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201.
202.
A Pseudomonas sp. was isolated with enantioselective epoxide hydrolase activity to ethyl 3-phenylglycidate. Cells grown on sucrose and suspended in 10% (v/v) dimethyl formamide as co-solvent produced (2R,3S) ethyl 3-phenylglycidate with 95% ee and 26% yield in 12 h from 0.2% (w/v) of the racemate. 相似文献
203.
Humanin peptides block calcium influx of rat hippocampal neurons by altering fibrogenesis of Abeta(1-40) 总被引:2,自引:0,他引:2
Humanin peptides (including HN, HNG and other mutants) were reported previously that antagonize neurotoxicity caused by various familial Alzheimer's disease (FAD) genes and Abeta derivatives. Herein, we describe the aggregation dynamics and the representative morphological characteristics of Abeta(1-40) after different time of addition humanin peptides, which revealed that (a) the interactions of both HN and HNG with Abeta(1-40) induced quick and significant increase of light-scattering intensity, and (b) HNG also caused obvious morphological alteration from fibrillary to amorphous. In the meantime, the experiments also revealed that the interaction of HNG with Abeta(1-40) could decrease Abeta(1-40)-induced calcium rise, an initial event accompanying Abeta(1-40)-induced apoptosis of cultured neurons. Our results indicate that HNG can protect neurons by altering Abeta(1-40) morphology. 相似文献
204.
A two-hit model for development of multiple endocrine neoplasia type 2B by RET mutations 总被引:2,自引:0,他引:2
Iwashita T Murakami H Kurokawa K Kawai K Miyauchi A Futami H Qiao S Ichihara M Takahashi M 《Biochemical and biophysical research communications》2000,268(3):804-808
Multiple endocrine neoplasia (MEN) type 2B mutations have been reported at methionine 918 or alanine 883 in the tyrosine kinase domain of the RET proto-oncogene. Recently, a new combination of two germline missense mutations at valine 804 and tyrosine 806 was identified in a patient with MEN 2B-like clinical phenotypes including medullary thyroid carcinoma, mucosal neuroma, and marfanoid habitus. In this case, valine 804 and tyrosine 806 were replaced with methionine and cysteine, respectively. In the present study, biological activities of RET with these new mutations were compared with those with known MEN 2A or MEN 2B mutations. The transforming activity of RET with the V804M/Y806C mutation was about 8- to 13-fold higher than that of RET with a single V804M or Y806C mutation. Like RET with the M918T or A883F MEN 2B mutation, the transforming activity of RET with the V804M/Y806C mutation was not affected by substitution of phenylalanine for tyrosine 905 that abolished the activity of RET with the MEN 2A mutation. On the other hand, substitution of phenylalanine for tyrosines 864 and 952 drastically diminished the activity of RET with the V804M/Y806C, M918T or A883F mutation, suggesting that these three mutant proteins have similar biological properties. 相似文献
205.
Specific Single or Double Proline Substitutions in the “Spring-loaded” Coiled-Coil Region of the Influenza Hemagglutinin Impair or Abolish Membrane Fusion Activity
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Hui Qiao Sandra L. Pelletier Lucas Hoffman Jill Hacker R. Todd Armstrong Judith M. White 《The Journal of cell biology》1998,141(6):1335-1347
We tested the role of the “spring-loaded” conformational change in the fusion mechanism of the influenza hemagglutinin (HA) by assessing the effects of 10 point mutants in the region of high coiled-coil propensity, HA2 54–81. The mutants included proline substitutions at HA2 55, 71, and 80, as well as a double proline substitution at residues 55 and 71. Mutants were expressed in COS or 293T cells and assayed for cell surface expression and structural features as well as for their ability to change conformation and induce fusion at low pH. We found the following: Specific mutations affected the precise carbohydrate structure and folding of the HA trimer. All of the mutants, however, formed trimers that could be expressed at the cell surface in a form that could be proteolytically cleaved from the precursor, HA0, to the fusion-permissive form, HA1-S-S-HA2. All mutants reacted with an antibody against the major antigenic site and bound red blood cells. Seven out of ten mutants displayed a wild-type (wt) or moderately elevated pH dependence for the conformational change. V55P displayed a substantial reduction (~60– 80%) in the initial rate of lipid mixing. The other single mutants displayed efficient fusion with the same pH dependence as wt-HA. The double proline mutant V55P/ S71P displayed no fusion activity despite being well expressed at the cell surface as a proteolytically cleaved trimer that could bind red blood cells and change conformation at low pH. The impairment in fusion for both V55P and V55P/S71P was at the level of outer leaflet lipid mixing. We interpret our results in support of the hypothesis that the spring-loaded conformational change is required for fusion. An alternate model is discussed. 相似文献
206.
本文记述中国二叉蚜属Schizaphis Borner 6种,其中包括3新种:贴梗海棠二叉蚜Schizaphis(Schizaphis)chaenometicola Zhang,sp.nov.,香草二叉蚜Schizaphis(Schizaphis)hierochlophaga Zhanget Chen,sp.nov.和长管二叉蚜Schizaphis(Schizaphis)longituberclata Zhang et Qiao,sp.nov.,并附亚属、种检索表。模式标本存放中国科学院动物研究所标本馆。 相似文献
207.
作者系统整理了中国五节根蚜亚科Fordinae标本,发现2新属:离倍蚜属DimelaphisZhang,gen.nov.和拟孕蚜属SicifordaZhng,gen.nov.;5新种:榆钱毛根蚜ChaetogeolcaulmidrupaZhang,sp.nov,钝镰离倍蚜D.obtusifalcataZhang,sp.nov,金黄五节根蚜FordaauralentaZhngetQiao,sp.nov,毛多五节很蚜F.multicomaZhng,sp.nov.及六节拟孕蚜S.sexiarticulataZhang,sp.nov.二新亚种:麦拟根蚜沾化亚种ParacletuscimicformiszhanhuanusZhng,ssp.nov。模式标本保存在中国科学院动物研究所。 相似文献
208.
本文介绍了用单个棉铃虫测定杀虫药剂抗性基因频率的灵敏方法。该技术是基于比较三个相等量单个棉铃虫的乙酰胆碱酯酶的活性,每个棉铃虫要用微量滴定板同时做3个试验(也可用Enppen-dorf管)(No.1-3):1)不加抑制剂(No.1);2)不加酶源(No.2);3)加一定浓度的残杀威以抑制编码敏感AceS等位基因的乙酰胆碱酯酶,但不能抑制编码抗性AceR等位基因的乙酰胆碱酯酶。如果No.1和No.3的强度一样强,说明残杀威对乙酰胆碱酯酶的活性没有影响,那么基因型应是纯合抗性(AceRR,No3=No.1)。No.2和地.3的强度一样弱时,说明残杀威完全抑制了乙酰碱酯酶的活性,那么基因型应是纯合敏感(AceSS,No.3=No.2)。No.3的强度介于No.1(强)和No.2(弱)之间显示出残杀威部分地抑制了乙酰胆碱酯酶的活性;基因型是杂合型(AceSR,No.2<No.3<No.1)。作者用该方法测定了1995,1996两年从河北省邯郸和固安县棉田采集的棉铃虫,在邯郸棉铃虫抗药性高发地区,其抗性基因频率AceRR分别是68.3%和65.3%;但在棉铃虫抗药性低发区的固安县其抗性基因频率分别是23.9%和29.4%。 相似文献
209.
黑曲霉T21是由黑曲霉3.795经诱变育种获得的糖化酶高产菌株,为阐明其高产的分子机制,由黑曲霉3.795克隆了糖化酶结构基因及其5′旁侧序列,并与黑曲霉T21的相应序列进行了比较.由黑曲霉3.795菌丝体分离染色体DNA,Southern杂交分析表明,糖化酶结构基因位于~2.5kb的EcoRⅠ-EcoRⅤ染色体DNA片段上,在此EcoRⅠ位点上游约1.0kb处有一SalⅠ位点.为构建糖化酶结构基因及其5′旁侧序列的基因组文库,该染色体DNA分别用EcoRⅠ+EcoRⅤ和EcoR+SalⅠ消化,琼脂糖凝胶电泳分离并回收长度在1.0kb左右和2.5kb左右的DNA片段,分别与pUC19载体连接后转化入E.coliDH5.用原位杂交方法筛选到了携带糖化酶基因编码区及其1505bp5′旁侧序列的阳性克隆.对克隆片段的DNA序列进行了测定并与黑曲霉T21的相应序列进行了比较,结果表明,在糖化酶基因编码区及其150bp3′非编码区内,未发现碱基差异,但在-340~-1505的5′上游区内发生了9个位置的碱基变化,包括缺失、插入和替换.这些结果表明,黑曲霉T21与3.795的糖化酶产量的差异与其结构基因无关,但可能与其 相似文献
210.
Abstract This paper deals with two genera, Karamicrosiphum Zhang and Antimacrosiphon Zhang and four new species, Antimacrosiphon bullacaudatum Zhang et Qiao, Karamicrosiphum humuliosum Zhang et Qiao, Acyrthosiphon capitellum Zhang and Acyrthosiphon fragum Zhang of Macrosiphinae from China. All type specimens are deposited in Institute of Zoology, Academia Sinica. 相似文献