[Structural transitions in DNA, isolated from normal and neoplastic cells].

A decrease of temperature transition in spin-labeled DNA isolated from leucose cells compared with normal cells is found. It is shown by kinetic formaldehyde method that it may be the result of many defects in the secondary structure of macromolecule in DNA1. The spin label method is shown to be used for the analysis of DNA macromolecule damaged with small irradiation doses.