The limits of specificity: An experimental analysis with RNA aptamers to MS2 coat protein variants

It has been hypothesized that selections for aptamers with high affinity for a given target molecule will of necessity identify aptamers that have high specificity for that target. We have attempted to assess this hypothesis by selecting aptamers that can bind to MS2 coat protein or to single- or double-substitution variants of the coat protein. Some aptamers selected to bind MS2 coat protein or its variants were mildly specific for their cognate targets, discriminating by two- to fourfold against closely related proteins. Specificity determinants on both the coat proteins and the aptamers could be identified. However, many aptamers could readily bind to each of the different coat proteins. The identification of such aptamer 'generalists belies the proposed relationship between the affinities and specificities of selected RNA ligands. These results imply that, while aptamers may not finely discriminate between closely related targets, neither will their binding be negated by mutations in targets. Aptamer pharmaceuticals may therefore better resist the evolution of resistance.     

The use of micro-thermal analysis as a means of in situ characterisation of a pharmaceutical tablet coat

The technique of micro-thermal analysis (MTA) has been applied to a commercial sugar coated ibuprofen tablet in order to identify the ability of the method to differentiate between the coat and the tablet core and to characterise the thermal properties of both components using localised thermal analysis. Thermal conductivity measurements in conjunction with intensity histogram analysis indicated that differentiation across the coat/core interface was possible, with a bimodal distribution of pixel intensities corresponding to thermal conductivity noted. Localised thermal analysis studies indicated that the bulk response was dominated by the incorporated ibuprofen, with a discontinuity seen at ca. 70–80°C, corresponding to the published melting point of the drug. The coat showed a discontinuity at ca. 220°C that may be reasonably ascribed to the melting process. It was also noted that the coat showed a small discontinuity at a temperature corresponding to the melting of ibuprofen. In summary, the technique was shown to be capable of identifying the core/coat interface using thermal conductivity measurements, while localised thermal analysis experiments enable the operator to perform thermal analysis experiments on the individual components in situ.     

"格陵兰长衣"的构成意识和方法探究

“格陵兰长衣”在构成意识和方法上较前几个世纪大为不同,开始在前后及两侧收省,使上身的褶皱基本消除。同时为了加大下摆而进行了分片裁剪,出现了前所未有的侧身衣片,从而彻底脱离了平面结构,而展现了近世纪的三维、四面、立体结构形式,这种长衣因为特殊的裁剪方法而确立了它在服装史上的地位。     

一罐装防锈底漆的研制

研究以聚乙烯缩丁醛改性树脂为漆料 ,以磷酸锌 ,氧化锌 ,四盐基铬酸锌 ,滑石粉等为颜填料制备一罐装防锈底漆的生产工艺 ,并对其性能进行测试 ,讨论了影响防锈底漆性能的因素     

陶瓷涂层活塞环精密成形磨削

陶瓷活塞环的加工应采用超硬磨粒金刚石砂轮磨削，但传统的金刚石笔修整方法由于修整笔易被磨耗而不能用于金刚石砂轮。为了修整金刚石砂轮使其获得要求的微凹的砂轮廓形，提出了用碳化硅（ＧＣ）杯形砂轮取偏斜α角的方位修整金刚石砂轮，获得中凹的金刚石砂轮修整廓形，以成形磨削陶瓷涂层活塞环桶形外环面的方法，分析了这种方法的修整成形机理，提出了计算α角和计算砂轮修整廓形的理论公式。     

Cloning and expression of the Chinese wheat mosaic virus RNA2 coat protein readthrough and 19 ku cysteinerich domains and localization of these proteins

The 5′-terminal (RTn) and 3′-terminal (RTc) halves of the coat protein readthrough domain and the 19 ku cysteine-rich protein of Chinese wheat mosaic virus (CWMV) were amplified by RT-PCR, cloned and expressed in E. coli. Antisera and monoclonal antibodies against these proteins were prepared by immunising these purified proteins to mice. Detection of RTn, RTc and 19 ku proteins in CWMV infected wheat sap and leaf tissue indicated that the RTn and RTc proteins were distributed on the surface of virus particles whereas the 19 ku protein was in the cytoplasm of the infected wheat cells.     

激光表面处理灰铁的工艺实验研究

本文探讨了激光表面处理灰铁的工艺。运用1.2kW CO_2激光加工机重熔普通灰铸铁表面并进行合金化处理。结果表明,激光表面处理时白口深度的大小与激光器工艺参数P/(Dv)~2/1成线性关系,且受表面涂料的影响;白口层深度与熔区表面硬度成指数关系,白口深度越大,则硬度值越高。激光表面处理后,试样自表层起可划分为3个区域,即:熔化区,组织为莱氏体;热影响区,组织为针片状马氏体和隐晶马氏体;基体区,组织为珠光体。     

濒危植物小花木兰种子初步研究

通过扫描电镜观察小花木兰的种子,发现它的种皮木质化程度较高,种子在自然状态下难于萌发;用四唑染色法检测了保存方法不同的小花木兰(Magnolia sieboldii)种子的生活力,冷湿适宜能使它保持较长时间的活力;对不同处理方法的种子萌发率进行比较分析,沙藏冷湿处理翌年春播萌发率良好;调查了自然条件下的种子库动态后显示:种子在自然状态下散布后损失大;加上种子质量差,自身的结构让它萌发困难,造成了自然条件下小花木兰林下幼苗极其稀少,天然更新不足,使它生存受到严重威胁.     

变螺距螺旋桨的实验应力分析

采用应力涂层和应变电测组合试验技术，分析几种类型变螺距螺旋桨的变厚度截面桨叶的应力分布规律与量值。分析结果可供变螺距螺旋桨的新型结构设计和流体动力特性研究参考。     

珍珠花种子发芽条件的研究

试验表明去除种皮珍珠花种子很快萌发,但幼苗的培养和移植较麻烦;采用９８％的硫酸处理种子３ｄ,然后插于土壤中,萌发的速度稍慢一些,但方法简单,幼苗成活率高,是一种行之有效的萌发方法,种子萌发和轩生长的最适温度为１５￣２０℃。种皮对珍珠花种子的萌发起着机械性限制作用,解剖结构显示由于种皮由多层石细胞组成防碍了种子胚乳和胚对水分的吸收而导致种子不能萌发。