2011
Volume 11, Number 3, pp. 107–112
The effect of some ions on DNA thermal stability
Giorgi Gogoladze,1 Ketevan Tsakadze2 and Anna Ivanova1
1 Department of Exact Sciences, Tbilisi State University, 3 Chavchavadze Ave, 0128 Tbilisi, Georgia
2 Department of Biological Systems, Andronikashvili Institute of Physics, 6 Tamarashvili St, 0177 Tbilisi, Georgia
We report a differential scanning calorimetry (DSC) study of the thermodynamic parameters of DNA melting in diluted solutions containing different types of ions. Substitution of Cl– by F–affected the denaturation heat capacity excess, increasing DCP from 0.39 ± 0.04 J g–1K–1 in NaCl up to 1.2 ± 0.1 J g–1K–1 in NaF-containing solutions. An increase of Ni2+ concentration from zero to 40 mM resulted in significant differences in the DNA melting process, which was divided into two heat absorption stages: the transition temperature and transition enthalpy were decreased from 87.6 ± 0.1 °C and 52 ± 5 J g–1 (in the absence of Ni2+) to 66.0 ± 0.1 °C and 40 ± 4 J g–1. At [Ce3+]/[P] = 0.0 and [Ce3+]/[P] = 0.1, the value of the DNA melting enthalpy did not change and remained equal to 58 ± 6 J g–1 but at [Ce3+]/[P] = 0.2, the DNA melting process was divided into two coöperative stages. Presumably, the peaks with maxima at 53.4 ± 0.1 °C and 91.9 ± 0.1 °C corresponded to the melting of A–T- and G–C-rich sites of DNA. At [Ce3+]/[P] = 0.2, the transition enthalpy dropped from 58 ± 6 to 43 ± 4 J g–1. It is proposed that Ce3+ binds to the DNA in the grooves and leads to destruction of the DNA hydration water layer.
Keywords: DNA melting; heat capacity excess; melting enthalpy; melting temperature