新试剂8Q5SAC 双波长增敏法测定镍

2 - ( 8 -羟基喹啉 - 5-磺酸 - 7-偶氮 ) - 1 ,8-二羟基 - 3,6 -萘二磺酸简称 8Ｑ5ＳＡＣ ,是新合成的一个测定镁的优良试剂[1] .本文利用 8Ｑ5ＳＡＣ这个试剂建立测定镍的新方法 ,并用双峰双波长法使测定的灵敏度得到提高 .1　实验部分1 1　仪器与试剂ＵＶ - 340紫外可见分光光度计 (日本日立 ) ;72 1型分光光度计 (上海第三分析仪器厂 ) ;ｐＨｓ- 3ｃ酸度计 (上海雷磁电子厂 )镍标准溶液 :将 0 2 5ｇ高纯镍片置于 1 0 0ｍＬ的烧杯中 ,加 1∶1的硝酸 ,溶解并煮沸近干 ,冷却后加蒸馏水定容至 2 50ｍＬ ,得 1ｍｇ/ｍＬ镍储备液 ,取镍储备液…     

C.Thomassen猜想的证明

证明了若 G是 3连通无爪图 ,且 G的每个同构于 A的导出子图都满足 ( a1,a2 ) ,则 G是泛连通图 (除了 u,v∈ V( G) ,d( u,v) =1时 ,G中可能不存在 ( u,v)—k路外 )。由此立得C.Thomassen猜想 :每个 4连通线图均是 Hamilton图     

取代氧化吡啶气相质子化能的分子轨道法研究

在LCAO-MO-AM1水平上计算了取代氧化吡啶的气相质子化能.发现质子化能大小与取代氧化吡啶中发生质子化的氧原子上净电荷分布有较好的线性关系.△H=1228.73kJmol~(-1),qo/e为-158.98,相关系数为0.995.     

Compensatory caspase activation in MPP+-induced cell death in dopaminergic neurons

Many have hypothesized that cell death in Parkinsons disease is via apoptosis and, specifically, by the mitochondrial-mediated apoptotic pathway. We tested this hypothesis using a mouse dopaminergic cell line of mesencephalic origin, MN9D, challenged with the Parkinsonism-causing neurotoxin MPP⁺ (1-methyl-4-phenylpyridinium ion). Apoptosis was the main mode of cell death when the cells were subjected to MPP⁺ treatment under serum-free conditions for 24 h. Caspase-3 and caspase-9, however, were not activated, thus indicating the existence of alternate or compensatory cell death pathway(s) in dopaminergic neuronal cells. Using caspase inhibitors, we demonstrated that these pathways involve caspase-2, –8, –6 and –7. A time-course study indicated that activation of caspase-2 and –8 occurred upstream of caspase-6 and caspase-7. Upon MPP⁺ challenge, the apoptosis-inducing factor was translocated from the mitochondria into the MN9D cytosol and nucleus. These results suggest the existence of alternative apoptotic pathways in dopaminergic neurons.Received 20 September 2004; received after revision 5 November 2004; accepted 22 November 2004     

土壤和沉积物中1,2,4-三氯苯的超声波提取

以土壤和沉积物中的1,2,4-三氯苯为研究对象,应用超声波提取并以气相色谱进行定量分析。研究结果表明：在一定的超声波处理条件下,1,2,4-三氯苯较为稳定且降解比率很小;最适宜的超声波提取条件为：超声波功率20W、提取温度35℃、提取时间60min、提取剂为石油醚-丙酮混合溶剂(体积比1：1);三种不同提取方法(索氏、振荡和超声波)相比较以超声波提取法最优;该方法的平均回收率为92．18％、变异系数0．82%、检测限0．000μg／g,可满足土壤中微量有机物定量分析要求。     

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     

A novel pattern of fast calcium oscillations points to calcium and electrical activity cross-talk in rat chromaffin cells

Slow oscillations of cytosolic calcium ion concentration – – typically originate from release by intracellular stores, but in some cell types can be triggered and sustained by Ca²⁺ influx as well. In this study we simultaneously monitored changes in and in the electrical activity of the cell membrane by combining indo-1 and patch-clamp measurements in single rat chromaffin cells. By this approach we observed a novel type of spontaneous oscillations, much faster than those previously described in these cells. These oscillations are triggered and sustained by complex electrical activity (slow action potentials and spike bursts), require Ca²⁺ influx and do not involve release from intracellular stores. The possible physiological implications of this new pathway of intracellular signalling are discussed.Received 30 July 2004; received after revision 14 October 2004; accepted 1 November 2004     

HAMILTONICITY IN 2-CONNECTED {K_(1,3) F}-FREE GRAPHS

ＨＡＭＩＬＴＯＮＩＣＩＴＹＩＮ２－ＣＯＮＮＥＣＴＥＤ｛Ｋ_（１，３）Ｆ｝－ＦＲＥＥＧＲＡＰＨＳ￥ＬＩＧｕｏｊｕｎ（ＭａｔｈｅｍａｔｉｃｓＤｅｐｅｒｔｍｅｎｔｏｆＹａｎｔａｉＴｅａｃｈｅｒ＇ｓＣｏｌｌｅｇｅ，Ｙａｎｔａｉ２６４０００，Ｃｈｉｎａ）ＬＩＵ?..     

一个带羟基的C_（60）吡咯烷衍生物的合成与表征

氮气流保护下，Ｃ６０与聚甲醇和苏氨酸在干燥的甲苯中反应生成一个带羟基的Ｃ６０。吡咯烷衍生物。标题化合物用ＦＤ－ＭＳ，ＦＴ－ＩＲ，ＵＶ－ＶＩＳ和１Ｈ－ＮＭＲ进行了表征。