Repeated polyketide synthase modules involved in the biosynthesis of a heptaene macrolide by Streptomyces sp. FR-008

Genes for biosynthesis of a Streptomyces sp. FR-008 heptaene macrolide antibiotic with antifungal and mosquito larvicidal activity were cloned in Escherichia coli using heterologous DNA probes. The cloned genes were implicated in heptaene biosynthiesis by gene replacement. The FR-008 antibiotic contains a 38-membered, poiyketide-derived macrolide ring. Southern hybridization using probes encoding domains of the type i modular erythromycin polyketide synthase (PKS) showed that the Streptomyces sp. FR-008 PKS gene cluster contains repeated sequences spanning c. 105 kb of contiguous DNA; assuming c. 5 kb for each PKS module, this is in striking agreement with the expectation for the 21-step condensation process required for synthesis of the FR-008 carbon chain. The methods developed for transformation and gene replacement in Streptomyces sp. FR-008 make it possible to genetically manipulate polyene macrolide production, and may later lead to the biosynthesis of novel polyene macrolides.     

人结肠癌(CCA)单克隆抗体及其识别抗原的分析(简报)

正常细胞转化成癌细胞后,其表型发生了一系列不同于正常细胞的变化,成为肿瘤细胞的标志。Gold和Freeman(1965)用人结肠癌组织的抽提物免疫兔,发现有些用人正常结肠组织吸收后的抗血清能够与肿瘤组织和胚胎肠道抽提物起反应,但不与正常组织抽提物起反应,由于这种抗原最初被发现在胚胎组织,故名为癌胚抗原(embryonic carcinoma antigen,简称CEA)。用敏感的放射免疫或免疫酶标方     

零下低温对杂交杨树皮层膜脂组成的影响

以不耐寒的美洲黑杨（Ｐｏｐｕｌｕｓｄｅｌｔｏｉｄｅｓｃｖ．“Ｌｕｘ”Ｉ－６９／５５,父本）和耐寒性较强的欧美杨（Ｐ．ｅｕｒａｍｅｒｉｃａｎａｃｌｃｖ．Ｉ－４５／５１,母本）的４个杂交Ｆ＿１代无性系（９５杨、５５９杨、６００杨和１３８１杨）为材料,分析了零下低温寒潮前后枝条皮层的脂质组成。结果表明,寒潮影响下,皮层中磷脂含量增加而组成基本不变,膜脂脂肪酸组成的变化规律是：寒潮前脂肪酸不饱和指数（ＩＵＦＡ）值大的无性系,寒潮前后的ＩＵＦＡ值变化量小;寒潮前ＩＵＦＡ值较小的无性系,寒潮前后ＩＵＦＡ值变化量较大。本文借用力学概念,提出相对抗性概念,给出杨树无性系的相对抗性序列。序列表明Ｆ＿１代无性系的耐寒性已较不耐寒的父本提高,这与田间观察基本一致。     

激光辐照对绵羊精子代谢和体外获能的影响

本文采用He—Ne激光处理绵羊精液,通过测试精于超弱化学发光强度、TST染色,以了解精子代谢的变化,观察精子顶体反应的发生情况,进一步从受精学角度了解激光的辐照效应。     

尖孢镰孢一新硝酸盐营养突变类型与营养体亲和性

从73个尖孢镰孢(Fusarium oxysporum)不同专化型菌株上获得684个硝酸盐营养突变株(nit mutant)。作相关氮源利用试验及亚硝酸反应后,鉴定出一新硝酸盐营养突变类型:亚硝酸盐还原酶结构基因类型,命名为nit8,占总突变株的6.7%。同时被鉴别的还有nit1、nit3和Nit M三种突变类型,它们分别占突变株总数的81.0%,3.8%和8.5%。此外,首次引入一种亚硝酸反应在这类研究中的应用,还提出了互补指数概念与公式来表示nit突变株营养体之间亲和的能力。     

茶刺蛾颗粒体病毒病毒粒子的表面增强拉曼散射(SERS)光谱研究

得到并分析了茶刺蛾颗粒体病毒(Darna trima Granulosis Virus缩写为DtGV)病毒粒子的SERS谱.DtGV病毒粒子通过COO(COOH)和NH_2(NH_3)基因被吸附到银溶胶表面上.Trp、Tyr和Phe残基侧链靠近银表面、以Trp残基侧链的振动增强效应最显著.上还增强特性与溶液的pH值密切相关.     

By-Products of Zea mays L.: A Promising Source of Medicinal Properties with Phytochemistry and Pharmacological Activities: A Comprehensive Review

Zea mays (Z. mays) is one of the main cereal crops in the world, and it′s by-products have exhibited medicinal properties to explore. This article intends to review the chemical compositions and pharmacological activities of by-products of Z. mays (corn silks, roots, bract, stems, bran, and leaves) which support the therapeutic potential in the treatment of different diseases, with emphasis on the natural occurring compounds and detailed pharmacological developments. Based on this review, 231 natural compounds are presented. Among them, flavonoids, terpenes, phenylpropanoids, and alkaloids are the most frequently reported. The by-products of Z. mays possess diuretic effects, hepatoprotective, anti-diabetic, antioxidant, neuroprotective, anti-inflammatory, anti-cancer, plant protection activity, and other activities. This article reviewed the phytochemistry and pharmacological activities of Z. mays for comprehensive quality control and the safety and effectiveness to enhance future application.     

迷宫漏斗蛛Agelena labyrinthica的染色体(蜘蛛目:漏斗蛛科)

报告迷宫漏斗蛛的染色体数目、形态结构和性染色体组成。结果表明,迷宫漏斗蛛体细胞染色体数目是:雄性2n=42,雌性2n=44,性别决定机制属X_1X_2O型。X染色体是全部染色体中最长的和最短的2个(对)。染色体似乎均为端或亚端着丝粒染色体,这由C-显带标本分析所证实,没有亚中着丝粒染色体的证据。C-带标本分析表明,常染色体中,各条染色体的C-带纹,其大小和染色深浅无明显差异,但X_2染色体上有明显宽的C-带纹。C-显带处理没有得到稳定的有重复性的带纹。     

油麻藤凝集素的荧光光谱研究

用化学修饰、内源荧光和荧光淬灭等方法研究了油麻藤凝集素（ＭＳＬ）的溶液构象变化和微环境的构象特征。研究发现ＭＳＬ分子中总共有９个色氨酸（Ｔｒｐ）残基,它们的荧光能被丙烯酰胺淬灭,但不易为ＫＩ接近而淬灭,ＭＳＬ经Ｎ－溴代琥珀酰亚胺（ＮＢＳ）修饰后,其内源性荧光发射谱发生相应变化,结果表明ＭＳＬ分子中部分Ｔｒｐ残基埋藏于分子内部,而位于分子表面的Ｔｒｐ残基可能处于分子的疏水袋中。     

水稻巯基蛋白酶抑制剂的分子修饰与其对稻瘟病菌的抑制作用

水稻巯基蛋白酶抑制剂（ＣＰＩ）经用二硫苏糖醇,对氯汞苯甲酸和碘乙酸修饰后,对木瓜蛋白酶的抑制活性并无改变;用Ｎ－乙基顺丁烯二酰亚胺与ＣＰＩ反应,可以测出ＣＰＩ分子内有１９个巯基被修饰,被修饰后,抑制活性仍无改变,表明水稻ＣＰＩ的抑制活性不需要巯基参与;应用Ｎ－溴代丁二酰亚胺与ＣＰＩ反应,可测出ＣＰＩ分子内有２个Ｔｒｐ被修饰,修饰后,抑制活性全部丧失,表明Ｔｒｐ是保持抑制活性所必需的基团。水稻巯基蛋白酶抑制剂和丝氨酸蛋白酶抑制剂对稻瘟病菌丝体的生长均有抑制作用,但后者的抑制作用比前者更强,若将两种抑制剂混合使用,则对稻瘟病菌丝体的抑制作用非常强烈;当抑制剂加入量达７２μｇ时,即可产生明显的抑制作用。