title: d(G3T4G3) forms an asymmetric diagonally looped dimeric quadruplex with guanosine 5'-syn-syn-anti and 5'-syn-anti-anti N-glycosidic conformations.
abstract: The structure formed by the DNA oligonucleotide d(G3T4G3) has been studied by one- and two-dimensional 1H NMR spectroscopy. In NaCl solution, d(G3T4G3), like d(G4T4G4) (Oxy-1.5), forms a dimeric quadruplex with the thymines in loops across the diagonal of the end quartets. Unlike Oxy-1.5, the dimer is not symmetric, and both monomer strands are observed in NMR spectra. Three quartets are formed from the GGG tracts. Glycosidic conformations of the guanines are 5'-syn-syn-anti-(loop)-syn-anti-anti in one strand and 5'-syn-anti-anti-(loop)-syn-syn-anti in the other strand. Thus, the stacking of the quartets (tail-to-tail, head-to-tail) is unlike all previously described fold-back (tail-to-tail, head-to-head) and parallel-stranded (head-to-tail, head-to-tail) quadruplexes.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles 90024.
authors.forename: F W
authors.initials: FW
authors.lastname: Smith
authors.forename: F W
authors.initials: FW
authors.lastname: Lau
authors.forename: J
authors.initials: J
authors.lastname: Feigon
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D006151:Guanosine; D006859:Hydrogen; D007536:Isomerism; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008961:Models, Structural; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides; D006151:Guanosine; D006859:Hydrogen; D004247:DNA