title: Parallel and antiparallel triple helices with G, A-containing third strands.
abstract: A triple helix, formed by a 13 nucleotide (nt) all-purine oligonucleotide, containing six contiguous guanines, oriented parallel to a homopurine strand present in the polypurine tract of Friend leukemia virus, was obtained in 0.1 M LiCl. Its dissociation constant at 25 degrees C, given by electrophoretic titration, of the order of 50 nM, is at least ten times lower than that of the corresponding antiparallel triplex formed on the same target. At 4 degrees C, the parallel orientation of the homopurine strands is favored to the point that the guanine block of 6 nt, present in the 'antiparallel' oligonucleotide, attaches in a parallel fashion to the corresponding block in the target strand, to generate a partial, parallel triplex, that coexists with the antiparallel one.
authors.affiliation: Laboratoire de Spectroscopie Biomoléculaire, UPRESA CNRS 7031, Université Paris-Nord, Bobigny, France. porumb@infobiogen.fr
authors.forename: H
authors.initials: H
authors.lastname: Porumb
authors.forename: H
authors.initials: H
authors.lastname: Gousset
authors.forename: E
authors.initials: E
authors.lastname: Taillandier
mesh_terms: D000225:Adenine; D000818:Animals; D004279:DNA, Viral; D005622:Friend murine leukemia virus / Q000235:genetics*; D006147:Guanine; D051379:Mice; D009838:Oligodeoxyribonucleotides; D011687:Purines
chemical_list: D004279:DNA, Viral; D009838:Oligodeoxyribonucleotides; D011687:Purines; D006147:Guanine; D000225:Adenine