基于DNA纳米结构的细胞间相互作用的调控

细胞通过化学信号、 电子交换和直接接触等方式交换彼此之间的物质和信息, 以调节生命体的生长发育. 因此, 细胞间的相互作用研究与调控在细胞功能的机制研究和疾病的诊断及治疗等领域具有非常重要的意义. DNA纳米结构具有易合成、 易修饰、 可编程性设计及生物安全性高等优点, 有望实现操作简单、 精确可调、 智能响应的细胞间相互作用调控, 受到了广泛关注. 本文综述了寡核苷酸链杂交、 受体-配体结合和核酸适体靶向识别等基于DNA纳米结构的细胞组装策略, 总结了pH调控、 金属离子调控和DNA链激活等细胞间相互作用的调控手段, 并重点介绍了其在细胞间作用力的测量和成像、 体外组织模型的构建、 细胞间的通讯交流和细胞免疫治疗等领域的应用. 最后对该领域进行了总结和展望, 希望为相关研究提供有益参考.     

气相色谱法测定养殖环境沉积物中硫丹及代谢物残留

建立了养殖环境沉积物中α-硫丹、β-硫丹和硫丹硫酸盐残留的气相色谱测定方法.用丙酮和石油醚提取沉积物中的硫丹,用由下至上依次填充弗罗里硅土、活性炭和无水硫酸钠的玻璃层析柱净化提取物,浓缩后气相色谱(ECD检测器)检测.结果显示,浓度范围为0.500～100μg/L线性良好,最低检出限和最低定量限分别为0.9μg/kg和...     

“小学生互联网使用行为调查”应用案例

实际调研课题中常常面对各种条件的限制,无法按照教科书上严格的抽样设计去实施。但是,研究者完全有可能通过简化的、兼顾学性和操作性的设计,以及各个环节认真细致的质量控制,得到相对高质量的调查数据和分析结论。本文拟用2009年暑假笔者主持完成的"小学生互联网使用行为调查"课题为案例,实事求是地展示一个实际的抽样调查的全过程,希望笔者的体会和思考能对读者有所启示。     

指数函数系的不完备性和极小性

Necessary and sufficient conditions are obtained for the incompleteness and the minimality of the exponential system E（Λ,M） = {z l e λ n z ： l = 0,1,...,m n-1;n = 1,2,...} in the Banach space E 2 [σ] consisting of some analytic functions in a half strip.If the incompleteness holds,each function in the closure of the linear span of exponential system E（Λ,M） can be extended to an analytic function represented by a Taylor-Dirichlet series.Moreover,by the conformal mapping ζ = φ（z） = e z ,the similar results hold for the incompleteness and the minimality of the power function system F （Λ,M） = {（log ζ） l ζ λ n ： l = 0,1,...,m n-1;n = 1,2,...} in the Banach space F 2 [σ] consisting of some analytic functions in a sector.     

Phenomenological study on the significance of the scalar potential and Lamb shift

We indicated in our previous work that for QED the contributions of the scalar potential, which appears at the loop level, is much smaller than that of the vector potential, and in fact negligible. But the situation may be different for QCD, the reason being that the loop effects are more significant because \alpha_m s is much larger than \alpha, and secondly the non-perturbative QCD effects may induce the scalar potential. In this work, we phenomenologically study the contribution of the scalar potential to the spectra of charmonia. Taking into account both vector and scalar potentials, by fitting the well measured charmonia spectra, we re-fix the relevant parameters and test them by calculating other states of the charmonia family. We also consider the role of the Lamb shift and present the numerical results with and without involving the Lamb shift.     

Catalytic ipso-Nitration of Organosilanes Enabled by Electrophilic N-Nitrosaccharin Reagent

Nitroaromatic compounds represent one of the essential classes of molecules that are widely used as feedstock for the synthesis of intermediates, the preparation of nitro-derived pharmaceuticals, agrochemicals, and materials on both laboratory and industrial scales. We herein disclose the efficient, mild, and catalytic ipso-nitration of organotrimethylsilanes, enabled by an electrophilic N-nitrosaccharin reagent and allows chemoselective nitration under mild reaction conditions, while exhibiting remarkable substrate generality and functional group compatibility. Additionally, the reaction conditions proved to be orthogonal to other common functionalities, allowing programming of molecular complexity via successive transformations or late-stage nitration. Detailed mechanistic investigation by experimental and computational approaches strongly supported a classical electrophilic aromatic substitution (S_EAr) mechanism, which was found to proceed through a highly ordered transition state.     

Construction and Application of DNAzyme-based Nanodevices

The development of stimuli-responsive nanodevices with high efficiency and specificity is very important in biosensing, drug delivery, and so on. DNAzymes are a class of DNA molecules with the specific catalytic activity. Owing to their unique catalytic activity and easy design and synthesis, the construction and application of DNAzymes-based nanodevices have attracted much attention in recent years. In this review, the classification and properties of DNAzyme are first introduced. The construction of several common kinds of DNAzyme-based nanodevices, such as DNA motors, signal amplifiers, and logic gates, is then systematically summarized. We also introduce the application of DNAzyme-based nanodevices in sensing and therapeutic fields. In addition, current limitations and future directions are discussed.     

高能电子束辐照模式蛋白辣根过氧化物酶的损伤作用研究

作为一种载能粒子,高能电子束具有能量利用率高、贯穿深度大、方便实用等优点,可以用来杀灭细菌和抑制病原体生长,因而被广泛应用于食品保质储藏和医疗卫生等方面。但是,对于高能电子如何与生物及其生物分子发生作用,以及作用的过程、方式、效果和机理等方面,人们还缺乏深入、细致的了解。本研究利用高能电子束辐照模式蛋白酶辣根过氧化物酶(HRP:horseradish peroxidase),研究了电子束对它的损伤作用和机理。研究发现,电子束损伤HRP 的方式主要通过羟基自由基破坏蛋白质肽链,同时,辐照产生的活性氧物质也会作用于HRP 分子活性中心引起其辅基血红素的损伤。这与我们以前研究的等离子体放电辐照HRP其损伤主要通过H2O2 作用于变性蛋白血红素引起酶失活有所不同。进一步,通过利用活性氧和自由基清除剂的方法,具体分析和阐明了电子束辐射条件下同活性氧和自由基在损伤HRP 过程中所起的破坏作用。As one kind of charged energetic particles, high-energy electron-beam (e-beam) can kill bacteria effectively; and because of its advantages of low-cost and high-efficiency, e-beam has been widely applied in food sterilization and storage industry as well as biomedical areas. However, currently we still lack the in-depth understanding of the mechanism of the interactions between high-energy particles and biological systems. To this end, we thus initiated the study of e-beam induced damage of horseradish peroxidase (HRP: horseradish peroxidase). Our results revealed that the e-beam induced damage of HRP was mainly through the hydroxyl radical attack on the polypeptide chains, and at the same time, the heme active site of HRP was also injured by the reactive oxygen species (ROS) produced by the electron-beam. This hydroxyl radical damage mechanism is different from the hydrogen peroxide damage mechanism that plays the dominant role in non-thermal plasma treatment as we reported previously. Moreover, by using the ROS and free radical scavengers, we analyzed and identified the major factors that contributed to the HRP damages.