Vol. 13, no.2, 2021


What properties of non-electrolyte solutions does a DNA molecule feel?

George G. Malenkov

Frumkin Institute of Physical Chemistry and Electrochemistry RAS, http://www.phyche.ac.ru/
Moscow 119991, Russian Federation
E-mail: egor38@mail.ru

Received 27 April, 2021, peer-reviewed 10 May, 2021, accepted 17 May, 2021

Abstract: As early as in 1953 it was reported that at low relative humidity of the atmosphere (about 70 %) DNA films were in A-form, while at higher humidity (more than 80%) they were in B-form. Relative humidity of the atmosphere corresponds to the water activity in the system. It was found in the beginning of the 70th that DNA transfers to the A-form when non-electrolytes, such as monoatomic alcohols, dioxane, tetrahydrofurane were added to water. It was reasonable to suppose that B to A transition of DNA occurs in the non-electrolyte solutions at the same values af water activity as in the moist atmosphere. This prediction was borne out. But in water solutions of very polar non-electrolytes such as methanol and ethylene glycol B to A DNA does not occur even at very low water activity values. It was supposed that A form of DNA can arise only in the medium with sufficiently low polarity. We used hyperfine splitting constant (A) of a nitroxide spin label determined from the EPR spectra as a measure of the liquid solvent polarity. It was found that DNA transition into B form occurs when A reached a certain value. Polarity of methanol and ethylene glycol is much higher than that of the solutions in which B to A DNA transition takes place. This transition also occurs in water solutions of trifluoroethanol. But in these solutions the transition takes place at hyperfine splitting values, which are much greater than in other non-electrolyte solutions. Water activity in the zone of B-A DNA transition in trifluoroethanol solutions does not correspond water activity which was calculated for other nob-electrolyte solutions in which B-A transition is observed.

Keywords: water activity, non-electrolytes, A and B forms of DNA, polarity, EPR spectra, hyperfine splitting constants

UDC 577.113

RENSIT, 2021, 13(2):129-136. DOI: 10.17725/rensit.2021.13.129.

Full-text electronic version of this article - web site http://en.rensit.ru/vypuski/article/386/13(2)129-136e.pdf