DENATURATION OF HETEROGENEOUS DNA

The effect of heterogeneous sequence composition on the denaturation o f double-stranded DNA is investigated. The resulting pair-binding ener gy variation is found to have a negligible effect on the critical prop erties of the smooth second-order melting transition in the simplest ( Peyrard-Bishop) model. However, sequence heterogeneity is dramatically amplified upon adopting a more realistic treatment of the backbone st iffness. The model yields features of ''multistep melting'' similar to those observed in experiments.