[Effect of water on the structural modification and stabilization of DNA from Clostridium perfringens]

By the methods of infrared spectroscopy, piezogravimetry and microcalorimetry the process of forming of the structure and hydration environment of DNA from Clostridium perfringens in the wet films has been investigated. It were found three intervals of relative humidity (r.h.) in which three structural states of DNA: an unordered state (0-44% r.h.), the A-form (46-75% r.h.) and the B-form (80-86% r.h.) are realized. We measured the heat of water evaporation from the DNA-water samples with the differential scanning microcalorimeter. From these calorimetric data the distribution of the water molecules on the bond energy with DNA was determined. The contribution of the water molecules of hydration shell (73%) and hydrogen bonds in the Watson-Crick pairs (27%) to the total energy of stabilization of the helical B-form DNA from Cl. perfringens has been evaluated.