Salt-induced conformational changes of poly(dA-dT).

Conformational changes of poly(dA-dT) . poly(dA-dT) induced by increasing ionic strength were studied using CD spectroscopy. It was found that a pronounced noncooperative inversion of the long-wavelength part of the CD spectrum of poly(dA-dT) . poly(dA-dT) occurred at high concentrations of CsF in solution. It was suggested that a great difference between the geometries of the purine and pyrimidine residues in the helix was characteristic of the structure of poly(dA-dT) . poly(dA-dT) in concentrated CsF solutions.