[Thermodynamics of stacking-interactions in polyA and polyC]

Thermodynamics of stacking-contacts breakdown in single chains of polyA and polyC was studied by scanning microcalorimetry. Temperature relationships of partial heat capacities of polymers within 5 divided by 130 degrees C were measured for the first time and contributions to heat capacity of corresponding nucleosidemonophosphates were taken into account. As a result of the data analysis on the basis of Ising linear model entalpies and entropies of stacking-interactions were determined, as well as the values of the cooperativity factor, which in the scale of mole contacts equaled: delta Hm = 14.5 +/- 8 kJ/mole, delta Sm = 46.3 +/- 3 J/K.mole, delta Cp,m = 110 J/K.mole, delta = 0.18 and delta Hm = 13.8 +/- 0.8 kJ/mole, delta Sm = 41.6 +/- 3 J/K.mole, delta Cp,m = 80 J/K.mole, sigma = 0.13 for polyA and polyC respectively in solution with 0.12 M NaCl and pH 7.0.