as the partition functions restricted to the true dimer states, but neglecting the initiation energies ΘI. An additional symmetry correction is needed in the case of the homo-dimers: A structure of a homo-dimer is symmetric if for any base pair (i, j) there exists a pair (i', j'), where i' (j') denotes the equivalent of position i in the other copy of the molecule. Such symmetric structures have a two-fold rotational symmetry that reduces their conformation space by a factor of 2, resulting in an entropic penalty of ΔGsym = RT ln 2. On the other hand, since the recursion for the partition functions eq. 6 assumes two distinguishable molecules A and B, any asymmetric structures of a homo-dimer are in fact counted twice by the recursion. Leading to the same correction as for symmetric structures.