SODIUM DODECYL SULFATE, GUANIDINE HYDROCHLORIDE, pH AND TEMPERATURE

The effects of sodium dodecyl sulfate, guanidine · HCl, heat and pH on the tertiary structure of Clostridium perfringens type A enterotoxin were determined by UV difference spectroscopy and by accessibility of the amino groups to 2, 4, 6-trinitrobenzene sulfonic acid (TNBS) and the one sulfhydryl group to 5, 5'-dithiobis (2-nitrobenzoic acid) (DTNB). Biological stability of enterotoxin at several pH's at 55°C in the presence and absence of borate and dipicolinate ions was determined by the guinea pig skin test. Sodium dodecyl sulfate and heat did not unfold the molecule while treatment with >4.5 M guanidine · HCl at ≥25°C completely unfolded the molecule based on UV difference spectral changes and the accessibility of the amino groups to reaction with TNBS. Sodium dodecyl sulfate, at 0.2%, made the sulfhydryl group accessible to DTNB but did not affect the accessibility of the amino groups (7.89 ± 0.15 groups in the native molecule). Guanidine · HCl, at 6.5 M for 30 min and ≥25°C, made all 17 e-amino groups and the one α-amino group accessible to TNBS. At pH's above 8 spectral differences, in relation to the spectrum at pH 6.8, were associated primarily with ionization of the tyrosine residues while at pH's below 5.5 the spectral changes were probably a result of protonation of carboxyl groups in the vicinity of tyrosine and tryptophan residues, and of aggregation.     

聚丙烯酰胺凝胶电泳研究硫酸铵盐析分离猪血清IgG

通过聚丙烯酰胺凝胶电泳对硫酸铵盐析分离猪血清G型免疫球蛋白进行了研究，结果显示pH值7．4时，猪血清IgG主要沉淀区间为硫酸铵饱和度25-40％，10倍稀释猪血清IgG最佳硫酸铵沉淀参数为：pH值7．4，硫酸铵饱和度37％，此时IgG得率为80．5％，纯度为72．9％。沉淀的血清蛋白中还含有约12％白蛋白和9％其它γ-球蛋白。沉淀时IgG活性保持不变。     

小麦淀粉与谷朊粉生产

指出了小麦淀粉与谷朊粉生产的重要性；简要叙述了小麦淀粉与谷朊粉生产的历史、典型工艺及最新动态。着重介绍了韦斯伐里亚公司的三相卧螺工艺，并对新旧工艺进行对比，指出了小麦淀粉与谷朊粉生产中的关键问题，并进行了探讨。     

EFFECT OF HEN EGG PRODUCTION AND PROTEIN COMPOSITION ON TEXTURAL PROPERTIES OF EGG ALBUMEN GELS

The effect of hen age, strain and dietary amino acid intake on the egg albumen gel textural properties was studied in two experiments by textural profile analysis (TPA) and uniaxial compression (UC) tests. In experiment 1, eggs from 4 different hen flocks were heat processed industrially. Egg rejection due to poor albumen gelling was correlated to hen age (r = 0.502), albumen dry matter (r =−0.632), gel hardness of 1^st compression (r =−0.765), and gel work of 1^st compression (r =−0.740) in TPA. In experiment 2 two hen strains, representing two levels of egg production, were fed diets with supplementation of L-lysine, methionine or both amino acids compared to a control diet. The lysine intake ranged from 818–1272 mg/hen/day and methionine intake from 377–575 mg/hen/day among hen groups, but without significant effect on the albumen gel texture parameters. The hen strains differed significantly in egg production (P<0.001), physical (P<0.001), chemical (P<0.05) and gel textural parameters of egg albumen (P<0.01). Hen age was essential, and correlated to the industrial egg rejection (r = 0.729), albumen dry matter (r =−0.902) and gel stress at fracture (r =−0.884). Albumen gels with high fracture stress values were found to contain a modified form of ovofransferrin.     

十二烷基硫酸钠对盐酸的标准热力学性质的影响

本文测定了Pt,H_2(1.01325×10~5Pa)|HCI(m) SDS H_2O|AgCI-Ag电池的电动势,应用最小二乘法确定了标准电动势E和E随温度变化的关系式。依据热力学函数关系式,求出HCI在十二烷基硫酸钠(SDS)溶液中处于标准状态和在纯水中处于标准状态时,诸热力学函数的差值,即△G_t、△H_t和△S_t之值。结果表明△G_t均为负值,△H_t和△S_t均为正值。     

IDENTIFICATION OF MILK FROM GOAT, EWE AND COW IN THEIR MIXTURES BY POLYACRYLAMIDE GEL ELECTROPHORESIS

A rapid identification of milk from goat, ewe and cow was done in the raw milk mixtures by polyacrylamide gel electrophoresis method. Two kinds of milk were mixed in the following proportions: 75:25%, 50:50%, 25:75% (V/V). Raw goat milk was adulterated with increasing proportions of cow milk or ewe milk, and ewe milk was adulterated with cow milk. Ewe milk in goat milk was detected by the electrophoretic resolution of the casein fraction whereas cow milk in goat and in ewe milk was identified by the presence of two fast-moving whey proteins.     

毛细管胶束电动色谱分离测定大米中水胺硫磷和灭多威的残留量

用毛细管胶束电动色谱成功地分离了2种农药：水胺硫磷和灭多威。研究了电泳缓冲液的pH、浓度及表面活性剂浓度等影响因素,在选定的最佳分离条件：pH7.0,20mmol/L硼砂缓冲溶液＋70mmol/LSDS＋20%甲醇,20kV分析电压,检测波长214nm下,二组份在12min内得到基线分离。检测限分别为：水胺硫磷1.2μg/mL和灭多威0.9μg/mL。同时用该方法对通辽地区的大米样品进行了抽检,抽检结果表明：开鲁县大米样品中水胺硫磷和灭多威的残留量最高;科左后旗的大米样品中未检测到水胺硫磷和灭多威这两种农药。