title: Effects of an 8-bromodeoxyguanosine incorporation on the parallel quadruplex structure [d(TGGGT)]4.
abstract: NMR, molecular dynamics and mechanics calculations, and CD spectroscopy were used to characterise three tetramolecular quadruplex complexes: [d(TG(Br)GGT)](4), [d(TGG(Br)GT)](4) and [d(TGGG(Br)T)](4), where G(Br) indicates an 8-bromoguanine residue. All three quadruplexes are characterised by a 4-fold symmetry with all strands parallel to each other and, differently to what has been observed for other parallel quadruplex structures, with a tetrad (formed by 8-Br-dGs) in a syn conformation. The whole of the data demonstrates that the replacement in turn of different dG residues with 8-Br-dG in the sequence 5[prime or minute]-TGGGT-3[prime or minute] affects the resulting structures in different ways, leading to different CD profiles and thermal stabilities. Particularly, [d(TG(Br)GGT)](4) and [d(TGG(Br)GT)](4) are more stable than the unmodified sequence, whereas [d(TGGG(Br)T)](4) is much less stable than the natural counterpart. The conformational features found in the three quadruplexes might, in principle, amplify the range of applicability of synthetic oligonucleotides as aptamers or catalysts, by providing novel structural motifs with different molecular recognition capabilities from those of native DNA sequences.
authors.affiliation: Dipartimento di Chimica delle Sostanze Naturali, Università degli Studi di Napoli "Federico II", via D. Montesano 49, I-80131 Napoli, Italy. mayoll@unina.it
authors.forename: Veronica
authors.initials: V
authors.lastname: Esposito
authors.forename: Antonio
authors.initials: A
authors.lastname: Randazzo
authors.forename: Gennaro
authors.initials: G
authors.lastname: Piccialli
authors.forename: Luigi
authors.initials: L
authors.lastname: Petraccone
authors.forename: Concetta
authors.initials: C
authors.lastname: Giancola
authors.forename: Luciano
authors.initials: L
authors.lastname: Mayol
mesh_terms: D001483:Base Sequence; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry* / Q000235:genetics*; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000737:chemistry*; D054856:G-Quadruplexes; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D013696:Temperature
chemical_list: C439365:8-bromo-2'-deoxyguanosine; D004247:DNA; D003849:Deoxyguanosine