Left-handed DNA in restriction fragments and a recombinant plasmid

Circular dichroism and 31P-NMR on synthetic oligomers of (dC-dG) inserted within DNA restriction fragments indicate that the right-handed B-structure can exist in close proximity to the left-handed Z-structure. Also, this salt-induced transition to Z-form in a small (dC-dG) segment (1.3%) of a recombinant plasmid markedly influenced the supercoil of the plasmid. These observations have implications for the postulated role of naturally occurring related simple sequences in the regulation of gene activity.     

短双链DNA分子成环及微环缺陷结构研究

选用长为316 bp的双链DNA片段研究其柔韧性和成环能力,并用两种核酸内切酶探测微环DNA结构的完整性.结果表明,在T4连接酶的催化作用下,与Widom的报道一致,短双链DNA确实能够自发弯曲成环.用两种核酸酶——BAL31和S1作用之后,DNA环发生不同程度的消失,说明环状分子上存在非常规的缺陷结构.这种缺陷结构与短双链DNA的弯折刚性大大降低之间可能存在一定关系.     

DNA restriction fragments associated with alpha 1-antitrypsin indicate a single origin for deficiency allele PI Z

The alpha 1-protease inhibitor, or alpha-antitrypsin (AAT), a major plasma inhibitor of leukocyte elastase and bacterial proteases, is encoded at the PI locus on chromosome 14 (14q24.3-q32.1). A deficiency of AAT in individuals homozygous for the PI Z allele occurs in about 1 in 2,000-8,000 caucasians and is associated with an increased risk of early adult onset emphysema and liver disease in childhood. We have now used DNA polymorphisms associated with the AAT gene to investigate the origin of the PI Z allele. Using two genomic probes extending into the 5' and 3' flanking regions, respectively, we have identified eight polymorphic restriction sites. Extensive linkage disequilibrium occurs throughout the probed region with the PI Z allele, but not with normal PI M alleles. The Z allele occurs mainly with one haplotype, indicating a single, relatively recent, origin in caucasians.     

Analysis of length distribution of short DNA fragments induced by ^7Li ions using the random-breakage model

Deoxyribonucleic acid (DNA) is an important bio-macromolecule. DNA double strand breaks (DSBs) are considered to be the most important initial damage responsible for all biological effects induced by ionizing radiation. In this paper the length distribution of DNA fragments induced by ^7Li ionizing radiation is fitted with the random breakage model. In this model, the parameter u is the average number of DSBs on every DNA molecule induced by ionizing radiation. The fitting result shows that the random breakage model cannot describe the distribution of DNA fragments in lower doses, while the random breakage model is in better accordance with the experimental data in higher doses. It is shown that the length distribution of DNA fragments has random statistical feature in higher doses. In this situation, the random breakage model looks like a model without any parameter since the u has specific physical meaning and can directly be obtained from experimental data.     

不同体积分数二甲基亚砜对DNA变性的影响

利用原子力显微镜和动态光散射研究不同体积分数二甲基亚砜(DMSO)对质粒及线性DNA变性的影响。结果表明,体积分数1%的DMSO也能导致DNA发生局部变性,这个结果可以用原子力显微镜直接观测。同时,由于质粒DNA连接数的守恒以及DNA单链的产生,通过原子力显微镜和动态光散射发现,DNA随DMSO体积分数的增加逐渐形成超螺旋结构,DNA聚拢程度增加;DMSO体积分数从0增加到10%时,pBR322 DNA、5 000 bp DNA及λ-DNA的平均粒径分别从(474±10) nm、(554±11) nm和(871±17) nm降低到(257±8) nm、(282±18) nm和(449±21) nm。     

Long-range restriction site mapping of mammalian genomic DNA

Molecular analysis of many problems in genetics would be facilitated by the ability to construct restriction site maps of long stretches of genomic DNA and to directly place genes on these maps. Pulsed-field gradient gel electrophoresis allows measurement of the size of DNA fragments up to at least 2,000 kilobase pairs (kb) long and we have used this technique here to map sites for one class of infrequently cutting restriction enzyme over a total of 1,500 kb of mouse genomic DNA. The sites for these enzymes tend to be clustered in the genome. These clusters may correspond to the short stretches of C + G-rich unmethylated DNA often associated with mammalian genes.     

甲状腺癌甲基化差异片断的筛选

目的筛选甲状腺癌与甲状腺癌旁组织的甲基化差异片段。方法采用甲基敏感性代表性差异分析（MS-RDA）方法,用甲基化敏感性内切酶消化甲状腺癌及癌旁组织基因组DNA,连上接头制备扩增子后,进行两轮消减杂交,筛选甲状腺癌与癌旁组织的甲基化差异片段。结果经过两轮消减杂交后,筛选出3个低甲基化差异片段,2个高甲基化差异片断。筛选出的低甲基化差异片段C913位于BC029276基因上,该基因编码一种rRNA结合蛋白,可能与肿瘤有关。另外2个低甲基化差异片段C915与C917尚未见相关结构和功能的报道。两个高甲基化差异片断与已知基因同源性在20%-35%之间。5个片断均为新的甲基化差异片断。结论在甲状腺癌组织中存在异常甲基化,筛选出的甲基化差异片断有助于进一步了解异常甲基化在甲状腺癌发生发展中的作用。     

Separation of DNA fragments by cross-linked polymer coating capillary electrophoresis with non-gel sieving matrix

A new type of flush/fill equipment driven by high-pressure (1MPa) nitrogen gas for filling the capillary is demonstrated. High-viscous and microlitre grade volume solution can be filled into a capillary by means of this equipment. The capillary coated by cross-linked polyacrylamide and filled with “interpenetrating polymer networks” non-gels sieving matrix (0.8% hydroxyethyl cellulose, 10% sucrose in 1×TBE buffer) was applied for separating DNA fragments. All 11 fragments of Ø174/Hae III DNA were successfully separated. The man-made circle plasmid from E. coli were separated and detected.     

Simulation of ChIP-Seq based on extra-sonication of IPed DNA fragments

The combination of chromatin immunoprecipitation with sequencing (ChIP-Seq) is an effective method for obtaining an in vivo genome-wide profile of the interaction of a protein with DNA. With the dramatic development of high-throughput short sequencing technologies, several new algorithms have been developed to process ChIP-Seq. However, the reported analytical tools for ChIP-Seq based on size selection of immunoprecipitated (IPed) DNA fragments are mainly adopted on the Solexa system. As a sequencer with the highest throughput, few studies of ChIP-Seq based on SOLiD system have been reported. The main difference of the SOLiD and Solexa systems exists in the length of DNA fragments during preparing sequencing libraries. The SOLiD system has relatively short DNA fragments if it processes a further sonication of IPed DNA fragments in order to meet the length requirement of DNA frag-ments for emulsion-PCR (ePCR). This work aims to investigate the influences of DNA fragment length on data analysis from ChIP-Seq. Previous studies show that typical bimodal peaks can be observed in Solexa ChIP-Seq data, but based on the analysis of the real SOLiD ChIP-Seq data in this study, we found that there were no double peaks with apparent reads shift in a local enriched region and the local reads distribution of peaks were tested by normal distribution. Using real and simulated ChIP-Seq data, three main ChIP-Seq algorithms (CisGenome, SISSRs and MACS) have been investigated. We found that algorithms developed for processing ChIP-Seq data generated from Solexa library protocol, cannot efficiently capture the feature of the ChIP-Seq data from SOLiD library. Misuse of those analytical tools would be a possible reason for failure of ChIP-Seq on the SOLiD system. Therefore, a new ChIP-Seq analytical strategy for an extra-sonication of IPed DNA fragments needs to be developed.     

Theory of restriction degree of Triple I method with total inference rules of fuzzy reasoning

Based on the theory of sustentation degree of Triple I method together with the formulas of a-Triple I modus ponens (MP) and a-Triple I modus tollens( MT), the theory of restriction degree of Triple I method is proposed. Its properties are analyzed, and the general formulas of supremum of a-Triple IMP and infimum of a-Triple I MT are obtained.     

核反应堆不同温度流体热混合的机理及实验研究

探讨了在核反应堆热工流体力学中具有普遍意义的不同温度流体达到热混合均匀状态的过程和机理。１０ＭＷ高温气冷实验堆（ＨＴＲ－１０）热气导管内的流体热混合主要是径向对流扩散过程。用流体温度空间分布的方差表示混合效果，通过雷诺比拟方法求得在点热源下游流动流体的径向扩散系数解析解，与在模拟热气导管内的点热源下游流动流体的扩散混合实验的结果相符合。在雷诺数Ｒｅ为（１．００～３．５０）×１０５范围内，径向湍动系数εｒ的相应范围是（１．００～４．００）×１０－３ｍ２／ｓ。反映混合效果的湍动系数与流速ｕ之比εｒ／ｕ随雷诺数Ｒｅ变化不大，解释了在高温堆堆芯底部结构中Ｒｅ对流体混合效果影响不大的现象。     

差热分析(DTA)实验条件的研究

通常涉及热分析的文献中都会表明实验条件 ,除此以外 ,还应重视防震条件和环境中轻微震动对DTA曲线的影响 ,特别是把 DTA曲线当作指纹信息应用时 .     

短切玄武岩纤维增强低导热型加气混凝土的试验研究

对低导热性加气混凝土进行了短切玄武岩纤维增强实验研究.测试5种不同体积掺量的加气混凝土的抗压强度与抗折强度,采用立体变焦显微镜对不同孔径的发气气孔的含量进行统计与计算.采用扫描电子显微镜观察其微观形貌,并与未掺短切玄武岩纤维的加气混凝土做对比.研究结果表明,短切玄武岩纤维能显著提高加气混凝土的强度,尤其是抗折强度.当体积掺量为0.6%时,加气混凝土的抗压强度与抗折强度均达到最大值.     

Partial denaturation mapping of cloned histone DNA from the sea urchin Psammechinus miliaris.

A cloned 5.6-kb DNA repeat unit of Psammechinus miliaris containing all five histone coding sequences of known order and polarity has been shown to fall clearly into a low melting and a high melting half by thermal denaturation. The topoligies of the DNA sequences thus defined were determined by partial denaturation mapping in the electron microscope to gain further insight into the distribution of spacers and genes within histone DNA.     

Unique allelic restriction fragments of the human Ha-ras locus in leukocyte and tumour DNAs of cancer patients

White blood cell DNA from cancer patients and DNA from tumours and tumour-derived cell lines frequently demonstrated allelic restriction fragments of the Harvey ras oncogene locus not found in the unaffected population. The presence of such unusual alleles may be linked to susceptibility to cancer.     

流体热工基础实验教学综合改革的探讨

流体热工基础实验传统上是流体力学、工程热力学、传热学课程内容的实践教学部分,也是能源类专业的专业基础课程。流体热工基础实验的教学质量提高对专业人才的培养有至关重要的意义。通过整合各门课程实验教学部分成为一门独立设课的实验课程,构建了实验课程教学的实验项目体系。从物性测量的基本方法、经典实验的再现与基本理论的验证到开创性实验项目的开发与实验研究,分析了在流体热工基础实验教学中培养学生创新意识与创新能力的途径,并对实验教学的改革方向和思路进行了一些探讨。