title: Assembly of supramolecular DNA complexes containing both G-quadruplexes and i-motifs by enhancing the G-repeat-bearing capacity of i-motifs.
abstract: The single-step assembly of supramolecular complexes containing both i-motifs and G-quadruplexes (G4s) is demonstrated. This can be achieved because the formation of four-stranded i-motifs appears to be little affected by certain terminal residues: a five-cytosine tetrameric i-motif can bear ten-base flanking residues. However, things become complex when different lengths of guanine-repeats are added at the 3' or 5' ends of the cytosine-repeats. Here, a series of oligomers d(XGiXC5X) and d(XC5XGiX) (X = A, T or none; i < 5) are designed to study the impact of G-repeats on the formation of tetrameric i-motifs. Our data demonstrate that tetramolecular i-motif structure can tolerate specific flanking G-repeats. Assemblies of these oligonucleotides are polymorphic, but may be controlled by solution pH and counter ion species. Importantly, we find that the sequences d(TGiAC5) can form the tetrameric i-motif in large quantities. This leads to the design of two oligonucleotides d(TG4AC7) and d(TGBrGGBrGAC7) that self-assemble to form quadruplex supramolecules under certain conditions. d(TG4AC7) forms supramolecules under acidic conditions in the presence of K+that are mainly V-shaped or ring-like containing parallel G4s and antiparallel i-motifs. d(TGBrGGBrGAC7) forms long linear quadruplex wires under acidic conditions in the presence of Na+that consist of both antiparallel G4s and i-motifs.
authors.affiliation: College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China.
authors.forename: Yanwei
authors.initials: Y
authors.lastname: Cao
authors.affiliation: College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China.
authors.forename: Shang
authors.initials: S
authors.lastname: Gao
authors.affiliation: College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China.
authors.forename: Yuting
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Department of Chemistry & Biochemistry, University of the Sciences, 600 South 43rd Street, Philadelphia, PA 19104, USA m.bruist@usciences.edu.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Bruist
authors.affiliation: College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China.
authors.forename: Bing
authors.initials: B
authors.lastname: Wang
authors.affiliation: College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China guoxh@jlu.edu.cn.
authors.forename: Xinhua
authors.initials: X
authors.lastname: Guo
mesh_terms: D020029:Base Pairing; D002414:Cations, Monovalent; D004247:DNA / Q000737:chemistry*; D054856:G-Quadruplexes; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D059372:Nucleotide Motifs; D009841:Oligonucleotides / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D002414:Cations, Monovalent; D009841:Oligonucleotides; D004247:DNA; D012964:Sodium