[Investigation of hydration of poly[d(A-T)] polynucleotide in helical and random coli states by the method of low temperature scanning microcalorimetry].

Thermodynamic parameters of the process of water phase transition in poly[d(A-T)] solutions in the wide range of polymer concentration have been studied. Curves of the heat capacity changes (delta Cp) depending on concentration of polymer and the temperature in the area of ice-water phase transition have been plotted. Thermodynamic parameters of the process of helix--random coli transition in water solutions of poly[d(A-T)] have been measured. Hydration (n) of poly[d(A-T)]: nAT = 28 mol H2O . mol-1 b. p. has been determined. Comparison of poly[d(A-T)] hydration with hydration of natural DNA shows that the hydration of AT-pairs exceed the amount of water, bound with GC-pairs (nGC congruent to 16--20 mol H2O . mol-1 b. p.). It was concluded that when describing the process of helix-random coil transition in DNA it is necessary to take into account not only the phenomenon of heterogeneity of stacking interactions, but also heterogeneity ("aperiodicity") in the structure of the hydrate shell of DNA molecules.