Are proteins ultrametric?
  A simple and surprisingly accurate description of spectral diffusion in deeply frozen globular proteins is constructed directly using the concept of ultrametricity of protein dynamics. Earlier the similar concept has been used for successful description of ligand-rebinding kinetics of myoglobin at temperatures about of 200 K. Hence the ultrametricity offers a universal background for the protein dynamics in a wide range of scales of protein motions. 
Vladik A. Avetisov and Albert Kh. Bikulov