Polarity modified triplex DNA by bromide

Conclusion A py-pu-py triplex DNA containing the polarity modification by replacing the atom H5 of cytosine with Br was examined, mainly for the stability of the formation of the triplex DNA. Our computational results show that the conformation of the strand that contained a replaced H5 by cytosine to Br was destabilized, but the Hoogsteen base pairs were stabilized. Although this approach of modifying the polarity of DNA base has not been tried before, it shows the possibility to improve the stability by the polarity modification.     

Circular dichroism spectra of different structures formed by the oligonucleotides

Under different conditions, oligonucleotides can form several different DNA structures such as duplex, triplex and quadruplex. All these structures exhibit an obvious difference in their CD spectra. The common characteristic is that they show a negative band at 240 nm, while in the range of 260–300 nm, the spectra are different from each other. Many factors such as chain direction, sugar puckering mode, orientation of the glycosyl bond, base stacking and sequence can affect their conformation and then show diversity and complexity in their spectra. By studying and comparing these spectra, more information about their conformations can be obtained to help predict some new structures. Furthermore, the spectra can also provide a base to study their potential biological functions.     

改型环形灌注泵的径向力研究

为解决灌注泵的泄漏问题 ,对灌注泵的 3个特征及轴封泄漏量的解析式进行了分析 .认为轴封间隙过大是导致灌注泵泄漏的主要原因 ,而轴封间隙是由作用在叶轮上的径向力引起的 .普通离心泵径向力及轴封间隙过大因而不适合用作灌注泵 .设计出一种改型环形离心泵 ,其压水室由一段环形流道和一段螺旋形流道组成 .对环形压水室、螺旋形压水室及环形 -螺旋形压水室泵径向力的定性分析表明 :这种改型环形灌注泵的径向力小 ,且最小径向力点向小流量方向偏移 ,正好满足灌注泵小流量下小径向力的要求 .对这种改型环形泵的径向力进行了测试 ,并将结果与相同比转速下涡形泵和环形泵径向力的计算值进行了比较 ,也证实了上述结论     

单作用直线电机三缸往复泵运动特性研究

针对传统单作用三缸往复泵结构复杂,排量、压力波动大,排量调节困难等缺点,提出了一种采用直线电机驱动技术的单作用三缸往复泵,介绍了该往复泵的工作原理,提出了能使该种往复泵理论上实现“恒排量”的运动规律和运动相位,讨论了运动相位误差对往复泵排量波动的影响。研究结果表明,在给定运动规律和运动相位下,往复泵的冲程和控制系统的控制精度是影响其排量不均匀度的主要因素,控制精度越高,冲程越长,排量不均匀度越小。通过实例计算可以看出,单作用直线电机三缸往复泵不需设置排出空气包就可以使排量不均匀度达到曲柄滑块机构单作用三缸往复泵的使用高性能排出空气包的水平。研究结果为开发新型的“恒排量”往复泵及其控制系统的设计提供了理论依据。     

靶序列三链DNA对质粒pBR322的Ampr基因表达的抑制

利用ＣａＣｌ２法成功地将寡核苷酸导入大肠杆菌ＪＭ１０９细胞。质粒ｐＢＲ３２２转化结果表明,寡革酸片段５’－ＡＧＣＧＧＧＡＡＴＡＡＧＧＧＡＡ－３’在转化前（或后）与靶序列结合均能抑制β－内酰胺酶基因的表达,细菌生长受到抑制。体外聚丙烯酰胺凝胶电泳结果表明,该片段能与靶序列形成三链结构。这些结果表明多聚嘌呤寡核苷酸是通过与靶序列形成三链ＤＮＡ来抑制β－内酰胺酶基因的表达。     

阀滞后角对三缸泵排出空气包后流量不均度的影响

在考虑泵阀滞后角的情况下 ,推导了三缸单作用往复泵排出空气包后管路流量表达式及其傅里叶级数 ,并据此分析了泵阀滞后角对空气包后管路流量不均度的影响     

WXG-4型旋光仪问题的探讨

在使用旋光仪过程中,文章针对光学原理、视野中现象、视场标准判定及刻度盘读数方法等一些问题做了探讨。