title: Effect of the alkaline cations on the stability of the model polynucleotide poly(dG-dC)·poly(dG-dC).
abstract: When the model polynucleotide poly(dG-dC)∙poly(dG-dC) [polyGC] is titrated with a strong acid (HCl) in unbuffered aqueous solutions containing the chlorides of the alkali metals in the concentration range 0.010 M-0.600 M, two transitions in the absorbance vs. pH plots are evidenced, characterized by the constants pK(a(₁)) and pK(a(₂)). The limiting values at infinite saline concentrations of these two constants, namely pK(∞)(a(₁)) and pK(∞)(a(₂)) obtained making use of the "one site saturation constant" equation or, in turn, of the double logarithmic plot: pK(a) vs. log([salt]⁻¹), exhibit a clear dependence on the nature of the cations. The effects of the different alkali cations on the pK(∞)(a) values follow the Hofmeister series. In fact, the pK(∞)(a(₁)) and the pK(∞)(a(₂)) values are smaller for Li+ and Na+ than for Rb+ and Cs+, with K+ at the border between the two, showing that the transitions require higher concentrations of protons to occur in the presence of high concentrations of the cosmotropic ions.
authors: Dipartimento di Chimica "S. Cannizzaro", Universita di Palermo, Viale delle Scienze, Pad. 17, 90128 Palermo, Italy.
authors: Marta
authors: M
authors: Airoldi
authors: Giuseppe
authors: G
authors: Gennaro
authors: Marcello
authors: M
authors: Giomini
authors: Anna Maria
authors: AM
authors: Giuliani
authors: Mauro
authors: M
authors: Giustini
mesh_terms: D002412:Cations / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008672:Metals, Alkali / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides / Q000737:chemistry*; D011119:Polynucleotides / Q000737:chemistry*; D012965:Sodium Chloride
chemical_list: D002412:Cations; D008672:Metals, Alkali; D011089:Polydeoxyribonucleotides; D011119:Polynucleotides; C019530:poly(dC-dG); D012965:Sodium Chloride