6-氧代胞苷：一种用于稳定三链螺旋形成的新型质子化C碱基类似物。
6-Oxocytidine a novel protonated C-base analogue for stable triple helix formation.
作者信息
Berressem R, Engels J W
机构信息
Johann Wolfgang Goethe-Universität Frankfurt am Main, Institut für Organische Chemie, Germany.
出版信息
Nucleic Acids Res. 1995 Sep 11;23(17):3465-72. doi: 10.1093/nar/23.17.3465.
2'-O-Methyl-3'-O-phosphoramidite building blocks of 6-oxocytidine 6 and its 5-methyl derivative 7, respectively, were synthesized and incorporated via phosphoramidite chemistry in 15 mer oligodeoxynucleotides [d(T72T7), S2; d(T73T7), S3] to obtain potential Py.Pu.Py triplex forming homopyrimidine strands. UV thermal denaturation studies and CD spectroscopy of 1:1 mixtures of these oligomers and a 21 mer target duplex [d(C3A7GA7C3)-d(G3T7CT7G3), D1] with a complementary purine tract showed a nearly pH-independent (6.0-8.0) triple helix formation with melting temperatures of 21-19 degrees C and 18.5-17.5 degrees C, respectively (buffer system: 50 mM sodium cacodylate, 100 mM NaCl, 20 mM MgCl2). In contrast, with the corresponding 15mer deoxy-C-containing oligonucleotide [d(T(7)1T7), S1] triplex formation was observed only below pH 6.6. Specificity for the recognition of Watson-Crick GC-base pairs was observed by pairing the modified C-bases of the 15mers with all other possible Watson-Crick-base compositions in the target duplex [d(C3A7XA7C3)-d(G3T7YT7G3), X = A,C,T; Y = T,G,A, D2-4]. Additionally, the Watson-Crick-pairing of the modified oligomers S2 and S3 was studied.
分别合成了6 - 氧代胞苷6及其5 - 甲基衍生物7的2'-O - 甲基 - 3'-O - 亚磷酰胺砌块，并通过亚磷酰胺化学法将其掺入15聚体寡脱氧核苷酸[d(T72T7)，S2；d(T73T7)，S3]中，以获得潜在的Py.Pu.Py三链体形成同型嘧啶链。对这些寡聚物与具有互补嘌呤序列的21聚体靶双链体[d(C3A7GA7C3)-d(G3T7CT7G3)，D1]的1:1混合物进行紫外热变性研究和圆二色光谱分析，结果表明形成了几乎与pH无关(6.0 - 8.0)的三链体，解链温度分别为21 - 19℃和18.5 - 17.5℃(缓冲体系：50 mM 二甲胂酸钠，100 mM NaCl，20 mM MgCl2)。相比之下，对于相应的含15聚体脱氧C的寡核苷酸[d(T(7)1T7)，S1]，仅在pH 6.6以下观察到三链体形成。通过将15聚体的修饰C碱基与靶双链体[d(C3A7XA7C3)-d(G3T7YT7G3)，X = A、C、T；Y = T、G、A，D2 - 4]中所有其他可能的沃森 - 克里克碱基组成配对，观察到对沃森 - 克里克GC碱基对识别的特异性。此外，还研究了修饰寡聚物S2和S3的沃森 - 克里克配对。
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