[Anomalous optical activity induced during condensation of various spatial forms of double-stranded circular DNA]

Formation of dispersed phases from complexes of (closed circular DNA (c.c. DNA)--antibiotics (drugs) in PEG-containing solutions has been studied. It is shown that under definite concentrations of bound antibiotics relatively intense bands in the CD spectra of dispersed phases in the absorption region of DNA and antibiotics chromophores appear. The properties of liquid crystalline phases formed from the complexes of linear DNA with antibiotics were compared to those of dispersed phases formed from c. c. DNA. Such comparison demonstrates existence of some differences in the optical properties of the phases formed from linear and c.c. DNA molecules. For example a change of the bands sign in the CD spectra of dispersed phases formed from the complexes (c.c. DNA--antibiotics), which is the case with all the substances studied, does not exist in the case of liquid crystalline phases formed from the complexes of (linear DNA--antibiotics). It was shown that a change of the bands sign in the CD spectra correlates with a change of the sign of superhelical twist of closed circular DNA molecules.