Uesugi S, Lee B L, Ikehara M, Kobayashi Y, Kyogoku Y
Faculty of Pharmaceutical Sciences Osaka University, Japan.
J Biomol Struct Dyn. 1985 Oct;3(2):339-47. doi: 10.1080/07391102.1985.10508421.
It has been shown by us that oligonucleotides containing cyclonucleosides with a high anti glycosidic conformation take left-handed, single and double helical structures (S. Uesugi, J. Yano, E. Yano and M. Ikehara, J. Am. Chem. Soc. 99,2313 (1977) and references therein). In order to see whether DNA can adopt the high anti left-handed double helical structure or not, a self-complementary hexanucleotide containing 6,2'-O-cyclocytidine (C 0). 8,2'-O-cycloguanosine (G 0), deoxycytidine and deoxyguanosine, C 0 G 0 dCdGC 0 G 0, was synthesized. Corresponding hexanucleotide containing only cyclonucleosides, C 0 G 0 C 0 G 0 C 0 G 0, was also synthesized. Their conformation was examined by UV, CD and 1H NMR spectroscopy. C 0 G 0 C 0 G 0 C 0 G 0 forms an unusually stable, left-handed duplex. Imino proton NMR spectra and the results of nuclear Overhauser effect experiments strongly suggest that C 0 G 0 dCdGC0 G 0 take a left-handed double helical structure where the deoxynucleoside residues are involved in hydrogen bonding and take a high anti glycosidic conformation. Thus it is revealed that DNA could form a high anti, left-handed double helix which is different from that of Z-DNA under some constrained conditions.
我们已经证明，含有具有高反糖苷构象的环核苷的寡核苷酸会形成左手单链和双链螺旋结构（上杉修、矢野纯、矢野荣子和池原敏，《美国化学会志》99, 2313 (1977) 及其参考文献）。为了探究DNA是否能够采取高反左手双链螺旋结构，合成了一种含有6,2'-O-环胞苷（C₀）、8,2'-O-环鸟苷（G₀）、脱氧胞苷和脱氧鸟苷的自互补六核苷酸，即C₀G₀dCdGC₀G₀。还合成了仅含有环核苷的相应六核苷酸C₀G₀C₀G₀C₀G₀。通过紫外光谱、圆二色光谱和¹H核磁共振光谱对它们的构象进行了检测。C₀G₀C₀G₀C₀G₀形成了一种异常稳定的左手双链体。亚氨基质子核磁共振光谱以及核Overhauser效应实验结果强烈表明，C₀G₀dCdGC₀G₀采取左手双链螺旋结构，其中脱氧核苷残基参与氢键形成并采取高反糖苷构象。因此揭示出，在某些受限条件下，DNA能够形成一种与Z-DNA不同的高反左手双螺旋结构。
