PHYSICAL CHEMISTRY OF RECOMBINATIONAL INTERMEDIATES

重组是一种产生基因的基本现象 生物有机体的多样性。这是我们的长远目标。 努力获得对DNA化学的详细了解 描述了这一过程的特点。所寻求的信息将负担得起 遗传物质重排的分子尺度数据 活着的有机体。重组发生在减数分裂，在那里配子 在抗体的发展过程中产生，在世代中 锥虫可变表面抗原，并在插入 病毒DNA进入宿主基因组。既有一般性的，也有站点特定的 重组通过四链中间体进行，已知 作为假日交汇点。 稳定的假日交叉口似乎形成了2-Tell对称 由四条DNA组成的复合体；两条DNA是螺旋的， 而另外两条链在螺旋结构域之间交叉。 该结构对温度和二价阳离子的响应 将会被确定。异构体这种结构的异构体，其中 链的反向螺旋和交叉作用存在：这 异构化将被表征，使用羟基自由基作为 结构探头。分支点迁移是另一种异构化 反应；它是结的不稳定性的原因。这 异构化反应将通过核磁共振进行研究。对…的依赖 T4核酸内切酶VII拆分连接的底物 将会被研究。结合点将被结晶成 结晶学研究结形成的热力学 将通过量热实验来确定。结，相关的 重组特定的DNA不寻常的拓扑结构，将从 合成的寡聚脱氧核苷酸；这些将被描述为 井。 这一系列实验将产生的信息将 中提供有关重组的详细了解 生物体的发展和进化。

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.