title: Tetraplex formation of d(GGGGGTTTTT): 1H NMR study in solution.
abstract: The oligonucleotide d(G5T5) can in principle form a fully matched duplex with G.T pairing and/or a tetraplex. Non-denaturing gel electrophoresis, circular dichroism and NMR experiments show that the tetraplex is exclusively formed by this oligomer in solution. In the presence of its complementary strand d(A5C5) at low temperature, d(G5T5) forms the tetraplex over the normally expected Watson-Crick duplex. However, when d(G5T5) and d(A5C5) are mixed together in equimolar amounts and heated for several minutes at 85 degrees C, and then allowed to cool, the product was essentially the Watson-Crick duplex. The lack of resolution in the 500 MHz 1H NMR spectra and the presence of extensive spin diffusion do not allow us to derive a quantitative structure for the tetraplex from the NMR data. However, we find good qualitative agreement between the NOESY and MINSY data and a theoretically derived stereochemically sound structure in which the G's and T's are part of a parallel tetraplex.
authors.affiliation: Department of Chemistry, State University of New York, Albany 12222.
authors.forename: M H
authors.initials: MH
authors.lastname: Sarma
authors.forename: J
authors.initials: J
authors.lastname: Luo
authors.forename: K
authors.initials: K
authors.lastname: Umemoto
authors.forename: R D
authors.initials: RD
authors.lastname: Yuan
authors.forename: R H
authors.initials: RH
authors.lastname: Sarma
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry; D011522:Protons; D012996:Solutions; D013237:Stereoisomerism; D014961:X-Ray Diffraction
chemical_list: D009692:Nucleic Acid Heteroduplexes; D011522:Protons; D012996:Solutions; D004247:DNA