title: Mg(II) and Ni(II) induce aggregation of poly(rA)poly(rU) to either tetra-aggregate or triplex depending on the metal ion concentration.
abstract: The ability of magnesium(II) and nickel(II) to induce dramatic conformational changes in the synthetic RNA poly(rA)poly(rU) has been investigated. Kinetic experiments, spectrofluorometric titrations, melting experiments and DSC measurements contribute in shedding light on a complex behaviour where the action of metal ions (Na(+), Mg(2+), Ni(2+)), in synergism with other operators as the intercalating dye coralyne and temperature, all concur in stabilising a peculiar RNA form. Mg(2+) and Ni(2+) (M) bind rapidly and almost quantitatively to the duplex (AU) to give a RNA/metal ion complex (AUM). Then, by the union of two AUM units, an unstable tetra-aggregate (UAUA(M2)*) is formed which, in the presence of a relatively modest excess of metal, evolves to the UAUM triplex by releasing a single AM strand. On the other hand, under conditions of high metal content, the UAUA(M2)* intermediate rearranges to give a more stable tetra-aggregate (UAUA(M2)). As concerns the role of coralyne (D), it is found that D strongly interacts with UAUA(M2). Also, in the presence of coralyne, the ability of divalent ions to promote the transition of AUD into UAUD is enhanced, according to the efficiency sequence [Ni(2+)]≫[Mg(2+)]≫[Na(+)].
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Moruzzi 13, 56124 Pisa, Italy. Electronic address: tarita.biver@unipi.it.
authors.forename: Tarita
authors.initials: T
authors.lastname: Biver
authors.affiliation: Departamento de Química, Universidad de Burgos, Plaza Misael Bañuelos s/n, 09001 Burgos, Spain.
authors.forename: Natalia
authors.initials: N
authors.lastname: Busto
authors.affiliation: Departamento de Química, Universidad de Burgos, Plaza Misael Bañuelos s/n, 09001 Burgos, Spain.
authors.forename: Begoña
authors.initials: B
authors.lastname: García
authors.affiliation: Departamento de Química, Universidad de Burgos, Plaza Misael Bañuelos s/n, 09001 Burgos, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Leal
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Moruzzi 13, 56124 Pisa, Italy.
authors.forename: Luisa
authors.initials: L
authors.lastname: Menichetti
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Moruzzi 13, 56124 Pisa, Italy.
authors.forename: Fernando
authors.initials: F
authors.lastname: Secco
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Moruzzi 13, 56124 Pisa, Italy.
authors.forename: Marcella
authors.initials: M
authors.lastname: Venturini
mesh_terms: D001600:Berberine Alkaloids / Q000737:chemistry; D002942:Circular Dichroism; D007477:Ions; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry* / Q000494:pharmacology; D009532:Nickel / Q000737:chemistry* / Q000494:pharmacology; D011061:Poly A / Q000737:chemistry*; D011072:Poly U / Q000737:chemistry*; D012313:RNA / Q000737:chemistry*
chemical_list: D001600:Berberine Alkaloids; D007477:Ions; D011061:Poly A; D011072:Poly U; D012313:RNA; C000666:coralyne; D009532:Nickel; D008274:Magnesium
keywords: Disproportionation; Non-canonical structure; Quadruplex; RNA; Stabilisation