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131.
132.
以水为沉淀剂,在室温未加恒温装置的情况下方便而有效地实现对1.00wt%PSA的DMAc 溶液中的PSA进行沉淀分级,使分子量分布宽度由原来多分散指数为3.8降低到2.0左右,分级回收率为 95.0%,为研究膜材料分子量及其分布对膜性能的影响提供了条件。 相似文献
133.
Nicotinamide adenine dinucleotide phosphate phosphomonoesterase was isolated and partially purified from wheat (Triticum aestivum L. var. Selkirk) leaves. The enzyme had KNADP value of 1.4 X 10(-4) M and a pH optimum of 5.9. In vitro activity of this enzyme was unaffected by precursors of NAD (nicotinamide and nicotinic acid) or cytokinins (kinetin and benzimidazole). However, when detached wheat leaves were treated with solutions of these compounds, the precursors lowered the specific activity while the cytokinins enhanced the activity. It is suggested that spatial separation and compartmentation of the enzyme and its substrate NADP account for the similar effect of benzimidazole on both. 相似文献
134.
文章介绍了一种基于PowerBuilder7.0的集成设计系统的图形数据、文本数据及电子表格数据的管理系统.该系统是通用集成设计系统的一个子系统,它集产品结构设计、设计资料统计、汇总于一体. 相似文献
135.
136.
Kim JH Kim B Cai L Choi HJ Ohgi KA Tran C Chen C Chung CH Huber O Rose DW Sawyers CL Rosenfeld MG Baek SH 《Nature》2005,434(7035):921-926
Defining the molecular strategies that integrate diverse signalling pathways in the expression of specific gene programmes that are critical in homeostasis and disease remains a central issue in biology. This is particularly pertinent in cancer biology because downregulation of tumour metastasis suppressor genes is a common occurrence, and the underlying molecular mechanisms are not well established. Here we report that the downregulation of a metastasis suppressor gene, KAI1, in prostate cancer cells involves the inhibitory actions of beta-catenin, along with a reptin chromatin remodelling complex. This inhibitory function of beta-catenin-reptin requires both increased beta-catenin expression and recruitment of histone deacetylase activity. The coordinated actions of beta-catenin-reptin components that mediate the repressive state serve to antagonize a Tip60 coactivator complex that is required for activation; the balance of these opposing complexes controls the expression of KAI1 and metastatic potential. The molecular mechanisms underlying the antagonistic regulation of beta-catenin-reptin and the Tip60 coactivator complexes for the metastasis suppressor gene, KAI1, are likely to be prototypic of a selective downregulation strategy for many genes, including a subset of NF-kappaB target genes. 相似文献
137.
M Chinkers D L Garbers M S Chang D G Lowe H M Chin D V Goeddel S Schulz 《Nature》1989,338(6210):78-83
Atrial natriuretic peptide (ANP) is a polypeptide hormone whose effects include the induction of diuresis, natriuresis and vasorelaxation. One of the earliest events following binding of ANP to receptors on target cells is an increase in cyclic GMP concentration, indicating that this nucleotide might act as a mediator of the physiological effects of the hormone. Guanylate cyclase exists in at least two different molecular forms: a soluble haem-containing enzyme consisting of two subunits and a non-haem-containing transmembrane protein having a single subunit. It is the membrane form of guanylate cyclase that is activated following binding of ANP to target cells. We report here the isolation, sequence and expression of a complementary DNA clone encoding the membrane form of guanylate cyclase from rat brain. Transfection of this cDNA into cultured mammalian cells results in expression of guanylate cyclase activity and ANP-binding activity. The ANP receptor/guanylate cyclase represents a new class of mammalian cell-surface receptors which contain an extracellular ligand-binding domain and an intracellular guanylate cyclase catalytic domain. 相似文献
138.
利用高能量(〉15keV)、脉冲氮离子束增强沉积(IBED)Fe-N磁性薄膜。合成了含有α-Fe、α″-Fe16N2、γ'-Fe4N和ε-Fe2 ̄3N相的纳米多晶薄膜。Fe-N薄膜的磁性取决于膜层的相结构及微观形貌。纳米尺度的α″-Fe16N2和α-Fe相的混合物膜层的饱和磁性强度可达245emu/g。多元IBED Fe-Co-N合金薄膜与相同制备条件下合成的Fe-N薄膜相比,其相结构相似,但饱和 相似文献
139.
SeongahChin 《潍坊学院学报》2004,4(4):9-11,4
In this paper an improved fog effect algorithm in VRML and X3D is presented with respect to expressing density. The fundamental idea in the approach is to adapt local fog density having influence on Iocal regions with various grades of fog density whereas existing VRML and X3 D only make use of global fog effect. Several filters for making different fog density are presented along with experiments showing the correctness of the proposed method. 相似文献
140.
本文利用X衍射仪和透射电子显微镜研究了ZnA127Cu2Mg0.01合金自然时效过程中η相的析出速度和析出方式。η相的析出主要依靠胞状析出,但在时效初期,η相也会连续析出。特别强调的是,某些晶内连续析出的η相也会作为核心使晶内胞状析出得以进行。本文还建立了η相的生长模型,定量的描述了η相的析出速度。 相似文献