Leitner D, Weisz K
Institut für Chemie der Freien Universität Berlin, Germany.
J Biomol Struct Dyn. 2000 Jun;17(6):993-1000. doi: 10.1080/07391102.2000.10506587.
A set of 21 oligodeoxynucleotides were designed to fold into intramolecular triple helices of the pyrimidine motif under appropriate conditions. UV melting experiments on the triplexes which only differ in the number and distribution of third strand cytosines reveal the influence of sequence and pH on triplex stability and can be summarized as follows: (1) increasing the cytosine content in the third strand results in a higher thermal stability of the triplex at acidic pH but lowers the triplex to duplex melting temperature at neutral pH; (2) cytosines at terminal positions destabilize the triple helical structure as compared to non-terminal positions; (3) contiguous cytosines lead to a pH dependent destabilization of the triplex, the destabilizing effect being more pronounced at higher pH. Analysis of these effects in terms of the various interactions within a triple helical complex indicate that the sequence-dependent stabilities are largely determined by the extent of protonation for individual third strand cytosines.
设计了一组21个寡脱氧核苷酸，使其在适当条件下折叠成嘧啶基序的分子内三链螺旋。对仅在第三条链胞嘧啶的数量和分布上有所不同的三链体进行的紫外熔解实验揭示了序列和pH对三链体稳定性的影响，可总结如下：（1）增加第三条链中的胞嘧啶含量会导致三链体在酸性pH下具有更高的热稳定性，但会降低中性pH下三链体向双链体的熔解温度；（2）与非末端位置相比，末端位置的胞嘧啶会使三链螺旋结构不稳定；（3）连续的胞嘧啶会导致三链体的pH依赖性不稳定，在较高pH下这种不稳定作用更为明显。根据三链螺旋复合物内的各种相互作用对这些影响进行分析表明，序列依赖性稳定性在很大程度上由单个第三条链胞嘧啶的质子化程度决定。
