卟啉-蒽醌二元化合物催化DNA光断裂的性质研究

研究了3种以不同烷氧链-O(CH2)n--(n=1，4，10)连接的卟啉-蒽醌二元化合物催化DNA光断裂的性质。研究表明，卟啉-蒽醌二元化合物催化DNA光断裂性质与连接卟啉和蒽醌的链长有关，从卟啉-蒽醌二元化合物构像平衡对蒽醌插入DNA程度的影响讨论了实验结果。     

Stretching and imaging studies of single DNA molecules

DNA molecules were stretched on silanized mica surface with the molecular combing technique, and detected with fluorescence microscopy and atomic force microscopy. Meantime, DNA molecules were stretched with a modified dynamic molecular combing technique and studied with atomic force microscopy. The results indicate that, compared with the dynamic molecular combing technique, the modified dynamic molecular combing technique has advantages of less-sample demand and less contamination to sample; as compared with the molecular combing technique, it has better aligning effect and reproducibility. Combination of this kind of DNA molecular manipulating technique with the single DNA molecule detecting technique by atomic force microscopy and fluorescence microscopy will play an important role in the basic research of molecular dynamics and the application of gene research.     

萘亚胺类化合物对DNA光敏剪切作用的初步研究

研究了Ｎ－（Ｎ,Ｎ－二甲基）－乙胺－１,８－萘硫酰亚胺和Ｎ－（Ｎ,Ｎ－二甲基）－乙胺－１,８－萘酰亚胺对小牛胸腺ＤＮＡ的嵌入结合反应,并求取了嵌入常数,它们可以把质粒ｐＵＣ１９的超螺旋ＤＮＡ剪切为开环ＤＮＡ,在紫外光作用下,这种能力会得到不同程度的提高。     

Study of the interaction of DNA and histones by spin-stretching and droplet evaporation

Molecular combing is a powerful and simple method for aligning DNA molecules onto a surface. Using this technique combined with fluorescence microscopy, DNA-histone complexes are stretched on a hydrophobic polymethyl methacrylate (PMMA) surface and observed directly. We have developed a new method to stretch single DNA-histone complexes, termed spin-stretching. The results show that the histones markedly enhance DNA binding to the PMMA surface. DNA winds around the histones and therefore decreases in length. The number of histones that bind to each DNA molecule is found to correlate with the histone concentration. The combed DNA-histone complexes are found to depend on two factors: the binding force on the surface and the centrifugal force at its local position. Na+ ions should compete with histones for binding to DNA; however, the observed competitive binding effect of Na+ ions at low concentrations was negligible.     

钌(Ⅱ)配合物合成、表征与DNA 相互作用及其抗氧化性研究

 设计合成一个新的钌(Ⅱ)多吡啶配合物［Ru(dip)₂(DBHIP)］(ClO₄)₂ {dip = 4,7-二苯基-1,10-邻菲咯啉;DBHIP = 2-(3,5-二溴-4-羟基苯)并咪唑［4,4-f］-(1,10-邻菲啰啉)},采用元素分析,质谱和1H NMR对其进行表征。用电子吸收光谱、黏度测试、Job plot荧光滴定法研究配合物与CT DNA作用,结果表明配合物以经典的插入模式与DNA键合。采用琼脂糖凝胶电泳实验研究配合物诱导pBR322DNA断裂。同时也研究配合物在高浓度情况下使pGL3 DNA缩合。     

Mechanochemical analysis of DNA gyrase using rotor bead tracking

DNA gyrase is a molecular machine that uses the energy of ATP hydrolysis to introduce essential negative supercoils into DNA. The directionality of supercoiling is ensured by chiral wrapping of the DNA around a specialized domain of the enzyme before strand passage. Here we observe the activity of gyrase in real time by tracking the rotation of a submicrometre bead attached to the side of a stretched DNA molecule. In the presence of gyrase and ATP, we observe bursts of rotation corresponding to the processive, stepwise introduction of negative supercoils in strict multiples of two. Changes in DNA tension have no detectable effect on supercoiling velocity, but the enzyme becomes markedly less processive as tension is increased over a range of only a few tenths of piconewtons. This behaviour is quantitatively explained by a simple mechanochemical model in which processivity depends on a kinetic competition between dissociation and rapid, tension-sensitive DNA wrapping. In a high-resolution variant of our assay, we directly detect rotational pauses corresponding to two kinetic substeps: an ATP-independent step at the end of the reaction cycle, and an ATP-binding step in the middle of the cycle, subsequent to DNA wrapping.     

Mechanism of homologous recombination from the RecA-ssDNA/dsDNA structures

The RecA family of ATPases mediates homologous recombination, a reaction essential for maintaining genomic integrity and for generating genetic diversity. RecA, ATP and single-stranded DNA (ssDNA) form a helical filament that binds to double-stranded DNA (dsDNA), searches for homology, and then catalyses the exchange of the complementary strand, producing a new heteroduplex. Here we have solved the crystal structures of the Escherichia coli RecA-ssDNA and RecA-heteroduplex filaments. They show that ssDNA and ATP bind to RecA-RecA interfaces cooperatively, explaining the ATP dependency of DNA binding. The ATP gamma-phosphate is sensed across the RecA-RecA interface by two lysine residues that also stimulate ATP hydrolysis, providing a mechanism for DNA release. The DNA is underwound and stretched globally, but locally it adopts a B-DNA-like conformation that restricts the homology search to Watson-Crick-type base pairing. The complementary strand interacts primarily through base pairing, making heteroduplex formation strictly dependent on complementarity. The underwound, stretched filament conformation probably evolved to destabilize the donor duplex, freeing the complementary strand for homology sampling.     

Si基底上DNA分子的自组装

利用自组装方法将DNA分子吸附于Si基底表面, 并通过原子力显微镜（AFM）观察不同质量浓度的DNA溶液在Si基底表面进行自组装后的结构： 当DNA溶液的质量浓度较低时, Si基底表面会吸附单个、 拉伸、 环状的分子; 当DNA溶液的质量浓度为60~160 ng/μL时, 在Si基底表面会形成网状结构; 当DNA溶液的质量浓度超过200 ng/μL时, 仅形成DNA薄膜. 实验结果表明, 可以利用该方法制作基于Si材料的DNA分子器件.     

Single-molecule analysis of DNA uncoiling by a type II topoisomerase

Type II DNA topoisomerases are ubiquitous ATP-dependent enzymes capable of transporting a DNA through a transient double-strand break in a second DNA segment. This enables them to untangle DNA and relax the interwound supercoils (plectonemes) that arise in twisted DNA. In vivo, they are responsible for untangling replicated chromosomes and their absence at mitosis or meiosis ultimately causes cell death. Here we describe a micromanipulation experiment in which we follow in real time a single Drosophila melanogaster topoisomerase II acting on a linear DNA molecule which is mechanically stretched and supercoiled. By monitoring the DNA's extension in the presence of ATP, we directly observe the relaxation of two supercoils during a single catalytic turnover. By controlling the force pulling on the molecule, we determine the variation of the reaction rate with the applied stress. Finally, in the absence of ATP, we observe the damping of a DNA crossover by a single topoisomerase on at least two different timescales (configurations). These results show that single molecule experiments are a powerful new tool for the study of topoisomerases.     

矩形钢管混凝土波纹腹板组合梁局部受压承载力研究

利用数值模拟方法对矩形钢管混凝土-波纹腹板组合梁(RCFTFG-CW)的局部承压承载力进行研究。建立了在集中荷载作用下RCFTFG-CW与波纹腹板工字形梁(IG-CW)腹板发生局部承压破坏的有限元分析模型。通过与相关文献结果对比,验证了有限元模型的可靠性。利用验证后的有限元模型研究了RCFTFG-CW的局部承压承载力、应力发展过程以及荷载作用位置对承载力的影响。分析了几何尺寸、材料特性、荷载作用长度(沿梁跨度方向)以及波纹展开长度和波长的比值对RCFTFG-CW局部承压承载力的影响。在参数分析的基础上,提出了RCFTFG-CW的局部承压承载力的设计表达式,并利用有限元分析结果验证了公式的准确性。结果表明,与IG-CW相比,RCFTFG-CW具有更高的局部承压承载力;RCFTFG-CW的局部承压承载力分别与钢管混凝土上翼缘等效惯性矩的1/4次方、腹板厚度、波纹展开长度与波长的比值、荷载作用长度呈线性增长关系;所提出的计算公式能够精确预测RCFTFG-CW的局部承压承载力。     

DNA分子在云母表面拉直技术的研究

对DNA分子的生物、物理和化学性质的很多研究,都要求对单个DNA分子的性质进行深入探索,实现DNA分子在基底表面上的拉直是对其深入研究的物理基础。文章在APS溶液处理过的云母片表面,通过不同的方法完成了对DNA分子的拉直操作,利用原予力显微镜对拉直后的DNA分子进行了表征,获得了DNA分子拉直后的形貌,并对每种拉直方法进行了比较和讨论。     

中国臭蛙类一新种

通过形态学比较和12S、16SmtDNA序列比对分析,结果显示分布于浙江省西天目山的花臭蛙(Odorrana schmackeri Boettger,1892)与地模产地花臭蛙以及花臭蛙2个新隐种南江臭蛙和黄岗臭蛙之间存在显著差异,其主要鉴别特征为:1)雌性成体体长约为雄性的1.75倍;2)头长大于头宽,吻端钝尖;3)后肢前伸胫跗关节达眼鼻间;4)趾间全蹼,第4趾两侧及第2、3趾内侧蹼以缘膜达趾吸盘基部;5)背部褐色斑稀疏,形状、大小、排列不规则;6)四肢背面浅褐色横纹宽窄不一,胫部横纹4或5条;7)雄性具1对咽侧下外声囊,背面有肉粉色雄性线,第1指具乳白色婚垫;8)雌性成熟卵动物极棕褐色、植物极米黄色,卵径2.17mm左右.故将浙江省西天目山区的花臭蛙鉴定为一新种--天目臭蛙(Odorrana.tianmuii.sp.nov.).     

肝癌细胞形态和生长行为对基底拉伸的响应

采用“四点弯曲梁加载装置”，对培养的人肝癌细胞株SMMC－7721旋以拉伸刺激，通过显微计算机图像处理系统了解其形态变化，流式细胞仪了解其增殖行为，结果发现1）加载24h后SMMC－7721 G2－M期8．63％，对照组15．92％；2）加载72h后SMMC－7721铺展投影面积缩小；3）加载24h后SMMC－7721分裂指数0．46，对照组0．55。加载可部份抑制SMMC－7721的生长。     

石墨烯薄膜拉伸性能的分子动力学模拟

通过分子动力学模拟,对单层和多层石墨烯薄膜在两个方向上的拉伸力学性能进行了研究,得到了相应的应力-应变关系以及拉伸破坏形态.对单层石墨烯薄膜,研究了薄膜尺寸对其拉伸性能的影响;对多层石墨烯薄膜,研究了薄膜尺寸相同时层数对其拉伸性能的影响.结果表明:单层石墨烯薄膜两个方向的弹性模量分别为1078.02GPa(扶手椅型)和1041.53GPa(锯齿型);在拉伸线弹性变形阶段,单层石墨烯薄膜是各向同性的,且薄膜尺寸变化对单层石墨烯薄膜拉伸性能的影响不大;多层石墨烯薄膜在拉伸过程中的应力-应变关系与单层石墨烯薄膜类似,且在拉伸线弹性变形阶段表现出比单层石墨烯薄膜更为明显的各向同性;扶手椅型石墨烯薄膜的破坏从一侧边缘开始,并沿45°方向向薄膜内部延伸,锯齿型石墨烯薄膜的破坏从两侧边缘开始,对称地向内部延伸.     

一种非专用器械的离心力量练习——强制性拉伸肌肉

离心练习对肌肉是一种强刺激。但目前还缺乏专用的练习器械,现行传统的离心练习也有许多不足之处,因而难以普遍应用。本文介绍一种简便易行的强制性拉伸肌肉的力量练习方法,它不仅能达到离心练习的训练效果,而且还可克服传统离心练习的不足。     

Physiological responses of osteoblasts to cyclic stretching and the change of intracellular calcium concentration

The development of bone tissues is regulated by mechanical stimulation.Cyclic stretching was applied to the osteoblasts that were delivered from rat calvarie,The results showed that stretching at 500με increased the cell proliferation while loading at 1000με and 1500με inhabited cell growth ,Loading also increased the adhesive force between cells and substrate as well as spreading areas of osteobalsts.Furthermore,the fluorescence probe Fluo-3/AM was used to investigate the effect of stretching stimulation on the intracellular calcium concentration of osteoblasts.The intracellular calcium concentration of osteoblasts that were stretched at 500 με for 5 min was 92.9% higher than the control ,After being treated with the panax ontoginseng saponins,the streteched osteoblasts still expressed 28.6% higher intracellular calcium concentration than that of the control ,which proved that both the influx of extracellualr calcium and the release of intracellular calcium store were involved in the increase of intracellular calcium concentration when osteoblasts responded to the cyclic stretching And the influx of extracellular calcium through transmembrance channel played a main role.     

HIV感染的治疗性DNA疫苗（综述）

DNA疫苗被称为继完速病原体疫苗和基因工程重组蛋白疫苗后的第3代疫苗,其兼有重组亚单位疫苗的安全性和减毒活疫苗的有效性。HIV感染的防治则以激发细胞免疫为主,以激发细胞免疫为主的DNA疫苗给HIV感染防治带来曙光。目前DNA疫苗在HIV感染防治研究方面已取得显著进展,其临床研究已证明具有明显的刺激机体细胞免疫的效果,尤其是一些细胞因子、趋化因子可明显增强HIV DNA疫苗的免疫反应。就DNA免疫佐剂、HIV病毒基因DNA疫苗作用机制以及加强HIV DNA疫苗的各种调节因素方面的研究进展进行综述,以促进HIV DNA疫苗防治的研究。