[Spectrophotometric study of the system DNA-lipid]

The effect of some physical and chemical factors on the system DNA-lipid and its components was studied by spectrophotometry. A change of optical density (D) of watersalt suspensions of lipid total fraction in the range of wavelengths from 200 to 350 nm with the change of ionic strength from 0 to 1 M NaC1 and temperature from 20 to 100 degrees C was investigated. Measurements were carried out under various temperature regemes. In all cases a bell-like irreversible dependence of D on temperature was observed. Its parameters were essentially dependent on the temperature heating of the samples and medium composition. In the presence of DNA the parameters of the curve were changed significantly and depended on the ratio DNA:lipid. An inhibiting effect of DNA on the oxidation of lipids and stabilization of liposomes as well as thermic destruction of DNA stabilized by lipids were observed under certain conditions. The data obtained allowed a conclusion concerning the formation of lipodesoxinucleic complex. It was shown that when a large number of lipid oxidation products was accumulated in the system a chemical modification of DNA with the change of its secondary structure went on.