Tang R S, Draper D E
Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218.
Nucleic Acids Res. 1994 Mar 11;22(5):835-41. doi: 10.1093/nar/22.5.835.
In a phasing experiment, two bends are introduced into a long duplex RNA or DNA and the number of base pairs between them varied. When electrophoresed in a gel, the set of molecules may show a periodic variation in mobility that contains information about the twist associated with the bends and the intervening helix. We show how a set of three phasing experiments can be used to extract this information, and apply it to an RNA helix bend at the bulge sequence A2. The bulge introduces a negative (left-handed) twist of approximately 30 degrees; at low temperatures, it is mostly confined to the 5' side of the bulge. The apparent helical repeat of random sequence RNA measured in these experiments was 10.2 +/- 0.1 base pairs, an unexpectedly low value. It is likely that moderate curvative of the RNA helix axis (30-40 degrees over 80 bp) has affected the measurement.
在一项相位实验中，在一条长双链RNA或DNA中引入两个弯曲，并改变它们之间的碱基对数量。当在凝胶中进行电泳时，这组分子可能会显示出迁移率的周期性变化，其中包含与弯曲以及中间螺旋相关的扭曲信息。我们展示了如何使用一组三个相位实验来提取此信息，并将其应用于凸起序列A2处的RNA螺旋弯曲。该凸起引入了约30度的负（左旋）扭曲；在低温下，它主要局限于凸起的5'侧。在这些实验中测量的随机序列RNA的表观螺旋重复为10.2 +/- 0.1个碱基对，这是一个出乎意料的低值。RNA螺旋轴的适度弯曲（在80个碱基对中为30 - 40度）很可能影响了测量结果。
