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91.
92.
描述的介形类化石标本采集于新疆塔里木盆地库车和喀什两地区,其中,齐古组产Darwinula-Timiriasevia组合,恰克马克组产Darwinula-Bisulcocypris为代表的介形类化石组合,其时代前者为晚侏罗世,后者为中侏罗世;俄霍布拉克组和克拉玛依组产以Bisulcompris-TungchuaniaDarwinula为代表的组合,其时代为早-中三叠世。 相似文献
93.
Xue Bin Zheng Misao Tsubokura Yongkun Wang Chun Xie Tetsuji Nagano Kazuhiko Someya Tomoko Kiyohara Kiyomi Suzuki Takeshi Sanekata 《Microbiology and immunology》1995,39(10):821-824
Thirty strains of Yersinia pseudotuberculosis were isolated from rabbits (17 strains), wild rats (9 strains) and house rats (4 strains) in China between 1990 and 1993. The biochemical properties of these isolates were identical with those of Y. pseudotuberculosis and no special characteristics were found in these strains. Serologically, serogroups 4b and 5b were identical to isolates found in Japan, and a new serogroup 1c and unclassified strains have also been detected. The existence of virulence-associated properties were different among strains. The pYV plasmid was detected from 6 strains of 30 isolates. This report documents the presence of Y. pseudotuberculosis in China, providing important epidemiological information. 相似文献
94.
通过定点诱变技术得到6个生物活性剧烈下降的人白细胞介素-2(IL-2)突变体,其中两个突变体即15Val-IL-2和126Asp-IL-2可以在一定浓度范围内使IL-2的生物效应降低。在对高亲和力IL-2受体(IL-2R)的竞争抑制实验中,15Val-IL-2和126Asp-Il-2又表现了一定的竞争能力。这些结果表明15Val-IL-2和126Asp-IL-2可部分拮抗天然IL-2的作用。结合I 相似文献
95.
96.
周口店地区仓鼠材料的重新观察 总被引:12,自引:5,他引:7
经重新鉴定,周口店地区第四纪期间共有4属7种仓鼠,包括大型种类Allocricetus ehiki、A. teilhardi sp. nov. 及Cricetinus varians和小型种类Cricetulus longicaudatus, C. barabensis griseus, C. b. obscurus, C. cf. migratorius, Phodopus sp.其中A. ehiki-A. teilhardi sp. nov.,C. varians-现生种“C.”triton及小型仓鼠可能分别和中国新第三纪晚期的Sinocricetus, Kowalskia等有较密切的亲缘关系。 相似文献
97.
Baked-bean waste was found to be a favorable substrate for amylase production by Aspergillus foetidus NRRL 337. Under optimum conditions, the yields of α-amylase (EC 3.2.1.1) and glucoamylase (EC 3.2.1.3) were 47 and 226 U, respectively, per ml of the waste fermented. 相似文献
98.
The beta subunit of tomato fruit polygalacturonase isoenzyme 1: isolation, characterization, and identification of unique structural features. 下载免费PDF全文
We have purified and isolated cDNAs encoding the beta subunit of tomato fruit polygalacturonase isoenzyme 1 (PG1), a cell wall protein that associates with, and apparently regulates, the catalytic PG2 polypeptides. Expression of the beta subunit is fruit specific and temporally separated from the expression of PG2 during fruit development. The 37- to 39-kD beta subunit is encoded as a 69-kD precursor protein containing a signal sequence and two propeptide domains. The mature protein is composed almost entirely of the novel 14-amino acid motif FTNYGxxGNGGxxx in which many of the phenylalanine residues are post-translationally modified. The unique structural features of the motif suggest an important role in the function of the protein and hence in the activity of PG1. The beta subunit may represent a class of bifunctional plant proteins that interact both with structural components of the cell wall and catalytic proteins to localize and/or regulate metabolic activities within the cell wall. 相似文献
99.
We investigated the effects of the non-phorbol tumor promoter okadaic acid on human leukemia K562 cells. It was found that okadaic acid potently and reversibly inhibited cell growth, with a nearly complete inhibition of thymidine uptake seen at about 10 nM. The cytotoxicity of okadaic acid was characterized by a marked mitotic arrest of the cells exhibiting scattered chromosomes and abnormal anaphase-like structures, a phenomenon distinct from the typical metaphase arrest caused by colchicine. Okadaic acid (10-1,000 nM) greatly stimulated phosphorylation of a number of nuclear proteins in K562 cells. Phosphorylation of many of the same proteins was also stimulated by 12-O-tetradecanoylphorbol-13-O-acetate, a protein kinase C activator. The present findings, consistent with recent reports that okadaic acid is a potent inhibitor of protein phosphatases 1 and 2A (PP1 and PP2A) shown to be essential for normal mitosis, provided evidence for the first time that okadaic acid inhibition of PP1/PP2A resulted in enhanced nuclear protein phosphorylation and subsequent mitotic arrest. 相似文献
100.
The tyrosine at position 60 of the Flp recombinase of the Saccharomyces cerevisiae plasmid, 2 mu circle, is invariant among site-specific recombinases of the "yeast plasmid family". Alterations of this residue give rise to Flp variants that show no recombination activity when assayed in vivo in Escherichia coli. Upon purification, they bind substrate, execute DNA cleavage and catalyze recombination. The efficiency of strand cleavage follows the order: Flp(Y60F) greater than Flp greater than Flp(Y60S) greater than Flp(Y60D); efficiency of recombination between Flp sites on a linear substrate and a circular one follows the order: Flp greater than Flp(Y60F) greater than Flp(Y60S) greater than Flp(Y60D). Methylation footprints of the DNA-protein complexes formed by two of the Flp variants, Flp(Y60S) and Flp(Y60D), do not show hypermethylation of the G residues within the substrate core that is characteristic of complexes formed by wild-type Flp. The third variant, Flp(Y60F), causes significant distortion (although less than wild-type Flp) of the substrate core, as indicated by enhanced G-methylation. Binding profiles with circularly permuted substrates indicate that Flp(Y60S) and Flp(Y60D), but not Flp(Y60F), are defective in bending substrate DNA. In recombination between two Flp half-sites, the variant proteins are significantly more active than in normal full-site recombination. 相似文献