Zhang Xiao-Yan, Cao En-Hua, Zhang Yan, Chou Chunqing, Bai Chunli
Centre for Molecular Biology, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, P. R. China.
J Biomol Struct Dyn. 2003 Apr;20(5):693-702. doi: 10.1080/07391102.2003.10506886.
The telomeric DNA oligomers, d(TTAGGG)(n), where n=1, 2, 4, could self-associate into the multi-stranded structures in appropriate condition, exhibited different CD spectra. The presense of Na(+) was more advantage to facilitate the formation of anti-parallel conformation, but the presense of K(+) enhanced their thermal stability. Spectroscopic analysis of 3, 3'-diethyloxadicarbocyanine (DODC) showed the formation of hairpin quadruplex structures for d(TTAGGG)(2) and d(TTAGGG)(4), but d(TTAGGG) could not. The four-stranded tetraplexes and branched nanowire formed in the presense of K(+) or Na(+) alone were observed by atomic force microscopy (AFM). The ability of d(TTAGGG)(n) to self-assemble into four-stranded tetraplexes and nanowires depends strongly on the number of repeating units and ionic environment. A model to explain how these structures formed is proposed.
端粒DNA寡聚物d(TTAGGG)(n)（其中n = 1、2、4）在适当条件下可自组装成多链结构，呈现出不同的圆二色光谱。Na(+)的存在更有利于促进反平行构象的形成，但K(+)的存在增强了它们的热稳定性。对3,3'-二乙基恶二碳菁（DODC）的光谱分析表明，d(TTAGGG)(2)和d(TTAGGG)(4)形成了发夹四重结构，但d(TTAGGG)则不能。通过原子力显微镜（AFM）观察到，单独存在K(+)或Na(+)时会形成四链四重结构和分支纳米线。d(TTAGGG)(n)自组装成四链四重结构和纳米线的能力在很大程度上取决于重复单元的数量和离子环境。本文提出了一个解释这些结构如何形成的模型。
