Investigation of the thermal stability of nucleic acids and their structural components

The thermal stability of homopolynucleotides (poly(A), poly(G), poly(C), poly(U)) and natural DNA, as well as their structural components: nucleoside (uridine), nucleotides (uridine-5′-monaphosphate, uridine-5′-diphosphate, and uridine-5′-triphosphate) and sugar (D-ribose) have been studied by the method of differential scanning microcalorimetry. The dependences of the heat flow on temperature have been obtained for the compounds having individual features in the temperature range from 20 to 400°C. All samples showed exothermic peaks at temperatures higher than 200°C (for DNA, this peak was found at a temperature of ~160°C), which are related to processes of irreversible thermal destruction. The temperatures of thermal destruction and the effective energy of activation of this process for all compounds studied have been determined. The values of the effective heat of exothermal processes have been calculated for the polynucleotides. The experimental results indicate that there is a significant difference in the thermal stability between these homopolynucleotides and DNA, poly(G) being the most stable and DNA, the least stable. Based on the analysis of D-ribose, nucleoside, and nucleotides, it was concluded that the sugar ring is the most probable region of the destruction. © 2011 Pleiades Publishing, Ltd.