[Study of structural transformations of the sugar-phosphate chain and nitrogen bases of DNA hydrate by...

The IR-spectra (900-1800 cm-1) of films of native and denatured DNA were studied within the temperature range 4-100 degrees C at different relative humidity (r.h.). Two temperature intervals of S-like change of spectral parameters of absorption bands of sugar-phosphate chain of double-helical DNA are found on temperature relationships at high humidity. These two intervals point to two types of cooperative transitions of sugar-phosphate pattern. The band parameters of nitrous bases are changed only under high temperature transition. In the region of structural transitions of different subsystems of DNA hydrate hyperchromism was wound for the bands of sugar-phosphate chain and hydrate cover unlike hyperchromism specific of most nitrous bases bands. From the data obtained it is proposed to use the basic characteristics of temperature relationship of spectral parameters of the absorption bands of sugar-phosphate pattern and hydrate envelope in the region of low-temperature transition for the "in vivo" analysis of the DNA structure in complex biological systems.