Energetics of the B-to-Z and Zhelix-to-coil transitions in water solutions of Poly(DG-DC)
DOI:
https://doi.org/10.7124/bc.00027BAbstract
Differential scanning calorimetry, CD- and UV-spectroscopy were used to study thermodynamics of the B-Z and Z-helix-coil transitions of poly(dG-dC). The experiments were performed under conditions of 0.5 mM water solutions of sodium cacodylate (pH 6.5) + 1 mM MgCl2 + 0.02 mM EDTA. The reversible transition of the polymer observed calorimetrically at 76 °C was identified as B-Z transition. The left-handed helix-coil transition was observed at 97 °C. The enthalpy of B-Z transition is small. A//Cai = 0.2 ± 0.02 kcal/mole bp, indicating a fine energy balance between the DNA left- and right-handed conformations in water solutions. The enthalpy of Z-helix-coil transition is A//Cai=10.1 ± l.l kcal/mole bp.References
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