芽四糖淀粉酶产生菌的筛选与发酵条件的研究

从290个土样中分离到1380株细菌,加上本所其他课题组提供的细菌共1870株,其中有707株能分解淀粉,经过复筛、纸层析鉴定有3株菌的淀粉酶酶解液中主要产物是麦芽四糖,进一步用β－淀粉酶水解为麦芽糖,用萄葡糖淀粉酶水解为萄葡糖,确证为麦芽四糖。其中最优菌株为537．1,其酶解产物中麦芽四糖占90％,而其他两株菌的酶解产物中除麦芽四糖外,还有较多的麦芽糖及麦芽三糖,因此选择了537．1作为形成麦芽四糖淀粉酶的优良菌株,经鉴定,该菌属于产碱菌(Alcaligenessp．)。菌株537．1产酶的较好条件为t培养基中麦芽糖1．5％,蛋白胨0．5％,起始pH7—7．5,在27—28℃振荡培养48h。株537．1培养液可以酶解谷类、薯类和野生植物淀粉生成麦芽四糖。     

螺旋藻POD、CAT和SOD同工酶的研究*

采用聚丙烯酰胺凝胶电泳法对毛乌素沙地碱湖的钝顶螺旋藻S3和鄂尔多斯螺旋藻S4与国外引进的钝顶螺旋藻S₁和极大螺旋藻S₂ 的POD、CAT和SOD同工酶进行了比较研究。结果表明 :4个样品的 3种酶同工酶带数目不同 ,依次是S₄ >S₃>S₁>S₂ ;S₃和S₄ 酶带数多 ,对环境适应性强 ,进化程度较高。螺旋藻不同种间的酶谱相似系数     

植物细胞离析酶的制备和应用

用 Aspergillus sp．A-19菌经固体发酵研制成一种新的植物细胞离析酶(SeparatasezA—P)。其离析单细胞的酶活力平均为70 767u／g,有效作用的pH在3．0—7．0,温度为20—45℃。发酵培养基配方是麸皮：桔皮粉：(NH₄)₂SO₄(w／w)为100:100:O．63,料水比为1 :2．0,培养适宜条件为25℃、60小时。     

产碱菌麦芽四糖淀粉酶的纯化及性质

产碱菌(Alcaligenes sp．)537．1除去菌体的培养液经硫酸铵沉淀及DEAE-纤维素离子交换柱层析,得到了凝胶电泳均一的麦芽四糖淀粉酶。纯化了141倍,酶活力回收40.1％,比活力达3308U／mg。用浓度梯度PAGE和SDS—PAGE测定酶分子量分别为68000和66000,不具亚基。用PAG-1EF测定等电点为4．45。酶反应最适pH和温度分别为7.0和60C。在pH7—10范围内稳定,该酶半衰期为37C 12小时,50 C 1小时和62 C 6分钟。 麦芽四糖淀粉酶是糖蛋白,含有4％左右的糖,含有27．10％酸性氨基酸、11.08％碱性氨基酸和1．82％色氨酸。     

康氏木霉纤维素酶系中Cx酶多分子型的分离纯化及某些性质

从康氐木霉(Trichoderma kkoningii) 白色变异株 AS 3．4001的粗酶制剂中,获得了纤维素酶系中的一组C_x酶(C_xt C_xz C_z3 C_z4)。分离步骤包括Sephadcx G-75凝胶过滤,DEAE-Sephadex A-50离子交换层析,ConA-Sepharnse亲合层析,SE—Sephadcx C-50离子交换层析及聚丙烯酰胺凝胶电泳。C_xt 与C_xt 的分子量不同而所带电荷相同,它们的分子量各自为44,500和34,000。C_xz—C_x4 的分子量相同而所带电荷不同。纯化的C_xt—C_z4“经聚丙烯酰胺凝胶电泳鉴定为单带。比较它们对羧甲基纤维素钠(CMC—Na)的糖化力及液化力表明在作用方式的随机性上C_xz>C_z3>C_z1>C_x4。     

电击法介导的紫孢侧耳原生质体转化

使用基因脉冲导入仪成功地将糙皮侧耳DNA导入紫孢侧耳单核原生质体内,获得了具有"锁状联合”特征的双核转化菌株T₁,和T₂。转化率为8．2×10^-5,转化比为3．6％。酯酶同I酶分析结果表明,转化菌株除具有受体菌的酶带外,还存在供体菌的酶带,由此证明转化菌株确为紫孢侧耳和糙皮侧耳DNA重组的产物。转化菌株子实体形态也发生了变化。两菌株子实体均不释放孢子;T₁。菌柄中生,T₂成熟子实体菌盖中部易长出菌丝。     

产蛋白酶枯草杆菌的选育及应用研究——Ⅱ.N1025菌产酶条件与酶性质的初步考察

本文报道产蛋白酶菌株枯草杆菌N1025的产酶条件及酶性质的初步考察。在45℃培养,最适产酶时间为20小时,培养基以自然pH为好,CaCl₂、MgSO₄、FeCl₃及CaCO₃有促进产酶作用,尿素、(NH₄)₂SO₄及NaNO₃对产酶有明显的抑制作用。以酪蛋白为底物,在45℃时,pH7—8酶活性较高;在52—55℃,出现pH 7及9两     

硫霉素生物合成酶基因克隆的研究

利用NTG诱变从硫霉素产生菌中获得了生物合成阻断变株Y₃。通过对Y3变株原生质体形成、再生条件及DNA转化的研究,初步建立了以变株为受体的克隆系统,以pIJ680为载体,从硫霉素产生菌S．Cattleya中鸟枪克隆,获得了能使Y₃变株恢复产生硫霉素的酶基因。根据对Y₃积累的中间产物的分析,认为该酶基因可能与硫霉素生物合成过程中肽的环化作用有关。重组质粒分子大小为9．8kb左右,插入片段大小为4．5kb,分子杂交试验证明插入片段来源于硫霉素产生菌S．Cattleya。     

玉米跨代干旱胁迫记忆生理机制及DNA甲基化变化分析

为研究亲代干旱锻炼对后代玉米生理特性和DNA甲基化修饰的影响,以亲代(G₀代)经干旱锻炼的玉米自交系B73和H99自交后代(G₁代)为材料,利用20% PEG 6000模拟干旱胁迫条件,检测G₁和G₀代叶片相对含水量(RWC)与丙二醛(MDA)、可溶性糖、脯氨酸含量以及超氧化物歧化酶(SOD)、过氧化物酶(POD)活性变化,并利用甲基化敏感扩增多态性技术(MSAP)检测G₁和G₀代基因组DNA甲基化状况,分析2个世代玉米生理指标和基因组DNA甲基化修饰的变异规律。结果表明：(1)在相同干旱胁迫条件下,玉米B73和H99 自交系G₁代叶片的RWC、可溶性糖与脯氨酸含量以及SOD和POD活性均高于G₀代,其G₁代MDA含量则低于G₀代;G₁代叶片的RWC减少量和MDA增加量小于G₀代,G₁代可溶性糖和脯氨酸含量以及SOD和POD活性增加量均大于G₀代。(2)干旱胁迫诱发了B73和H99 自交系G₁和G₀代DNA甲基化水平和甲基化模式的改变;在相同干旱胁迫条件下,两自交系G₁代DNA甲基化修饰变化均大于G₀代。(3)B73和H99 自交系DNA甲基化修饰变异规律不同,随胁迫时间延长,B73 自交系2个世代CG、CHG甲基化水平均呈上升趋势,H99 自交系2个世代CG甲基化水平呈上升趋势,CHG甲基化水平呈下降趋势;B73 自交系2个世代均以CG hypo和CHG hypo变化为主,H99 自交系2个世代均以CHG hypo和CG hyper变化为主。研究发现,B73和H99玉米自交系G₁代植株的抗氧化和渗透调解能力以及DNA甲基化修饰变化均大于G₀代,其抗旱性也强于G₀代,从而证明玉米存在跨代干旱胁迫记忆。     

黄土高原苹果园蒸腾导度大气驱动规律比较

植物蒸腾导度是表征土壤-植物-大气连续体（SPAC）中植物-大气间水汽传导过程、反映植物水分调控能力的一类重要变量，常见有冠层导度（G_c）、冠层气孔导度（G_s）与叶片气孔导度（g_s），明确三者在反映冠层蒸腾过程时的异同或关联性对于理解植物水分利用机制具有重要意义。本研究基于对黄土高原果园苹果树生长季内树干液流（J_s）及环境因子的连续观测，计算了G_c、G_s及脱耦联系数（Ω）等变量，并与短期连续观测的叶片气孔导度（g_s）比较，分析了G_c、G_s和g_s在反映冠层蒸腾特征方面的异同及其关系。结果表明，日变化过程中G_s、g_s呈"单峰"型曲线，而G_c则呈"先增后减，午后抬升"的"双峰"型曲线。g_s与G_s存在较紧密的线性关系（R²=0.80），但与G_c的线性关系较弱（R²=0.02）。G_c、G_s均随大气水汽压亏缺（VPD）的变化呈现确定的规律，其中，上边界函数呈递减的对数函数关系，平均值则符合先增后减的Log-Normal函数关系（R²>0.95），拐点对应的VPD值分别为1.33和1.16 kPa。在一日内，G_s对VPD变化的响应过程与g_s对VPDL （基于叶片温度计算的水汽压亏缺）变化的响应过程总体一致，其一致性高于G_c对VPD变化的响应。整个生长季（4-10月）中果树的Ω平均值为0.12，随着Ω递减，G_c与G_s的线性相关性愈趋紧密，其斜率呈递增趋势，G_c越来越趋近于G_s。研究结果表明，在北方地区，基于树干液流的监测能较准确的推导整株并估算林分的冠层蒸腾导度。与实测g_s的变化过程比较，G_s比G_c具有更高的一致性，G_s可以作为描述苹果树水分利用过程响应大气驱动的更为恰当的变量。     

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.