keeps the same conformational flexibility as in the free state, corroborating that this moiety is not involved in direct and persistent intermolecular interactions with the lectin. In contrast, a single conformation is selected upon binding to L-SIGN, which is in agreement with the X-ray crystallography data. There are additional contacts with the protein that strengthens the interaction from the enthalpy point of view. Moreover, this conformational selection process also accounts for the observed entropy penalty upon binding.