An energetic model for macromolecules unfolding in stretching experiments

We propose a simple approach, based onthe minimization of the total (entropic plus unfolding) energyofatwo-state system, todescribe the unfolding of multidomain macromolecules (proteins, silks, polysaccharides, nanopolymers). The model is fully analytical and enlightens the role of the different energetic components regulating the unfolding evolution. As an explicit example, we compare the analytical results with a titin atomic force microscopy stretch-induced unfolding experiment showing the ability of the model to quantitatively reproduce the experimental behaviour. In the thermodynamic limit, the sawtooth force-elongation unfolding curve degenerates to a constant force unfolding plateau.