Induction of DNA-double-strand breaks by auger electrons from 99mTc complexes with DNA-binding ligands

The potential of certain Auger electron emitting nuclides for systemic radiotherapeutic applications has recently gained much attention. In particular, the ability of several nuclides, including 111In, 125I, and 123I, to induce DNA double-strand breaks (dsb), a good indicator of cytotoxicity, has been extensively studied. However, this ability has never previously been shown experimentally for 99mTc, which, besides the well-known gamma radiation that is used for diagnostic applications, also emits an average of 1.1 conversion electrons and 4 Auger or Coster-Kronig electrons per decay. Owing to the short range of Auger electrons, the radionuclide needs to be located very close to the DNA for dsb to occur. We synthesized two cationic 99mTcI-tricarbonyl complexes with pendant DNA binders, pyrene and anthraquinone. The X-ray crystal structures of the two complexes could be elucidated. Linear dichroism and UV/Vis spectroscopy revealed that the complex with pyrene intercalates DNA with a stability constant, K, of 1.1 x 10(6) M(-1), while the analogous complex with anthraquinone interacts with DNA in a groove-binding mode and has an affinity value of K=8.9 x 10(4) M(-1). We showed with phiX174 double-stranded DNA that the corresponding 99mTc complexes induce a significant amount of dsb, whereas non-DNA-binding [TcO4]- and nonradioactive Re compounds did not. These results indicate that the Auger electron emitter 99mTc can induce dsb in DNA when decaying in its direct vicinity and this implies potential for systemic radiotherapy with 99mTc complexes.     

近代湿法磷酸工艺技术概况

湿法磷酸的生产从1870年以后就已经工业化了,这种酸主要是用作肥料生产的中间产品。目前大部分开工的湿法磷酸厂都是二水物法,因为二水物法设计和操作都比较简单。其他工业上使用的方法还有半水物法,半水二水物联合法,或者无水物法。所有湿法磷酸工艺操作的基本方法大致都一样,即磷酸盐岩用硫酸酸化,生成的硫酸钙以及其他不溶性杂质通过过滤和磷酸分离。各种不同类型的工艺方法在本文中作了比较。最近的研究与进展主要集中在二水物法,半水物法或半水二水物联合法以及酸的     

尿素嵌入法制备纤维素氨基甲酸酯的研究

探讨了尿素嵌入法制备纤维素氨基甲酸酯(CC)的生产工艺。指出:选用聚合度为450~625、α-纤维素含量大于90/的纤维素浆粕,用14/~16/的氢氧化钠溶液,于40~50℃条件下活化处理30~40min后,与尿素以1∶2~3的比例混合,在137℃的二甲苯体系中反应2~3h,便可得到含氮量为2.4/~3.5/的纤维素氨基甲酸酯产物。该产物在氢氧化钠溶液中可形成良好的稳定溶液,过滤性好,可直接用于纺丝。     

Optimal control of molecular motion: design, implementation, and inversion

This paper reviews recent theoretical and experimental developments aimed at controlling molecular motion using tailored laser fields. Emphasis is given to seeking optimal designs for the laser controls and optimal implementation of the controls in the laboratory. Optimization on both counts provides a rigorous, flexible, and physically attractive means for obtaining the best possible control over molecular motion under any specified conditions. The theoretical design and laboratory implementation of control are best effected by a closed-loop process that draws on observations of the evolving molecular sample to steer it toward the desired target. Going beyond control, similar closed-loop laboratory learning concepts may lead to automated molecular monitors for inversion to systematically identify details of molecular Hamiltonians.     

纳米技术与纳米材料(X)--纳米二氧化钛的表面处理

表面处理被用来提高纳米TiO2的耐久性和分散性。介绍了纳米TiO2表面处理效果的评价和表征方法。综述了纳米TiO2的表面处理的原理、方法和研究进展。预测新表面处理剂的合成、新的表面处理方法以及表面处理剂与纳米TiO2核体之间的作用机理将是下一步研究的重点。指出在对纳米TiO2进行表面处理的规模化生产中，关键要解决分散和异相成核的技术问题。     

硫黄促进剂体系用非迁移性助活性剂低聚物

本文报道的研究目的是开发迟效性促进剂硫黄硫化体系用助活性剂。这种添加剂可以提高交联键的形成速率而很少改变或者根本不改变混炼胶或其硫化胶的抗焦烧性性能或其他性能。本研究的另一目的是要设计一种具有慢效作用的硫化体系助活性剂。它不会从橡胶贴合制品(如轮胎)的一个部分迁移或者扩散到相邻的部分中去。本研究的初期阶段曾致力于评价一系列用作乳聚丁苯橡胶(SBR)硫化助活性剂的高分子量乙烯基吡啶二烯烃乳液共聚物。这些共聚物在室温下绝大部分是橡胶态的,它们都很容易分散于丁苯橡胶混炼胶中。使用乙烯基吡啶共聚物得到的初步结果是令人鼓舞的。     

Photoresponsive dendritic azobenzene peptides

Two dendritic peptides containing a branched lysine core and up to eight azobenzene moieties in the periphery were synthesized on solid support employing the omega-amino acid 4-(aminomethyl)phenylazobenzoic acid. With an additional peptidic tail consisting of an oligolysine portion, water solubility was achieved for the dendrimers, which allowed for the characterization of the cis/trans photoisomerization of the dendritic azobenzene species in both organic and aqueous media. Despite the interactions between the chromophores, which occur particularly in aqueous media, at higher dilution the photoisomerization process was found to proceed to extents that should permit photomodulation of molecular recognition processes between ligands grafted to the photosensitive azobenzene units and receptor molecules.     

Chemical inhibitors when timing is critical: a pharmacological concept for the maturation of T cell contacts

Cellular signal transduction proceeds through a complex network of molecular interactions and enzymatic activities. The timing of these molecular events is critical for the propagation of a signal and the generation of a specific cellular response. To define the timing of signalling events, we introduce the combination of high-resolution confocal microscopy with the application of small-molecule inhibitors at various stages of signal transduction in T cells. Inhibitors of Src-family tyrosine kinases and actin dynamics were employed to dissect the role of the lymphocyte-specific tyrosine kinase Lck in the formation and maintenance of T cell receptor/CD3-dependent contacts. Anti-CD3epsilon-coated coverslips served as a highly defined stimulus. The kinetics of the recruitment of the yellow fluorescent protein-tagged signalling protein ZAP-70 were detected by high-resolution confocal microscopy. The analysis revealed that at 5 min after receptor engagement, Lck activity was required for maintenance of contacts. In contrast, after 20 min of receptor engagement, the contacts were Lck-independent. The relevance of the timing of inhibitor application provides a pharmacological concept for the maturation of T cell-substrate contacts.