  We develop further a statistical model coupling denaturation and chain
conformations in DNA (Palmeri J, Manghi M and Destainville N 2007 Phys. Rev.
Lett. 99 088103). Our Discrete Helical Wormlike Chain model takes explicitly
into account the three elastic degrees of freedom, namely stretching, bending
and torsion of the polymer. By integrating out these external variables, the
conformational entropy contributes to bubble nucleation (opening of
base-pairs), which sheds light on the DNA melting mechanism. Because the values
of monomer length, bending and torsional moduli differ significantly in dsDNA
and ssDNA, these effects are important. Moreover, we explore in this context
the role of an additional loop entropy and analyze finite-size effects in an
experimental context where polydA-polydT is clamped by two G-C strands, as well
as for free polymers.
