title: Characterization of parallel and antiparallel G-tetraplex structures by vibrational spectroscopy.
abstract: A series of G-rich oligonucleotides able to form tetraplexes has been studied by FTIR spectroscopy. Characteristic markers of the formation of guanine tetrads are given. Moreover, we propose a new marker discriminating between parallel and antiparallel tetraplexes: the position of the C6O6 guanine carbonyl stretching vibration. In intermolecular parallel tetrameric structures formed by four separate strands this absorption is observed at 1693 cm-1 while for antiparallel tetrameric structures, either intramolecular or formed by dimerization of hairpins, this vibrational mode is observed at 1682 cm-1. These shifts to higher wavenumbers, when compared to the position of a free guanine C6O6 carbonyl stretching vibration observed at 1666 cm-1(Deltanu=27 cm-1 for parallel tetraplexes and Deltanu=16 cm-1 for antiparallel tetraplexes) reflect different strand orientations in the structures. This marker has been used to evidence the possibility of an antiparallel-parallel tetraplex reorganization for Oxytricha nova d(G4T4G4) and d((G4T4)3G4) and human d(G3T2AG3) telomeric sequences induced by Na+/K+ or Na+/Ca2+ ion exchange. Formation of the guanine tetrads, characterization of the phosphate geometries and of the sugar conformations have also been obtained by FTIR for the different tetraplexes.
authors.affiliation: Laboratoire BioMoCeTi, UMR CNRS 7033, Université Paris 13, 74, rue Marcel Cachin, F93017 Bobigny Cedex, France.
authors.forename: M Romero
authors.initials: MR
authors.lastname: Guzmán
authors.forename: J
authors.initials: J
authors.lastname: Liquier
authors.forename: S K
authors.initials: SK
authors.lastname: Brahmachari
authors.forename: E
authors.initials: E
authors.lastname: Taillandier
mesh_terms: D000818:Animals; D002236:Carbohydrate Conformation; D004247:DNA / Q000737:chemistry*; D016054:DNA, Protozoan / Q000737:chemistry; D017666:Deuterium Oxide / Q000737:chemistry; D054856:G-Quadruplexes; D006147:Guanine / Q000737:chemistry*; D006801:Humans; D006860:Hydrogen Bonding; D009690:Nucleic Acid Conformation; D016813:Oxytricha; D010710:Phosphates / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D016615:Telomere / Q000235:genetics; D014732:Vibration
chemical_list: D016054:DNA, Protozoan; D010710:Phosphates; D006147:Guanine; D004247:DNA; D017666:Deuterium Oxide