Many marvelous biological functions in proteins and DNA as well as their profound dynamic mechanisms, such as switch between active and inactive states [56, 57] , cooperative effects [58] , allosteric transition [59, 60] , intercalation of drugs into DNA [61] , and assembly of microtubules [62] , can be revealed by studying their internal motions [63] . Likewise, to really understand the interaction mechanism of a receptor with its ligand, investigations should be aimed not only at their static structures but also at the dynamic process obtained by simulating their internal motions.