DNA POLYMORPHISM UNDER LOW SALT CONDITIONS

低盐条件下的DNA多态性

• 批准号: 3289595
• 负责人: RICHARD H SHAFER
• 金额: $ 8.77万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 1986
• 资助国家: 美国
• 起止时间: 1986-01-01 至 1988-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3289595
• 关键词: DNA; cations; chemical chain length; circular dichroism; conformation; deuterium; ionic strengths; nonradiation isotope effect; nuclear magnetic resonance spectroscopy; nucleic acid chemical synthesis; nucleic acid structure; oligonucleotides; polynucleotides; sodium; spermine

This proposal is concerned with the conformational properties of DNA under very low salt conditions. The left-handed, Z form of poly(dG-dC) and ply(dG-m5dC) exists in solutions containing high salt or oligovalent cations and the right-handed, B form exists under low salt conditions. We have recently observed the unexpected result that in very low salt solutions (less than 2mM Na+) poly(dG-m5dC) is again left-handed. Hence, as the ionic strength is increased above millimolar levels, poly(dG-m5dC) is first left-handed, then right-handed, and finally left-handed again. The research is designed to delineate the solution conditions which stabilize the low salt, left-handed form of poly(dG-m5dC) using circular dichroism, to analyze equilibrium and kinetic aspects of the low salt left-handed form to B form transition, to characterize its conformation, in particular relative to that of the high salt Z form, using 1H and 31P NMR, to examine (dG-m5dC)n oligonucleotides and other sequences for this effect, to investigate the H-D exchange properties of the low salt form using hand mixing and stopped-flow techniques, and to measure the relative rise per base pair in the low salt and intermediate salt forms of poly(dG-m5dC) with transient electric birefringence. The ability to exist in a left-handed conformation at both low and high salt increases the conformational lability of poly(dG-m5dC). Since dG-m5dC sequences have been implicated in gene expression, this conformational flexibility may play an important biological role.

这一建议涉及DNA的构象性质， 低盐条件下。 左手，聚（dG-dC）的Z形式和 层（dG-m5 dC）存在于含有高盐或寡价盐的溶液中 阳离子和右旋B形式存在于低盐条件下。 我们 我最近观察到一个意想不到的结果， 溶液（小于2 mM Na+）聚（dG-m5 dC）再次是左手性的。 因此，我们认为， 当离子强度增加到高于毫摩尔水平时，聚（dG-m5 dC） 先是左撇子，然后是右撇子，最后又是左撇子 研究的目的是描绘解决方案的条件， 使用环状聚（dG-m5 dC）稳定低盐左手形式的聚（dG-m5 dC）， 二色性，分析低盐的平衡和动力学方面 左手形式到B形式转变，以表征其构象， 特别是相对于高盐Z形式，使用1H和31 P NMR， 为了检测（dG-m5 dC）n寡核苷酸和其它序列的这种作用， 用手工方法研究低盐型H-D交换性质 混合和停流技术，并测量相对上升每 聚（dG-m5 dC）的低盐和中间盐形式中的碱基对， 瞬态电双折射 在低温和高温下以左手构象存在的能力 盐增加了聚（dG-m5 dC）的构象不稳定性。 由于dG-m5 dC 序列与基因表达有关，这种构象 灵活性可能发挥重要的生物学作用。