Applications of the twist difference to DNA structural analysis.
Applications of the twist difference to DNA structural analysis.
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扭曲差异在 DNA 结构分析中的应用。
DOI：
10.1073/pnas.85.3.772
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发表时间：
1988
影响因子：
11.1
通讯作者：
Bauer,WR
中科院分区：
文献类型：
--
作者：
White,JH;Bauer,WR
扭曲是核酸的基本几何特性。最一般情况下的捻度计算需要详细说明每根股线的三维路径，但许多重要情况可以仅考虑捻度差异来分析。如果C1、C2和C3是三个不同的空间曲线，则关于C1的扭曲差被定义为Tw(C3,C1)-Tw(C2,C1)。我们在此表明，该差异测量了连接 C1 至 C2 的对应表面相对于连接 C1 至 C3 的对应表面的旋转。这一结果适用于含有局部不均匀性的 DNA，例如变性区域、十字形和其他改变的结构。它还有助于计算三链结构的扭曲，包括线粒体 DNA 中的 D 环以及复制和转录中间体。扭曲差异还可用于极大地简化对由于表面（例如组蛋白和某些酶）上的缠绕而导致的双链 DNA 扭曲变化的分析。在这种情况下，DNA 的链轴扭曲分为两个独立的部分。第一项由局部参考系的扭曲产生，第二项由任一股线围绕在局部参考系中测量的双工轴的旋转产生。例如，核小体缠绕引起的扭曲变化是由核小体轴（一条直线）绕 DNA 轴的扭曲加上 DNA 的任一链绕其在圆柱体参考系中的轴的旋转引起的。
The twist is a fundamental geometric property of nucleic acids. Calculation of the twist in the most general case requires detailed specification of the three-dimensional path of each strand, but many important cases may be analyzed by considering only the twist difference. If C1, C2, and C3 are three distinct space curves, the twist difference about C1 is defined as Tw(C3, C1) - Tw(C2, C1). We show here that this difference measures the rotation of the correspondence surface joining C1 to C2 about the correspondence surface joining C1 to C3. This result has application to DNA containing local nonuniformities, such as denatured regions, cruciforms, and other altered structures. It also facilitates the calculation of twist for three-stranded structures, including D-loops in mitochondrial DNA and replication and transcription intermediates. The twist difference may also be used to simplify greatly the analysis of twist changes in duplex DNA due to winding on surfaces, such as histones and certain enzymes. In such cases the strand-axis twist of DNA divides into two independent terms. The first term arises from the twist of the local reference frame, and the second arises from the rotation of either strand about the duplex axis as measured in the local reference frame. Twist changes consequent to nucleosome winding, for example, arise from the twist of the nucleosome axis, a straight line, about the DNA axis plus the rotation of either strand of the DNA about its axis in the reference frame of the cylinder.