title: K+ and Na+-induced self-assembly of telomeric oligonucleotide d(TTAGGG)n.
abstract: 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.
authors.affiliation: Centre for Molecular Biology, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, P. R. China.
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Zhang
authors.forename: En-Hua
authors.initials: EH
authors.lastname: Cao
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Chunqing
authors.initials: C
authors.lastname: Chou
authors.forename: Chunli
authors.initials: C
authors.lastname: Bai
mesh_terms: D002414:Cations, Monovalent / Q000737:chemistry; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D054856:G-Quadruplexes; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D009841:Oligonucleotides / Q000737:chemistry; D011188:Potassium / Q000494:pharmacology*; D012964:Sodium / Q000494:pharmacology*; D020080:Tandem Repeat Sequences; D016615:Telomere / Q000737:chemistry*
chemical_list: D002414:Cations, Monovalent; D009841:Oligonucleotides; D004247:DNA; D012964:Sodium; D011188:Potassium