Na-DNA films with ions of metals

Abstract

The structures of films received by evaporation from solutions of Na-DNA of calf thymus with a concentration of 0.2 mg/ml, containing salts Li, K, Na, Cs, Mg, Zn, Ca are analyzed at various levels of relative humidity and temperatures. The solution of the salt of Na-DNA in a volume of 0.5 ml was poured into a glass quartz cell placed in a hermetically closed vessel with inputs for air pumping. The cell has an area of 420 mm" and the height of lateral walls of 1 mm. The error of stabilization of temperature in the thermostat came to 0.5°C, the error of humidity was 2%. The research was carried out at temperatures of 30 and 40°C. The received films of Na-DNA were photographed in white polarized light. The volume of the formed liquid crystal phase depends on the type of ions in Na-DNA solutions and defines the correlation between the area of structure on the film and the area of all the film and depends on the correlation of concentrations of salt of metal and DNA. The area occupied by liquid crystal structures was calculated as the area limited to a curve, connecting boundary elements of structures. The relative areas of structures received from solutions containing a salt of NaCl with concentrations of 20 and 1.25 mM have values of 0.73 and 0.09 accordingly. The films containing a salt of MgCl₂ has spherulite structures collapsing under the conditions of room temperature and humidity. The films received from the solutions containing salt LiCl, CsCl, CaCl_2, or MgCl₂ with a concentration of 10 mM do not form structures with the allocated direction of growth of clusters. The films received from the solutions containing salt NaCl with the concentration of 10 mM and salts ZnCl₂ or CuCl₂ with the concentration of 0.4 mM and 0.2 mM respectively do not form structures with the allocated direction of growth of clusters also. It is assumed, the film can be characterized by a set of values of fractal dimensions; one of the signs of the existence of DNA in native form is the presence of such fractal structures as percolation anisotropic cluster in the received film.