Sharp DNA denaturation in 3D mesoscopic DNA

The mesoscopic Peyrard-Bishop DNA Hamiltonian describes the main molecular interactions with simple potentials, resulting in an efficient calculation of the melting of the duplex helix. It is based on a 2D model which can be simplified to calculate the classical partition function with the transfer-integral technique. At the heart of this approach are simplifications that leave only a single variable to integrate, but also make it impossible to apply the model to situations where a more detailed structural description is needed. Here, we start from a more realistic 3D description and work out several approximations to arrive at a form that can be handled by the transfer-integral technique. We show that this new approach naturally results very sharp opening transition.