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排序方式: 共有29条查询结果,搜索用时 31 毫秒
1.
The protein-tyrosine kinases (PTKs) are a burgeoning family of proteins, each of which bears a conserved domain of 250 to 300 amino acids capable of phosphorylating substrate proteins on tyrosine residues. We recently exploited the existence of two highly conserved sequence elements within the catalytic domain to generate PTK-specific degenerate oligonucleotide primers (A. F. Wilks, Proc. Natl. Acad. Sci. USA 86:1603-1607, 1989). By application of the polymerase chain reaction, portions of the catalytic domains of several novel PTKs were amplified. We describe here the primary sequence of one of these new PTKs, JAK1 (from Janus kinase), a member of a new class of PTK characterized by the presence of a second phosphotransferase-related domain immediately N terminal to the PTK domain. The second phosphotransferase domain bears all the hallmarks of a protein kinase, although its structure differs significantly from that of the PTK and threonine/serine kinase family members. A second member of this family (JAK2) has been partially characterized and exhibits a similar array of kinase-related domains. JAK1 is a large, widely expressed membrane-associated phosphoprotein of approximately 130,000 Da. The PTK activity of JAK1 has been located in the C-terminal PTK-like domain. The role of the second kinaselike domain is unknown.  相似文献   
2.
为查明塔里木河下游不同水分梯度下胡杨种内竞争以及空间分布格局的变化规律,在塔里木河下游阿拉干断面选取3条样带,每条样带内依照水分梯度布设3个样方,采用Hegyi单木竞争模型与点格局等分析方法,探究了水分梯度下胡杨林种内竞争及空间格局变化特征。结果表明:1)塔里木河下游胡杨的最适竞争范围为10m; 2)胡杨竞争指数与胸径服从幂函数关系(P<0.001),胡杨竞争指数随对象木胸径的增加而逐渐减小,当对象木胸径达到20cm以上时,其竞争指数逐渐稳定,且维持在较低水平;3)随水分梯度的降低,胡杨林分竞争指数呈下降趋势;4)在塔里木河下游,胡杨空间格局主要为聚集分布,随空间尺度的增加,胡杨逐渐趋向于随机分布;5)随水分梯度的降低,胡杨空间格局由聚集分布逐渐转变为随机分布。水分是决定极端干旱区荒漠植被空间分布与结构的主要因子;在胡杨林分管理中,应充分考虑胡杨的种内竞争、空间格局及其与水分梯度之间关系,为塔里木河下游胡杨林的保护与更新提供科学依据。  相似文献   
3.
目的:将新疆南疆地区栽种的主要经济作物之一小白杏应用于化妆品领域,发挥其保持皮肤弹性、柔软和透明的功效。方法:以小白杏杏仁油为原料,运用正交实验设计,加入一定量的乳化剂,通过改变乳化温度、时间、转速,使油相与水相搅拌均匀。结果:最佳配方为:杏仁油13%,羊毛脂4%,蜂蜡3%,尿素3%,乳化剂1.5%,温度85℃,时间7 min,转速140 r/min。结论:以新疆小白杏杏仁油为主要原料,可研制适合于干性皮肤的防皲裂护手霜。  相似文献   
4.
塔里木河下游胡杨林胸径结构及林木分布特征   总被引:2,自引:0,他引:2  
采用“面”上宏观调查与“点”上典型研究相结合,集中对塔里木河下游阿拉干断面100hm^2的胡杨(Populus euphratica)林木分布与胸径结构进行了调查。结果发现,在距河道0—20m的范围内,胸径为0—4cm的幼龄胡杨占最多,达到13.24%。以后随着离河道距离的增加,幼龄胡杨所占比例逐渐减小。胸径分布范围简单,胸径为16—36cm的林木株数在胡杨林中所占的比例最多。另外,随着离河道距离的增加,胸径在48cm以上的过熟林和衰老林的比例逐渐增多。距河道0—200m的范围内,胡杨分布占整个胡杨林的80%以上。其中以疏失度为0—50%的长势较好的胡杨为主。在200—400m的范围内,疏失度为50%-75%的长势较差的过熟林和衰老林的比例开始增多。距河道400m以上,胡杨密度开始急剧下降,胡杨株数所占的比例几乎下降到5%以下。  相似文献   
5.
以沙棘为研究对象,通过RACE、基因克隆和定量PCR技术,克隆并分析沙棘磷酸烯醇式丙酮酸羧激酶基因(PEPCK)的序列信息,以及进化树构建和氨基酸的二级结构分析,比较NaCl胁迫后PEPCK基因的表达变化,为揭示PEPCK基因在沙棘抗性方面的功能研究奠定基础。结果显示:(1)成功克隆了沙棘PEPCK基因,该基因开放阅读框(ORF)为2 001bp,编码666个氨基酸。(2)序列分析表明,沙棘PEPCK与蓖麻、黄顶菊、核桃等序列一致性高达85%以上;进化上沙棘PEPCK基因与蓖麻和狭叶羽扇豆较近,与烟草、拟南芥进化关系较远。(3)在300mmol·L~(-1) NaCl盐胁迫下,沙棘PEPCK基因表达在胁迫组中显著上升,胁迫后7d时为未处理的2.5倍,15d时达到未处理的3.2倍。研究表明,沙棘PEPCK基因在沙棘适应外源盐胁迫的过程中可能发挥了重要作用。  相似文献   
6.
短毛柽柳不同部位中总黄酮含量及稳定性研究   总被引:1,自引:0,他引:1  
目的:比较短毛柽柳中不同部位总黄酮的含量差异,研究黄酮化合物保存的条件,方法:采用超声波乙醇浸提法,在正交优先的最佳条件(料液比为1∶15,超声处理时间为40min,乙醇浓度为45%,超声温度50℃,提取3次)下提取不同部位总黄酮,并测定不同条件下其吸光度的变化。结果:柽柳花、叶、茎中总黄酮得率分别为24.585mg/g、25.623mg/g、41.726mg/g,柽柳中提取的黄酮溶液在光照、高温、高浓度蔗糖溶液和Na+存在条件下不稳定;pH 4~7条件下较稳定;氧化剂对其稳定性的影响不大。结论:柽柳茎中总黄酮含量明显高于其他两个部位。柽柳黄酮保存时应避免接触碳水化合物和盐离子,在避光、常温、中性条件下保存。  相似文献   
7.
The karyotypes of 3 species of Ceratoides (C. arborescens, C. ewersmanniana and C. latens) were studied. The results show that C. arborescens is a diploid, with karyotype formula 2n=2x=18=16m+2sm, C. ewersmanniana is also a diploid, with 2n=2x=18=14m+4sm, while C. latens is a tetraploid, with 2n=4x=36=24m+12sm. According to the karyotypes, the morphological features and geographical distribution, C. arborescens seems to be a primitive species and it might have originated in northern China. C. arborescens and C. ewersmanniana are similar to each other, not only in morphology but also in karyotype, which shows that they are closely related and that C. arborescens might be the progenitor of C. ewersmanniana. The karyotypes of the 3 speciesof Ceratoides are basically identical, with only minor differences.  相似文献   
8.
干旱区胡杨叶片含水量和叶绿素含量特征   总被引:2,自引:0,他引:2  
在阿拉干样区内,距河道不同距离选取40棵胡杨树(Populus euphratica)采样,使用相关分析方法探讨胡杨叶片相对含水量(fuel moisture content,FMC)、等效水厚度(equiv-alent water thickness,EWT)、叶绿素含量随距河道距离的空间差异,以及随地面温度的变化特征,并讨论了FMC、EWT和叶绿素含量之间的相关性。结果表明:FMC、EWT、叶绿素含量与河道距离有极显著的相关关系(P<0.01)。距河道越远,3项指标均随距河道距离的增加极显著的减少,其中EWT与距河道距离的相关性最大(-0.577)。温度变化对FMC和EWT均有极显著的影响(P<0.01),但对叶绿素含量影响不大(P>0.05)。因FMC、EWT的物理含义不同,它们的平均值在胡杨树个体尺度/水平上极显著相关,但在单片叶子尺度上FMC和EWT之间无显著相关(P>0.05),而胡杨树个体平均和单片叶子的EWT与叶绿素含量均极显著相关(P<0.01)。由于EWT与距河道距离和叶绿素含量的相关性极显著,而且对温度变化不敏感,因此,具有很好的开发应用潜力,建议将EWT作为干旱区河岸生态系统植被含水量遥感监测的一个指标。  相似文献   
9.
Lung cancer is one of the most common causes of death in the world. Considering the severe side effects, toxicity and high costs of chemotherapeutics used in cancer treatment, there is a need for more economical and natural treatment methods such as essential oils. The purpose of this study is to determine the efficacy of Canarium commune (Elemi) essential oil (EO) and nanoparticles. Elemi EO is analysed by GC-FID/MS. The antiproliferative effect of Elemi EO and prepared nanoparticles on human lung adenocarcinoma (A549) and their effect on normal fibroblast cells (CCD-19Lu) were determined by the MTT test. The levels of TAS, TOS, CYCS, CASP3, TNF-α and IL-6 parameters of the experimental groups were determined using specific ELISA. BAX and Bcl-2 genes were studied with qRT-PCR to investigate the different ways that cancer cells undergo apoptosis. Limonene (53.7%), a-phellandrene (14.5%) and elemol (10.1%) were the major components of Elemi EO. 24-Hour IC50 values in the cells were measured for Elemi EO; A549: 1199 μg/mL, CCD-19Lu: 37.181 μg/mL. TAS and TOS values were found to be higher in cancer cells than in normal cells, and it was found that cancerous cells were dragged into stress and that cancer cells were directed to apoptosis. BAX genes stimulation supported the results. It was determined that Elemi EO and nanoparticles showed anticancer activity without damaging normal cells. Based on these promising results, potential drug candidate Elemi EO loaded nanoparticles may be cell-specific targeted, oral use possible, new generation nanoparticular drugs.  相似文献   
10.
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