The influence of millimetric electromagnetic waves (MMEMW) of weak capacity on aqua-saline solution of DNA is investigated. There are numerous works devoted to nonthermal influence of MMEMW on normal and pathological tissues. Despite of a plenty of works in this field, there is no scientifically proved theory yet, which may explain experimental data. According to the accepted point of view, MMEMW of weak capability are absorbed by water, which lead to their influence on biosystems. The researches devoted to nonthermal influence of MMEMW on a molecule of DNA are very few and inconsistent.

The water solutions of DNA, prepared for spectrophotometric measurement, were irradiated for 30, 40, 60, and 90 min. The irradiation of samples was carried out at room temperature, the target capacity at frequency 64,5 GHz was ∼50mW/cm². This parameter coincides with maximum of aqua absorbance. The MMEMW irradiation almost does not cause of the alterations of pH values of DNA solutions. The characteristic parameters of DNA melting temperature (T_m) and interval of melting (ΔT) were obtained from melting curves. The melting curves have been obtained both after an irradiation and after 10 and 24 hours of storage.

The experiments have shown that a form of a melting curve, values of T_m and ΔT of irradiated DNA do not depend on a storage time. Depending on time of an irradiation ΔT does not change, while the thermostability of DNA is increased; at an irradiation up to 90 min T_m increased on ∼1,5°.

The assumption is made, that the increase of thermostability of DNA is caused by more effective stabilization of a double helix DNA takes place due to dehydration of Na⁺-ions present in a solution.