Melting of DNA in ethanol–water solutions

Abstract
The thermal denaturation curves of DNA have been investigated over a wide range of temperatures T and ethanol concentrations C by CD and uv absorption methods. The phase diagram of conformational DNA states has been constructed in T,C plane. The range of the A, B, and coiled forms of DNA was determined. The behavior of the DNA denaturation curve in the neighborhood of the triple point shows that the conformational transition B → A is realized by short parts of the DNA double helix. This is the reason for the coincidence of the melting temperatures of the A and B forms of DNA throughout the range of their coexistence.