Hydration water rotational motion as a source of configurational entropy driving protein dynamics. Crossovers at 150 and 220 K.
The existence of a protein dynamic transition around 220 K is widely known and the central role of the protein hydration shell is now largely recognized as the driving force for this transition. In this paper, we propose a mechanism, at the molecular level, for the contribution of hydration water. In particular, we identify the key importance of rotational motion of the hydration water as a source of configurational entropy triggering (i) the 220 K protein dynamic crossover (the so-called dynamic transition) but also (ii) a much less intense and scarcely reported protein dynamic crossover, associated to a calorimetric glass transition, at 150 K.
Zanotti
J-M
JM
Commissariat à l'Energie Atomique, IRAMIS, Laboratoire Léon Brillouin, CEA Saclay, Gif-sur-Yvette, France. jmzanotti@cea.fr
Gibrat
G
G
Bellissent-Funel
M-C
MC