Before revision:  Thus, mutations disrupting this equilibrium beyond the protein marginal stability upper bound ( 7.4 kcal/ mol) will be subject to negative selection and mutations that preserve it will be neutral or nearly neutral , with respect to the marginal stability.
After revision:  Thus, mutations disrupting this equilibrium beyond the protein marginal stability upper bound ( 7.4 kcal/ mol) is a universal property that includes macro-molecular complexes and is not affected by molecular changes such as mutations and Post-Translational Modifications. Its existence is, essentially, a consequence of the Anfinsen thermodynamic hypothesis rather than a result of an evolutive process. This result enables us to conjecture that neutral evolution should also be , with respect to the marginal stability.