CATION-BINDING ENVIRONMENTS ON DEOXYOLIGONUCLEOTIDES

寡核苷酸的局部结构可以对 溶液中存在多价阳离子。这一结构 可变性在很大程度上取决于寡核苷酸序列以及 阳离子类型，因此不是非特定阳离子的结果 联想。拟议工作的目标是澄清 这些结构性效应。结合阳离子的动力学行为是 对特定和非特定的相对贡献敏感 阳离子结合。这些动态将通过绑定的核磁共振进行监测 阳离子。阳离子结合的结构性后果将依次是 由二维质子核磁共振确定。 提出了多核核磁共振和平衡结合研究，以期 考察简单阳离子在稳定寡核苷酸中的作用 在构象和促进寡核苷酸结构转变方面。 圆二色谱将提供对 阳离子诱导的结构扰动。阳离子核磁共振弛豫和 将使用脉冲场梯度扩散实验来监测 阳离子的迁移率(平移、转动和内部) 寡核苷酸溶液。阳离子核磁共振实验还将用于 考察DNA长度和盐浓度对比和 非特异性阳离子缔合。这些研究将得到以下补充 唐南平衡的热力学束缚测量。质子核磁共振， X射线衍射研究和分子模拟将提供额外的 关于阳离子诱导结构性质的信息 微扰和阳离子结合位的几何构型。 拟议工作的主要重点将是双螺旋 涉及Watson-Crick碱基配对的寡核苷酸结构。然而， 还提出了探索性工作，以考察阳离子对不寻常的影响。 可能对同源重组很重要的结构(例如 连接结构)，转录调控(例如，三螺旋 结构)和稳定染色体末端(例如 富含G的端粒序列)。具体地说，实验是在 顺序(1)以定义阳离子对选定的整体几何图形的影响 寡核苷酸。(2)描述……的当地环境 特别结合的阳离子。(3)关联边界的动力学 阳离子到阳离子诱导的寡核苷酸结构转变。(4)至 实验测定DNA长度对局部和全局的影响 阳离子与短寡核苷酸结合。(5)探索阳离子结合 到不寻常的寡核苷酸结构。

The local structure of oligonucleotides can be exquisitely sensitive to the presence of multivalent cations in solution. This structural variability depends significantly on oligonucleotide sequence as well as cation type, and hence does not result from nonspecific cation associations. The goal of the proposed work is to clarify the origins of these structural effects. The dynamic behavior of bound cations is sensitive to the relative contributions of specific and nonspecific cation binding. These dynamics will be monitored by the nmr of the bound cations. The structural consequences of cation binding will in turn be determined by two-dimensional proton nmr. Multinuclear nmr and equilibrium binding studies are proposed in order to examine the roles of simple cations in stabilizing oligonucleotide conformations and in promoting oligonucleotide structural transitions. Circular dichroism will provide an initial characterization of cation-induced structural perturbations. Cation nmr relaxation and pulsed field gradient diffusion experiments will be used to monitor the mobility (translational, rotational and internal) of cations in oligonucleotide solution. Cation nmr experiments will also be used to examine the effect of DNA length and salt concentration on specific and nonspecific cation associations. These studies will be complemented by thermodynamic binding measurements of Donnan equilibria. Proton nmr, x-ray diffraction studies and molecular modelling will provide additional information regarding the nature of cation-induced structural perturbations, and the geometry of cation binding sites. The primary focus of the proposed work will be on double-helical oligonucleotide structures involving Watson-Crick base-pairing. However, exploratory work is also proposed to examine cation effects on unusual structures that may be important for homologous recombination (e.g. junction structures), regulation of transcription (e.g. triple helical structures) and for the stabilization of the ends of chromosomes (e.g. G-rich telomeric sequences). Specifically, experiments are proposed in order (1) To define cation effects on the overall geometry of selected oligonucleotides. (2) To characterize the local environment of specifically bound cations. (3) To correlate the dynamics of bound cations to cation-induced oligonucleotide structural transitions. (4) To determine experimentally the effect of DNA length on local and global cation binding to short oligonucleotides. (5) To explore cation binding to unusual oligonucleotide structures.