8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P4.44Fri 911:10-14:00Possible mechanism of formation of anisotropic texturesin DNA filmsSergiy Perepelytsya, 1 Gennadiy Glibitskiy, 2 and Sergey Volkov 11 Bogolyubov Institute for Theoretical Physics, NAS of Ukraine, 14-b Metrolohichna St. ,03680, Kiev, Ukraine2 Usikov Institute of Radiophysics and Electronics, NAS of Ukraine, Kharkov,UkraineUnder the presence of special excess salts the DNA macromolecules may form the textures in dryfilms. The mechanism of counterion influence on texture formation in DNA films is not determinedyet. In the present work the formation of anisotropic textures in dry films of DNA with chloridesof alkaline metals is studied. The films are prepared by evaporating water solution of DNA fromcalf thymus with excess salt 10 mM. The obtained DNA films with NaCl, KCl, and RbCl saltsare characterized by dendritic textures, while in the case of LiCl and CsCl do not. To determinethe character of interaction between DNA macromolecules the interaction energy between twoparallel unlimited double helixes is estimated for different degree of phosphate neutralization. Theresults show that the macromolecules attract when the negatively charged phosphate groups ofDNA backbone are completely neutralized. Otherwise the macromolecules repel. In the case ofNaCl, KCl, and RbCl the analysis show that the phosphate groups of the double helix are neutralbefore the DNA coil is squeezed between surface of the film and substrate. This a process leadsto the formation of anisotropic textures in the film. In the case of LiCl and CsCl excess salts thetotal neutralization of DNA phosphate groups occurs when the coil size is about the same as thethickness of the film. Under such conditions the DNA macromolecules precipitate on the substratethat interrupts the formation of anisotropic textures.44