原生质体电融合酵母多倍体生理特性的研究

对原生质体电融合技术获得的11株酵母多倍体融合株,进行了一系列生理特性的分析比较．结果发现,在电融合过程中,融合株的细胞体积及DNA含量并不随着核倍性呈线性递增．而是有其特殊的变化规律。当糖化酵母sta1、sta2和sta3在细胞核中各自纯合时,明显表现出表达的剂量效应。其中sta1、sta2纯合的融合株．在YEPS培养中,GA分泌可被淀粉大量诱导,表现出一定的二次生长特性。从分析结果推测,在亲株5301-14D及HU-TY—1A中可能有对GA分泌不利的因素。     

兔感觉神经特异蛋白的纯化及稳定性观察

以兔脊神经节及背根纤维为材料,通过制备匀浆,DEAE-Sephacel阴离子交换层析,高压液相凝胶过滤层析分离纯化了感觉神经特异蛋白29 ku,并进行了该蛋白的稳定性观察.     

抗白粉病小麦染色体组型的分子标记与生化标记分析

应用与小麦第六同源群有关的分子和生化标记,包括ＤＮＡ探针ｐＳｃ５·３Ｈ３和ｐＳＲ１６７以及同工酶Ｅｓｔ－５和ａ－Ａｍｙ－１,对来自六倍体小黑麦Ｂｅａｇｌｅ与普通小麦科冬５８杂交后代Ｆ１花粉植株的抗白粉病株系Ｍ２４．Ｍ０９及Ｍ１７进行了分析。结果表明,Ｍ２４、Ｍ０９及Ｍ１７不同程度地含有黑麦染色体成分,而且电泳谱带差别较大,据此推断,Ｍ０９为６ＲＬ的易位系。因此,生化和分子标记不仅可以用于确定外源片段的存在,而且可以帮助确定染色体组型和外源片段的位置     

Construction and use of a nontoxigenic strain of Pseudomonas aeruginosa for the production of recombinant exotoxin A.

To express recombinant forms of Pseudomonas aeruginosa exotoxin A in high yield, we have developed a nontoxigenic strain of P. aeruginosa derived from the hypertoxigenic strain PA103. The nontoxigenic strain, designated PA103A, was produced by the excision marker rescue technique to replace the toxA structural gene in PA103 with an insertionally inactivated toxA gene. The PA103A strain (ToxA-) was used subsequently as the host strain for the expression and production of several recombinant versions of exotoxin A, and the results were compared with exotoxin A production in other P. aeruginosa and Escherichia coli strains. Use of the PA103A strain transformed with the high-copy-number pRO1614 plasmid bearing various toxA alleles resulted in final purification yields of exotoxin A averaging 23 mg/liter of culture. By comparison, exotoxin A production in other expression systems and host strains yields approximately 1/4 to 1/10 as much toxin.     

Enzyme-linked immunosorbent assay (ELISA) using a glycolipid antigen for the serodiagnosis of melioidosis

Abstract The serodiagnosis of melioidosis is commonly performed with tests using protein or polysaccharide as antigen. However, due to the low sensitivity, specificity and difficulty in the preparation of the antigens, more simple, precise and reproducible diagnostic tests were required. A purified glycolipid antigen (GL) which is a specific lipid component of Burkholderia pseudomallei has been used in an ELISA. With this antigen, specific immunoglobulin G (IgG) was detected in 49 out of 50 melioidosis sera. IgG was also detected in 2 out of 185 (Japanese) and 16 out of 181 (Vietnamese) control sera. Thus, the sensitivity was 98.0%, and specificity was 98.9% and 91.1% in the Japanese and Vietnamese sera, respectively. When the ELISA and indirect haemagglutination (IHA) tests were combined, a sensitivity of 100% and specificity of 97.8% were achieved. The advantages of the glycolipid antigen are ease of preparation, stability, high sensitivity and specificity.     

新型平均势函数在蛋白质反向折叠中的应用

利用蛋白质主链的极性分数及主链二面角为参量,构建了一种基于蛋白质结构数据库的势函数。将该势函数应用于蛋白质反向折叠研究中,发现该函数可成功地将蛋白质分子的天然构象从构建的构象库中识别出来;将一目标序列与构象库的每一可能的构象匹配,并用该势函数计算相应的能量,结果表明对绝大多数蛋白质分子来说,天然的构象的能量值总是最低。此外,该函数还将一些序列相似性较低,而结构相似性较高的蛋白质分子识别出来。我们认     

Production of Glucose Isomerase by Streptomyces flavogriseus

A microorganism that produces glucose isomerase was isolated from soil and identified as a strain of Streptomyces flavogriseus. The organism produced a large quantity of glucose isomerase when grown on straw hemicellulose, xylan, xylose, and H₂SO₄ hydrolysate of ryegrass straw. The organism produced glucose isomerase both intra- and extra-cellularly. The highest level of intracellular glucose isomerase (3.5 U/ml) was obtained in about 36 h by a culture grown on straw hemicellulose; the extracellular enzyme (1.5 U/ml) appeared in cultures grown for about 72 h. About equal levels of enzyme were produced in cultures grown on straw hemicellulose, xylan, xylose, and H₂SO₄ hydrolysate of straw, but production of the enzyme was drastically reduced when the organism was grown on other carbon sources. As a nitrogen source, corn steep liquor produced the best results. Soy flour extract, yeast extract, and various peptones also were adequate substrates for glucose isomerase production. Addition of Mg²⁺, Mn²⁺, or Fe²⁺ to the growth medium significantly enhanced enzyme production. The organism, however, did not require Co²⁺, which is commonly required by microorganisms used in the production of glucose isomerase.     

Some cellular immune reactions in infants. MIF,E-rosette formation and changes in nucleolar morphology

The cellular immune response (MIF, E-rosette formation and changes in nucleolar morphology of lymphocytes) was followed as related to age and antigenic stimulation. MIF in healthy infants increased from the 2nd to the 12th week of life as compared with the first week, probably due to BCG vaccination. The total and active E-rosette formation did not change during the whole period of investigation. Ring-shaped nucleoli increased gradually from the second week of life. Active nucleoli increased up to the 4th week,i.e. after BCG vaccination and then slowly decreased. Micronucleoli being high in the first week, decreased during 24 weeks of life. After artificial colonization of the intestine the production of MIF was slightly lower in colonized infants than in controls from the 2nd to the 12th week. The other parameters followed were not influenced by colonization.