SO42-/ZrO2系列固体超强酸的制备与应用

本文对采用不同方法制备了两种SO4^2-/ZrO2系列的SO4^2-/ZrO2-TiO2和SO4^2-/ZrO2-Al2O3固体超强酸催化剂，并以顺丁烯二酸酐和正丁醇的酯化反应为探针反应，考察了Zr：A1，Zr：Ti的原于配比，焙烧温度，焙烧时间以及浸渍液硫酸的浓度对催化剂活性的影响。     

RAPD鉴定远缘杂交牧草蔗新品系94-42

应用RAPD技术对远缘杂交牧草蔗新品系94—42，父本PT43—52及母本甘蔗栽培良种C0419进行分子鉴定．67个引物共扩增出284条带，其中l16条为多态性带，占40．85％．计算相似性系数，并对3个品种进行亲缘关系的分析，结果分别为：新品系和母本：0．9138；新品系和父本：0．8009；父本和母本：0．7658．RAPD结果证明，牧草蔗94—42基因组出现多态性，具有父、母本特异DNA带，是两者远缘杂交的后代．提示RAPD技术是一种适合远缘杂交物种分子鉴定的有效方法．     

纳米固体超强酸SO42-/Fe2O3催化合成柠檬酸三丁酯

合成了纳米固体超强酸，考察了该催化剂在柠檬酸三丁酯合成中的催化活性，并与非纳米的SO4^2-/TiO2,SO4^2-/ZrO2,SO4^2-/Fe2O3，浓H2SO4催化剂进行了比较，同时对酯化反应的几种影响因素进行了研究。     

Targeting of the Akt/PKB kinase to the actin skeleton

Serine/threonine kinase Akt/PKB intracellular distribution undergoes rapid changes in response to agonists such as Platelet-derived growth factor (PDGF) or Insulin-like growth factor (IGF). The concept has recently emerged that Akt subcellular movements are facilitated by interaction with nonsubstrate ligands. Here we show that Akt is bound to the actin skeleton in in situ cytoskeletal matrix preparations from PDGF-treated Saos2 cells, suggesting an interaction between the two proteins. Indeed, by immunoprecipitation and subcellular fractioning, we demonstrate that endogenous Akt and actin physically interact. Using recombinant proteins in in vitro binding and overlay assays, we further demonstrate that Akt interacts with actin directly. Expression of Akt mutants strongly indicates that the N-terminal PH domain of Akt mediates this interaction. More important, we show that the partition between actin bound and unbound Akt is not constant, but is modulated by growth factor stimulation. In fact, PDGF treatment of serum-starved cells triggers an increase in the amount of Akt associated with the actin skeleton, concomitant with an increase in Akt phosphorylation. Conversely, expression of an Akt mutant in which both Ser473 and Thr308 have been mutated to alanine completely abrogates PDGF-induced binding. The small GTPases Rac1 and Cdc42 seem to facilitate actin binding, possibly increasing Akt phosphorylation.Received 10 September 2003; accepted 25 September 2003     

Monogenetic determinants of Alzheimer's disease: APP mutations

Mutations within exons 16 and 17 of the β-amyloid precursor protein (APP) gene were the first known cause of familial Alzheimer's disease. These mutations are rare and have been reported in a handful of families exhibiting autosomal dominant inheritance of Alzheimer's disease with age of onset around 50 years. In vitro and in vivo studies have demonstrated that each of these mutations alters proteolytic processing of APP, resulting in an increase in the production of Aβ42, a highly fibrillogenic peptide, that spontaneously aggregates and deposits in the brain. Transgenic mice carrying a mutant human APP gene also show age-dependent β-amyloid (Aβ) deposition in the brain. The rate of deposition in these mice can be modified by apolipoprotein E expression.     

Emodin inhibits tumor cell migration through suppression of the phosphatidylinositol 3-kinase-Cdc42/Rac1 pathway

Enhanced cell migration is one of the underlying mechanisms in cancer invasion and metastasis. Therefore, inhibition of cell migration is considered to be an effective strategy for prevention of cancer metastasis. We found that emodin (3-methyl-1,6,8-trihydroxyanthraquinone), an active component from the rhizome of Rheum palmatum, significantly inhibited epidermal growth factor (EGF)- induced migration in various human cancer cell lines. In the search for the underlying molecular mechanisms, we demonstrated that phosphatidylinositol 3-kinase (PI3K) serves as the molecular target for emodin. In addition, emodin markedly suppressed EGF-induced activation of Cdc42 and Rac1 and the corresponding cytoskeleton changes. Moreover, emodin, but not LY294002, was able to block cell migration in cells transfected with constitutively active (CA)-Cdc42 and CA-Rac1 by interference with the formation of Cdc42/Rac1 and the p21-activated kinase complex. Taken together, data from this study suggest that emodin inhibits human cancer cell migration by suppressing the PI3K-Cdc42/Rac1 signaling pathway.Received 7 February 2005; received after revision 11 March 2005; accepted 18 March 2005     

2024-T42铝合金点焊接头性能研究

为改善高强铝合金接头连接性能,提高焊接质量,研究了2024-T42铝合金回填式搅拌摩擦点焊(RFSSW)、电阻点焊和铆接3种不同接头的连接性能,采用显微组织观察试验、拉伸试验、拉剪试验和显微硬度试验等方法,对接头组织和性能进行表征与分析.结果 表明:RFSSW接头的力学性能最优,拉剪性能达到7.23 kN,较铆接和电阻...     

焙烧温度对SO_4~(2-)/TiO_2固体超强酸抗水稳定性的影响

通过水预处理方法对比研究了不同焙烧温度制备的SO_4~(2-)/TiO_2固体超强酸的抗水稳定性,借助XRD、NH_3-TPD、FT-IR、TG和BET等表征技术分析材料的结构特征。结果表明,当焙烧温度在500℃以下时,所制得的SO_4~(2-)/TiO_2固体超强酸具有相近的优异酯化性能;当焙烧温度提升至600℃以上时,SO_4~(2-)/TiO_2的孔结构坍塌,SO_4~(2-)含量下降,酯化性能显著下降。经过水预处理后,所有固体超强酸酯化活性降低,主要与其SO_4~(2-)脱落和酸量明显减小有关。相比之下,400℃制备的SO_4~(2-)/TiO_2固体超强酸催化剂具有较好的稳定性。     

瓦雷兹芽孢杆菌FZB42菌株拮抗两种树木病原真菌及其机理研究

镰刀菌和交链孢菌是导致树木病害的两种常见病原真菌,常导致苗圃植物严重的危害和经济损失。瓦雷兹芽孢杆菌FZB42菌株具有高效生防性能和植物促生活性,为进一步探明该菌株的生防机理,首先测试了FZB42对镰刀菌和交链孢菌的抑制效果。在了解该菌株抑制作用的基础上,进一步构建质粒,通过同源重组的方式构建了FZB42的3个抗生素合成缺损菌株(ΔbmyA,ΔfenA、ΔbmyAΔfenA)。对这3个突变株进一步测试表明,FZB42合成的物质bacillomycin D和fengycin是抑制两种真菌生长的重要原因,且这两种物质的拮抗作用具有明显的协同强化效果。     

SO42-/MxOy型固体超强酸催化醇与甲缩醛反应的研究

采用沉淀-浸渍法制备了SO42-/ZrO2和SO42-/TiO2两种SO42-/MxOy型固体超强酸催化剂,将其用于催化醇羟基与甲缩醛的甲氧基甲基化反应。分别选用伯醇、仲醇和二醇与甲缩醛反应,考察了硫酸浸渍浓度和催化剂焙烧温度对催化剂活性的影响。结果表明:SO42-/MxOy型固体超强酸催化剂在温和条件下能有效催化醇与甲缩醛反应,生成目的产物;不同类型的醇与甲缩醛反应的难易程度有较大的区别,由易到难的顺序为:伯醇,仲醇,二醇。