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《中国科学C辑》2007,(6)
题目作者期快报磷酸化TrkA受体在与其核转位相关的运输膜泡内的定位............................龚爱华张志坚肖德生杨勇王永忠陈永昌1综述胚胎干细胞自我复制及亚全能分化特性维持的分子机制..............................................................刘雨潇吉蕾王韫芳裴雪涛32转基因鱼生态风险评价及其对策研究进展......................................................................................................胡炜汪亚平朱作言43论文人类组织特异性DNA聚合酶POLλ2基因的克隆、表达纯化和鉴定..................… 相似文献
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利用人类全基因组Affymetrix芯片检测人胚胎干细胞与其自发分化7d的拟胚体之间的差异表达基因.结果显示:与未分化的人胚胎干细胞相比.在分化7d的拟胚体中表达下调2倍及以上的已知和未知基因共有1100个,表达上调2倍及以上的已知或未知基因共有2283个.利用Gostat对这些差异表达基因进行功能分析,发现它们分别与细胞的生物代谢过程、信号传导通路、系统发育、细胞分化、分子功能及亚细胞组分相关.胚胎干细胞具有自我更新能力,是研究早期胚胎发育理想的细胞模型,因此对差异表达基因的功能研究有助于了解维持人胚胎干细胞自我更新的分子机制以及胚胎发育早期的分子事件. 相似文献
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多能性干细胞是一类具有体外无限自我复制和分化为体内多种细胞类型能力的多潜能细胞,是研究基因功能、建立疾病模型和促进再生医学领域发展的一种重要工具。自1981年小鼠胚胎干细胞建立以来,科学家们已经先后成功地建立了灵长类、人、大鼠的胚胎干细胞和小鼠、大鼠的上胚层干细胞等。但是,目前研究表明,维持人、灵长类胚胎干细胞的多能性信号通路与维持小鼠、大鼠胚胎干细胞的截然不同,而与维持小鼠、大鼠上胚层干细胞的信号通路比较类似。因此,该文对目前研究较多的维持小鼠胚胎干细胞、人胚胎干细胞和小鼠上胚层干细胞的多能性信号通路进行了综述,希望能够对其它物种的多能性干细胞研究提供有益的借鉴。 相似文献
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Zfx基因与干细胞自我更新 总被引:1,自引:0,他引:1
干细胞具有自我更新保持不分化状态的特性,不同的干细胞具有不同的自我更新机制. Zfx基因(zinc fin ger-X gene)在部分胚胎干细胞和造血干细胞中高表达,该基因高表达有利于胚胎干细胞和造血干细胞自我更新; Zfx基因表达不足或缺乏的胚胎干细胞和造血干细胞自我更新的能力下降,细胞凋亡明显增加.在胚胎干细胞和造血干细胞中发现一些Zfx基因直接调控的靶基因,Zfx 基因可能是控制各种干细胞自我更新的共同的分子机制. Zfx基因表达不足不影响胚胎干细胞和造血干细胞的分化,缺乏 Zfx基因的胚胎干细胞和造血干细胞能够正常分化为各自的功能细胞. 相似文献
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The ATP/ADP exchange is shown to be a partial reaction of the by the absence of measurable nucleoside diphosphokinase activity and the insensitivity of the reaction to , -di(adenosine-5′) pentaphosphate, a myokinase inhibitor. The exchange demonstrates an absolute requirement for Mg2+ and is optimal at an ADP/ATP ratio of 2. The high ATP concentration () required for maximal exchange is interpreted as evidence for the involvement of a low affinity form of nucleotide site. The ATP/ADP exchange is regarded as evidence for an ADP-sensitive form of the phosphoenzyme. In native enzyme, pre-steady state kinetics show that the formation of the phosphoenzyme is partially sensitive to ADP while modification of the enzyme by pretreatment with 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB) in the absence of Mg2+ results in a steady-state phosphoenzyme population, a component of which is ADP sensitive. The ATP/ADP exchange reaction can be either stimulated or inhibited by the presence of K+ as a function of pH and Mg2+. 相似文献
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目的甲型H1N1流感病毒A/California/7/2009与A/California/4/2009病毒序列比较同源性在99%以上,本实验旨在比较两株病毒感染BALB/c小鼠研究感染力强弱。方法分别将A/California/7/2009(CA7)与A/California/4/2009(CA4)两株病毒分别连续10倍稀释后,对4~6周龄雌性BALB/c小鼠经乙醚麻醉后进行滴鼻攻毒,每个稀释度接种10只实验小鼠,测定CA7 MLD50为101.24/0.05 mL,检测小鼠感染、致病的多项指标,观察期为14 d。结果相同TCID50的CA7和CA4病毒感染小鼠,CA4感染小鼠后14 d内死亡率为20%,而CA7感染小鼠后8 d内死亡率为100%。CA7 106TCID50感染的小鼠病理表现为重度弥漫性间质性肺炎,CA4 106TCID50感染的小鼠病理表现为中度-重度间质性肺炎。结论在相同条件下,CA7感染力明显强于CA4。 相似文献
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Background
Assignment of function to new molecular sequence data is an essential step in genomics projects. The usual process involves similarity searches of a given sequence against one or more databases, an arduous process for large datasets. 相似文献14.
Purified cytochrome from bovine adrenocortical mitochondria was incorporated into liposomes by the cholate-dilution method utilizing either dialysis or Sephadex gel filtration. Among synthetic phospholipids tested, dioleoylglycerophosphocholine showed the best stability during the incorporation of into liposomes. A maximum amount of heme was incorporated into liposomes at a molar ratio of phospholipid to the cytochrome of approx. 200. When was incorporated into the dioleoylglycerophosphocholine liposomes by the cholate-filtration method, the showed two major populations on the elution pattern of the Sepharose 4B gel filtration, and were seen at a diameter of 200–600 Å and its aggregated forms. When the cytochrome was incorporated into dioleoylglycerophosphocholine liposomes or cholesterol-free adrenocortical mitochondrial liposomes, was less stable than in aqueous solution. Cholesterol or adrenodoxin markedly stabilized the liposomal . Liposomal required cholesterol for its optimum reduction with adrenodoxin, adrenodoxin reductase, and NADPH in the presence of CO. About 70% of the total heme in the dioleoylglycerophosphocholine liposomes was reduced by the enzymatic reduction in the presence of cholesterol, indicating that 70% of the total molecules are exposed to the surface of the outer monolayer. In order to see the location of the heme in membrane, the dioleoylglycerophosphocholine-liposomal was subjected to treatment. This reagent destroyed the liposomal . These results suggest that the heme is located in the proximity of the reacting sites which are exposed to the surface, or located on the vincinity of polar heads of the membrane. 相似文献
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The parameters estimated from traditional A/C
i curve analysis are dependent upon some underlying assumptions that substomatal CO2 concentration (C
i) equals the chloroplast CO2 concentration (C
c) and the C
i value at which the A/C
i curve switches between Rubisco- and electron transport-limited portions of the curve (C
i-t) is set to a constant. However, the assumptions reduced the accuracy of parameter estimation significantly without taking
the influence of C
i-t value and mesophyll conductance (g
m) on parameters into account. Based on the analysis of Larix gmelinii’s A/C
i curves, it showed the C
i-t value varied significantly, ranging from 24 Pa to 72 Pa and averaging 38 Pa. t-test demonstrated there were significant differences in parameters respectively estimated from A/C
i and A/C
c curve analysis (p<0.01). Compared with the maximum ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation rate (Vcmax), the maximum electron transport rate (Jmax) and Jmax/Vcmax estimated from A/C
c curve analysis which considers the effects of g
m limit and simultaneously fits parameters with the whole A/C
c curve, mean Vcmax estimated from A/C
i curve analysis (Vcmax-C
i) was underestimated by 37.49%; mean Jmax estimated from A/C
i curve analysis (Jmax-C
i) was overestimated by 17.8% and (Jmax-C
i)/(Vcmax-C
i) was overestimated by 24.2%. However, there was a significant linear relationship between Vcmax estimated from A/C
i curve analysis and Vcmax estimated from A/C
c curve analysis, so was it Jmax (p<0.05). 相似文献
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The partial purification of from pig lens has been achieved by treatment with deoxycholate followed by density gradient centrifugation. The specific activity of the final preparation, ranging from 300 to 500 nmol/h per mg protein, is increased approx. 100-fold compared to the homogenate. A parallel increase in activity is also observed. Sodium dodecyl sulfate (SDS) gel electrophoresis reveals six major protein bands, one of which is the 93 kDa α subunit of which can be phosphorylated by reaction with [γ-32P]ATP. A second band contains a glycoprotein which displays an apparent molecular weight of 51 000 and thus appears to be the β subunit of the enzyme. The enzyme is sensitive to ouabain with the for and inhibition being 1.2 and 1.3 μM, respectively. Several agents which inhibit from other tissues such as oligomycin, Ca2+, vanadate, , (PCMBS) and 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) also inhibit the lens enzyme. Monovalent cations other than K+ are partially effective in activating the ()-ATPase and activities. The K+ congeners were relatively more effective in supporting compared to activity. Other kinetic properties of the lens enzyme are also comparable to those of the enzyme from other tissues. Utilizing the partially purified membrane bound enzyme, discontinuities in Arrhenius plots of activity, activity and fluoresence polarization of the fluidity probe, 1,6-diphenyl-1,3,5-hexatriene (DPH), are observed near the physiological temperature of lens. The possible significance of these observations for the mechanism of cataract formation are discussed. 相似文献
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The modulating effect of membrane lipids on enzyme function has been described by several investigators. We have used the spin probe methyl stearate (M 12-NSE) to study this interaction in ox brain membranes enriched with . This methyl ester of stearic acid is practically insoluble in aqueous media, and consequently spectra of M 12-NSE-labelled preparations are free of “liquid lines”.At least two types of spectra may be obtained when ox brain microsomes are spin labelled with M 12-NSE, indicating the presence of two distinct binding sites. At one site the spin label is relatively unrestricted and gives rise to an isotropic spectrum. A second spectrum, which is obtained from spin label at another site, is similar to that which is observed after incorporation of M 12-NSE into phospholipid bilayers. This suggests that this latter site is within the core of the microsomal membrane.The two binding sites differ in their affinity for the spin probe. The low affinity site is both more abundant in crude preparations and is more easily removed by detergent treatment; spin labels at this site produce isotropic spectra. The high affinity sites are fewer in number and produce broad spectra. In addition these high affinity sites increase in concentration as the enzyme undergoes purification.The two sites are quite distinct in their sensitivity to ascorbic acid, the low affinity site showing a considerably greater rate of reduction by this agent.This study also demonstrates that the delipidation effects of sodium dodecyl sulfate and sodium deoxycholate on microsomes from ox brain are not identical.It is suggested that the two spin probe binding sites represent two different lipid domains, one of which is very closely associated with the enzyme and may reflect a protein-directed phospholipid specificity for this enzyme. 相似文献
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Tadashi Ogawa Mitsuru Fukuda Kei Sasaoka 《Biochimica et Biophysica Acta (BBA)/General Subjects》1973,297(1):60-69
One of the ninhydrin-negative alanine conjugates isolated from pea seedlings was identified as .The identification of this conjugate was carried out by a comparison of its gas-liquid chromatographic and mass spectrometric properties, and its nuclear magnetic resonance and infrared spectra with those of synthetic . The alanine in the conjugate was shown to be present as the D-isomer by enzymatic and chromatographic analyses. 相似文献
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Kristin K Nicodemus 《BMC bioinformatics》2008,9(1):130
Background
Risk for complex disease is thought to be controlled by multiple genetic risk factors, each with small individual effects. Meta-analyses of several independent studies may be helpful to increase the ability to detect association when effect sizes are modest. Although many software options are available for meta-analysis of genetic case-control data, no currently available software implements the method described by Kazeem and Farrall (2005), which combines data from independent family-based and case-control studies. 相似文献20.
Showdomycin inhibited pig brain ( with pseudo first-order kinetics. The rate of inhibition by showdomycin was examined in the presence of 16 combinations of four ligands, i.e., Na+, K+, Mg2+ and ATP, and was found to depend on the ligands added. Combinations of ligands were divided into five groups in terms of the magnitude of the rate constant; in the order of decreasing rate constants these were: (1), (2) , , and none, (3) , and , (4) and , , , and ATP. The highest rate was obtained in the presence of Na+, Mg2+ and ATP. The apparent concentrations of Na+, Mg2+ and ATP for half-maximum stimulation of inhibition () were 3 mM, 0.13 mM and 4μM, respectively. The rate was unchanged upon further increase in Na+ concentration from 140 to 1000 mM. The rates of inhibition could be explained on the basis of the enzyme forms present, including E1, E2, ES, E1-P and E2-P, i.e., E2 has higher reactivity with showdomycin than E1, while E2-P has almost the same reactivity as E1-P. We conclude that the reaction of ( proceeds via at least four kinds of enzyme form (E1, E2, E1 · nucleotide and EP), which all have different conformations. 相似文献