PHYSICAL CHEMISTRY OF RECOMBINATIONAL INTERMEDIATES

基因突变是一种基本现象， 生物多样性。 这是一个长期目标， 努力获得对DNA化学的详细了解， 这一过程的特点。 所寻求的信息将提供 分子尺度上的遗传物质重排的数据， 活的有机体。 减数分裂发生在配子 在抗体的发展过程中， 锥虫可变表面抗原，并在插入 病毒DNA进入宿主基因组 广义和特定地点 重组通过四链中间体进行，已知 作为假日路口。 稳定的假日结似乎形成2-told对称 四股DNA的复合物;两股DNA是螺旋的， 而另外两条链在螺旋结构域之间交叉。 这种结构对温度和二价阳离子的响应 将被确定。 该结构的一种异构体，其中 链反向螺旋和交叉作用存在：这 异构化的特点是，使用羟基自由基作为 结构探针 分支点迁移是另一种异构化 反应;它是负责结的不稳定性。 这 将通过NMR研究异构化。 依赖于 T4核酸内切酶VII分解连接的底物 将被研究。 结将结晶， 晶体学研究 结形成的热力学 将由量热实验确定。 Knots，一个相关的 重组特异性DNA的不寻常拓扑结构，将由 合成的寡脱氧核苷酸;这些将被表征为 好. 这一系列的实验将产生信息， 提供有关重组的详细了解， 生物的发展和进化。

Recombination is a fundamental phenomenon that generates genetic diversity in living organisms. It is the long-range goal of that work to obtain a detailed understanding of the DNA chemistry which characterizes this process. The information sought will afford molecular-scale data on the rearrangement of genetic material in living organisms. Recombination occurs in meiosis, where gametes are produced, in the development of antibodies, in the generation of trypanosome variable surface antigens, and in the insertion of viral DNA Into host genomes. Both generalized and site-specific recombination proceed through four-stranded intermediates, known as Holiday junctions. Stabilized Holiday junctions appear to form 2-told symmetric complexes from four strands of DNA; two strands of DNA are helical, while the other two strands cross over between helical domains. The response of this structure to temperature and divalent cations will be determined. An isomer of this structure in which the strands reverse helical and crossover roles exists: this isomerization will be characterized, using hydroxyl radical as a structural probe. Branch-point migration is another isomerization reaction; it is responsible for the instability of junction. This isomerization will be studied by NMR. The dependence upon substrate of the resolution of junctions by T4 Endonuclease VII will be studied. Junctions will be crystallized for crystallographic study. The thermodynamics of junction formation will be determined from calorimetric experiments. Knots, a related recombination-specific unusual topology of DNA, will be made from synthetic oligodeoxynucleotides; these will be characterized as well. This series of experiments will yield information which will provide detailed understanding about recombination in the development and evolution of organisms.