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141.
麦迪霉素产生菌具有启动功能的DNA片段的克隆和分析 总被引:3,自引:0,他引:3
利用启动子探针质粒载体pIJ486从麦迪霉素产生菌总DNA中克隆得到了一段具有启动功能的DNA片段.通过限制性酶酶切分析,测定插入DNA片段大小为2.3kb.又利用载体pIJ486和pIJ487的新霉素抗性结构基因上游有多酶切点方向相反的性质,分析了插入片段在两个不同方向上的启动能力.结果表明,在两个方向上均有启动功能,但强弱相差六倍.其中在XbaI-HindIII方向上具有较强的启动能力,在变铅青链霉菌中新霉素抗性水平可达20mg/ml以上.进一步对插入片段的三个BamHI小片段进行分析的结果表明,较强启动子区域集中在BamHI-BamHI 0.79kb DNA片段上. 相似文献
142.
Avoidance thresholds and 96-h LC50 values were determined for golden shiners, Noiemigonus crysoleucas , for five individual elements: chromium, Cr; copper, Cu; cadmium, Cd; arsenic, As; selenium, Se. The avoidance concentrations were 73, 26 and 28 μgl-1 for Cr-VI, Cu and As-III, respectively. Cadmium and Se were not avoided at experimental concentrations up to 68 and 3489 μg1-1 , respectively. Acute flow-through 96-h LC50 values were Cr-VI 55·0, Cu 84·6, and As-III 12·5 mg 1-1 , which were more than two orders of magnitude above avoidance concentrations. The acute flow-through 96-h LC50 values for Cd and Se were 2·8 and 11·2 mg 1-1 , respectively. These concentrations are 31 and 2·2 times the highest concentration employed in the avoidance tests, neither of which were avoided by the test organisms. Thus, simple toxicity tests do not identify the environmental hazard of some elements, and the most toxic elements may not elicit a behavioural response. When used in concert with tests of organism function, more realistic indicators of environmental hazard or safety may be determined. 相似文献
143.
Jisuo Jin 《Palaeontology》2003,46(5):885-902
Eocoelia akimiskii sp. nov. from the Lower Silurian (upper Telychian) Attawapiskat Formation of Akimiski Island, James Bay, Nunavut, is the first and oldest Eocoelia to be described from the Hudson Bay Basin, one of three largest inland basins of North America. The new species lacks dental plates, dental cavities, and marginal deflection or lip, which indicates a post-Aeronian form of the well-known Eocoelia lineage. In rib numbers, Eocoelia akimiskii falls between E. curtisi and E. sulcata , being closer to E. sulcata . In rib strength, however, the new species is more closely allied to E. curtisi . Although Eocoelia is currently assigned to the Rhynchonellida because of its lack of spiralia, several features (particularly the lack of a septalium, the presence of a unique notothyrial platform and cardinal process, and dense, free-hanging fibrous growth frills) of the genus and other leptocoeliids are distinctly atypical of the rhynchonellides. The new species occurs in an inter-reef, shelly packstone facies within the Attawapiskat Formation, which is characterized by coral-stromatoporoid reefs with abundant, diverse, reef-dwelling brachiopods and other shelly organisms. The close association of Eocoelia akimiskii with the Attawapiskat reefs supports a shallow subtidal (BA2) setting generally assigned to the Eocoelia Community. The reefs themselves, however, host an extremely abundant brachiopod fauna dominated by Pentameroides , Trimerella , Septatrypa , and Gypidula . Four species of Clorinda are also common elements of the reef-dwelling brachiopods. This demonstrates that the concept of the classic Early Silurian level-bottom brachiopod communities cannot be directly applied to reef-dwelling brachiopod communities. 相似文献
144.
A genomic hsp70 gene was isolated from a rice IR36 genomic library and 4 794 bp of the gene have been sequenoed. The 5' flanking region of the gene contained a putative TATA box and a typical heat shock element sequence 5'-CTcgGAAccTTCgAG-3'. The amino acid sequence of the rice HSP70 deduced from the coding region shared 84%-92% homologies with those of HSP70s from other plant species. An intron 1939bp long was identified in the coding region at the codon specifying amino acid 72 (Asp), the similar position introns occurring in other intron-containing hsp70 genes. In addition, another intron of 57 bp was found in the 3'-untranslated region in the rice hsp70 gene. Southern blot hybridization showed that rice hsp70 gene family contained at least three members. Analysis of the RNA leveis with the gene-specific and non-specific probes revealed that the rice hsp70 gene expressed at normal temperature and the expression was enhanced by heat shock treatment. 相似文献
145.
146.
Gene identification in a complex chromosomal continuum by local genomic cross-referencing 总被引:8,自引:0,他引:8
Zoya Avramova Alexander Tikhonov Phillip SanMiguel Young-Kwan Jin Changnong Liu Sung-Sick Woo Rod A. Wing Jeffrey L. Bennetzen 《The Plant journal : for cell and molecular biology》1996,10(6):1163-1168
Most higher plants have complex genomes containing large quantities of repetitive DNA interspersed with low-copy-number sequences. Many of these repetitive DNAs are mobile and have homology to RNAs in various cell types. This can make it difficult to identify the genes in a long chromosomal continuum. It was decided to use genic sequence conservation and grass genome co-linearity as tools for gene identification. A bacterial artificial chromosome (BAC) clone containing sorghum genomic DNA was selected using a maize Adh1 probe. The 165 kb sorghum BAC was tested for hybridization to a set of clones representing the contiguous 280 kb of DNA flanking maize Adh1. None of the repetitive maize DNAs hybridized, but most of the low-copy-number sequences did. A low-copy-number sequence that did cross-hybridize was found to be a gene, while one that did not was found to be a low-copy-number retrotransposon that was named Reina. Regions of cross-hybridization were co-linear between the two genomes, but closer together in the smaller sorghum genome. These results indicate that local genomic cross-referencing by hybridization of orthologous clones can be an efficient and rapid technique for gene identification and studies of genome organization. 相似文献
147.
视黄醇结合蛋白的结构与功能 总被引:7,自引:0,他引:7
金宏 《生物化学与生物物理进展》1996,23(2):126-129
视黄醇结合蛋白(RBP)是视黄醇转运的载体蛋白,作为结合小分子流水物质的载体蛋白家族(lipocalin)的一个重要成员,其结构与功能的研究正受到国外学者的重视,文章介绍了视黄醇结合蛋白的性质、结构研究进展,讨论了视黄醇结合蛋白与前蛋白和受体相互作用的位点和结构特点. 相似文献
148.
邻二氮菲-Fe2+氧化法检测H2O2/Fe2+产生的羟自由基 总被引:122,自引:0,他引:122
报告检测H2O2/Fe2+所产生羟自由基的新方法. 羟自由基氧化反应后, 邻二氮菲-Fe2+的A536明显下降, 且△A536与邻二氮菲, FeSO4及H2O2呈量效关系, 随反应时间延长, △A536依幂函数规律上升. 此法试验结果表明, 甘露醇, 抗坏血酸及硫肥清除羟自由基作用呈明显的量效关系. 相似文献
149.
150.
将人粒细胞-巨噬细胞集落刺激因子(GM-CSF)和人血清白蛋白第三功能区(HAS-D3)的基因串联后,在E.coli中获高效表达,表达量占菌体蛋白的32.6%.利用TF-1体外细胞活性测定表明,GM-HSA的活性单位为1.04×10~6U/mg,虽然其比活性低于GM-CSF,但比后者具有更高的体外热稳定性和储藏稳定性. 相似文献