三种提取苹果绵蚜基因组DNA方法的比较

参考国内外昆虫基因组DNA提取的常用方法,选取KAc法、氯仿-异戊醇法和盐析法3种方法对苹果绵蚜(Eriosoma lanigerum)基因组DNA进行提取.通过基因组DNA直接琼脂糖凝胶电泳、SSR引物扩增产物的琼脂糖凝胶电泳和聚丙烯酰胺凝胶电泳检测,对3种方法所提基因组DNA的质量进行了比较,并综合分析了提取所需时间及所用试剂的毒性大小等.结果表明,盐析法操作程序较简便快捷,节时省工,可得较好质量的DNA样本,且对试验操作人员无伤害,是一种值得推广应用的基因组DNA提取方法.     

烟粉虱全基因组DNA四种提取方法的比较

获得大量、高质量的全基因组DNA是在DNA水平上研究许多生物的分子机制的基本前提。微小昆虫由于其体型微小,单头提取DNA浓度低,无法满足部分试验所需。为寻找一种方便、快捷、高效的全基因组提取方法,参考国内外单头微小昆虫基因组DNA提取常用方法,以烟粉虱为研究材料,选取醋酸钾(KAc)法、盐析法、氯仿-异戊醇法和苯酚提取法四种方法进行多头烟粉虱的全基因组DNA提取。通过微量核酸蛋白分析仪、基因组DNA直接琼脂糖凝胶电泳、甲基化敏感扩增多态性(Methylation sensitive amplification polymorphism,MSAP)引物扩增产物的琼脂糖凝胶电泳对DNA样品进行检测,比较提取DNA的产量、质量,并综合分析各提取方法所需时间及所用试剂的毒性大小。结果表明,盐析法提取的DNA平均浓度为521 ng/μL,纯度能满足分子检测要求,用MSAP引物能得到较好的扩增结果,相比其它方法,盐析法更简便、快速且无毒。因此盐析法是多头烟粉虱全基因组DNA提取的最佳方法。     

家蚕浓核病毒(山梨株)DNA的电子显微镜研究

最近所分离的家蚕浓核病毒(DNV)山梨株(Y-DNV)与最初在家蚕中发现的DNV伊那株在各种理化性质方面有所不同。从Y-DNV中提取的病毒DNA在琼脂糖凝胶电泳中出现二条带(DNA Ⅰ和Ⅱ)。用限制性内切酶处理这些DNA,其结果也明显不同。为了弄清这些现象,用电子显微镜对这些DNA分子进行研究。通过琼脂糖凝胶电泳分离的DNA Ⅰ和DNA Ⅱ都是双链线状分子,但DNA Ⅰ分子的长度略长。在电子显微镜下,二种DNA的构象没有差异,因此可以肯定DNA Ⅰ和DNAⅡ有不同的碱基序列组成。这在DNV中是罕见的,因为到目前为止所知道的所有DNV都只有4种结构蛋白。基于这种情况,在前一篇论文我们曾推测这些蛋白质可能是来自两种DAV,它们各自具有其中3种或4种结构蛋白。应当指出的是,Y-DNV的衣壳本身是由一种还是由二种结构所组成的还需要进一步的研究给予证实。因为Y-DNV的病毒直径很小,它不可能包含二种DNA(分子量分别为2.1×10~6d,和1.7×10~6d.)所以家蚕Y-DNV很可能是由二种相似但是不相同的DNV所组成的混合物。     

煤地质环境微生物总基因组DNA提取方法的优化

高质量的DNA是进行分子生物学研究的基础。通过对传统DNA抽提方法(酚-氯仿法)进行改进,并以Rhodococcus sp.R04和煤粉为实验材料对细胞破碎条件进行优化,建立了一种可用于煤地质环境微生物基因组DNA高效提取的改良方法。以改良法和商业试剂盒提取煤地质环境微生物基因组DNA,通过琼脂糖凝胶电泳、细菌及古菌特异性片段的PCR扩增来评价所提取DNA的质量。改良法和试剂盒法均能获得煤地质环境微生物基因组DNA,并能用于多种特异性PCR扩增。与试剂盒提取的DNA相比,改良法获得的DNA片段主带明显,约占总DNA含量的50%,分子量大小接近23 kb,并且提取量大,约为试剂盒的5-10倍。同时,能用于如DNA文库构建和宏基因组测序等。此外,改良法所用试剂普通,价格便宜,提取的煤地质环境微生物基因组DNA质量较高,适于实验室和科学研究。     

香蕉枯萎菌基因组DNA提取方法的研究

以香蕉枯萎菌菌株为试验材料,在SDS～CTAB法和高盐沉淀法等基础上加以改进,对两种提纯香蕉枯萎菌基因组DNA的方法进行了比较研究。结果表明：高盐沉淀法是适合于香蕉枯萎菌基因组DNA提取的方法。该方法提取的DNA OD260／OD280的比值为1．841,DNA产量为0．81mgDNA／g菌丝体。基因组DNA经琼脂糖凝胶电泳得到一条带型较宽且清晰的DNA谱带,基本无DNA碎带;将提取的DNA直接用于PCR扩增,得到带多而且清晰、整齐、基本无拖尾的RAPD图谱。     

水稻线粒体DNA酶切带型研究

水稻IR36线粒体DNA经6种限制酶酶切,用脉冲电泳和长距离琼脂糖凝胶电泳分离酶切片段,获得高分辨率的清晰带型。每组酶切片段加和测得水稻IR36线粒体基因组大小分别为227kb(HindⅢ)、253kb(EcoRⅠ)、253kb(XhoⅠ)、294kb(BamHⅠ)、239kb(SalⅠ)和283kb(xbal)采用9个来自水稻和玉米线粒体基因组的基因探针与酶切条带杂交发现,水稻线粒体基因组含有包括编码基因在内的重复顺序。     

家蚕核多角体病毒DNA

用酚或pH10缓冲液抽提家蚕核多角体病毒DNA 时,得到两种不同的结果。酚抽提的DNA 超离心沉降系数(S_20,w)是28.5S,电镜观察到的是线型DNA 分子,长约8微米,最长的可达10微米以上。聚丙烯酰胺凝胶电泳、Sepharose 柱分析和蔗糖密度梯度超离心等分析中,都是一个组分。pH10缓冲液抽提的DNA,超离心沉降系数(S_(20),w)只有4.7S,聚丙烯酰胺凝胶电泳中迁移速度远比酚抽提的快,并且是一条扩散的宽带,Sepharose 柱分析亦表明分子量远比酚抽提的小。文章对这种不同的结果进行了讨论。     

微量法鼠疫菌质粒DNA抽提的优化

旨在分析微量法抽提鼠疫菌质粒DNA的效果,探讨其在鼠疫菌分子生物学实验研究中的应用价值.采用微量法分别提取鼠疫菌EV76株,假结核耶尔森菌PstII株及大肠杆菌V517株质粒DNA,琼脂糖凝胶电泳对质粒DNA抽提结果进行分析.结果显示,微量法能在较短时间内获取开环较少的闭合环状鼠疫菌质粒DNA,经琼脂糖凝胶电泳图示其电泳条带清晰、亮度均一.微量法鼠疫菌质粒DNA抽提效率和纯度较好,抽提结果稳定,重复性良好.经微量法抽提的质粒DNA符合多数鼠疫菌分子生物学试验的要求,可广泛应用于鼠疫菌分子生物学试验研究中.     

5种常见植物DNA提取效率的比较

以小麦、玉米、甘蓝、花生、菠菜的幼嫩叶片为实验材料,采用高盐低pH值法、SDS法和CTAB法3种不同的DNA提取方法,提取其总DNA,用琼脂糖凝胶电泳检测和紫外分光光度法对所得DNA进行比较分析.结果表明:玉米和菠菜采用SDS法提取基因组DNA效果明显优于CTAB和高盐低pH法.CTAB法对高脂肪花生的DNA提取,所得浓度较高.而高盐低pH值法建议减少使用.     

香菇基因组高分子量DNA的提取

介绍了一种简便快速提取香菇基因组DNA的方法,该法是对提取真菌DNA的SDS和CTAB法进行改进而成,经过修改后的SDS-CTAB法可在较短时间内高效地提取香菇基因组总DNA.制备物经琼脂糖凝胶电泳检测到大于20kb的DNA主带,基本无DNA碎带;OD260/280值显示产物纯度高,完全符合AFLP分析的要求。     

Restriction endonuclease cleavage of linear and closed circular murine leukemia viral DNAs: discovery of a smaller circular form.

Both linear (form III) and closed circular (form I) viral DNAs obtained from mouse cells infected with Moloney murine leukemia virus were cleaved by Sal I, Sma I, Bam HI and Pst I restriction endonucleases. DNA fragments generated by these cleavages were ordered with respect to the 5' and 3' ends of the RNA genome by several techniques, including comparisons of the DNA fragments from cleavages of the linear and closed circular forms, double digestions using different combinations of enzymes and the use of an RNA probe specific for the 3' end. DNA from Hirt extractions of infected cells yielded a discrete species of linear viral DNA whose size was determined by agarose gel electrophoresis to be 5.7 x 10(6) daltons. In the course of characterizing the closed circular DNA, we observed two form I DNA molecules. The larger molecule was the same size as the linear DNA. The second molecule migrated faster on agarose gels and was the predominant species of the two closed circular DNAs. Using the restriction endonuclease maps which we derived, we demonstrate that this novel form I DNA is a smaller homogeneous species of viral DNA, missing about 600 nucleotides found in the linear and larger closed circular DNA molecules. We have localized the site of this missing DNA piece to be at either one or both ends of the linear viral DNA.     

The influence of agarose--DNA affinity on the electrophoretic separation of DNA fragments in agarose gels

The effects of DNA concentration, buffer composition, added "carrier" DNA, and chemical modification of agarose on the electrophoretic separation of DNA restriction fragments in agarose gels were tested. Electrophoretic zones of migrating DNA were found to broaden by trailing as sample load was decreased, and this effect was found to be more pronounced for species of higher molecular weight. As DNA sample load was increased, DNA fragments were found to move faster in the direction of electrophoresis (front forward). Sharp, well-resolved electrophoretic zones were obtained at very low DNA loads only when a high-salt, high-pH, high-EDTA buffer was employed or when "carrier DNA" having a broad and uniform molecular weight distribution was included in the sample. Moreover, DNA in high concentration was found to displace DNA in low concentration from a given gel region. Unmodified agaroses were found to differ only slightly in their effectiveness in retarding DNA fragments at a given agarose concentration. However, hydroxyethylated agarose was much more effective in retarding DNA, at a given gel concentration, than the unmodified agaroses tested. These results show that it is useful to consider the agarose gel matrix as possessing the properties of both a molecular sieve and a chromatographic adsorbent when designing electrophoretic separation techniques for DNA. A model for these separations which includes the effects of DNA-agarose interaction and molecular sieving is discussed.     

High-resolution separation and accurate size determination in pulsed-field gel electrophoresis of DNA. 1. DNA size standards and the effect of agarose and temperature

Pulsed-field gel electrophoresis (PGF) subjects DNA alternately to two electrical fields to resolve DNA ranging from 10,000 base pairs (10 kb) to 10,000 kb in size. The separations are quite sensitive to a variety of experimental variables. This makes it critical to have a wide range of reliable size standards. A technique is described for preparing mixtures of bacteriophage DNA oligomers that span a size range from monomer to more than 30-mer. The relationship between size and mobility of oligomers of different bacteriophage DNA monomers is generally self-consistent. Thus, these samples can serve as primary length standards for DNAs ranging from 10 kb to more than 1500 kb. They have been used to estimate the size of the chromosomal DNAs from various Saccharomyces cerevisiae strains and to test the effect of gel concentration and temperature on PFG. DNA resolution during PFG is slightly improved in agarose gels with small pore sizes, in contrast to continuous electrophoresis where the opposite is observed. PFG mobility is surprisingly sensitive to changes in the running temperature.     

Improved DNA Electrophoresis in Conditions Favoring Polyborates and Lewis Acid Complexation

Spatial compression among the longer DNA fragments occurs during DNA electrophoresis in agarose and non-agarose gels when using certain ions in the conductive buffer, impairing the range of fragment sizes resolved well in a single gel. Substitutions using various polyhydroxyl anions supported the underlying phenomenon as the complexation of Lewis acids to DNA. We saw significant improvements using conditions (lithium borate 10 mM cations, pH 6.5) favoring the formation of borate polyanions and having lower conductance and Joule heating, delayed electrolyte exhaustion, faster electrophoretic run-speed, and sharper separation of DNA bands from 100bp to 12 kb in a single run.     

Ethidium DNA agarose gel electrophoresis: how it started

We started ethidium DNA agarose gel electrophoresis when our ultracentrifuge broke down and we needed an alternative method to check the quality of our mitochondrial DNA preparations. Agarose proved convenient for sizing DNA; ethidium in gel and buffer allowed visualization of DNA bands immediately after the run and improved the separation of the closed and open duplex forms of mitochondrial DNA circles. At smaller gel pore size mitochondrial DNA circles were excluded from the gel, whereas long linear DNAs were not. We concluded that the linear DNAs 'crawl like snakes head on through the gel'. This paper reviews some of the early experiments preceding the introduction of ethidium agarose gel electrophoresis.     

Characterization of two circular plasmids from the marine diatom Cylindrotheca fusiformis: plasmids hybridize to chloroplast and nuclear DNA.

Summary This paper reports the discovery and initial characterization of two small plasmids, pCfl and pCf2, in the marine diatomCylindrotheca fusiformis. Extracted diatom DNA separates into two bands in CsCI-Hoechst 33258 dye gradients. Upon agarose gel electrophoresis of a sample of the upper band of the gradient we observed, in addition to high molecular weight (genomic) chloroplast and mitochondrial DNA, pairs of lower molecular weight bands. These bands contained two species of circular plasmid DNA molecules, as shown by electron microscopy. The nucleotide composition of the plasmids, and chloroplast and mitochondrial DNAs is similar, as indicated by their co-banding in the gradients. They were cloned, and their restriction maps determined, showing that pCfl is 4.27 and pCf2 4.08 kb in size. By hybridization analysis, we showed that pCfl and pCf2 share regions of similarity, but not identity. Neither plasmid hybridizes with mitochondrial DNA. Both plasmids hybridize with chloroplast DNA, and pCf2 also hybridizes with nuclear DNA.     

Molecular cloning of AKR xenotropic murine leukemia virus unintegrated proviral DNA

Suprahelical proviral DNA of AKR xenotropic murine leukemia virus was purified from agarose gels and cloned in lambda Charon 28 DNA (BamHI sites). Nine viral DNA recombinants were identified and mapped with 12 restriction endonucleases. Three calsses of cloned viral DNA inserts were found: (1) Six inserts were apparently full-length 9.0-kb DNA with tandem long terminal repeat (LTR) elements; (2) two inserts contained DNAs with deletions in or adjacent to the LTR regions; (3) a single isolate contained an inversion of 2.3 kb around the LTR in the envelope gene.