ELECTRIC BIREFRINGENCE OF DNA RESTRICTION FRAGMENTS

本提案中描述的研究旨在调查 异常慢电泳率的分子基础 在聚丙烯酰胺凝胶中观察某些DNA片段，调查 琼脂糖凝胶基质的内部结构和凝胶的取向 琼脂糖凝胶在脉冲电场中，并表征横向 DNA分子在溶液中的诱导偶极矩。 具有排列序列的千碱基大小的DNA分子将通过 圆排列法和瞬变电双折射法， 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片段位于 DNA分子的表观弯曲中心，以及 表观弯曲中心，也将进行研究，以确定 这两类异常类型之间存在结构性差异 缓慢迁移的限制性片段。定向力的机制 DNA分子在电场中将被电学研究 双折射，以查看初始定向方向是否为 由快速横向感应偶极矩决定。电动车 琼脂糖凝胶的双折射将在不同的位置进行测定 在每一种凝胶中。胶凝诱导的本征双折射 涂抹前后还将测量琼脂糖凝胶基质 电场脉冲作用于凝胶。 这项研究的长期目标是描述序列的特征- 依赖于DNA构象的可变性，以了解分子 DNA凝胶电泳的基础，并对其作用机制进行了表征。 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.