[Interactions of DNA with ampholytes based on actinocin]

The interaction of DNA with actinocin monoamides containing a substitute with the cationoide center in one of the amide groups were studied by spectrophotometry, induced circular dichroism, viscometry and flow birefringence methods. At pH values of solution exceeding their isoelectric point, these substances, which are in nature ampholytes, occur as zwitterions. At lover pH values they occur in the cationoid form. The constants of binding of these compounds to DNA were determined, and changes in DNA macromolecular structure caused by complexation were revealed. Models for the binding of these compounds to DNA were advanced. It was shown that compounds in the zwitterion form do not intercalate into the DNA double helix. The mode of binding of compounds to DNA in the cationoid form depends on the position of the cationoid center within the chromophore actinocin. Circular dichroism spectra of actinocyn-based ampholytes that bind to DNA in a different manner were obtained.