[DNA compact form in solution. XI. Melting of the DNA compact state, formed in water-salt solutions, containing poly(ethylene glycol)].

Temperature dependences of absorption and CD spectra of DNA compact particles, formed in water-salt solutions in the presence of poly(ethylene glycol) (PEG), have been compared. It has been shown that the disappearance of a specific negative CD band, characteristic of the DNA compact form, occures prior to the destruction of the DNA secondary structure and is not connected with changes of the number or the size of compact particles. The disappearance of this band is believed to reflect the destruction of ordered structure of microcrystalline regions in DNA compact particles.