Dhingra M M, Sarma R H, Uesugi S, Shida T, Ikehara M
Biochemistry. 1981 Aug 18;20(17):5002-11. doi: 10.1021/bi00520a029.
The conformational properties of purine-pyrimidine and pyrimidine-purine dinucleoside monophosphates in which the glycosidic torsion is fixed to congruent to 120 degree by the formation of a covalent link between the base and the sugar ring are explored by 1H NMR spectroscopy in order to obtain information about the spatial configuration of high anti nucleic acids. The intramolecular stack of the high anti dimers were found to be left handed, in contrast to that (right handed) for natural oligomers, which are low anti. Even though both the high anti pyrimidine-purine and purine-pyrimidine dimers have similar backbone torsion angles, they display widely different relative geometry between the bases; thus in the former there is extensive base-base overlap in the stack, and in the latter there is negligible intramolecular base-base overlap. In addition it was found that purine-pyrimidine systems form miniature double helices in which there is substantial interstrand purine-purine interaction; on the other hand the pyridine-purine high anti dinucleosides have no proclivity to form such base-paired complexes in solution. Mathematical polymerization of the conformation of the high anti purine-pyrimidine dinucleoside monophosphates generates a left handed helix for high anti polynucleotides. This also means that the double helix for high anti-nucleic acids containing purine-pyrimidine repeated units may also be left handed, as had been suggested [Sundaralingam, M., & Yathindra, N. (1977) Int. J. Quantum Chem., Quantum Biol. Symp. 4, 285]. It is suggested that the plasticity in the structure of genomic DNA is such that, if under certain conditions of interactions the sugar-base torsion of certain domains assume high anti values, that domain will become left handed, and this in turn can be a mechanism for the control of expression by genomic DNA.
通过¹H NMR光谱研究嘌呤 - 嘧啶和嘧啶 - 嘌呤二核苷单磷酸的构象性质，其中糖苷扭转通过碱基与糖环之间形成共价键固定在约120度，以获取有关高反式核酸空间构型的信息。发现高反式二聚体的分子内堆积是左手螺旋，这与天然低反式寡聚体的右手螺旋相反。尽管高反式嘧啶 - 嘌呤和嘌呤 - 嘧啶二聚体具有相似的主链扭转角，但它们在碱基之间显示出广泛不同的相对几何形状；因此，在前者中堆积有广泛的碱基 - 碱基重叠，而在后者中分子内碱基 - 碱基重叠可忽略不计。此外，发现嘌呤 - 嘧啶系统形成微型双螺旋，其中存在大量链间嘌呤 - 嘌呤相互作用；另一方面，吡啶 - 嘌呤高反式二核苷在溶液中没有形成这种碱基配对复合物的倾向。高反式嘌呤 - 嘧啶二核苷单磷酸构象的数学聚合产生高反式多核苷酸的左手螺旋。这也意味着含有嘌呤 - 嘧啶重复单元的高反式核酸的双螺旋也可能是左手螺旋，正如之前所建议的那样 [Sundaralingam, M., & Yathindra, N. (1977) Int. J. Quantum Chem., Quantum Biol. Symp. 4, 285]。有人提出，基因组DNA结构的可塑性在于，如果在某些相互作用条件下某些结构域的糖 - 碱基扭转呈现高反式值，该结构域将变为左手螺旋，这反过来可能是基因组DNA控制表达的一种机制。
