气相色谱法测定用重氮甲烷预处理的戊二酸

建立了一种采用重氮甲烷甲酯化后,以气相色谱测定戊二酸含量的分析方法.被测物质戊二酸沸点较高,未衍生时峰形拖尾十分严重.经酯化后,可降低沸点,峰形也得到很好的改善,能满足气相色谱法的分析要求.使用重氮甲烷在常温常压下滴加到戊二酸样品中,进行预处理,待溶液呈现亮黄色,摇动不褪色且无气泡产生,说明酯化反应已完全.由于样品中含有丁二酸、己二酸等结构相似的物质,选用SPBTM-5石英毛细管柱(30 m×0.25 mm i.d×0.25 μm)进行分离,氢火焰离子化检测器(FID)检测,以改善峰形并检测微量杂质.通过改变色谱条件和用气相色谱-质谱的选择性离子检测,未发现目标物质峰中掺有其它杂质峰,说明戊二酸二甲酯与其他物质分离良好;并且未发现有戊二酸分子离子峰及戊二酸单甲酯的分子离子峰,说明戊二酸已酯化完全.本文所用方法平均回收率为98.9%,相对标准偏差(RSD)为0.11%,最低检出限为5×10-11 g/mL;且所得衍生物-戊二酸二甲酯也很稳定,在48 h内重复测定6次,结果未见明显变化.因而该方法可用于该类物质的纯度检验,也可用于新产品开发及生产、科研中的过程分析.本文作者已成功运用上述方法,为企业进行了数批样品的检测.     

戊二酸的气相色谱测定研究

建立了一种采用重氮甲烷甲酯化后,以气相色谱测定戊二酸含量的分析方法.用重氮甲烷对戊二酸样品进行酯化预处理,以SPBTM-5石英毛细管柱(30m×0.25 mm i.d×0.25μm)分离,氢火焰离子化检测器(FID)检测,归一化法定量.平均回收率为98.91%,相对标准偏差(RSD)为0.11%,最低检出限为5×10-11 g/mL.方法可用于该类物质的纯度检验,也可用于新产品开发及生产、科研中的过程分析.     

Dynamic Simulation of Single DNA Molecule at the Base Level

A mesoscopic discrete dsDNA model at the base level is proposed based on the statistical model (Phys. Rev. Lett.82 (1999) 4560). The numerical simulations reproduce the 65 pN plateau and those on the force vs extension for different supercoiling degrees are favourable with the experimental data. Our model has potential applications on the study of short DNA segments and provides a bridge between the statistical models and atomic modelling.     

新型离子交换硅胶键合相的制备及评价

二甲基氯硅烷与硅胶表面反应,形成牢固的ＳｉＨ键之后,连接上活泼的中间体——烯丙基缩甘油醚作为柔软的分子臂,最后接上二乙基氨基,由此制得了新型的离子交换硅胶键合相。经漫反射红外光谱、元素分析和高效液相色谱法对键合相进行了鉴定和评价。结果表明：键合反应按预定路线进行,键合相具有较好的色谱性能。此种方法可有效地运用于无孔硅胶填料的制备。     

竞争型二元风险模型破产概率

本文研究了竞争型的二元风险模型,定义了两类破产概率以及状态过程,利用经典风险模型的已有结果和条件期望的性质,得到两类破产概率表达式,以及单个保险公司有限时间破产概率和最终破产概率,并给出两个保险公司的状态过程的概率分布列.     

竞争型的n元风险模型

保险市场中存在激烈的竞争,针对这种情形提出竞争型的n元风险模型,定义了两种破产时间,利用经典风险模型已有结论和条件期望的性质,得到相应的有限时间破产概率和最终破产概率表达式,以及每个保险公司有限时间破产概率和最终破产概率.     

用液流操纵单个DNA分子形成纳米悬链线图形

首先用液流拉伸单分子DNA,使其吸附在修饰过的云母基片上.然后让二次液流沿着垂直于已拉伸的DNA的方向流过云母片,用原子力显微镜(AFM)观测,可见DNA单分子片段在基片上形成了一些纳米尺度的悬链线.提出一种“S悬桥”模型能定量地解释这一现象.该研究工作揭示,在DNA的单分子操作中,经典的弹性力学理论足以描述和控制DNA分子二维图形的形成 关键词： DNA 单分子DNA操纵 原子力显微镜(AFM) 纳米悬链线     

Adsorption dynamics of double-stranded DNA on a graphene oxide surface with both large unoxidized and oxidized regions

The adsorption dynamics of double-stranded DNA (dsDNA) molecules on a graphene oxide (GO) surface are important for applications of DNA/GO functional structures in biosensors, biomedicine and materials science. In this work, molecular dynamics simulations were used to examine the adsorption of different length dsDNA molecules (from 4 bp to 24 bp) on the GO surface. The dsDNA molecules could be adsorbed on the GO surface through the terminal bases and stand on the GO surface. For short dsDNA (4 bp) molecules, the double-helix structure was partially or totally broken and the adsorption dynamics was affected by the structural fluctuation of short dsDNA and the distribution of the oxidized groups on the GO surface. For long dsDNA molecules (from 8 bp to 24 bp) adsorption is stable. By nonlinear fitting of the contact angle between the axis of the dsDNA molecule and the GO surface, we found that a dsDNA molecule adsorbed on a GO surface has the chance of orienting parallel to the GO surface if the length of the dsDNA molecule is longer than 54 bp. We attributed this behavior to the flexibility of dsDNA molecules. With increasing length, the flexibility of dsDNA molecules also increases, and this increasing flexibility gives an adsorbed dsDNA molecule more chance of reaching the GO surface with the free terminal. This work provides a whole picture of adsorption of dsDNA molecules on the GO surface and should be of benefit for the design of DNA/GO based biosensors.     

Stable water droplets on composite structures formed by embedded water into fully hydroxylated β-cristobalite silica

Using molecular dynamics simulations, we have revealed a novel wetting phenomenon with a droplet on composite structures formed by embedded water into(111) surface of β-cristobalite hydroxylated silica. This can be attributed to the formation of a composite structure composed of embedded water molecules and the surface hydroxyl(–OH) groups,which reduces the number of hydrogen bonds between the composite structure and the water droplet above the composite structure. Interestingly, a small uniform strain(±3%) applied to the crystal lattice of the hydroxylated silica surface can result in a notable change of the contact angles(> 40°) on the surface. The finding provides new insights into the correlation between the molecular-scale interfacial water structures and the macroscopic wettability of the hydroxylated silica surface.     

无孔单分散离子交换硅胶键合相用于蛋白质的高效液相色谱分离

将新合成的无孔硅胶二乙基氨基新型离子交换填料 (NPS-DEA)用于蛋白质的液相色谱分离。考察了流动相的pH值、盐浓度、流速及梯度程序对蛋白质分离的影响 ,并考察了蛋白质的质量回收率。实验结果表明 ,所得阴离子交换固定相的色谱性能良好。在梯度淋洗条件下 ,卵清蛋白、牛血清蛋白、胰岛素、γ-球蛋白、核糖核酸酶、溶菌酶获得了较好的分离。蛋白质的保留符合一般的保留值规律。柱填充床稳定 ,而柱负载较小 ,可用于高纯度的微量制备。