ELECTRIC BIREFRINGENCE OF DNA RESTRICTION FRAGMENTS

本提案中描述的研究旨在调查 慢电泳迁移率的分子基础 观察某些DNA片段在聚丙烯酰胺凝胶，调查 琼脂糖凝胶基质的内部结构和 琼脂糖凝胶在脉冲电场，并表征横向 溶液中DNA分子的诱导偶极矩。 具有排列序列的千碱基大小的DNA分子将通过以下方法进行研究： 圆形排列分析和瞬态电双折射， 看看它们的凝胶迁移率是否与它们的表观端到端相关 长度异常缓慢迁移的限制性片段位于 DNA分子的明显弯曲中心，以及 表观弯曲中心，也将进行研究，以确定是否 在这两类人之间存在着结构上的差异。 缓慢迁移的限制性片段 的取向机制 电场中的DNA分子将通过电场来研究 双折射，以查看取向的初始方向是否 由快速横向诱导偶极矩确定。 电动 琼脂糖凝胶的双折射将在不同位置测定 在每个凝胶中。 本征（凝胶化诱导）双折射的 琼脂糖凝胶基质也将在施用前和施用后测量 向凝胶施加电场脉冲。 这项研究的长期目标是表征序列- 依赖于DNA的构象变异性，以了解分子 DNA凝胶电泳的基础上，并表征的机制， DNA在电场中的取向。

The research described in this proposal is designed to investigate the molecular basis of the anomalously slow electrophoretic mobilities observed for certain DNA fragments in polyacrylamide gels, investigate the internal structure of the agarose gel matrix and the orientation of agarose gels in pulsed electric fields, and characterize the transverse induced dipole moment of DNA molecules in solution. Kilobase-sized DNA molecules with permuted sequences will be studied by the circular permutation assay and by transient electric birefringence, to see whether their gel mobilities correlate with their apparent end-to-end lengths. Anomalously slowly migrating restriction fragments located at the apparent bend centers of the DNA molecules, and midway between the apparent bend centers, will also be studied, to determine whether structural differences exist between these two classes of anomalously slowly migrating restriction fragments. The mechanism of orientation of DNA molecules in an electric field will be studied by electric birefringence, to see whether the initial direction of orientation is determined by a fast transverse induced dipole moment. The electric birefringence of agarose gels will be determined at various locations within each gel. The intrinsic (gelation induced) birefringence of the agarose gel matrix will also be measured before and after applying electric field pulses to the gel. The long term goals of this research are to characterize the sequence- dependent conformational variability of DNA, to understand the molecular basis of DNA gel electrophoresis, and to characterize the mechanism of orientation of DNA in an electric field.