CALORIMETRIC STUDY OF THE HELIX-COIL TRAN SITION IN DNA UPON INTERACTION WITH CU2+ IONS

Using the method of differential scanning calorimetry, the DNA helix-c oil transition was studied in solutions (10(-3) M Na+, 10(-3) M tris H Cl, pH 7.0) containing divalent copper ions at relative metal ion conc entrations (Mt(2+)/P-DNA) ranging from 0,2 to 20. Dependences of the m elting temperature and enthalpy on relative ion concentration were det ermined. An aggregation of Cu2+ + DNA complexes in the range of averag e ion concentration was established. It is shown that the melting enth alpy of <<units>> increases with copper ion concentration. The data ob tained were compared with values determined by UV-spectroscopy. Associ ation constants for Cu2+ binding to DNA were defined by the ligand the ory.