Conformations of alternating purine-pyrimidine DNAs in high-CsF solutions and their reversal by dipyrandium, ethidium and high temperature.

Chiroptical properties of synthetic DNAs with alternating purine-pyrimidine sequences were studied in high-CsF solutions. It was found that this salt transformed all the DNAs to non-canonical conformations like Z or X, which show striking negative bands in the long wavelength part of the CD spectra. The negative bands were reversed upon interaction with dipyrandium, ethidium and at high temperature.