title: 8-methyl-2'-deoxyguanosine incorporation into parallel DNA quadruplex structures.
abstract: This paper concerns the Circular Dichroism (CD) and Nuclear Magnetic Resonance (NMR) structural studies of the quadruple helix arrangements adopted by three tailored oligodeoxyribonucleotide analogues, namely d(TG(Me)GGT), d(TGG(Me)GT) and d(TGGG(Me)T), where dG(Me) represents a 8-methyl-2'-deoxyguanosine residue. The results of this study clearly demonstrate that the effects of the incorporation of dG(Me) instead of a dG residue are strongly dependant upon the positioning of a single base replacement along the sequence. As such, d(TG(Me)GGT), d(TGG(Me)GT) have been found to form 4-fold symmetric quadruplexes with all strands parallel and equivalent to each other, each more stable than their natural counterpart. NMR experiments clearly indicate that [d(TG(Me)GGT)]4 possesses a G(Me)-tetrad with all dG(Me) residues in a syn-glycosidic conformation while an anti-arrangement is apparent for the four dG(Me) of [d(TGG(Me)GT)]4. As the two complexes show a quite different CD behaviour, a possible relationship between the presence of residues adopting syn-glycosidic conformations and CD profiles is briefly discussed. As far as d(TGGG(Me)T) is concerned, NMR data indicate that at 25 degrees C it exists primarily as a single-strand conformation in equilibrium with minor amounts of a quadruplex structure.
authors.affiliation: Dipartimento di Chimica delle Sostanze Naturali, Università degli Studi di Napoli Federico II, via D. Montesano 49, I-80131 Napoli, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Virgilio
authors.forename: Veronica
authors.initials: V
authors.lastname: Esposito
authors.forename: Antonio
authors.initials: A
authors.lastname: Randazzo
authors.forename: Luciano
authors.initials: L
authors.lastname: Mayol
authors.forename: Aldo
authors.initials: A
authors.lastname: Galeone
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000737:chemistry; D054856:G-Quadruplexes; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D009691:Nucleic Acid Denaturation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011522:Protons
chemical_list: C104538:8-methyl-2'-deoxyguanosine; D009838:Oligodeoxyribonucleotides; D011522:Protons; D004247:DNA; D003849:Deoxyguanosine