Interaction of the alternating double stranded copolymer poly(dA-dT) x poly(dA-dT) with NiCl(2) and CdCl(2): solution behavior.
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.
Dipartimento di Chimica Inorganica e Analitica "Stanislao Cannizzaro", Universita di Palermo--Viale delle Scienze, Pad.17, 90128 Palermo, Italy.
Marta
M
Airoldi
Giuseppe
G
Gennaro
Marcello
M
Giomini
Anna Maria
AM
Giuliani
Mauro
M
Giustini
D019256:Cadmium Chloride / Q000737:chemistry*; D002942:Circular Dichroism; D007477:Ions / Q000737:chemistry; D009532:Nickel / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D009994:Osmolar Concentration; D011067:Poly dA-dT / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry*; D013816:Thermodynamics
D007477:Ions; D012996:Solutions; D011067:Poly dA-dT; C022838:nickel chloride; D009532:Nickel; D019256:Cadmium Chloride