A site-specific endonuclease from thermophilic strain Bacillus species ZE is a ClaI isoschizomer

Strain Bacillus species ZE with a maximal yield of the ClaI isoschizomer was chosen from 12 natural thermophilic strains producing ClaI isomers. The yield is 110 times higher than that of the ClaI prototype endonuclease from Caryophanon latum L. The enzyme is sensitive to DNA dam-methylation and is highly stable under storage.     

倒装芯片焊点可靠性的有限元模拟法探讨

随着集成电路封装技术的发展,倒装芯片技术得到广泛应用.由于材料的热膨胀失配,使倒装焊点成为芯片封装中失效率最高的部位,而利用快捷又极具参考价值的有限元模拟法是研究焊点可靠性的重要手段之一.简单介绍了集成电路芯片焊点可靠性分析的有限元模拟法,重点概括了利用该方法对芯片焊点进行可靠性评价常见的材料性质和疲劳寿命预测模型.     

PDZ proteins bind, cluster, and synaptically colocalize with Eph receptors and their ephrin ligands

Localizing cell surface receptors to specific subcellular positions can be critical for their proper functioning, as most notably demonstrated at neuronal synapses. PDZ proteins apparently play critical roles in such protein localizations. Receptor tyrosine kinases have not been previously shown to interact with PDZ proteins in vertebrates. We report that Eph receptors and their membrane-linked ligands all contain PDZ recognition motifs and can bind and be clustered by PDZ proteins. In addition, we find that Eph receptors and ligands colocalize with PDZ proteins at synapses. Thus, PDZ proteins may play critical roles in localizing vertebrate receptor tyrosine kinases and/or their ligands and may be particularly important for Eph function in guidance or patterning or at the synapse.     

Assumption testing in population pharmacokinetic models: illustrated with an analysis of moxonidine data from congestive heart failure patients

Deriving a population pharmacokinetic model from real data is always associated with numerous assumptions. Violations of these assumptions, especially if undetected, may lead to inappropriate conclusions being made from the analysis. Routinely, only a few of the assumptions are explicitly stated and justified in the reporting of a population model. Here, we attempt to be exhaustive in the presentation of the assumptions made in the course of an analysis of moxonidine pharmacokinetics. The different ways that assumptions were justified, through experience, graphical examination, or additional modeling, are outlined. Models for relaxing assumptions regarding the covariate and statistical submodels, not previously reported in the area of population pharmacokinetic modeling, are also described.     

Probing the topography of HIV-1 nucleocapsid protein with the alkylating agent N-ethylmaleimide

Retroviral nucleocapsid (NC) proteins contain one or two zinc fingers (ZFs) consisting of a CCHC peptide motif that coordinates Zn(II). Mutational and biochemical analyses have shown that NC ZFs are directly involved in multiple stages of viral replication, including genomic RNA encapsidation, virus maturation, and the early infection process. The multiple roles of the conserved retroviral ZFs make them attractive targets for antiviral agents. We have previously shown that a variety of chemical compounds can inactivate the whole virus by attacking NC ZFs. For the enhancement of the specificity of antiviral reagents, it is desirable to have a detailed knowledge of the spatial organization of reactive sites on the NC protein in its free and oligonucleotide-bound states. A method has been developed using chemical probes to assess the reactivity of specific Cys residues in the NC protein, and is being used to investigate the topography of ZFs in different contexts. In this study we focus on the reaction mechanism of N-ethylmaleimide (NEM) with free HIV-1 NCp7 protein. Our results show that the conformation of free NCp7 restricts the initial site of attack to Cys-49 (the most distal Cys residue in the second ZF) and that the reactivity of thiols in full-length protein differs from that of the isolated ZF peptides. A moderate to near complete reduction in reaction rate was observed when NCp7 was complexed with different oligonucleotides. These findings provide a set of experimentally determined parameters that can serve to guide computational modeling of the NC protein and will be useful for the rational design of drugs directed against retroviral ZFs.     

自主创新攀高峰为用户提供先进技术装备

产品是企业的基础，而适应市场则是其竞争力的标志。国内外的企业要在竞争中取胜并得到不断发展，就必须加强加快产品的自主开发。秦川机床集团公司董事长龙兴元同志说的好：“自主的、独有的、民族的才是可持续的”。马克思曾说：“大工业必须掌握它特有的生产资料即机器本身，必须用机器生产机器。这样大工业才能建立起与自己相应的技术基础，才得以自立。”他还说：“各种经济时代的区别，不在于生产什么，而在于怎样生产，用什么劳动资料生产”。毛泽东同志从建国之初一直关心机床工具工业新产品开发，1956年1月12日毛泽东到天津第一机床厂视察，     

28 nm超大规模FPGA的BRAM单粒子效应测试方法研究

为了建立一种28 nm工艺超大规模SRAM型FPGA块随机读取存储器(BRAM:Block Random Access Memory)模块的单粒子效应测试方法,实现敏感位的精确定位,通过研究逻辑位置文件和回读文件,建立了敏感位和FPGA逻辑地址的对应机制,推导出了对应的关系公式,并提出了一组针对BRAM模块的系统测试方法.该方法大幅度地提高了现有测试方法的效果,并且为器件失效机理的分析和下一步的器件加固设计提供了指导.     

基于Fabry-Perot腔阵列光谱传感器的集成化研究

提出了一种微型集成化光谱传感器,其结构包括不同腔长的Fabry-Perot腔阵列、光电探测器阵列、读出电路几部分.一个光谱探测单元包括一个Fabry-Perot腔和其下的光电探测器,各Fabry-Perot腔腔长的不同,可实现对不同波长的检测.该光谱传感器无可动部件,结构性能稳定,用CMOS工艺和MEMS工艺实现一体化集成,制作体积为mm量级.文章中将详细阐述该传感器的各部分结构设计和工艺实现等问题.     

爆炸焊接结合区波形形成的金属物理学机理Ⅰ.外因和内因

探讨了爆炸焊接结合区波形形成的机理 ,指出了这种波形是在爆炸载荷下在相互撞击的金属界面上所发生的一种不可逆的和周期性波动分布的塑性变形 .它的形成必有外因和内因 ,外因是在金属中波动传播的爆炸载荷 ,内因是待焊接的金属材料 .在爆炸载荷下在金属材料界面上所发生的冲击碰撞是波形形成的不可缺少的过程和手段 ,为此提出了一个与此波形形成的流体力学机理相对立的金属物理学机理 .本文从金属物理学和哲学的基本原理出发分析了此波形形成的原因 ,并用大量实验事实论证了此波形形成的外因的存在和内因的影响 .