维生素C·Cu·菲咯啉系统对DNA的定位损伤

维生素Ｃ·Ｃｕ·菲咯啉系统对ＤＮＡ的定位损伤柯德森,王爱国,罗广华（中国科学院华南植物研究所,广州５１０６５０）关键词活性氧;ＤＮＡ;定位损伤活性氧对ＤＮＡ的损伤已经被很多工作所证实”””,这种伤害是由０Ｂ”直接作用于ＤＮＡ所引起的”’“。但是ＯＨ’...     

Purification and partial characterization of an elastolytic serine protease of Prevotella intermedia.

Elastolytic strains of Prevotella intermedia were isolated from pus samples of adult periodontal lesions. Elastase was found to associate with envelope, and it could be solubilized with guanidine-HCl. The enzyme was purified to homogeneity by sequential procedures including ion-exchange chromatography, gel filtration, and hydrophobic interaction chromatography. This elastase was a serine protease, and its mass was 31 kDa. It hydrolyzed elastin powder, but collagen and azodye-conjugated proteins were not degraded by this enzyme. Both synthetic substrates for human pancreatic (glutaryl-L-alanyl-L-alanyl-L-prolyl-L-leucine p-nitroanilide) and leukocyte elastase (methoxy succinyl-L-alanyl-alanyl-L-prolyl-L-valine p-nitroanilide) were hydrolyzed.     

我国微茎类吸虫的研究Ⅻ.类茎属及多黄属二新种报道：复殖目：微茎科

本文报道在湛江市附近海域海鸟体内获得的两种吸虫,经鉴定为新种,命名为巨口类茎吸虫,新种Ｍｉｃｒｏｐｈａｌｌｏｉｄｅｓ ｍａｃｒｏｓｔｏｎｒｓ ｓｐ．ｎｏｖ．,珊瑚多黄吸虫,新种Ｍｕｌｔｉｖｉｔｅｌｌｕｓ ｃｏｒａｌｉｕｓ ｓｐ．ｎｏｖ．     

Genetic diagnosis of cytoplasmic male sterile cybrid plants of rice

Twelve Japanese rice cultivars were converted to CMS by asymmetric protoplast fusion with MTC-5A, the cytoplasm of which was derived from an indica rice, Chinsurah Boro II. With the exception of the cybrids that had a nucleus from Hoshiyutaka, most of these cybrid plants were sterile. The unique sequence downstream from the mitochondrial atp6 of MTC-5A was specifically amplified in the sterile cybrid plants by PCR. All progenies of the cybrid plants carrying this unique sequence were sterile. On the other hand, in some of the sterile cybrid plants in which the unique sequence was not amplified by PCR, fertility was recovered in their progenies. Somaclonal mutation may have caused sterility in these cybrids. Only the cybrid plants that had the unique sequence detected by PCR were CMS. Thus, the CMS plants can be selected rapidly and easily by PCR, at an early stage of plant regeneration. Soon after transplanting the regenerated plants to a green house, fertile cybrids and sterile cybrids produced by somaclonal mutation can be removed. These findings also show that the unique region downstream from atp6 is tightly linked with the CMS phenotype.     

Mechanism of T5-induced DNA polymerase. II. Characterization of the dead-end complex.

We have shown that bacteriophage T5-induced DNA polymerase replicates short primer-templates (400 to 600 nucleotides long) at a rapid rate initially, followed by a slower rate sustained for much longer periods (Das, S. K., and Fujimura, R. K. (1977) J. Biol. Chem. 252, 8700-8707). In order to explain the slower steady rate and the results of polymer-challenge experiments, we conjectured the presence of a "dead-end complex" formed by the enzyme with the primer-template at the end of the primer elongation process. In this communication we present evidence which indicates that the presumed complex shows a first order kinetics of decay with a half-life of 3.5 min at 37 degrees. Energies of activation for the steady phase of synthesis and the decay of the dead-end complex were both found to be about 23 kcal/mol. This indicates that the dissociation of the aforesaid complex might be the rate-limiting step during the steady phase of synthesis. Correlation between the salt-induced reduction in the half-life of the complex and the increase in the steady rate of synthesis is in agreement with the above mentioned possibility.     

Mechanism of T5-induced DNA polymerase. I. Replication of short primer templates.

Bacteriophage T5-induced DNA polymerase shows an initial phase of rapid synthesis, followed by a slower steady rate for much longer periods, with short DNA primer-templates (400 to 600 nucleotides long), in vitro. On extrapolating the line of steady rate back to 0 min, an intercept is obtained on the ordinate. With large DNA primer-templates, such as denatured T5 DNA (average chain length approximately 50,000 bases), the rate of synthesis remains constant and is equal to the initial rate obtained with short primer-templates. The zero time intercept was proportional to the amount of enzyme used and independent of temperature. Polymer challenge experiments indicate that the initial phase of rapid synthesis can be attributed to the processive mode of synthesis by T5 DNA polymerase. After synthesizing a stretch of DNA processively for about 200 nucleotide residues, the enzyme apparently forms a "dead-end complex" with the primer-templates used and must dissociate from the primer-template in order to resume synthesis. The average size of the product made processively, during various phase of synthesis, remains invariant and is in good agreement with the size of the zero time intercept per enzyme molecule.     

以化学纯饲料饲养北京的桃蚜

应用修改后的Dadd和Mitter(1966)全纯饲料配方配制成人工饲料饲养定居在北京温室烟草上的桃蚜 Myzus persicae可完成生活史井连续饲养3代。本文描述饲料配制、饲养和取食量测定的方法。这3代初羽化无翅孤雌胎生雌蚜的平均体重分别为:440±90.7μg,264±104.9μg和312±127.9μg。用放射性同位素稀释法测定取食量的结果得悉若虫期的总取食量每蚜约为1.74μg,相当于1.16μl。     

Interaction of N-ethyl-N'-nitro-n-nitrosoguanidine with nucleic acids and proteins in comparison with N-methyl-N'-nitro-N-nitrosoguanidine

Reactivity of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) was studied in comparison with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The radioactivity of [guanidino-14C]-ENNG was incorporated only into the protein fraction and that of [ethyl-14C]ENNG was incorporated into DNA, RNA and protein fractions in ascites hepatoma AH7974 cells, as were those of [guanidino-14C]- and [methyl-14C]MNNG, respectively. The amounts of the binding of ENNG were less than those of MNNG, especially in the corporation of the ethyl moiety of ENNG into nucleic acid fractions. In a non-cellular system, the radioactivity of [guanidino-14C]ENNG was incorporated into proteins, preferentially into basic proteins such as cytochrome c, but was not incorporated into nucleic acids. This behavior is similar to that of [guanidino-14C]MNNG, while the amount of binding of the former was about half of that of the latter. The radioactivity of [ethyl-14C]ENNG was also incorporated into basic proteins to almost the same extent as that of [methyl-14C]MNNG. However, the binding of the ethyl moiety of ENNG to nucleic acids was much lower than that of the methyl moiety of MNNG. Horse heart cytochrome c, bovine pancreatic RNase A and regenerating rat liver chromatin had altered their biological activities to various degrees after modification by ENNG or MNNG.