Quantum interference device made by DNA templating of superconducting nanowires

The application of single molecules as templates for nanodevices is a promising direction for nanotechnology. We used a pair of suspended DNA molecules as templates for superconducting two-nanowire devices. Because the resulting wires are very thin, comparable to the DNA molecules themselves, they are susceptible to thermal fluctuations typical for one-dimensional superconductors and exhibit a nonzero resistance over a broad temperature range. We observed resistance oscillations in these two-nanowire structures that are different from the usual Little-Parks oscillations. Here, we provide a quantitative explanation for the observed quantum interference phenomenon, which takes into account strong phase gradients created in the leads by the applied magnetic field.     

金花梨基因组DNA提取及其RAPD分析

以金花梨嫩芽为试材 ,通过在磨样时添加不同量的抗氧化剂Vc ,对CTAB法作了一定的改进 ,比较了不同处理的提取效果 ,再分别以成熟叶片、新梢和嫩芽为材料 ,采用改进的CTAB法提取基因组DNA ,进一步比较了不同材料的提取效果 ,并以金花梨及其 18个变异单系的基因组DNA为模板 ,4 0个随机引物进行RAPD分析。结果表明 :以嫩芽为试材 ,在磨样时每克鲜样添加 0 10g的Vc ,能够提取到高质量的基因组DNA ;采用改进的CTAB法 ,用成熟叶片、新梢和嫩芽均能提取到可直接用于RAPD分析的基因组DNA ;大部分引物可以在不同模板上扩增出条带 ,但仅有 5个引物可以同时在金花梨及其 18个变异单系基因组DNA上扩增出条带 ;用RAPD结果对金花梨及其 18个变异单系进行聚类分析     

DNA binding by proteins

Study of proteins that recognize specific DNA sequences has yielded much information, but the field is still in its infancy. Already two major structural motifs have been discovered, the helix-turn-helix and zinc finger, and numerous examples of DNA-binding proteins containing either of them are known. The restriction enzyme Eco RI uses yet a different motif. Additional motifs are likely to be found as well. There is a growing understanding of some of the physical chemistry involved in protein-DNA binding, but much remains to be learned before it becomes possible to engineer a protein that binds to a specific DNA sequence.     

Programming DNA tube circumferences

Synthesizing molecular tubes with monodisperse, programmable circumferences is an important goal shared by nanotechnology, materials science, and supermolecular chemistry. We program molecular tube circumferences by specifying the complementarity relationships between modular domains in a 42-base single-stranded DNA motif. Single-step annealing results in the self-assembly of long tubes displaying monodisperse circumferences of 4, 5, 6, 7, 8, 10, or 20 DNA helices.     

From micro- to nanofabrication with soft materials

Soft materials are finding applications in areas ranging from microfluidic device technology to nanofabrication. We review recent work in these areas, discuss the motivation for device fabrication with soft materials, and describe applications of soft materials. In particular, we discuss active microfluidic devices for cell sorting and biochemical assays, replication-molded optics with subdiffraction limit features, and nanometer-scale resonators and wires formed from single-molecule DNA templates as examples of how the special properties of soft materials address outstanding problems in device fabrication.     

小麦不同抗性材料中抗条锈病基因Yr24分子标记分布研究

以26个不同抗性的小麦品种及12个野生近缘物种为材料,检测了抗性基因分子标记yr24-1的分布情况.结果表明:22个抗性材料中有10个能扩增出特异性目标条带;4个感病材料中有2个能扩增出特异性目标条带;野生近缘材料中3种硬粒小麦均能扩增出特异件目标条带,暗示了这些材料中可能含有Yr24目标基因.     

Chelex-100法快速提取白粉菌基因组DNA及ITS2序列的克隆

[目的]建立快速提取及克隆白粉病菌基因组DNA的方法。[方法]以豌豆白粉菌分生孢子为材料,用Chlex-100法快速提取白粉菌基因组DNA,并以此为模板对内转录间隔区Ⅱ（ITS2）序列进行了巢式PCR扩增、克隆、测序及分析。[结果]Chlex-100法可高效的提取白粉病菌基因组DNA,适用于PCR扩增及相关分析。[结论]为快速有效地对白粉病资源进行大规模分子分类鉴定奠定了基础。     

Replicating form of a single-stranded DNA virus: isolation and properties

The replicating form of single-stranded DNA virus has been isolated in pure form by chromatography on columns of methylated albumin. Its buoyant density in CsCl and "melting temperature" are characteristic of a double stranded DNA structure containing 43 percent guanine-cytosine. The nearest neighbors to uridylate were compared in the RNA synthesized when replicating-form DNA and mature single-stranded DNA were employed as templates in an in vitro system. The mature DNA component of the replicating duplex does not serve as the sole source of complementary RNA. The results agree best with the assumption that both strands of the replicating form function as templates. It is important to note that this is contrary to the situation found in the intact cell where only one of the two strands appears to be transcribed into message.     

无机/有机纳米复合材料的制备方法

随着纳米科学研究与技术开发的日益深入和完善,纳米杂化和纳米复合材料的研究已经发展成为当今物理、化学、材料科学等学科中1个非常活跃的研究领域,其中集有机和无机特性于一身的无机/有机纳米复合材料倍受研究者们的青睐。本文对制备无机/有机纳米复合材料的方法进行了总结。     

纳米材料与技术在农业上的应用研究进展

近几年纳米材料与技术在农业领域的应用取得了一定进展,综述了纳米材料与技术在农业投入品的传输、动植物遗传育种、农产品加工、农业环境改良和农业纳米检测技术等方面的应用。目前纳米技术在农业中的应用研究仍处于初期阶段,一些研究成果实现商业化还需要更大的努力。此外,纳米材料因其特性可能存在潜在的安全性问题,选择生物安全型、环境友好型纳米材料进行农业应用研究对于发展农业纳米技术至关重要。     

食品纳米包装材料的应用与安全性评价

纳米技术是当今科学界最具前景的科学技术之一,生物纳米复合材料的研究和开发将取得巨大突破。本文概述了纳米材料在食品包装领域的基本应用现状,并对相关的安全性评价问题进行了探讨。     

S phase of the cell cycle

In each cell cycle the complex structure of the chromosome must be replicated accurately. In the last few years there have been major advances in understanding eukaryotic chromosome replication. Patterns of replication origins have been mapped accurately in yeast chromosomes. Cellular replication proteins have been identified by fractionating cell extracts that replicate viral DNA templates in vitro. Cell-free systems that initiate eukaryotic DNA replication in vitro have demonstrated the importance of complex nuclear architecture in the control of DNA replication. Although the events of S phase were relatively neglected for many years, knowledge of DNA replication is now advancing rapidly in step with other phases of the cell cycle.     

不同方法提取鳗鲡病原茵DNA模板的差异分析

利用吸光值、琼脂糖电泳及PCR差异扩增等指标，对酚一氯仿法、水煮法、碱裂解法3种方法制备的鳗鲡病原菌DNA模板进行了差异分析．结果表明：1）不同方法提取的病原菌模板DNA的浓度、纯度及分子质量大小存在差异，但以这3种方法提取的病原菌DNA为模板，均能成功扩增到细菌16SrD．NA和外膜蛋白的保守序列．其中，酚一氯仿提取的模板DNA浓度较低、纯度较高；水煮法和碱裂解法提取的模板DNA浓度较高、纯度较低．2）电泳显示，3种方法获得的模板DNA扩增出的16SrDNA保守序列条带均一，没有显著差异，但在外膜蛋白保守序列的扩增中却因菌种和模板提取方法的不同而存在差异．     

舞毒蛾核型多角体病毒的基因及其在害虫防治中的应用

介绍了舞毒蛾核型多角体病毒（LdMNPV)的基因组结构、UDP－转葡糖基酶基因、增强子基因（enhancin基因）、蛋白激酶基因（vPK基因）、多角体蛋白（polyhedrin)基因、PE基因、P39－衣壳基因、DNA聚合酶基因（DNA pol)、25K FP基因以及LdMNPV的同源区（hrs)的结构和功能。这些基因或同源区的编码产物有的作为结构组分存在于包含体中，有的作为调节因子在病毒复制过程中参与病毒DNA的复制和基因表达的调节，有的负责协调病毒与虫体之间的关系。通过分析用于外源基因表达的LdMNPV的基因工程的实例，阐明了在害虫的防治领域，构建LdMNPV重组杆状病毒杀虫剂是LdMNPV分子生物学和基因工程的发展方向。     

彩色甜椒基因组DNA提取方法的优化

以不同颜色的甜椒为试验材料．采用CTAB法、SDS法、ROSE法和氯化苄法提取彩色甜椒基因组DNA。结果表明,CTAB法所提取DNA的质量和纯度较高,以此DNA为模板进行RAPD—PCR分析,DNA扩增效果较好,带形清晰、整齐,说明CTAB法提取的DNA较为完整,能用作RAPD—PCR模板来开展彩色甜椒分子水平的研究。     

枸杞nrDNA ITS测序鉴定的初步研究

ITS区序列指DNA基因内的转录间隔区序列,包括ITSl、ITS2及5．8S3个区段。ITS区序列测定分析能够鉴别同属植物相似种以及药用植物混淆种。笔者以枸杞属内不同种间ITS序列为切入点,对枸杞nrDNA ITS序列进行分析研究,为从分子水平鉴定枸杞品种提供参考。     

枸杞nrDNA ITS测序鉴定的初步研究（英文）

[Objective] The study aimed to identify wolfberry(Lycium Linn.)germplasm resources at molecular level by analyzing the nrDNA ITS sequence.[Method] Genomic DNA from wolfberry leaves extracted by modified CTAB method were regarded as templates for PCR amplification by specific primer,clone and sequencing.[Result] The nrDNA ITS sequences were obtained and then differentiated among three tested materials.[Conclusion] PCR amplification and sequencing on nrDNA ITS is a feasible approach to identify different wolfberry germplasm resources.     

纳米技术在水产养殖工程中的应用研究

纳米技术是在纳米尺度基础上研究物质的特性及相互作用,纳米为毫微米,既十亿分之一 米,利用纳米特性可解决实际生产中的多种问题。纳米技术在水产养殖工程中应用正处于初级阶段, 和发达国家还存在明显差异,故文章对纳米技术在水产养殖工程中的应用详细分析,旨在为实际水产 养殖开展提供理论参考。     

Scissors-grip model for DNA recognition by a family of leucine zipper proteins

C/EBP is a sequence-specific DNA binding protein that regulates gene expression in certain mammalian cells. The region of the C/EBP polypeptide required for specific recognition of DNA is related in amino acid sequence to other regulatory proteins, including the Fos and Jun transforming proteins. It has been proposed that these proteins bind DNA via a bipartite structural motif, consisting of a dimerization interface termed the "leucine zipper" and a DNA contact surface termed the "basic region." An evaluation of the properties of conserved amino acids within the basic region of 11 deduced protein sequences, coupled with the observation that they are located at an invariant distance from the leucine zipper, has led to the formulation of a "scissors-grip" model for DNA binding. The architectural features of this model are well suited for interaction with directly abutted, dyadsymmetric DNA sequences. Data supportive of the model were obtained with chemical probes of protein: DNA complexes.     

Block copolymer self-assembly-directed single-crystal homo- and heteroepitaxial nanostructures

Epitaxy is a widely used method to grow high-quality crystals. One of the key challenges in the field of inorganic solids is the development of epitaxial single-crystal nanostructures. We describe their formation from block copolymer self-assembly-directed nanoporous templates on single-crystal Si backfilled with Si or NiSi through a laser-induced transient melt process. Depending on thickness, template removal leaves either an array of nanopillars or porous nanostructures behind. For stoichiometric NiSi deposition, the template pores provide confinement, enabling heteroepitaxial growth. Irradiation through a mask provides access to hierarchically structured materials. These results on etchable and non-etchable materials suggest a general strategy for growing epitaxial single-crystal nanostructured thin films for fundamental studies and a wide variety of applications, including energy conversion and storage.