Interaction of the Alternating Double Stranded Copolymer poly(dA-dT)·poly(dA-dT) with NiCl₂and CdCl₂2: Solution Behavior

Abstract

The thermal denaturation of the synthetic high molecular weight double stranded polynucleotide poly(dA-dT) x poly(dA-dT) has been studied in aqueous buffered solution (Tris 1.0 mM; pH 7.8+/-0.2) in the presence of increasing concentrations of either Ni(2+) (borderline cation) or Cd(2+) (soft cation) at four different constant ionic strength values (NaCl), making use of UV and circular dichroism (CD) spectroscopies. The experimental results show that the B-type double helix of the polymer is stabilized against thermal denaturation in the presence of both cations at low concentrations, relative to the systems where only NaCl is present, in the same conditions of ionic strength and pH. The effect is more pronounced for Ni(2+) than for Cd(2+). At higher concentrations, both cations start to destabilize the double helix, with Cd cations inducing larger variations of T(m). In many cases, when denaturation starts, interstrand cross-linking occurs with formation of aggregates that precipitate.

Circular dichroism of polynucleotides: Interactions of NiCl2 with poly(dA‐dT)·poly(dA‐dT) and poly(dG‐dC)·poly(dG‐dC) in a water‐in‐oil microemulsion

“…The effects of NiCl 2 on the thermal stability of polyAT in aqueous solution 35 are consistent with the borderline nature of the metal, i.e. a stabilization is observed at low concentrations due to preferential binding of the metal cations to the phosphate groups, while destabilization and formation of aggregates occurs at high concentrations.…”

“…55 Scattering at k >300 nm, ascribable to sedimentation of aggregates 14,15,35,56,57 was never observed.…”

“…The melting temperature of the double helix to random coil transition increases with ionic strength at constant NiCl 2 concentration and decreases with Ni(II) concentration at constant ionic strength. 35 Poly-GC, instead, exhibits a B-to Z-conformational transition induced by NiCl 2 , requiring increasing nickel concentrations at increasing ionic strength. 36 The model, high molecular weight polynucleotide duplexes polyAT and polyGC were solubilized in the quaternary cationic w/o microemulsion CTAB|n-hexane|n-pentanol|water in the presence of increasing amounts of NiCl 2 and at several ionic strength values and their thermal behavior was studied by means of circular dichroism and electronic absorption spectroscopies.…”

The CdCl2 effects on synthetic DNAs encaged in the nanodomains of a cationic water-in-oil microemulsion

“…5 The conformational behaviour and thermal stability of the model polynucleotide duplex poly(dA-dT)Ápoly(dA-dT), from now on polyAT, in the presence of increasing amounts of NiCl 2 in a large range of ionic strength values, has been shown to be very different in the cationic w/o microemulsion CTAB/pentanol/hexane/water and in the matched aqueous solutions. 10,28 In solution, at constant ionic strength, increasing concentrations of the metal reduce progressively the thermal a Dipartimento di Chimica ''S. Cannizzaro'', Universita`di Palermo, Viale delle Scienze, Parco d'Orleans, Pad.…”

Effect of Ni2+ and Cd2+ ions on thermally induced conformational transitions in poly(dA)-poly(dT) system

“…However, only limited data are available for polydeoxynucleotide systems. In particular such data are available for alternating double-stranded copolymer poly(dA-dT)Ápoly(dA-dT) (Airoldi et al 2007). Whereas the effect of Ni 2?…”