Fratini A V, Kopka M L, Drew H R, Dickerson R E
J Biol Chem. 1982 Dec 25;257(24):14686-707.
A double-helical B-DNA dodecamer has been analyzed by single crystal x-ray diffraction methods and refined independently in four variants: sequence CGCGAATTCGCG at 20 degrees C and at 16 K, and CGCGAATTBrCGCG in 60% methylpentanediol at 20 and at 7 degrees C. The first three forms show a 14-19 degrees bend in overall helix axis, but the fourth is straight and unbent. Detailed comparisons of the various forms have led to a better understanding of helix geometry and bending. Structural principles can be understood best if organized under four headings: 1) intrinsic geometry of the sugar rings, 2) stacking and relative motion of base pairs, 3) geometry of the connecting phosphate backbone, and 4) mechanics of bending in B-DNA. The observed bending is neither completely localized nor smooth and continuous, but an intermediate compromise that can be termed "annealed kinking."
通过单晶X射线衍射方法对一个双链螺旋B - DNA十二聚体进行了分析，并在四种变体中独立进行了精修：序列为CGCGAATTCGCG，温度分别为20℃和16K；以及序列为CGCGAATTBrCGCG，处于60%甲基戊二醇中，温度分别为20℃和7℃。前三种形式在整体螺旋轴上显示出14 - 19度的弯曲，但第四种是直的且未弯曲。对各种形式的详细比较有助于更好地理解螺旋几何结构和弯曲情况。如果按照四个标题进行组织，结构原理能得到最好的理解：1）糖环的固有几何结构，2）碱基对的堆积和相对运动，3）连接磷酸主链的几何结构，以及4）B - DNA中弯曲的力学原理。观察到的弯曲既不是完全局部化的，也不是平滑连续的，而是一种可称为“退火扭结”的中间折衷情况。
