ELECTRIC BIREFRINGENCE OF DNA RESTRICTION FRAGMENTS

DNA限制性片段与电场的相互作用 将使用瞬态电 双折射 将特别强调研究 DNA限制性片段定向和去定向 包埋在琼脂糖和聚丙烯酰胺凝胶中。 电动 双折射对于这些研究是特别有用的技术， 因为它直接测量DNA的方向 凝胶基质中的分子。 将研究方向， 不同幅度和持续时间的脉冲电场， 脉冲之间的可变延迟，并具有快速反转的电 领域的 含线性聚丙烯酰胺溶液中的取向 不同电荷密度的分子也将被研究。 电双折射研究将继续在 定向、定向障碍、反向场和饱和 两个147碱基对限制性片段的行为， 质粒pBR 322。 这两种碎片的流动性不同 聚丙烯酰胺凝胶，以及其他物理性能， 典型的序列相关的结构差异在沃森- 克里克螺旋。 其他正常和异常的对 迁移的DNA片段将被研究，以及合成 多核苷酸。 额外的电双折射研究将集中在 的DNA片段的饱和和反转场行为 自由溶液中不同分子量的B 一 DNA限制性片段的构象转变， 限制酶与DNA片段的结合， 溴化乙锭和DNA片段的其他配体， 溴化乙锭和其它配体与DNA片段的结合， 和线性聚丙烯酰胺的电双折射， 不同的分子量和电荷密度。 许多 电双折射测量将与 圆二色性和/或凝胶电泳研究。 结果 这些实验将阐明凝胶的机理 电泳在不同的凝胶介质中，并确定一些 序列依赖性构象差异对 DNA的物理性质。 这项研究的长期目标是 是了解DNA分子在溶液中的行为， 描述DNA和其他分子相互作用的机制 聚离子与电场。

The interaction of DNA restriction fragments with electric fields will be investigated using the technique of transient electric birefringence. Particular emphasis will be placed on a study of the orientation and disorientation of DNA restriction fragments imbedded in agarose and in polyacrylamide gels. Electric birefringence is a particularly useful technique for these studies, because it measures directly the orientation of the DNA molecules in the gel matrix. Orientation will be studied with pulsed electric fields of different amplitudes and durations, with a variable delay between pulses, and with rapidly reversing electric fields. Orientation in a solution containing linear polyacrylamide molecules of different charge densities will also be studied. Electric birefringence studies will be continued on the orientation, disorientation, reversing field, and saturation behavior of two 147 base pair restriction fragments obtained from the plasmid pBR322. These two fragments differ in their mobility on polyacrylamide gels, and in other physical properties, and typify sequence-related structural differences in the Watson- Crick helix. Other pairs of normally and abnormally slowly migrating DNA fragments will be studied, as well as synthetic polynucleotides. Additional electric birefringence studies will focus on the saturation and reversing field behavior of DNA fragments of different molecular weights in free solution, the B A conformational transition of DNA restriction fragments, the binding of restriction enzymes to DNA fragments, the binding of ethidium bromide and other ligands to DNA fragments, the binding of ethidium bromide and other ligands to DNA fragments, and the electric birefringence of linear polyacrylamides of different molecular weights and charge densities. Many of the electric birefringence measurements will be correlated with circular dichroism and/or gel electrophoretic studies. The result of these experiments will clarify the mechanism of gel electrophoresis in different gel media and identify some of the effects of sequence-dependent conformation differences on the physical properties of DNA. The long range goals of this research are to understand the behavior of DNA molecule in solution and to characterize the mechanism of interaction of DNA and other polyions with electric fields.