TY - JOUR AU - Bereznyak, E. G. AU - Kruglova, E. B. AU - Khrebtova, A. S. AU - Dukhopelnykov, Ye. V. AU - Zinchenko, A. V. PY - 2007/06/05 Y2 - 2024/03/29 TI - The influence of actinocine derivative ACT III on melting of DNA in the DNA ACT III complexes at different ligand concentrations JF - Biophysical Bulletin JA - Bioph. Bull. VL - 2 IS - 19 SE - Molecular biophysics DO - UR - https://periodicals.karazin.ua/biophysvisnyk/article/view/17112 SP - 29-35 AB - Spectrophotometric concentration dependencies of the system of calf thymus DNA and actinolite derivative Act III in 0.015 M Na + solution are analyzed. The information about binding modes and stoichiometry of complexes is obtained. Thermodynamic parameters of DNA in the complexes are found by means of differential scanning calorimetry technique. It is shown that two significantly thermodynamically and structurally different types of complexes can be formed depending on the ratio of polynucleotide-to-ligand concentrations (P/D). At low P/D values Act III binds preferentially to the sugar-phosphate backbone and forms a non-sequence-specific complex. At a high P/D ratio, the ligand intercalates into DNA and changes the structure of GC-rich blocks. In the intermediate P/D range both types of binding coexist. Melting of complexes results in redistribution of ligand and increase of the Act III concentration in the complex by aggregate type. It was found that the size of the binding sites depends on the experimental technique employed. ER -