title: Ammonium ion at low concentration stabilizes the G-quadruplex formation by telomeric sequence.
abstract: A synthetic analog of telomeric DNA, d(T6G16) or d(G4T2G4T2G4T2G4) was found to form G-quadruplex structure in NH4-ion environments as low as 1 mM. Other counter ions like K(I) or Sr(II) known to have a stabilizing effect on G-tetrad require much higher concentrations. The multiconformational form of G-tetrad could be identified in NH4(I) upon heating the sample up to 100 degrees C. Circular dichroism spectral studies indicated that on thermally treating the complex NH4(I) ion helps in intramolecular G-tetrad formation over intermolecular association. However the G-tetrad structure formed in NH4(I) was found to be unstable in the presence of intercalator Actinomycin D or Tb(III) ion. It appears that the ionic radius of NH4(I) influence tight fitting of this ion inside the cavity of the tetrad. The stability of G-tetrad in the presence of very low concentration of NH4(I) may have potential applications in future.
authors.affiliation: Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: N
authors.initials: N
authors.lastname: Nagesh
authors.forename: D
authors.initials: D
authors.lastname: Chatterji
mesh_terms: D004247:DNA / Q000187:drug effects / Q000235:genetics*; D003609:Dactinomycin / Q000494:pharmacology; D006358:Hot Temperature; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D016615:Telomere
chemical_list: D009838:Oligodeoxyribonucleotides; D000644:Quaternary Ammonium Compounds; D003609:Dactinomycin; D004247:DNA