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31.
1 Results This paper presents the development of platinum nanocomposites structures based on organically modified c.a.2 nm core platinum nanoparticles.The chemical modification of the 4-mercaptoaniline functionalized particles by various in coming molecules is evidenced and precisely quantified.The particles can be dissolved like molecules in various solvents depending on the features of the new crown and X-rays shows that the interparticle distance is affected by the crown modification.These platinum n... 相似文献
32.
1 Results The development of the concepts of nanotechnology has given an important impact on the design of new polymer based materials which are in most cases characterized by a multiphase morphology. When at least one phase has nanometric dimension(s) the system can be considered as a nanocomposite where the interface is not only determining for the adhesion but also may play a role in some bulk properties. Indeed in nanostructured multiphase solids the interface is significant as a bulk component. The... 相似文献
33.
为了给液压冲击器的系统研究及结构优化提供必要的实验依据,进一步研究了液压冲击器压力油入口尺寸变化对其动态压力和流量影响.以某冲击器做主要研究对象,利用测试液压冲击机械冲击性能的模拟载荷试验装置从试验角度对其进行实验,到了液压冲击机构工作中进油口管径尺寸对压力和流量影响的变化曲线和二者波动程度与油管直径尺寸之间的关系.结果表明:进油口管径直接影响液压冲击器冲击压力和流量的脉动值,在同频档下管径越小,冲击压力脉动愈大,则流量波动愈小. 相似文献
34.
僧帽牡蛎碱性磷酸酶功能基团的研究 总被引:2,自引:0,他引:2
采用化学修饰法研究僧帽牡蛎碱性磷酸酶活性功能基团性质.酶经0.4mmol·L-1PCMB修饰30min后活力仍然保持不变,提示巯基与酶的活力无关;用二巯基苏糖醇(DTT)对酶进行修饰,当DTT浓度达到2.5mmol·L-1时,酶活力丧失98%,表明硫 硫键与酶活力有密切的关系;以N 溴代琥珀酰亚胺(NBS)修饰酶的色氨酸残基,酶的修饰失活呈一级反应,当NBS浓度达到0.65mmol·L-1时,酶活力丧失100%,并辅以紫外吸收光谱的变化分析,表明色氨酸残基是酶催化活力所必需的;醋酸酐、马来酸酐、甲醛等氨基试剂对酶的修饰作用显示氨基是酶的必需基团. 相似文献
35.
为快速鉴别中药白花前胡(Peucedanum praeruptorum Dunn.)和紫花前胡(Peucedanum decursinum Maxim.),用气相色谱/质谱(GC/MS),气相色谱法(GC)分别定性,定量分析白花前胡丙素(Pd-1a),丁素(Pd-Ⅱ)和紫花前胡苷元(Nodakenetin),在白花前胡中检出白花前胡丙素(M/Z 386)和丁素(M/Z 426),但未检出紫花前胡苷元,在紫花前胡中检出紫花前胡苷元(M/Z 246),但未检出白花前胡丙素和丁素,线性关系:YPd-1a=1.111XPd-1a 0.021(n=6 r=0.9995),线性范围:0.175~1.919μg,YPd-Ⅱ=1.189XPd-Ⅱ-0.013(n=6 r=0.9996),线性范围:0.086~0.950μg。YNodakenetin=0.901XNodkenetin-0.024(n=6 r=0.9999),线性范围:0.089~1.062μg,回收率:白花前胡丙素97.29%,白花前胡丁素98.81%,紫花前胡苷元96.34%,分析结果表明,不同产地药材样品中各自特征成分含量不同,分析中未能找到白花前胡和紫花前胡苷元共有的相同的有效成分或指标性成分。表明可用GC/MS区分白花前胡和紫花前胡苷元,但未能用统一的化学对照品进行质量控制。 相似文献
36.
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38.
Human cytomegalovirus UL97 open reading frame encodes a protein that phosphorylates the antiviral nucleoside analogue ganciclovir. 总被引:32,自引:0,他引:32
Human cytomegalovirus (HCMV, a betaherpes virus) is the cause of serious disease in immunologically compromised individuals, including those with acquired immunodeficiency syndrome. One of the compounds used in the chemotherapy of HCMV infections is the nucleoside analogue 9-(1,3-dihydroxy-2-propoxymethyl)-guanine (ganciclovir). The mechanism of action of this drug is dependent on the formation of the nucleoside triphosphate, which is a strong inhibitor of the viral DNA polymerase. Thymidine kinase, which is encoded by many of the herpesviruses, catalyses the initial phosphorylation of ganciclovir. But there is no evidence for the coding of this enzyme by HCMV, and DNA sequence analysis of the HCMV genome has shown that there is no open reading frame characteristic of a herpesvirus thymidine kinase. Here we present biochemical and immunological evidence that the HCMV UL97 open reading frame codes for a protein capable of phosphorylating ganciclovir. This protein seems to be responsible for the selectivity of ganciclovir and will be useful tool in the understanding and refinement of the antiviral activity of new selective anti-HCMV compounds. 相似文献
39.
S. J. Leybourne 《Journal of forecasting》1993,12(1):49-62
A linear regression model with random walk coefficients is extended to allow for linear restrictions between the coefficients to be satisfied at each point in time. Estimation in this model is shown to be no more involved than estimation in the standard model. It is also demonstrated how, after a slight modification to the testing problem, classical test procedures may be applied to the problem of testing for such restrictions. The performance of the Lagrange Multiplier test for a variety of different restrictions is then investigated via simulation. An empirical application involving testing for homogeneity in a random walk coefficient version of the AIDS model is given. 相似文献
40.
Nuclear localization and signalling activity of phosphoinositidase C beta in Swiss 3T3 cells. 总被引:14,自引:0,他引:14
The hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdInsP2) is a widespread receptor-coupled signalling system at the plasma membrane of most eukaryotic cells. The existence of an entirely separate nuclear phosphoinositide signalling system is suggested from evidence that purified nuclei synthesize PtdInsP2 and phosphatidylinositol 4-phosphate (PtdInsP) in vitro and that a transient decrease in the mass of these lipids occurs when Swiss 3T3 cells are cultured in the presence of insulin-like growth factor-1 (IGF-1). These IGF-1-dependent changes in inositol lipids coincide with an increase in nuclear diacyglycerol and precede translocation to the nucleus and activation of protein kinase C (refs 5, 6). Circumstantial evidence that links these changes with mitosis comes from the isolation of a 3T3 clone that expresses the type-1 IGF receptor and binds IGF-1 peptide but does not respond mitogenically or show transient mass changes in nuclear inositol lipids. A key question is how IGF-1 initiates the rapid breakdown of PtdInsP and PtdInsP2 in the nucleus. Here we present evidence that nuclei of 3T3 cells contain the beta-isozyme of phosphoinositidase C, whereas the gamma-isozyme is confined to the cytoplasm and that IGF-1 treatment stimulates exclusively the activity of nuclear phosphoinositidase C. 相似文献