Frankia菌种保藏

对用4种方法保藏的Frankia菌,进行了培养物存活、形态及其固氮活性的检测.发现在无氮液体培养基中保藏6年的Frankia.菌丝断裂,孢囊不完整.同期经有氮液体保藏的Frankia菌孢囊较完整.冷冻干燥保藏3.5年和砂管保藏8年,孢囊和菌丝均较完整.上述方法保藏的菌种,经活化后均能生长,且具有典型的Frankia菌形态特征和固氮活性.4种方法比较,无氮液体保藏法的菌体细胞生长速度快,固氮活性强,有侵染结瘤能力.     

Production of chitinolytic enzymes from a novel species ofAeromonas

A bacterial strain secreting potent chitinolytic activity was isolated from shrimp-pond water by enrichment culture using colloidal crab-shell chitin as the major carbon source. The isolated bacterium, designated asAeromonas sp No. 16 exhibited a rod-like morphology with a polar flagellum. Under optimal culture conditions in 500-ml shaker flasks, it produced a chitinolytic activity of 1.4 U ml^–1. A slightly higher enzymatic activity of 1.5 U ml^–1 was obtained when cultivation was carried out in a 5-liter jar fermentor using a medium containing crystalline chitin as the carbon source. The secretion of the enzyme(s) was stimulated by several organic nitrogenous supplements. Most carbon sources tested (glucose, maltose, N-acetylglucosamine, etc) enhanced cell growth, but they slightly inhibited enzyme secretion. Glucosamine (0.5% w/v) severely inhibited cell growth (16% of the control), but it did not significantly affect enzyme secretion. The production of chitinolytic enzymes was pH sensitive and was enhanced by increasing the concentration of colloidal chitin to 1.5%. The observed chitinolytic activity could be attributed to the presence of -N-acetylglucosaminidase and chitinase. Chitinase was purified by ammonium sulfate fractionation and preparative gel electrophoresis to three major bands on SDS-PAGE. An in-gel enzymatic activity assay indicated that all three bands possessed chitinase activity. Analysis of the enzymatic products indicated that the purified enzyme(s) hydrolyzed colloidal chitin predominantly to N,N-diacetyl-chitobiose and, to a much lesser extent, the mono-, tri, and tetramer of N-acetylglucosamine, suggesting that they are mainly endochitinases.     

A glutamate/glutamine/aspartate/asparagine transport operon in Rhodobacter capsulatus

A mutant of Rhodobacter capsulatus was identified in which an operon encoding a binding-protein-dependent transporter was interrupted by Tn5 transposition. Cloning and sequence analysis of the wild-type operon revealed a four-gene cluster with similarities to genes encoding periplasmic binding proteins (BztA), integral membrane proteins (BztB and BztC), and ATP-binding proteins (BztD). To assess the function of this putative binding-protein-dependent transport system, a mutant was constructed in which most of the bztABCD operon was deleted and replaced by an antibiotic-resistance marker. The deletion mutant grew more slowly than the wild type in NH-free medium supplemented by glutamate, glutamine, aspartate or asparagine; it was resistant to toxic analogues of Glu, Asp, and Asn at concentrations that inhibited growth of the wild type; and it was defective in the uptake of Glu, Gin, and Asp. A complementing plasmid containing the wild-type copy of bztABCD was able to rescue all the mutant phenotypes. Taken together, these results indicate that the proteins encoded by bztABCD are active in the uptake of Glu, Gin, Asp, and Asn. In addition, competition experiments, in which the ability of each of the four amino acids to compete for the transport of one another was examined, demonstrated that all four substrates share at least one component of this transport system.     

玉米种子萌发成苗不同阶段需水阈值的研究

用渗透势不同的聚乙二醇（ＰＥＧ）６０００模拟外界环境水分条件,对玉米不同品种的种子在萌动、萌发及成苗三个阶段需水的量化研究表明,种苗的抗旱性随吸水进程的推进而减弱;种子在萌动、萌发及胚芽伸长至一定长度的时间（ｔ）与外界环境水势（ｗ）之间存在着１／ｔ＝ａ＋ｂｗ的关系,据此推算出不同品种在不同成苗阶段的需水阈值,发现不同品种在同一成苗过程中对环境水分条件的反应不同,它们的抗旱性也不同。     

Allergenic and antigenic proteins released in the apertural sporoderm during the activation process in grass pollen grains

A combination of transmission electron microscopy with immunocytochemical methods was used to localize antigenic and allergenic proteins during the maturation and activation processes of Poaceae pollen grains. The intine undergoes a series of modifications that play a decisive role in these processes. Allergenic and antigenic proteins were detected particularly in the intine of activated in vitro grass pollen grains. Labelling of antigenic proteins was more abundant and less specific than that of allergenic proteins. At the time of hydration, the operculum was lifted up, the intine was swollen and labelling of allergenic proteins appeared highly localized in the Zwischenkörper. No significant labelling was observed when the Zwischenkörper gelatinized. Immunolocalization of allergenic proteins in the activated Zwischenkörper indicated the presence of proteins related to activation of the pollen grains. This confirms that the intine function is involved in the processes of pollen tube formation and fertilization, and also suggests the possible mechanism activated in the pollen grains when allergenic proteins reach the mucosa of sensitive subjects.     

Efficient enzymatic synthesis of 13 C,15N-labeled DNA for NMR studies

The power of heteronuclear NMR spectroscopy to study macromoleculesand their complexes has been amply demonstrated over the last decade. Theobstacle to routinely applying these techniques to the study of DNA has beenthe synthesis of ¹³C,¹⁵N-labeled DNA. Here wepresent a simple and efficient method to generate isotope-labeled DNA forNMR studies that is as easy as that for isotope labeling of RNA. The methodwas used to synthesize a uniformly¹³ C,¹⁵N-labeled 32-nucleotide DNA that binds tohuman basic fibroblast growth factor with high affinity and specificity.Isotope-edited experiments were applied to the¹³ C,¹⁵N-labeled DNA bound to unlabeled protein,and the ¹³ C,¹⁵N-labeled DNA was also examined incomplex with ¹⁵N-labeled protein. The NMR experiments showthat the DNA adopts a well-defined stable structure when bound to theprotein, and illustrate the potential of¹³ C,¹⁵N-labeled DNA for structural studies ofDNA–protein complexes.     

Molecular structure of the halogenated anti-cancer drug iododoxorubicin complexed with d(TGTACA) and d(CGATCG).

4'-Deoxy-4'-iododoxorubicin, a halogenated anthracycline derivative, is an anticancer agent currently under Phase II clinical trials. In preclinical studies, it has demonstrated significantly reduced levels of cardiotoxicity compared to currently employed anthracyclines. It also has modified pharmacological properties resulting in an altered spectrum of experimental antitumor activity. The iodine atom at the 4' position of the sugar ring reduces the basicity and enhances the lipophilicity of this compound as compared to related anthracycline drugs. We report here single crystal X-ray diffraction studies of the complexes of 4'-deoxy-4'-iododoxorubicin with the hexanucleotide duplex sequences d(TGTACA) and d(CGATCG) at 1.6 and 1.5 A, respectively. The iodine substituent does not alter the geometry of intercalation as compared to previously solved anthracycline complexes, but appears to markedly affect the solvent environment of the structures. This could have consequences for the interaction of this drug with DNA and DNA binding proteins in cells.     

活血莲的核型分析

对活血莲的染色体数目及核型进行了研究,结果表明,活血莲的染色体数目为２ｎ＝６０,其核型公式为２ｎ＝２ｘ＝６０＝４６ｓｍ＋１２ｓｔ＋２ｍ。没有观察到带随体的染色体。     

三尖杉叶精油化学成分的研究

三尖杉叶精油化学成分的研究苏应娟,王艇,张宏达（中国科学院武汉植物研究所武汉４３００７４）（中山大学生命科学学院广州５１０２７５）关键词三尖杉,精油,化学分类ＡＳＴＵＤＹＯＮＣＨＥＭＩＣＡＬＣＯＮＳＴＩＴＵＥＮＴＳＯＦＥＳＳＥＮＴＩＡＬＯＩＬＦＲＯＭ...