title: Molecular modeling studies of a parallel stranded quadruplexes containing a 8-bromoadenosine.
abstract: Truncated sequences of human telomeric DNA can readily assemble to form parallel stranded quadruplexes containing A- and G-tetrads. The formation of an A-tetrad is highly context-dependent and the relationship between the formation of an A-tetrad and the glycosidic torsion angle of the adenosine residues implicated has not been completely clarified so far. In order to give a further insight in this issue we synthesized the modified oligomers d(ABrGGGT) and d(TABrGGGT), two different truncations of the human telomeric sequence containing a 8-bromoadenosine residue, named ABr. NMR data show that both the modified oligomers are able to perfectly fold into highly symmetric quadruplexes with all strands parallel to each other. Molecular modeling studies were performed on both [d(ABrGGGT)]4 and [d(TABrGGGT)]4, indicating that a bulky substituent, such as a bromine atom at the C8 position of adenines, can force the glycosidic bond to adopt a syn conformation, stabilizing the resulting quadruplexes.
authors.affiliation: Dipartimento di Chimica delle Sostanze Naturali, Università degli Studi di Napoli Federico II, Napoli, Italy.
authors.forename: Veronica
authors.initials: V
authors.lastname: Esposito
authors.forename: Antonio
authors.initials: A
authors.lastname: Randazzo
authors.forename: Luigi
authors.initials: L
authors.lastname: Petraccone
authors.forename: Concetta
authors.initials: C
authors.lastname: Giancola
authors.forename: Eva
authors.initials: E
authors.lastname: Erra
authors.forename: Antonella
authors.initials: A
authors.lastname: Virgilio
authors.forename: Luciano
authors.initials: L
authors.lastname: Mayol
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000737:chemistry; D006026:Glycoside Hydrolases / Q000737:chemistry; D006027:Glycosides / Q000737:chemistry; D006801:Humans; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D008967:Molecular Biology / Q000379:methods*; D008968:Molecular Conformation; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D016615:Telomere / Q000737:chemistry / Q000648:ultrastructure; D013696:Temperature
chemical_list: D006027:Glycosides; C036038:8-bromoadenosine; D006026:Glycoside Hydrolases; D000241:Adenosine