多检测GPC测试二醋片的分子量及其分布和特性粘度

采用凝胶渗透色谱(GPC)/示差(RI)/小角激光光散射(LALLS)/四毛细管示差粘度(DV)三检测器联用技术对二醋酸纤维素片(二醋片)的重均分子量(Mω)、数均分子量(Mn)、分子量分布(Mω/Mn)和特性粘度(Ⅳ)进行了测试.结果表明:①采用GPC/RI/LALLS/DV技术可以准确地测试二醋片的Mω、Mn、Mω/Mn<和Ⅳ;②以软木浆和短棉绒为原料生产的二醋片的Mω、Mn较高、Mω/Mn较宽;③热解后二醋片的Mω/Mn变宽,Ⅳ降低,并有裂解分子的聚合现象.     

超高分子量聚乙烯纤维/粘胶(50/50)混纺纱的生产工艺

超高分子量聚乙烯纤维具有良好的力学性能和化学性能,但其表面光滑,摩擦因数小,卷曲稳定性差,纺纱性能差,纱线手感发硬,舒适性、吸水性、弹性不如天然棉纤维。本文首先对超高分子量聚乙烯纤维进行抗静电柔软加湿预处理,在预处理之后依次进行清梳联、头道并条、二道并条、粗纱、细纱、络筒工序制成超高分子量聚乙烯纤维/粘胶混纺纱线。     

膜处理对食醋成分的影响

该文分别研究了10万和20万截留分子量超滤膜处理食醋原液前后理化和微生物指标的变化。结果表明:利用10万截留分子量或20万截留分子量超滤膜处理食醋原液,氨基酸态氮、无盐固形物、总酸等指标的保留率都超过90%,而浊度和菌落总数下降非常显著,经10万截留分子量超滤膜处理,除菌率达99.975%,浊度去除率达99.33%;经20万截留分子量超滤膜处理,除菌率达99.95%,浊度去除率达99.05%;经10万截留分子量超滤膜处理色度下降率达43.9%;经20万截留分子量超滤膜处理色度下降率为28.9%。经过300天的室温储藏,处理液未见明显浑浊,因此将膜处理技术应用于实际生产可有效地解决食醋的二次沉淀问题。     

绣球菌低分子量多糖的制备工艺优化及其分子量的测定

为研究绣球菌低分子量多糖的制备工艺,本文考察硫酸浓度、反应时间和料液比对多糖水解度的影响,以绣球菌多糖水解度为响应值,通过二次项数学模型拟合出最优酸解工艺参数,并采用多角度激光光散射仪测定酸解前后多糖的分子量。结果表明:在硫酸浓度0.46 mol/L、反应时间85 min、液料比6:1 mL/,绣球菌多糖水解度为67.06%±0.77%,与预测值接近,模型拟合效果良好。绣球菌多糖含有3个组分,重均分子量分别为3.32×107、1.79×106和3.18×106 Da,酸解后得到一种低分子量绣球菌多糖,含两个组分,重均分子量分别为3.25×105、5.61×105 Da,表明该法成功制备了一种绣球菌低分子量多糖。为后续的绣球菌低分子量多糖分离纯化和分子量-生物活性关系的研究提供了理论基础。     

膜处理对酱油成分的影响

文中研究了10×104截留分子量和20×104截留分子量超滤膜处理生酱油原液前后理化和微生物指标的变化.结果表明:利用10×104截留分子量或20×104截留分子量超滤膜处理生酱油,总酸、氨基酸态氮、全氮、可溶性同形物、食盐、无盐固形物等指标的保留率都在95%以上,而菌落总数和浊度指标下降非常显著,经10×104截留分子量超滤膜处理,除菌率达99.9992%,浊度去除率达98.84%;经20×104截留分子量超滤膜处理,除菌率达99.9975%.浊度去除率达98.78%;经10×104截留分子量超滤膜处理色度下降率达44.7%;经20×104截留分子量超滤膜处理色度下降率为16.3%.经过300d的室温储藏,处理液未见明显浑浊,因此将膜处理技术应用于实际生产可有效地解决酱油的二次沉淀问题.     

酱油生产中的头油、二油和三油组分分析及抗氧化活性评价的研究

文章选择还原力、对DPPH自由基清除能力、金属螯合能力三个指标,评价了酱油生产中头油、二油和三油的抗氧化活性,并对头油、二油和三油的基本组分和肽分子量分布进行分析.结果表明:二油和三油的抗氧化能力相比于头油下降的幅度比氨基酸态氮下降的幅度小,尤其是金属螯合能力下降的幅度最小;头油、二油和三油的肽分子量分布没有显著性差异(P>0.05),同一氨基酸态氮水平下,二油和头油中肽含量相当,三油中肽含量相比于头油有明显增加,从抗氧化活性和主要组分分析结果来看,二油、三油与头油没有显著差异.     

花生降血压肽的超滤分离研究

采用超滤技术对花生降血压肽进行分离,一级超滤用截留分子量为5000的超滤膜,二级超滤用截留分子量为1000的超滤膜。研究了操作压力、料液浓度和操作温度对超滤过程的影响。结果表明:一级超滤的最适操作条件为操作压力174Pa,料液浓度5%～7.5%,操作温度35℃;二级超滤的最适操作条件为操作压力209Pa,料液浓度7.5%,操作温度40℃;经超滤分离后,分子量小于1000的短肽降血压活性非常突出,IC50达到0.4mg/mL。     

蚕丝蛋白质的分子量与亚单位结构[二]

二丝素分子量与亚单位结构从熟蚕绢丝腺得到的液状丝素可用水溶解后直接来测定丝素的分子量;而若以茧层(生丝)为材料,应先将样品用碱精练除去     

α,ω二羟基二甲基硅氧烷齐聚物的合成与研究

本文介绍了用自制酸性催化剂、乙酸酐作助催化剂对八甲基环四硅氧烷进行开环聚合制备出低分子量的α,ω-二羟基二甲基硅氧烷齐聚物(PSi)的方法;研究过程中发现,通过改变乙酸酐用量可调节PSi分子量的大小,其收率可达90％以上。     

用宽分布标样测定二聚酸聚酰胺的分子量及其分布

本文用 WATERS 公司150-C ALD/GPC 凝胶渗透色谱仪,以氯仿为流动相,用μStyragel 10~3 、10~4 二根柱串接,用已知重均分子量(_w)和数均分子量(_n)的二聚酸聚酰胺作为宽分布标样,在 WATERS 730计算机上求得校正曲线,并将标样重复测定,控制分子量测定结果在仪器允许的误差范围之内,然后以此校正曲线为基准测定了不同二聚酸聚酰胺样品的分子量及其分布,进行对比分析。     

Purification and Characterization of Cathepsin B from the Skeletal Muscle of Fresh Water Fish, Tilapia mossambica

Cathepsin B from the skeletal muscle of a fresh water fish Tilapia mossambica was purified 4280-fold with 9% recovery. The electrophoretic homogeneity of the preparation was established both under native and denatured conditions. The molecular weight of cathepsin B on the basis of its gel filtration profile was 23,500 daltons. The enzyme, an endopeptidase, hydrolysed Z-arg-arg-NNap and Bz-arg-NNap, with Km values of 0.57 and 3.23 mM, respectively. Cathepsin B did not display aminopeptidase activity, but cleaved Bz-arg-NH₂, exhibiting the specificity of a carboxypeptidase. Among protein substrates tested, only azocoll was hydrolyzed at lower pH values. Leu-peptin, antipain and thiol blockers abolished the enzyme activity completely. The Kcat set^-1 value of fish cathepsin B seemed to be lower than that of mammalian enzyme.     

CATHEPTIC ACTIVITY OF FISH MUSCLE

Catheptic activity was found to be localized in the lysosomal fraction of skeletal muscle of winter flounder (Pseudopleuronectes americanus). The enzyme hydrolyzed hemoglobin, globin, bovine serum albumin and endogenous proteins. The hemoglobin splitting activity of the enzyme under different conditions was determined by gel electrophoresis. An optimum pH of 4.0 was found for both the hemoglobin breakdown and autolytic activity on the endogenous proteins. The enzyme was highly thermostable, dialysis had no effect on its activity, and the enzyme was inhibited by sodium chloride, cysteine, ATP, NAD and phenyl methyl sulfonyl fluoride. Its molecular weight was found to be about 32,000 using sucrose gradient centrifugation.     

Galactosyltransferase purified from rat milk is distinct from the human and bovine enzyme

N-Acetylglucosaminide beta 1, 4-galactosyltransferase (EC 2.4.1.22) was purified from rat milk by affinity chromatography on N-acetylglucosamine-Sepharose and alpha-lactalbumin-Sepharose columns. The purified enzyme migrated as three polypeptides of relative molecular weight 59,000, 54,000, and 27,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Antiserum raised against the 54K rat protein immunoprecipitated all three polypeptides, suggesting that they share common antigenic sites. The human milk galactosyltransferase, purified under similar conditions, was electrophoretically homogeneous on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with relative molecular weight 54K, and was not immunoprecipitated by the antiserum to the 54K rat milk protein. In addition, Michaelis constants for the enzyme from rat and human milk differed. The apparent Michaelis constant for N-acetylglucosamine and uridine 5'-diphosphate-galactose were 4.8 and .3 mM, respectively, for the rat enzyme, and 1.8 and .028 mM, respectively, for the human enzyme.     

PURIFICATION AND PROPERTIES OF GLUCOSE 6-PHOSPHATE DEHYDROGENASE FROM CORIANDER (CORIANDRUM SATIVUM) LEAVES

Glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP⁺ oxidoreductase, EC 1.1.1.49; G6PD) was purified from coriander (Coriandrum sativum) leaves; the kinetic behavior and some properties of the enzyme were also investigated. The purification was done at 4C and involved two steps: ammonium sulfate fractionation, and DEAE-Sephadex A50 ion exchange chromatography. The enzyme was obtained with a yield of 26.4% and had a specific activity of 1.826 U/mg protein. Optimum pH, stable pH, optimum temperature, molecular weight, K_M and V_max values for NADP⁺ and glucose 6-phosphate (G6-P) were also determined.
The overall purification was about 74-fold. SDS-PAGE of the purified enzyme showed a single band. Enzymatic activity was spectrophotometrically measured according to Beutler's method at 340 nm.
The molecular mass was estimated to be 74.4 kDa by SDS-PAGE and 73.2 kDa by Sephadex G-200 gel filtration column chromatography. The enzyme had an optimum pH at 8.5 and was stable at pH 8.0 in 0.1 M Tris-HCl buffer. The optimum temperature was at 30C. The K_M values for NADP⁺ and G6-P were 0.026 mM and 0.116 mM, respectively. The V_max values for these substrates were 0.035 EU/mL and 0.038 EU/mL, respectively.     

Purification and characterization of polyphenol oxidase from Trametes sp. MS39401

Two polyphenol oxidases (EC 1.14.18.1), P-1 and P-2, were purified as electrophoretically homogeneous proteins from the culture filtrate of Trametes sp. MS39401 by acetone precipitation and column chromatographies on DEAE-Sephadex A-50, Sephadex G-150 and hydroxylapatite. P-1 was purified 34-fold with a yield of 4.2%, while P-2 was purified 37-fold with a yield of 20.7%. The molecular masses of P-1 and P-2 were estimated to be 61 kDa and 90 kDa, respectively, by gel filtration. The isoelectric points of P-1 and P-2 were 3.4 and 2.7, respectively. The optimum pH range of both enzymes was 4.5-5.0 at 45 degrees C. The optimum temperature of both enzymes was 55 degrees C at pH 5.0. P-1 was stable at pH 5.0-7.5 and temperatures up to 60 degrees C. P-2 was stable at pH 3.0-7.5 and temperatures up to 50 degrees C. The thermostability of P-1 was comparable to that of the PM1 laccase of basidiomycetes, which was reported to be the most stable among basidiomycete laccases. Both enzymes were active toward various phenolic compounds and aminophenols. However, they lacked activity toward l-tyrosine. The K(m) values for (+)-catechin were 0.19 mM for P-1 and 0.67 mM for P-2. Both enzymes were appreciably inactivated by Hg(2+) and Sn(2+). Significant activation of neither enzyme was observed in the presence of metal ions and reagents. Both enzymes were significantly inhibited by copper-chelating agents, reducing agents and N-bromosuccinimide. Carbon monoxide caused appreciable inactivation of neither enzyme, so it is suggested that P-1 and P-2 belong to the group of laccases.     

Purification of Amylase from Honey

The major amylase in honey was concentrated by ultrafiltration, isolated by ultracentrifugation and gel filtration, and purified by ion‐exchange chromatography. The amylase activity was in the flow‐through fraction of the anion‐exchange column, suggesting a high isoelectric point (>7.4) for the enzyme. The enzyme fraction from the anion‐exchange chromatography was loaded onto a cation‐exchange column, and the amylase activity was eluted as a single band at 50 mM NaCl. The purification factor after this step was 531‐fold. The purified enzyme was an a‐amylase, as determined by thin‐layer chromatography, with a molecular weight of 57000 Da according to sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE). The results supported the concept that amylase in honey had a high degree of similarity with bee amylase.     

PURIFICATION OF AMINOPEPTIDASE FROM THE JAPANESE CLASSIFIED BARLEY FLOUR

In a search for biologically active materials from the classified barley flour produced in Japan an aminopeptidase activity was identified. In this paper, the purification of aminopeptidase is described. The activity of the enzyme was monitored using L-leucine-p-nitroanilide as the substrate. After extraction using 20 mM sodium acetate buffer, pH 5.5, from the 95–75% classification flour, ammonium sulfate fractionation was performed between 30 and 50% saturation. The aminopeptidase was then purified about 160-fold to homogeneity as assessed by HPLC using the following sequential chromatography steps: hydrophobic interaction chromatography, Sephacryl S-200HR gel chromatography, DEAM-ion exchange chromatography, hydroxylapatite chromatography, Sephacryl S-100HR gel chromatography. The molecular weight of this enzyme was estimated as 62 kDα by size exclusion HPLC. The enzyme had a K_m value of 0.22 mM and α pH optimum of 7.0.     

罗汉果蛋白酶的分离纯化和部分性质研究

对罗汉果蛋白酶的分离纯化和部分性质进行研究.利用硫酸铵盐析、离子交换和凝胶过滤柱层析对罗汉果蛋白酶进行了分离纯化,对纯化所得的酶进行了分子量和等电点测定.结果表明,纯化酶为电泳纯,回收率为4.2％,纯化倍数为31.1,凝胶过滤层析和SDS-PAGE电泳测得酶的分子量分别为40.3 ku和39.0 ku,等电聚焦电泳测得其等电点为8.55.     

Purification and characterization of an extracellular lipase from Mucor hiemalis f. corticola isolated from soil

We have screened 39 microfungi isolates originated from soil in terms of lipolytic activity. Out of all screened, a novel strain of Mucor hiemalis f. corticola was determined to have the highest lipase activity. The extracellular lipase was produced in response to 2% glucose and 2.1% peptone. The lipase was purified 12.63-folds with a final yield of 27.7% through following purification steps; ammonium sulfate precipitation, dialysis, gel filtration column chromatography and ion exchange chromatography, respectively. MALDI-TOF MS analysis revealed 31% amino-acid identity to a known lipase from Rhizomucor miehei species. The molecular weight of the lipase was determined as 46kDa using SDS-PAGE and analytical gel filtration. Optimal pH and temperature of the lipase were determined as 7.0 and 40°C, respectively. The enzyme activity was observed to be stable at the pH range of 7.0-9.0. Thermostability assays demonstrated that the lipase was stable up to 50°C for 60min. The lipase was more stable in ethanol and methanol than other organic solvents tested. Furthermore, the activity of the lipase was slightly enhanced by SDS and PMSF. In the presence of p-NPP as substrate, K(m) and V(max) values of the lipase were calculated by Hanes-Woolf plot as 1.327mM and 91.11μmol/min, respectively.     

淡豆豉纤溶酶的分离纯化

淡豆豉浸提液经过硫酸铵沉淀、CM-Sepharose-FF离子交换色谱和Sephacryl S-200凝胶过滤等步骤，得到豆豉纤溶酶，经SDS-PAGE表明豆豉纤溶酶为单一谱带。推断DCFE没有亚基，以单体形式存在。经过纯化，豆豉纤溶酶的回收率为3．7％，纯化倍数35．5倍，比活达到10898IU／mg。SDS-PAGE凝胶电泳和Sephacryl S-200凝胶过滤测定的DCFE相对分子质量分别为30．2kDa和31．OkDa，两种方法测定的分子量相近，说明该酶为单体酶。