黑曲霉A3木聚糖酶酶学性质研究*

黑曲霉A3（AspergillusnigerA3）的固体培养物浸出液,经过多步分离纯化后,获得三个组份的木聚糖酶,称为xⅠ、xⅡ和xⅢ。经7％凝胶浓度的盘状电泳分析均为单一组份。经等电聚焦电泳测xⅠ、xⅡ和xⅢ的等电点分别为6.8、5．5和6.1。SDS－PAGE测得亚基分子量（Da）分别为xⅠ,42000;xⅡ,20000;xⅢ,3000。三个酶组份的最适反应温度分别为xⅠ,40℃i;xⅡ,50℃;xⅢ,50℃。最适反应pHxⅠ,3．5;xⅢ,4．5;xⅢ,5．0。保温一个小时后,酶的半失活温度分别为xⅠ,55.6℃;xⅡ,54.8℃;xⅢ,46.6℃。金属离子Ag+、Hg2+、Ni2+和脲对不同的酶组份具有一定的影响。     

黑曲霉A3木聚糖酶酶学性质研究

黑曲霉A3(AspergillusnigerA3)的固体培养物浸出液,经过多步分离纯化后,获得三个组份的木聚糖酶,称为xⅠ、xⅡ和xⅢ.经7%凝胶浓度的盘状电泳分析均为单一组份.经等电聚焦电泳测xⅠ、xⅡ和xⅢ的等电点分别为6.8、5.5和6.1.SDS-PAGE测得亚基分子量(Da)分别为xⅠ,42000;xⅡ,20000;xⅢ,31000.三个酶组份的最适反应温度分别为xⅠ,40℃;xⅡ,50℃;xⅢ,50℃.最适反应pHxⅠ,3.5;xⅡ,4.5;xⅢ,5.0.保温一个小时后,酶的半失活温度分别为xⅠ,55.6℃;xⅡ,54.8℃;xⅢ,46.6℃.金属离子Ag+、Hg2+、Ni2+和脲对不同的酶组份具有一定的影响.     

应用正交旋转组合设计构建测定条件对木聚糖酶活力影响的数学模型

通过正交旋转试验,探讨了反应温度（X1）、pH值（X2）、反应时间（X3）、底物浓度（X4）、DNS用量（X5）5个测定条件对木聚糖酶活力（Y）测定结果的影响,并构建了测定条件对木聚糖酶活力影响的数学模型：Y=10．2950＋1．6563X1-0．0704X2＋0．3179X3＋1．7004X4-1．3413X5＋0．0669X1X2＋0．2094X1X3＋0．7631X1X4＋0．3301X1X5＋0．1256X2X3-0．0881X2X4＋0．1544X2X5＋0．2596X3X4＋0．1469X3X5-0．2594X4X5-0．4121X1^2-0．1258X2^2-0．2233X3^2-0．8358X1^2＋0．5217X3^2．实验结果表明：反应温度、底物浓度和DNS用量对木聚糖酶活力测定结果有极显著影响．     

黑曲霉A3木聚糖酶酶学性质研究

黑曲霉Ａ３（Ａｓｐｅｒｇｉｌｌｕｓ ｎｉｇｅｒ Ａ３）的固体培养物浸出液,经过多步分离纯化后,获得三个组份的木聚糖酶,称为ｘⅠ、ｘⅡ和ｘⅢ。经７％凝胶浓度的盘状电泳分析均为单一组份。经等电聚焦电泳测ｘⅠ、ｘⅡ和ｘⅢ。的等电点分别为６．８、５．５和６．１。ＳＤＳ－ＰＡＧＥ测得亚基分子量（Ｄａ）分别为ｘⅠ,４２０００;ｘⅡ,２００００;ｘⅢ,３１０００。三个酶组份的最适反应温度分别为ｘⅠ,４０℃;ｘⅡ     

黑曲霉M89菊粉酶的提纯与性质

黑曲霉(Aspergillusniger）M89菊粉酶经硫酸铵分级盐析、SephadexG-200凝胶过滤、DEAE-纤维素离子交换层析、聚丙烯酞胺凝胶电泳（PAGE）制备分离,提纯到4个菊粉酶组分EⅠ、EⅡ、EⅢ和EⅣ。用SDS-PAGE测定分子量分别为102．6、97．9、61．2和36．5kD;用等电聚焦电泳测得其等电点分别为4．15、4．24、4．48和4．15。4个组分的最适反应温度均为55～60℃;EⅠ的最适pH为pH4．0,其余3个组分为pH4．5．各组分的热稳定性有一定差异,分子量越小的组分,热稳定性越好,55℃处理90min,EⅠ有一定的热失活,其余3个组分无活力丧失,4个组分都是外切酶。     

粗毛栓菌木聚糖酶的纯化及性质

以麦草粉为基质培养粗毛栓菌Trametes gallica,浸提固态培养物得浸提液,后经超滤浓缩、硫酸铵盐析、Phenyl-Sepharose CL-4B疏水层析、DEAE Sepharose fast flow阴离子交换层析和Sephadex G-150分子筛层析等分离与纯化步骤,获得部分纯化的木聚糖酶,其回收率和纯化倍数分别为1.45%和15.6。进一步经活性-PAGE回收,获得三种SDS-PAGE电泳纯级的木聚糖酶同工酶组分:XⅠ、XⅡ和XⅢ(按等电点从大到小排列)。三种组分分子量均约为19.0kDa;等电点分别为:5.6、4.7和4.0;含糖量分别为:0.25%、0.63%和3.4%;XⅠ既能降解木聚糖,又能降解纤维素;XⅡ的最适作用pH值为5.0,最适作用温度45℃;Mg2+、Fe2+对XⅡ有激活作用;Mn2+和Co2+有抑制作用;测得XⅡ的Km值为0.75mg/mL,Vmax为5,000mmoL/min·mg。     

脱墨用棘孢曲霉SM-L22纤维素酶系中内切酶的纯化及性质

通过Bio GelP 60分子筛和DEAE 与Q sepharose离子交换层析等手段 ,分离纯化了棘孢曲霉SM L2 2纤维素酶系中五种内切酶组分EGⅡ 1、EGⅡ 2、EGⅢ 1、EGⅢ 2和EGⅣ ,并且对这五种内切酶组分的基本性质进行了研究。通过SDS PAGE和IEF电泳测得其分子量分别为 38 7,34 4,31 4,36 9和 2 3 7kD ,等电点分别为pH <3 5,<3 5,4 9,4 5和 5 0。 5个酶组分均属酸性纤维素酶 ,最适pH在 3 5～ 4 0之间 ;最适温度分别为 55℃、60℃、( 60～ 70 )℃、( 60～70 )℃和 60℃。各酶组分有较宽的pH稳定性 ;温度稳定性表现为EGⅡ 1 >EGⅡ 2 >EGⅢ 1>EGⅢ 2 >EGⅣ。EGⅡ 1和EGⅡ 2有较高的底物专一性 ,而EGⅢ 1、EGⅢ 2和EGⅣ对木聚糖有交叉活性。Fe2 +对除EGⅣ以外的四种酶组分都有激活作用 ,尤其是对EGⅢ 2有强烈的激活作用。动力学分析表明各纤维素酶组分对底物亲和力的大小与酶的催化率之间并无相关性。     

海枣曲霉木聚糖酶的提纯和性质

通过硫酸铵分段、异丙醇分段、Sephadex G一100凝胶过滤、及DEAE-Sephadex A-50离子交换柱层析等提纯步骤,从海枣曲霉(Aspetgillu,phornicis)的麦麸培养物抽提液中分离到4个成份的木聚糖酶,分别称之为X一1、X—II、x—III和X—IV。 经7％凝胶浓度的圆盘电泳及薄层等电聚焦分析,x一1、X．IJ和x—Ill皆为均一成分,x—Iv中则仍杂有少量X~llIo X-I的最适pH为4．0,最适温度45℃,在pH 5．0--9．0之间稳定,保温30分钟时的半失话温度t为90℃。X一和x一 的最适 分别为{．及5．,最适温度均为,稳定pH范I 11 IlI pH 50 50~(3画分别为6．0—10．0及7．0--10．0,t1分别为60及55"C。SDS一凝肢电泳法测得x一’、x-r／和x—111的分子量分别为26,500、35。,500及22,000。薄层凝胶等电聚焦法测得三者的等电点分别为{．7、{．4和4．0。在所测定的化学试剂中,Ag’、Hg’’和Mn冲对这三个酶均有较强烈的抑制作用。sDS对x—I活力影响较小,对x_I】和x—Ill则有强烈的抑制作用。脲对X-1的抑制作用大,对X-II和X—Ill的抑制作用小。     

黑曲霉木聚糖酶的纯化与性质

由凝胶电泳酶谱检测到黑曲霉１４９发本酵液中存在两型木聚糖酶,依次为Ｘ－Ⅰ和Ｘ－Ⅱ。通过硫酸铵分级沉淀及ＤＥＡＥ－Ｓｅｐｈａｄｅｘ Ａ５０柱层析分别将Ｘ－Ⅰ、Ｘ－Ⅱ纯化到凝胶电泳均一。由ＳＤＳ－凝胶电泳和浓度梯度凝胶电泳测得Ｘ－Ⅰ和Ｘ－Ⅱ的分子量分别为３７ｋＤａ,２４ｋＤａ和２３ｋＤａ,Ｘ－Ⅰ具有亚基。二者的含糖量分别为２７．６％和７．３％。Ｘ－Ⅰ和Ｘ－Ⅱ最适返应温度分别为５０℃和５５℃,ｐＨ为４．     

里氏木霉GXC木聚糖酶的研究

研究了里氏木霉GXC产木聚糖酶的条件和酶学性质。结果表明,适宜产酶碳源为乳糖、甘露糖、棉子糖、木聚糖和麸皮,氮源为牛肉膏和酵母膏;产酶的最适初始pH为4．0,30℃培养60h。对以麸皮为碳源的培养液进行纯化的酶特性研究表明,木聚糖酶的最适反应温度为50℃,pH为5．5,该酶在pH5．0－7．0和40℃以下相对稳定。Fe^2 和Mn^2 对木聚糖酶有较大的促进作用,Cu^2 、Fe^2 具有抑制作用。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.