GaAs/Al（0.4）Ga（0.6）As多量子肼红外探测器光吸收计算

于2010-11-23批量导入

2-C-支链-1,6-脱水吡喃葡萄糖的开环反应及吡喃烯糖的合成研究

在糖化学合成中，1,6-脱水吡喃糖不仅是合成具有生物活性低聚糖、糖共体、抗原、抗体以及天然产物等化合物重要原料，而且还是许多具有生物活性的天然产物的结构单元。同时，它还具有[3,2,1]的双环缩醛结构，使其在糖化学合成中具有高的立体选择性和区域选择性，同时减少了C-1 和C-6 位的保护和去保护的优点。此外，环内的缩醛开环后，又可以相应地在C-1 和C-6 位进行官能团转化以及糖苷化反应。 本文报道了一种新的1,6-脱水吡喃糖的合成方法，并设计合成了2-C-支链-1,6-脱水吡喃葡萄糖1-195、1-197、1-198 以及2-C-支链-6-硫代1,6-脱水吡喃葡萄糖1-225。到目前为止，1,6-脱水糖开环并进行糖苷化反应，存在选择性较差、产率低的缺点。我们发现，在乙腈做溶剂的条件下，NiCl5 能高立体选择性高产率地催化化合物1-195、1-197、1-198 开环并与ROH、RSH 发生糖苷化反应。在NiCl5-乙腈条件下，合成了一系列2-C-支链-α-糖苷和2-C-支链-β-硫代糖苷，并对2-C-支链1,6-脱水吡喃葡萄糖的生成机理以及开环机理进行了探讨。 烯糖在糖化学合成中是重要的起始原料，从Fischer 首次合成烯糖至今，一直不断地有新的合成方法出现。但目前文献报道的方法存在所用试剂有毒、价格贵和操作繁琐等缺点。我们对Fischer-Zach 方法进行了改进， 发现Zn-NaH2PO4-H2O 和Zn-PEG600-H2O 体系都能很好地合成烯糖。该方法具有条件温和、绿色环保、操作简单的优点。在Zn-NaH2PO4 溶液或Zn-PEG600 条件下，以溴代糖为原料，高产率地合成一系列的烯糖。 The 1,6-anhydrohexopyranoses are crucial subunits of myriad bioactive nature products, as well as important syntons of carbohydrate chemistry which have been extensively used to prepare the biologically potential oligosaccharides, glycoconjugates, antibiotics, and structurally varied nature products. Their particular [3.2.1] bicyclic skeleton makes them have high regio- and stereo-control in a variety of reactions, and such structure avoids protecting hydroxyl groups at C1 and C6.Additionally, the cleavage of the internal acetal under acidic conditions could be beneficial for further transformations of functional group and glycosylation of the corresponding pyranosyl sugar at the C6 or C1 site. Herein we developed a novel approach to prepare the 1,6-anhydrohexopyranose, and synthesized the 2-C-branched-1,6-anhydrohexopyranose 1-195, 1-197, 1-198 and 2-C-branched-6-thio-1,6-anhydrohexopyranose 1-225. Until now, glycosylation of 1,6-anhydrohexopyranoses has been limited because of the low yields and low stereoselectivity. In this paper, we found that NiCl5-MeCN system could selectively cleave the ring of 1,6-anhydrohexopyranoses with alcohols and thiols at room temperature in high yields. A series of 2-C-branched-α-glycosides and 2-C-branched-β-thioglycosides have been synthesized via NiCl5-catalyzed. Furthermore, we investigated the formation and ring-opening mechanism of 2-C-acetylmethyl-1,6-anhydrohexopyranose. Glycals are significant starting material in carbohydrate chemistry. After the Fischer-Zach method for forming glucal was reported for the first time, the numerous synthetic methods for glycals have been explored. However, there are several drawbacks in the existing methods, such as the usage of very expensive and toxic reagents, intricate operation, and the influence of acid-sensitive and base-sensitive functional group. We improved the Fischer-Zach method and developed a facile, mild and environmentally benign methodology towards the synthesis of the glycals in Zn-NaH2PO4-H2O or Zn-PEG600-H2O system. Our method involves the treatment of glycosyl bromides with Zn in NaH2PO4 aqueous solution or PEG600-H2O at room temperature, affording various glycals in excellent yields.

低剂量~(12)C~(6+)离子束预辐照对小鼠肝脏细胞DNA损伤和周期进程的影响

研究低剂量重离子束预辐照对小鼠肝脏辐射损伤程度的影响。分别用低剂量12C6+离子束全身均匀预辐照处理小鼠,剂量分别为0、0.05、0.1、0.25、0.5Gy,剂量率为1Gy/min,4h后用4Gy的12C6+离子束全身均匀辐照,照射8h后用流式细胞仪检测辐照小鼠肝脏细胞在各细胞周期时相的百分率,并用单细胞电泳技术检测辐照损伤小鼠肝脏细胞的DNA损伤程度。结果显示,和对照组相比,低剂量预辐射处理可以减轻辐照损伤小鼠肝脏细胞G0/G1期和G2/M的阻滞,促进肝脏细胞在S期的积累。此外,辐照小鼠肝脏细胞的拖尾率及拖尾长度也显著减少,其中以0.1Gy处理组效果最为显著(P<0.01)。提示:低剂量重离子预辐照能使细胞产生适应性反应,有效减轻辐照小鼠肝脏细胞G0/G1期和G2/M的阻滞,并显著减轻肝脏细胞DNA的辐射损伤程度。

~(12)C~(6+)离子束诱导HeLa细胞DNA损伤效应

本文研究了HeLa细胞经过12C6+离子束辐照之后的DNA损伤效应,及辐照后p53激活的分子机制。运用中性单细胞电泳技术,检测了HeLa细胞经过4Gy 12C6+离子束辐照间隔0、3、6和12h之后DNA的损伤情况,及0.5、1、2和4Gy 12C6+离子束辐照后即时的DNA损伤情况。同时运用细胞生长实时监测仪监测了HeLa细胞在经过0、0.5和1Gy 12C6+离子束辐照之后的生长变化,并运用AO/EB双染检测了辐照细胞24h后的凋亡情况。另外,利用8mmol/L的咖啡因[抑制ATM(ataxia-telangiectasia,mutated)和ATR(ATM and Rad3-related kinase)]和20μmol/L的wortmannin[抑制ATM和DNA-PK(DNA-dependent protein kinase)]处理HeLa细胞后再进行1Gy 12C6+离子束辐照,通过westernblot检测p53的表达。结果显示,12C6+离子束辐照可造成HeLa细胞的DNA损伤,损伤随剂量升高而升高但随测定间隔时间降低,诱导HeLa细胞发生凋亡;而且辐照后p53表达升高。结果证明12C6+离子束辐照可造成HeLa细胞的DNA损伤并诱导损伤修复及凋亡等效应,损伤效应相关因子p53被激活,并且激活依赖于ATM。

杜仲对~(12)C~(6+)离子束辐照小鼠防护作用的研究

<正>目的:研究杜仲对辐射损伤小鼠的保护作用。方法:照前2周给小鼠口服不同浓度的杜仲粗提物,后给予2Gy12C6+离子束全身均匀辐照。照后8h用流式细胞仪检测小鼠胸

褪黑素对~(12)C~(6+)束辐照损伤小鼠肺的防护作用研究

<正>目的:探讨褪黑素(Melatonin,MLT)对重离子辐照损伤小鼠肺的防护作用,为褪黑素的抗辐射功能[1][2]进一步提供实验依据。方法:预先给小鼠腹腔注射10mg/kg的