Drug binding and order-order and order-disorder transitions in DNA triple helices

The Zimm and Bragg theory for helix-to-coil transitions has been suitably a mended and applied to explain the two-step transition in the DNA tripler. T he experimental measurements reported elsewhere have been successfully inte rpreted. The order-order and order-disorder transitions associated with the melting of the DNA triple helix, with and without netropsin binding, were characterized by the nucleation parameter, enthalpy change, sharpness of tr ansition, and heat capacity. The destabilization of the tripler and stabili zation of the duplex on netropsin binding are reflected in these characteri stic parameters.