[Thermal properties of DNA and polydeoxyribonucleotides in a wide range of ionic concentration of neutral salts and a polymer].

deltaHm, deltaT, Tm of melting of polydesoxyribonucletides polydAdT,, polyd(A--T)d(A--T), polyd(A--C)d(T--G) and DNA with different basic composition in a wide range of (10-2--4.0 M) ions (C2H5)4N+, Cs+ and Na+ were determined by the method microcalorimetry. It was established that the difference in melting heats of deltaHpolydAdT--deltaHpolyd(A--T)d(A--T) being approximately 0.6 kcal/mol b. p. represents that part of the energy which is caused by the heterogeneity of Stacking of interaction between (formula: see text) pairs. It is shown that the narrowing of deltaTm with increasing DNA concentration is connected with the decrease of the difference of polyGC and poly AT melting temperatures, what is with the parameter TGC--TAT which characterizes the melting of a free macromolecule.