Theory of the Helix—Coil Transition in DNA Considered as a Periodic Copolymer

One of the major difficulties in calculating transition curves for the ``melting'' of DNA is to take into account the fact that all of the base pairs do not have the same stability. Two kinds of base pairs of differing stability corresponding to adenine—thymine and guanine—cytosine are recognized by the model used in this paper. For a periodic arrangement of the two base pairs we have reduced the problem of calculating the melting curve to find the largest real eigenvalue of a matrix. Some transition curves are computed for a model with nearest-neighbor correlation only.