X-RAY DIFFRACTION--NUCLEIC ACID STRUCTURES

这项建议旨在研究的分子基础， 核酸的构象变异性，包括DNA、RNA和DNA- 利用单晶X射线衍射技术， 主要工具。 它将得到其他光谱研究的补充， 特别是高分辨率核磁共振光谱。 大 大量的纯DNA和RNA寡核苷酸， 序列将在固体支持树脂上人工合成， 溶液或通过自动化DNA合成仪。 长RNA分子将 通过T7 RNA聚合酶系统在DNA模板上制备，它们将被 适当纯化用于结晶实验。 下面的DNA和RNA分子系统将是本研究的主要焦点。 提议 1.更高级的结构：三股，发夹，十字形， 假结，环状分子，分支RNA。 2.双螺旋核酸的序列依赖构象分析 酸，包括DNA、RNA、DNA-RNA杂合体。 3.稳定的替代核酸构象：Z-DNA、P-DNA、Hoogsteen 受阻。 4.有缺陷的核酸：错配、凸起、缺失 碱基（嘌呤/嘧啶），修饰碱基（O 6-mG/O 4-mT），磷酸三酯。 这些结构研究的结果，无论是在溶液中还是在固体中， 国家将进行比较，他们将是进一步的理论基础 分析，以充分了解结构、动力学和 在分子水平上的核酸能量学。

This proposal is designed to study the molecular basis of the conformational variabilities of nucleic acids, including DNA, RNA and DNA- RNA hybrid molecules by using single crystal x-ray diffraction technique as the major tool. It will be complemented by other spectroscopic studies, in particular high resolution nuclear magnetic resonance spectroscopy. Large amounts of pure DNA and RNA oligonucleotides with carefully chosen sequences will be synthesized on solid support resins either manually in solution, or by automated DNA synthesizer. Long RNA molecules will be prepared by T7 RNA polymerase system on DNA templates and they will be suitably purified for crystallization experiments. The following DNA and RNA molecular systems will be the major focus of this proposal. 1. Higher-ordered structures: triple-stranded, hairpins, cruciforms, pseudoknots, circular molecules, branched RNAs. 2. Sequence-dependent conformational analysis of double helical nucleic acids, including DNA, RNA, DNA-RNA hybrids. 3. Stable alternative nucleic acid conformations: Z-DNA, P-DNA, Hoogsteen Helix. 4. Nucleic acids with defects: Mismatch, bulge, missing base(apurine/apyrimidine), modified base (O6-mG/O4-mT), phosphotriester. The results from these structural studies both in solution and in solid states will be compared and they will be the basis for further theoretical analysis in order to fully understand the structure, dynamics and energetics of nucleic acids at the molecular level.