CALORIMETRIC STUDY OF CA2-COIL TRANSITION( AND MN2+ IONS EFFECT ON DNA HELIX)

Using the method of differential scanning calorimetry, the DNA helix-c oil transition studied in solutions (10(-3) M Na+, 10(-3) M tris HCl, pH 7,0) containing divalent metal ions (Mn2+ and Ca2+) at relative met al ion concentrations (Me/P-DNA) raning from 0,2 to 20. Dependences of the melting temperature and enthalpy on the ion relative concentratio n were stated. The fine structure of melting curves in DNA+Me complexe s was observed. The resolution degree of this structure was shown to i ncrease In the range of moderate ion concentrations. The data obtained were compared with values determined by UV-spectroscopy. Accosiation constants were defined for Mn2+ and Ca2+ binding to DNA by the ligand theory.