DNA: a model compound for solution studies of macromolecules

Well-defined, monodisperse, homologous series of oligonucleotides and DNA restriction fragments may now be produced and used as models of rigid and semirigid rodlike molecules in solution. Information from optical experiments on these model systems aids in the formulation and testing of theories of macromolecular dynamics in both dilute and concentrated solution.     

适于SSR-PCR的农作物基因组总DNA高通量提取方法的建立

[目的]建立一种新的、通用、快速的农作物基因组总DNA提取方法,为应用分子标记技术研究遗传多样性及变异提供方便.[方法]分别从甘蔗、水稻、玉米、花生和大豆5种作物中提取基因组DNA,用琼脂糖凝胶电泳对所提取的DNA质量进行检测,然后每种作物分别选取两对SSR引物进行PCR扩增,用聚丙烯酰胺凝胶电泳检测扩增结果.[结果]采用该提取方法,不同作物产生的纯DNA在100.0~160.0 g/g,提取DNA的A260/A280比率在1.80~1.95.此外,电泳凝胶未出现可见的RNA污染,每个作物基因组DNA单一条带非常清晰,DNA结构完整,质量较高,适用于分子标记的研究.应用SSR分子标记进行PCR扩增,重复性、稳定性好,经琼脂糖凝胶电泳检测,条带清晰且分辨率较高.[结论]建立的DNA提取方法为直接将叶片剪碎后装入EP管中,加入提取缓冲液进行DNA提取,省去了用液氮研磨的过程.与传统的DNA分离方法相比,新建立的DNA提取方法具有高通量、简单、快速、经济效益高等优点.     

野生天麻·栽培天麻的RAPD和AFLP标记遗传多态性分析

[目的]用RAPD和AFLP技术对采自主产区不同地域的2份野生天麻和7份栽培天麻进行多态性和聚类分析,研究天麻的遗传多样性及其原因。[方法]用酚-氯仿法提取的基因组DNA,经RAPD及AFLP程序扩增后分别用琼脂糖凝胶和PAGE电泳检测,使用NTSYSpc-2.10s软件的UPGMA方法对检测结果进行聚类。[结果]用RAPD和AFLP数据得到的聚类图相似,来自不同地方和不同海拔高度的样品在聚类图上得以区分。天麻与蜜环菌之间没有共同条带。[结论]包括海拔在内的地域隔阂,而非人工种植可能是产生天麻种内遗传多样性的重要原因;虽然天麻靠消化侵入其皮层内部的蜜环菌菌丝提供营养而进行发育,但是它们之间没有DNA的相互作用。     

银川市番茄白粉病病原菌的鉴定

对宁夏银川市收集的番茄白粉病病叶上的病原菌进行分离、纯化,分别进行形态学和分子生物学鉴定.形态学鉴定结果表明:银川市番茄白粉病病原菌分生孢子单生,呈卵圆形或腰鼓状;其顶端位置萌发出芽管,芽管末端生有乳突状附着胞,附着胞亦着生于菌丝上;分生孢子梗直立不分支;未发现闭囊壳.对病原菌的内部转录间隔区序列进行比对,其与新番茄粉...     

陆地棉花粉管通道形成时期的研究

用石蜡切片法观察陆地棉的花粉管生长、受精和受精卵分裂过程及花粉管通道形成时期。结果表明:①授粉后15 h花粉管通过珠孔进入胚囊;②授粉后18~21 h,精子和卵细胞开始融合,24 h后形成一个核仁的受精卵;③授粉后48 h,始见胚分裂;授粉后72 h,早期胚形成;④应用花粉管通道法对棉花导入外源DNA的适宜时期为授粉后18~48 h。     

从大体积的PAGE凝胶中纯化长链寡核苷酸的新方法

通过比较从大体积的PAGE凝胶中回收寡核苷酸的不同方法,提出回收未银染的长链寡核苷酸的最佳方案:用12 cm×1.5 cm的PAGE凝胶柱分离DNA,然后将凝胶切成长约0.5 cm的胶条,通过PCR反应挑选含有寡核苷酸的胶条。用2 mL的寡核苷酸洗脱缓冲液回收寡核苷酸,反复提取3次。用装填30 mg硅胶的C18 Sep-Pak反相层析柱进行纯化,最后经过离心冻干后即得到纯化的寡核苷酸,该方法的回收率可达(28.7±2.0)%。     

Structure-based carbon nanotube sorting by sequence-dependent DNA assembly

Wrapping of carbon nanotubes (CNTs) by single-stranded DNA (ssDNA) was found to be sequence-dependent. A systematic search of the ssDNA library selected a sequence d(GT)n, n = 10 to 45 that self-assembles into a helical structure around individual nanotubes in such a way that the electrostatics of the DNA-CNT hybrid depends on tube diameter and electronic properties, enabling nanotube separation by anion exchange chromatography. Optical absorption and Raman spectroscopy show that early fractions are enriched in the smaller diameter and metallic tubes, whereas late fractions are enriched in the larger diameter and semiconducting tubes.     

Synthesis of two-dimensional polymers

A synthetic pathway is described to construct "in bulk" two-dimensional (2D) polymers shaped as molecular sheets. A chiral oligomeric precursor is used that contains two reactive sites, a polymerizable group at one terminus and a reactive stereogenic center near the middle of the molecule. The bulk reaction yields bilayer 2D polymers of molecular weight in the order of millions and a monodisperse thickness of 50.2 angstroms. The 2D molecular objects form through molecular recognition by the oligomers, which self-organize into layers that place the reactive groups within specific planes. The oligomers become catenated by two different stitching reactions involving the reactive sites. At room temperature, stacks of these molecular objects can organize as single crystals and at higher temperatures melt into smectic liquid crystals. Nonlinear optical experiments reveal that solid films containing the 2D polymers form structures that are thermally and temporally more stable than those containing analogous 1D polymers. This observation suggests that the transformation of common polymers from a 1D to a 2D architecture may produce generations of organic materials with improved properties.     

Coalescence of single-walled carbon nanotubes

The coalescence of single-walled nanotubes is studied in situ under electron irradiation at high temperature in a transmission electron microscope. The merging process is investigated at the atomic level, using tight-binding molecular dynamics and Monte Carlo simulations. Vacancies induce coalescence via a zipper-like mechanism, imposing a continuous reorganization of atoms on individual tube lattices along adjacent tubes. Other topological defects induce the polymerization of tubes. Coalescence seems to be restricted to tubes with the same chirality, explaining the low frequency of occurrence of this event.     

Monodisperse metal clusters 10 angstroms in diameter in a polymeric host: the "monomer as solvent' approach

A general methodology is presented for the dispersion of an inorganic compound within an organic polymer host through the use of solubilizing and polymerizable ligands. The dispersion of metal cluster cations 10 angstroms in diameter within a polymer host is achieved by free-radical polymerization of the hexafunctional metal cluster [Mo(6)Cl(8)(NVI)(6)](triflate)(4) with bound polymerizable ligands in N-vinylimidazole (NVI) solutions. Copolymerization of the activated cluster-bound ligands with the surrounding medium probably plays a key role in preventing aggregation and produces near monodisperse molecular clusters within the polymer matrix.     

利用外源DNA导入玉米自交系创造变异的研究

采用玉米开苞导入技术通过花粉管通道将玉米自交系13A的总DNA导入玉米自交系沈109中,结果表明,D1和D2代的生育期、株高、穗位、株型等性状都发生了变异,总变异率为17.98%,并用原位杂交技术进行验证.讨论了后代变异、变异率和该项技术的特点.     

一种高通量提取桃DNA方法的建立与应用

【目的】DNA制备是大规模基因型筛选和分子标记辅助选种的重要前提,本研究采用一种1.2 mL八联排管代替单个离心管,探索一种操作简便、节约时间、成本低的桃DNA快速提取方法,以满足高通量遗传研究的需求,提高工作效率。【方法】以普通生长型桃（standard type,ST）‘中油桃8号’为母本,温度敏感半矮生型桃（temperature-sensitive semi-dwarf in Prunus persica,PpTssd）‘09-1-112’为父本,杂交获得F₁代分离群体500株实生苗为载体,包括温度敏感半矮生型246株,普通生长型254株,建立一种高通量、低成本桃DNA提取方法。利用1.2 mL八联排管结合八通道移液器,简化提取步骤,提取桃幼嫩叶片中的基因组DNA;通过紫外分光光度计和琼脂糖凝胶电泳对所提取的DNA浓度、纯度和完整性进行检测。基于高分辨率熔解曲线（high resolution melting,HRM）,采用96孔板对温度敏感半矮生型桃和普通生长型桃共500个F₁分离后代单株进行PCR扩增和基因分型,区分TSSDtssd基因型与tssdtssd基因型。基于双亲表型与基因型一致,开发InDel位点,PCR扩增后,采用SDS-PAGE在F₁群体中进行验证,确定利用分离的DNA是否正确区分不同基因型。【结果】分离的DNA经紫外分光光度计检测,浓度范围约为25-200 ng·μL^-1,OD_260nm/OD_280nm约为1.81-1.98,DNA纯度较高;琼脂糖凝胶电泳条带清晰、单一,DNA完整度较高。参考桃基因组（Version 2.0）,根据双亲深度测序数据,开发获得SNP标记SNP_Pp03_3758620,应用于高分辨率熔解曲线基因分型,发现温度敏感半矮生型和普通生长型呈现明显不同的峰型,证明提取的DNA模板可应用于HRM基因分型。基于双亲基因型与表型一致,开发InDel标记InDel_Pp03_3829009,聚丙烯酰胺凝胶电泳的验证结果显示PCR扩增具有较高的强度,获得与目的片段大小一致的特异性条带,且在两种不同生长型单株中具有明显的多态性,表明PCR扩增稳定,提取的DNA可用于基于InDel标记的多态性分析。使用该提取方法,每人每天可以完成1 000个样品的DNA提取,成本较低,且不会对幼苗早期生长造成影响。【结论】建立了一种简便、有效、低成本的桃基因组DNA提取方法,可以满足基因分型、品种鉴定及遗传分析等分子生物学研究,实现了大批量不同样本基因组DNA的同时提取,具有较高应用价值。     

钒胁迫下枸杞和芥菜幼苗蛋白的分子分布研究

通过G-75凝胶层析结合电泳分析,研究了不同V(Ⅴ)浓度胁迫下枸杞和芥菜的蛋白分子分布。经过凝胶层析后出现两个紫外吸收峰,第一峰主要集中在8号至15号管,第二峰集中在25号至33号管。对第一紫外吸收峰的电泳分析表明,V胁迫下植物蛋白的分子分布发生了变化:当V浓度为10 mg·L~(-1)时,枸杞根产生了分子量为58.6 KD蛋白,茎产生了分子量分别为64.5、46.9KD两种蛋白;当V浓度增大到20 mg·L~(-1),叶产生了分子量为20 KD蛋白。随着V胁迫浓度增大,芥菜中分子量为33.9 KD和36KD两条蛋白条带逐渐变浅,而27.3 KD蛋白条带逐渐加深。枸杞幼苗第一洗脱峰蛋白中V含量随V胁迫浓度增大而增加,而芥菜叶在V≥10 mg·L~(-1)时V含量降低。这与不同植物蛋白结合V的能力有关,因枸杞幼苗蛋白结合V的能力较强,生成的植物螯合肽较多,故对V有较强的耐受能力。     

Sequence-specific molecular lithography on single DNA molecules

Recent advances in the realization of individual molecular-scale electronic devices emphasize the need for novel tools and concepts capable of assembling such devices into large-scale functional circuits. We demonstrated sequence-specific molecular lithography on substrate DNA molecules by harnessing homologous recombination by RecA protein. In a sequence-specific manner, we patterned the coating of DNA with metal, localized labeled molecular objects and grew metal islands on specific sites along the DNA substrate, and generated molecularly accurate stable DNA junctions for patterning the DNA substrate connectivity. In our molecular lithography, the information encoded in the DNA molecules replaces the masks used in conventional microelectronics, and the RecA protein serves as the resist. The molecular lithography works with high resolution over a broad range of length scales from nanometers to many micrometers.     

Micro/nano encapsulation via electrified coaxial liquid jets

We report a method to generate steady coaxial jets of immiscible liquids with diameters in the range of micrometer/nanometer size. This compound jet is generated by the action of electro-hydrodynamic (EHD) forces with a diameter that ranges from tens of nanometers to tens of micrometers. The eventual jet breakup results in an aerosol of monodisperse compound droplets with the outer liquid surrounding or encapsulating the inner one. Following this approach, we have produced monodisperse capsules with diameters varying between 10 and 0.15 micrometers, depending on the running parameters.     

DNA标准分子量参照物的制备

采用较简便的方法制备了1130～500bp的DNA标准分子量参照物（NAmarker）。经电泳检测,所制备的DNAmarker与商品化的DNAmarker质量相当,可用于分子生物学试验。     

Sediment-Water Chemical Exchange in the Coastal Zone Traced by in situ Radon-222 Flux Measurements

In situ radon-222 flux experiments conducted in benthic chambers in Cape Lookout Bight, a small marine basin on the North Carolina coast, reveal that enhanced chemical transport across the sediment-water interface during summer months is caused by abiogenic bubble tube structures. Transport rates for dissolved radon, methane, and ammonium more than three times greater than those predicted on the basis of molecular diffusion occur when open tubes are maintained by semi-diurnal low-tide bubbling.     

槟榔基因组DNA的高效提取方法

以槟榔叶片为植物材料,采用改良的SDS-CTAB方法提取其基因组DNA。结果表明,以水饱和酚代替Tris饱和酚对样品进行抽提的SDS-CTAB法可以获得纯度高(OD260/OD280在1.7~1.9、OD260/OD230大于2)、一级结构完整、分子量大于23 kb的DNA,产率在50~120μg/g。该法所提DNA成功用于后续的分子生物学研究,并在花生、香蕉等植物上得到应用。     

Supramolecular self-assembly of macroscopic tubes

The macroscopic molecular self-assembly of an amphiphilic hyperbranched copolymer in acetone generated multiwalled tubes millimeters in diameter and centimeters in length. The thickness of the tube walls approaches 400 nanometers, and the walls have an inhomogeneous lamella structure that alternates between ordered hydrophilic domains and amorphous, partly irregular hydrophilic domains.     

Nanomaterials: a membrane-based synthetic approach

Materials with nanoscopic dimensions not only have potential technological applications in areas such as device technology and drug delivery but also are of fundamental interest in that the properties of a material can change in this regime of transition between the bulk and molecular scales. In this article, a relatively new method for preparing nanomaterials, membrane-based synthesis, is reviewed. This method entails synthesis of the desired material within the pores of a nanoporous membrane. Because the membranes used contain cylindrical pores of uniform diameter, monodisperse nanocylinders of the desired material, whose dimensions can be carefully controlled, are obtained. This "template" method has been used to prepare polymers, metals, semiconductors, and other materials on a nanoscopic scale.