排序方式: 共有72条查询结果,搜索用时 31 毫秒
1.
2.
【目的】葡聚糖酶是饲用添加剂的重要成分,本研究旨在从湖羊消化道微生物中挖掘性质优良的GH9家族葡聚糖酶基因,用于研发新型饲用酶制剂。【方法】从湖羊瘤胃微生物cDNA中扩增IDSGLUC9-25基因,在大肠杆菌中进行异源表达,对重组蛋白进行诱导表达和纯化,研究重组蛋白的酶学性质和底物水解模式。【结果】IDSGLUC9-25基因编码527个氨基酸,包含一个CelD_N结构和一个GH9家族催化结构域;重组蛋白rIDSGLUC9-25分子量约为62.7 kDa,最适反应温度和pH分别为40℃和6.0,在30-50℃下活性较高,在pH 4.0-8.0范围内能够保持较高的稳定性,经pH 4.0-8.0缓冲液处理1 h后残余活性均大于90%;底物谱分析表明,rIDSGLUC9-25能催化大麦β-葡聚糖、苔藓地衣多糖、魔芋胶和木葡聚糖,比活性分别为(443.55±24.48)、(65.56±5.98)、(122.37±2.85)和(159.16±7.73) U/mg;利用薄层色谱法(thin layer chromatography, TLC)和高效液相色谱法(high performance liquid chromatography, HPLC)分析水解产物发现,rIDSGLUC9-25降解大麦葡聚糖主要生成纤维三糖(占总还原糖64.19%±1.19%)和纤维四糖(占总还原糖26.24%±0.12%),催化地衣多糖主要生成纤维三糖(占总还原糖78.46%±0.89%)。【结论】本研究报道了一种来自密螺旋体属细菌的内切β-1,4-葡聚糖酶IDSGLUC9-25 (EC 3.2.1.4),能高效催化多糖底物生成纤维三糖和纤维四糖,为研发饲用酶制剂和制备低聚寡糖建立基础。 相似文献
3.
根据外切核酸酶Ⅲ酶解博莱霉素-Ce(Ⅲ)[BLMA5-Ce(Ⅲ)]作用过的双链直线型DNA时, 酶解速率明显增大, 酶解产物除5′-dAMP、5′-dGMP、5′-dCMP和5′-dTMP 4种单核苷酸外, 还有其他成分存在的实验事实, 推测出BLMA5-Ce(Ⅲ)在DNA双链的特定部位沿5′→3′的方向切断磷酸二酯键, 使DNA的双链上形成多个暴露的3′-OH末端. 相似文献
4.
5.
6.
Objective
To explore external validity of randomized controlled trials (RCTs) of hypertension within China from the view of sample representation.Methods
Comprehensive literature searches were performed in Medline, Embase, Cochrane Central Register of Controlled Trials (CCTR) et al and advanced search strategies were used to locate hypertension RCTs as well as observational studies conducted in China during 1996 to 2009 synchronously. The risk of bias in RCTs and observational studies was assessed by two modified scales respectively, and then both types of studies with 3 or more grading scores were included for the purpose of evaluating of external validity. Following that the study characteristics relative to sample representation were extracted from RCTs and observational studies synchronously, and the later were taken as external references for validating sample representation of RCTs.Results
226 hypertension RCTs and 21 observational studies were included for final analysis. Comparing samples with observational studies, the mean age of samples within RCTs was 54.46 years, significantly lower than that of observational studies (66.35 years) (P=0.002). The average disease course in patients of RCTs was 3.89 years and grade III hypertensive patients accounted for 17%; both were lower than that of the observational studies (12.96 years, P<0.001; 34%, P=0.026 respectively). In addition, the proportions of patients with complications due to heart failure, stroke, diabetes, or coronary heart disease in RCTs were 8%, 5%, 12% and 11% correspondingly, all of which were significantly less than that of observational studies (11%, 18%, 17% and 29%).Conclusion
Sample characteristics within hypertension RCTs were significantly different from those in observational studies. The samples in most RCTs were under-represented. It’s feasible to take samples of observational studies as a mirror of the actual composition of hypertension patients in the real world, if the reporting of observational studies is abundant and available. 相似文献7.
Shumei Liang Qingmin Yao Deying Wei Ming Liu Feng Geng Qin Wang Yun-shan Wang 《Journal of cellular biochemistry》2019,120(1):493-506
KDM6B, also known as JMJD3, is a member of the family of histone lysine demethylase (KDMs), which is closely related to many types of cancers. However, its role and the underlying mechanisms in ovarian cancer remain unknown. Here we show that KDM6B is elevated in epithelial ovarian cancer and its expression level is closely related with metastasis and invasion. In addition, survival analysis showed that high expression of KDM6B was associated with low overall survival in ovarian cancer patients. Overexpression of KDM6B in epithelial ovarian cancer cells promoted proliferation, epithelial-mesenchymal transition (EMT), migration and invasion in vitro, and enhanced metastatic capacities in vivo. On the contrary, silencing KDM6B in invasive and metastatic ovarian cancer cells inhibited these processes. Mechanistically, we found that KDM6B exerts its function by modulating the transforming growth factor-β1 (TGF-β1) expression, and TGF-β1 signal pathway inhibitor LY2157299 significantly inhibited KDM6B-induced proliferation, migration, metastasis, and EMT in ovarian cancer cells. Our findings, for the first time, reveal the pivotal role of KDM6B in the invasion and metastatic behavior of epithelial ovarian cancer. Thus, targeting KDM6B may be a useful strategy to interfere with these behaviors of epithelial ovarian cancer. 相似文献
8.
气候变化对我国红松林地理分布影响的研究 总被引:10,自引:0,他引:10
在红松林地理分布规律研究的基础上,应用地理信息系统IDRISI和专门计算机软件——生态信息系统GREEN,找出适宜红松林分布的地理气候参数区间,并以此确定了红松林适宜分布区,在此基础上,根据全球气候预测模型GCMs预测的2030年的气候变化结果,就气候变化对我国红松林地理分布的可能影响进行了预测。结果表明:到2030年,因气候变化的影响,我国适宜红松分布的面积将有所增加,但增加幅度不大,仅占当前气候条件下适宜红松分布面积的3.4%,局部地区变化的情况是:在黑龙江省的西北部适宜红松分布的面积将有所增加;在辽宁省的西南部适宜红松分布的面积将有所减少。红松林现实分布区的南界将向北移动0.1~0.6个纬度,北界将向北扩展0.3~0.5个纬度,黑龙江省境内的红松林分布区的西界将向西扩展0.1~0.5个经度。我国适宜红松分布的面积将由当前气候条件下的2.9×107hm2,增加到3.0×107hm2。就当前气候变化影响预测中存在的问题及未来研究的方向进行了讨论。 相似文献
9.
An exhaustive qualitative and quantitative profiling of the photosynthetic glycerolipids in three strains of the marine diatom
Skeletonema sp. was carried out by ultra performance liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry.
In the diatom thylakoid membrane, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) account for about
45–70% and 5–15% of the total membrane lipids, respectively. The anionic sulfoquinovosyldiacylglycerol (SQDG) as well as the
likewise anionic phosphatidylglycerol (PG) contribute between 10–40% and 4–10% each. The predominant species of MGDG were
those with C16:3/C16:3, C20:5/16:1, and C20:5/C16:3. Three main molecular species of DGDG contained C20:5/C16:1, C20:5/C16:2, and C16:1/C16:1. The major molecular species of SQDG were those containing combinations of C14:0/C14:0, C14:0/C16:0, C14:0/C16:1, and C14:0/C16:3. All the PG classes contained the C18:1/C18:1 as the main molecular species. Based on the fatty acid species in sn-2 position, it is indicated that MGDG and DGDG are biosynthesized through prokaryotic pathway exclusively within the chloroplast,
whereas PG and SQDG have a typical mixed biosynthetic pathway (both prokaryotic pathway and eukaryotic pathways). The chemical
characteristics of photosynthetic glycerolipids related with ecological physiology are discussed. 相似文献
10.
Xie Y Zhang Z Niu L Wang Q Wang C Lan J Deng J Fu Y Nie H Yan N Yang D Hao G Gu X Wang S Peng X Yang G 《PloS one》2011,6(10):e27066