Kabsch W, Sander C, Trifonov E N
Nucleic Acids Res. 1982 Feb 11;10(3):1097-104. doi: 10.1093/nar/10.3.1097.
On the assumption that the twist angles between adjacent base-pairs in the DNA molecule are additive a linear system of 40 equations was derived from experimental measurements of the total twist angles for different pieces of DNA of known sequences. This system of equations is found to be statistically consistent providing a solution for all ten possible twist angles of B-DNA by a least squares fitting procedure. Four of the calculated twist angles were not known before (tau AC, tau AG, tau CA, tau TA). The other six twist angles calculated are very close to the experimentally measured ones (tau AA, tau AT, tau CC, tau OG, tau GA, tau GC). The data used were obtained by the electrophoretic band-shift method (1-3), crystallography (4) and nuclease digestion of DNA adsorbed to mica or Ca-phosphate surface (5,6). The validity of the principle of additivity of the twist angles implies that the angle between any particular two base-pairs is a function of only these base-pairs, independent of nearest neighbours.
基于DNA分子中相邻碱基对之间的扭转角具有可加性这一假设，通过对已知序列的不同DNA片段的总扭转角进行实验测量，推导出了一个由40个方程组成的线性系统。通过最小二乘法拟合程序，发现该方程组在统计上是一致的，从而为B-DNA的所有十个可能的扭转角提供了解决方案。其中四个计算出的扭转角（tau AC、tau AG、tau CA、tau TA）此前并不为人所知。计算出的其他六个扭转角（tau AA、tau AT、tau CC、tau OG、tau GA、tau GC）与实验测量值非常接近。所使用的数据是通过电泳带移法（1 - 3）、晶体学（4）以及对吸附在云母或磷酸钙表面的DNA进行核酸酶消化（5,6）获得的。扭转角可加性原理的有效性意味着任何特定两个碱基对之间的角度仅是这两个碱基对的函数，与相邻碱基对无关。
