Search results for "UV-spectroscopy"
showing 3 items of 3 documents
Effect of the Alkaline Cations on the Stability of the Model Polynucleotide Poly(dG-dC)·Poly(dG-dC)
2011
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(…
Interactions of the alternating double stranded copolymer poly(dA-dT).poly(dA-dT) with NiCl2 and CdCl2: solution behaviour
2007
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 eff…
Interactions of tryptophan and serotonin with biomembrane models: Binding to reversed micellar systems of ionic and non ionic surfactants
2001
The interactions of Tryptophan (TRP) and Serotonin (5-HT), with water-containing sodium bis (2-ethylhexyl) sulfosuccinate (AOT), didodecyldimethylammonium bromide (DDAB) and tetraethylene glycol monododecyl ether (C12E4) reversed micelles have been investigated by UV absorption spectroscopy. Our results suggest that independently of the nature of the surfactant and the amount of the water encapsulated into the micellar core, TRP and 5-HT are solubilized in the micellar phase, preferring to be located in a shallow region constituted by the hydrated surfactant head groups. This is due to the amphiphilic nature of TRP and 5-HT and the biological implications are discussed.