Vologodskii A V, Yang X, Seeman N C
Department of Chemistry, New York University, New York, NY 10003, USA.
Nucleic Acids Res. 1998 Mar 15;26(6):1503-8. doi: 10.1093/nar/26.6.1503.
We have induced a local conformational transition by positive torsional stress in small synthetic circular DNA molecules containing cruciforms with immobile or tetramobile branched junctions. The immobile species correspond to the extruded and intruded extrema of the tetramobile junction. Under normal conditions the sequences of all the branched species prevent them from being re-absorbed into the circle. We have induced positive stress by addition of ethidium to the circle, in a low ionic strength medium. Alterations in gel electrophoretic mobility under increasing concentrations of ethidium suggest that the cruciforms undergo a transition under torsional stress. The product of this transition contains mispaired nucleotides, but interwound backbones. By comparing the electrophoretic mobilities of circles containing these structures with that of a completely complementary circle of the same length, we conclude that the twist in the mispairing region is similiar to that of completely paired species.
我们通过正向扭转应力在含有具有固定或四向移动分支连接点十字形结构的小型合成环状DNA分子中诱导了局部构象转变。固定型对应于四向移动连接点的挤出和侵入极端情况。在正常条件下，所有分支物种的序列都阻止它们重新吸收回环状结构中。我们在低离子强度介质中通过向环状结构中添加溴化乙锭诱导了正向应力。在溴化乙锭浓度增加时凝胶电泳迁移率的变化表明十字形结构在扭转应力下发生了转变。这种转变的产物包含错配核苷酸，但主链相互缠绕。通过将含有这些结构的环状物的电泳迁移率与相同长度的完全互补环状物的电泳迁移率进行比较，我们得出结论，错配区域的扭曲与完全配对物种的扭曲相似。
