[The thermodynamic parameters of the conformational transitions in Mycoplasma DNA]

DNA preparations have been isolated from 10 strains of phytopathogenic mycoplasms and collection culture Achole plasma laidlawii PG-8. Thermodynamic parameters of denaturation changes in the secondary structure (transconformation) of DNA of these mycoplasms have been determined. It is shown that denaturation temperature is 82.3-83.1 degree C and enthalpy of conformational DNA transitions calculated per 1 g of dry substance is 56.2-61.9 J/g. Changes in the enthalpy (delta H) and entropy (delta S) calculated per 1 mol of nucleotide pairs varied in the range of 35.6-39.0 J/m.p. and 995-109.6 J degree m.p. respectively. No linear dependence of transconformational thermal adsorption on the temperature of DNA denaturation of the studied strains of mycoplasms are revealed, which is probably connected with structural peculiarities of DNA of these microorganisms.