Wang A H, Hakoshima T, van der Marel G, van Boom J H, Rich A
Cell. 1984 May;37(1):321-31. doi: 10.1016/0092-8674(84)90328-3.
Two hexanucleoside pentaphosphates , 5-methyl and 5-bromo cytosine derivatives of d( CpGpTpApCpG ) have been synthesized, crystallized, and their three-dimensional structure solved. They both form left-handed Z-DNA and the methylated derivative has been refined to 1.2 A resolution. These are the first crystal Z-DNA structures that contain AT base pairs. The overall form of the molecule is very similar to that of the unmethylated or the fully methylated (dC-dG)3 hexamer although there are slight changes in base stacking. However, significant differences are found in the hydration of the helical groove. When GC base pairs are present, the helical groove is systematically filled with two water molecules per base pair hydrogen bonded to the bases. Both of these water molecules are not seen in the electron density map in the segments of the helix containing AT base pairs, probably because of solvent disorder. This could be one of the features that makes AT base pairs form Z-DNA less readily than GC base pairs.
已合成、结晶了两种六核苷五磷酸，即d（CpGpTpApCpG）的5-甲基和5-溴胞嘧啶衍生物，并解析了它们的三维结构。它们都形成左手Z-DNA，且甲基化衍生物已精修至1.2埃分辨率。这些是首批包含AT碱基对的晶体Z-DNA结构。尽管碱基堆积略有变化，但分子的整体形态与未甲基化或完全甲基化的（dC-dG）3六聚体非常相似。然而，在螺旋沟的水合作用方面发现了显著差异。当存在GC碱基对时，螺旋沟中每个碱基对会系统地填充两个与碱基形成氢键的水分子。在含有AT碱基对的螺旋片段的电子密度图中未观察到这两个水分子，可能是由于溶剂无序。这可能是使AT碱基对比GC碱基对更难形成Z-DNA的特征之一。
