A similar observation regarding the contribution of the RMSD free energies can be made in the case of the tetrameric CC-Tri, with the tetramer step having a positive ∆G • bind . Again, the separation PMF is negative (Table ), whereas the term ∆G RM SD bound +∆G RM SD unbound is highly positive, rendering the overall dissociation of a single helix from the tetrameric CC-Tri favourable. The 'receptor' in this case is composed of three helices with the sequence of CC-Tri, and the positive sign of the ∆G RM SD bound + ∆G RM SD unbound term indicates the preferential re-arrangement of the helices in the unbound state, where they can form the native trimeric CC-Tri structure, compared to the bound state, where they are confined by the presence of a fourth helix.