The Role of Chain Entropy in an Analytic Model of Protein Binding in   Single-DNA Stretching Experiments
  We show that the simple analytical model proposed by Zhang and Marko (Phys. Rev. E 77, 031916 (2008)) to illustrate Maxwell relations for single-DNA experiments can be improved by including the zero-force entropy of a Gaussian chain. The resulting model is in excellent agreement with the discrete persistent-chain model and is in a form convenient for analyzing experimental data. 
Pui-Man Lam and Richard M. Neumann
cond-mat.soft physics.bio-ph