有机相中脂肪酶L—1754促有机硅烷醇的酯化

在有机介质中脂肪酶Ｌ－１７５４催化非天然有机硅化合物三甲基硅烷醇酯化反应的速度高于Ｌｉｐｏｚｙｍｅ。Ｌ－１７５４对脂肪酸链长有很强的特异性且不同于Ｌｉｐｏｚｙｍｅ。     

底物中的硅原子对酶反应的影响

在酶工程学的研究史上,人们一方面不断地研制开发新的酶种;一方面利用固定化、酶分子改造和修饰等技术来提高酶的活性和稳定性;另一方面,则不断地开拓酶的新用途。酶催化非天然化合物的生物合成和转化（正是这一方面研究的新进展）。由于有机硅化合物在有机合成,尤其...     

脂肪酶催化有机硅化合物的生物转化

C.cylindracea脂肪酶可催化有机介质中有机硅醇与脂肪酸的酯化反应。微水有机介质比水-水不溶有机介质更有利于酶的反应,有机硅醇是比其碳结构类似物更好的酰基受体。对不同有机硅醇底物,当其空间障碍大时,不利于酶催化酯化反应,对不同脂肪酸底物,有机硅醇未影响该脂肪酶的脂肪酸底物特异性。     

用SOS显色法检测金属化合物的遗传毒性

用SOS显色法对12种金属化合物的遗传毒性进行了检测,发现多种金属化合物具有遗传毒性,在 SOS显色法中呈阳性反应,其中已知具有致癌作用的镍和钻化合物在Ames沙门氏菌／微粒体测试法 检测中呈阴性结果,镍化合物在枯草杆菌的Rec测试法中也呈阴性。uvrA基因的存在对SOS显色法 检测某些金属化合物的遗传毒性有重要的影响。     

农药助剂对茚虫威防治番茄潜叶蛾的减量增效作用

为评价农药助剂对15%茚虫威悬浮剂防治番茄潜叶蛾Tuta absoluta(Meyrick)的减量增效作用,分别向减量10%、20%、30%的15%茚虫威悬浮剂药液中添加500 ppm的有机硅silwet 408、矿物油、芦荟精油助剂,测定其对番茄潜叶蛾的田间防效。结果显示：相同浓度下,添加农药助剂后的防效均显著高于15%茚虫威悬浮剂的防效,相对常规用量通过添加有机硅Silwet 408、矿物油或芦荟精油可使农药减量10%～20%。田间应用将15%茚虫威悬浮剂按照常规用量减量10%～20%,通过添加有机硅Silwet 408、矿物油或芦荟精油可有效防治番茄潜叶蛾。     

非水相脂肪酶催化有机硅醇的酯化反应

非水相酶催化是酶工程研究热点之一。本文介绍了来自Ｃ．ｃｙｌｉｎｄｒａｃｅａ的脂肪酶催化有机硅醇和脂肪酸的酯化反应。该酶可催化有机硅醇与脂肪酸的酯化反应,并对不同链长的脂肪酸底物、有机溶剂极性及水含量等进行了初步研究。     

中国蒿属植物化学分类的初步研究――精油化学成分与系统分类的相关性

分析了171个中国蒿属植物样品的精油化学成分,鉴定出305个化合物。这些样品代表64个种,其中蒿亚属47种,龙蒿亚属17种。 分析结果表明,这些化合物在两亚属中的分布有一定的规律性。在蒿亚属精油中主要含单萜类和倍半萜类化合物,而在龙蒿亚屑精油中主要含倍半萜类化合物和芳香族化合物。这种分布与中国蒿属植物从较原始到进化划分为7个组的系统分类有一定的相关性,即蒿亚属:莳萝蒿组(单萜类化合物)→艾蒿组(单萜类化合物)→艾组(单萜类化合物)→腺毛蒿组(单萜类化合物和倍半萜类化合物)→白苞蒿组(倍半萜类化合物)。龙蒿亚属:龙蒿组(倍半萜类化合物和芳香族化合物)→牡蒿组(倍半萜类化合物和芳香族化合物)。     

有机溶剂中固定化脂肪酶催化硅醇的酯化反应

固定化Mucor miehei脂肪酶可催化有机硅醇和脂肪酸的酯化反应．对固定化酶用量、脂肪酸链长、不同有机硅醇底物、有机溶剂极性和水含量等影响因素进行了初步研究．     

细菌中倍半萜生物合成的研究进展

萜类化合物是一大类小分子天然产物,在生物体内扮演重要的角色。植物和真菌中萜类化合物的生物合成已被广泛研究,但是在真核生物中克隆或改造萜类化合物生物合成途径还有较大难度。许多细菌同样可以产生萜类化合物。在过去十多年间细菌萜类合酶的研究进展为我们对萜类化合物生物合成的理解做出了显著的贡献。这里我们主要关注细菌中合成的倍半萜化合物,概述其化学结构、倍半萜合酶对法尼基焦磷酸环化的机制、后修饰酶特别是氧化还原酶所参与的后修饰、代谢调控以及合成途径中尚未解决的问题等。     

中国蒿属植物化学分类的初步研究——精油化学成分与系统分类的相关性

分析了171个中国蒿属植物样品的精油化学成分,鉴定出305个化合物。这些样品代表64个种,其中蒿亚属47种,龙蒿亚属17种．分析结果表明,这些化合物在两亚属中的分布有一定的规律性。在蒿亚属糖油中主要含单萜类和倍半萜类化合物．而在龙蒿亚属精油中主要含倍半萜类化合物和芳香族化合物．这种分布与中国蒿属植物从较原始到进化划分为7个组的系统分类有一定的相关性,即蒿亚属：莳萝蒿组(单萜类化合物)→艾蒿组(单萜类化俣物)→艾组(单萜类化合物)→腺毛蒿组(单萜类化合物和倍半萜类化合物)→白苞蒿组(倍半萜类化合物)。龙蒿亚属：龙蒿组(倍半萜类化台物和芳香族化合物)→牡蒿组(倍半萜类化合物和芳香族化合物)。     

Divergence of tRNA genes in chloroplast DNA of higher plants

The saturation hybridization between spinach chloroplast (ct) DNA and spinach ¹²⁵I-labelled chloroplast tRNA has shown that about 1.1% of the spinach ctDNA codes for tRNAs. The observed hybridization is a result of specific base-pairing as shown by competition hybridization experiments and thermal stability of the ctDNA-tRNA hybrids. The amount of hybridization shows that spinach ctDNA contains about 40 tRNA genes. Similar hybridization studies have shown that corn ctDNA contains about 28 tRNA genes. The cross-hybridizations between ctDNA and tRNAs of corn, spinach and pea have shown that tRNAs in chloroplasts of higher plants have undergone significant divergence. The pea and spinach tRNAs have been found to have 50% of the base sequences in common. The corn tRNAs have been found to have only about 30% of the base sequences in common with pea and spinach. These data have been confirmed by extensive heterologous competition experiments and thermal stability of the heterologous DNA-tRNA hybrids. The experiments have also shown that the base sequences of tRNAs common in all three plants are the same.     

Biomass estimation of orange roughy: a summary and evaluation of techniques for measuring stock size of a deep-water fish species in New Zealand

A number of techniques have been employed to measure biomass of orange roughy in New Zealand. Time series of stratified random trawl surveys in a number of areas over periods of 5–10 years have given relative abundance indices, which have been used in stock reduction analyses to estimate true biomass. This has given confident results for the Chatham Rise stock, and surveys have also shown strong trends in other regions. Acoustic surveys have been carried out on three grounds. They can give relative indices of orange roughy abundance in areas of fiat or medium sloping bottom, and have the potential for estimation of absolute biomass from a single survey. Egg production surveys have been employed on two grounds on the east coast of the North Island, where conditions of tight spawning aggregations and steep bottom topography have limited the success of other methods. Both daily fecundity reduction and annual egg production methods have been used. These have given estimates of true biomass from one-off surveys, although results are imprecise. Both unstandardized and standardized analyses of commercial catch-per-unit-effort data have given relative indices of abundance, which have formed an important part of stock assessment for several fisheries. No single technique used to measure the size of orange roughy stocks has proven ideal or appropriate in all New Zealand situations. All have advantages and disadvantages, depending on the characteristics of the fishing area and fish behaviour. For two areas, a combination of methods have been applied, which has given more confident results than those from a single technique.     

植物硫转运蛋白研究进展

硫转运蛋白在植物对硫酸盐的吸收和转运中起着重要的作用。已经在拟南芥、大麦和小麦等植物中分离到了40多种硫转运蛋白基因。这些基因序列与其他种类生物的硫转运蛋白基因序列有着高度的保守性。利用CLUSTAL程序建立的系统进化树将植物硫转运蛋白划分为5个亚群。使用多种拓扑预测程序推测出不同植物硫转运蛋白的共同结构特点是均含有12个跨膜域。在柱花草和大麦中,硫转运蛋白基因表达调控包括植物体内硫水平的负调控和O—乙酰丝氨酸的正调控两种方式。对硫转运蛋白的组织定位和功能研究表明,高亲和硫转运蛋白主要定位于根部,在根系硫酸盐吸收中起重要作用。     

Genome evolution of allopolyploids: a process of cytological and genetic diploidization

Allopolyploidy is a prominent mode of speciation in higher plants. Due to the coexistence of closely related genomes, a successful allopolyploid must have the ability to invoke and maintain diploid-like behavior, both cytologically and genetically. Recent studies on natural and synthetic allopolyploids have raised many discrepancies. Most species have displayed non-Mendelian behavior in the allopolyploids, but others have not. Some species have demonstrated rapid genome changes following allopolyploid formation, while others have conserved progenitor genomes. Some have displayed directed, non-random genome changes, whereas others have shown random changes. Some of the genomic changes have appeared in the F1 hybrids, which have been attributed to the union of gametes from different progenitors, while other changes have occurred during or after genome doubling. Although these observations provide significant novel insights into the evolution of allopolyploids, the overall mechanisms of the event are still elusive. It appears that both genetic and epigenetic operations are involved in the diploidization process of allopolyploids. Overall, genetic and epigenetic variations are often associated with the activities of repetitive sequences and transposon elements. Specifically, genomic sequence elimination and chromosome rearrangement are probably the major forces guiding cytological diploidization. Gene non-functionalization, sub-functionalization, neo-functionalization, as well as other kinds of epigenetic modifications, are likely the leading factors promoting genetic diploidization.     

Cryopreservation of islets of Langerhans

Development of techniques for cryopreservation of pancreatic islets of Langerhans could potentially allow for increased freedom from the time restrictions presently affecting viability in islet cell transplantation. While several investigators have attempted islet cell freezing and have obtained favorable in vitro results after thawing, there have been few reported in vivo successes with islets transplanted after freezing. We have developed a simple system for freezing islet cell pancreatic fragments to ?196 °C and have either stored them in liquid nitrogen for 24 hr or immediately thawed the islets prior to transplantation. In addition, antilymphoblast globulin has been used as graft pretreatment modality in order to modify islet cell immunogenicity. We found that ALG was effective in prolongation of graft survival after freezing as well as on fresh nonfrozen transplants. The use of freezing and ALG appears, therefore, to have a favorable effect on the immunogenicity of the pancreatic islet cell allograft.     

Host defense mechanisms of cephalopods

Humoral and cellular mechanisms of defense have been described for cephalopods, a relatively advanced group of mollusks. Typical of other mollusks, cephalopod agglutinins are the most documented component of humoral immunity. Lectins, which have agglutinating properties, have been described and characterized from octopuses. Agglutinins from cephalopod hemolymph have also been shown to agglutinate a variety of vertebrate red blood cells, as well as potential bacterial pathogens. Hemocytes are the primary component of cellular immunity. Although the hemocyte role in phagocytosis has been extensively studied in other mollusks, the mechanisms of phagocytosis have not been described extensively for cephalopods. Cephalopod hemocytes have phagocytic capabilities and may function in encapsulation and neutralization of foreign substances; however, the effects of environmental factors and the full extent of phagocytic capabilities of cephalopod hemocytes have not been reported. Hemocytes from cephalopods have a role in wound healing and inflammation which have been reported in detail by several investigators.     

Phylogenetic analysis of the distribution of chromosomal races of Mus mnscuius domesticus Rutty in Europe

Robertsonian (Rb) translocation is a common chromosomal rearrangement in the house mouse. In free-living populations, 79 fusions with different combinations of chromosomes 1 to 18 have been found in some 45 populations. An updated list of these fusions is presented and analysed in order to reveal the possible processes by which the fusions spread within or among populations. A widespread hypothesis is that when two populations share the same fusion, it can be assumed that they have a common ancestor. This can serve as the basis for the use of the cladistic methods. While I present such an analysis on the updated list of Rbs, I also point to the problems associated with it in this case because many fusions have multiple origins and exchanges of Rbs between populations are frequent. I have tried to use a different approach, based on a critical and quantitative evaluation of the hypothesis of common ancestry. Assuming that the 153 possible fusions have an equal probability of occurrence, I give the formula to compute the probability that populations share a given number of fusions by chance alone. Only when this probability is lower than a chosen level (say 5%) can the populations be inferred to have a non-independent origin (i.e. they have a common ancestor or they have exchanged chromosomes by introgression). This probability measure is then used as a distance estimate to show the relationship between all the Rb populations. This analysis suggests that although some Rbs must have occurred more than once, most of the populations have non-independent origins. Almost all the populations from northern Africa to Belgium and Germany appear to have close karyotopic relationships and form a major group. Clearly independent Rb populations are mainly found in the periphery of this major group, for example in Scotland, Denmark and Spain. 'Chromosomal' flow between Rb populations appears to be a very important process.     

Diagnosis of Helicobacter pylori

The different invasive and noninvasive diagnostic tests for Helicobacter pylori have been applied mainly in emerging countries. Molecular methods have been developed, especially a test for detection of H. pylori and its clarithromycin resistance directly from stools. The long-term effects of eradication on histologic lesions have been studied in a meta-analysis and the prognostic value of post-treatment in gastric mucosa-associated lymphoid tissue lymphoma has been assessed. An operating link for gastritis assessment (the OLGA staging) has also been published. Attempts to simplify the urea breath test protocol have been made, and new stool antigen tests have been proposed and compared to those previously available.     

Quantification of the elevated rate of domain rearrangements in metazoa

Most eukaryotic proteins consist of multiple domains created through gene fusions or internal duplications. The most frequent change of a domain architecture (DA) is insertion or deletion of a domain at the N or C terminus. Still, the mechanisms underlying the evolution of multidomain proteins are not very well studied.Here, we have studied the evolution of multidomain architectures (MDA), guided by evolutionary information in the form of a phylogenetic tree. Our results show that Pfam domain families and MDAs have been created with comparable rates (0.1-1 per million years (My)). The major changes in DA evolution have occurred in the process of multicellularization and within the metazoan lineage. In contrast, creation of domains seems to have been frequent already in the early evolution. Furthermore, most of the architectures have been created from older domains or architectures, whereas novel domains are mainly found in single-domain proteins. However, a particular group of exon-bordering domains may have contributed to the rapid evolution of novel multidomain proteins in metazoan organisms. Finally, MDAs have evolved predominantly through insertions of domains, whereas domain deletions are less common.In conclusion, the rate of creation of multidomain proteins has accelerated in the metazoan lineage, which may partly be explained by the frequent insertion of exon-bordering domains into new architectures. However, our results indicate that other factors have contributed as well.