Dynamic transition of Poly(ethylene glycol) with or without the solvation water

Water is the source of life, but the effects of hydration water on the dynamics and function of biological and bio-compatible macromolecules are still full of debates. Chen et al. found a dynamic transition of the solvation water at about 220 K, and claimed that such a liquid-liquid transition of water command the dynamic and function of the proteins. However, Hong and colleagues found out that dry perdeuterated protein also experience a dynamic transition at about 200 K by quasi-elastic neutron scattering. To clarify the problem, a direct observation of the dynamics of the hydration layer about macromolecule in the transition process is crucial. Here, we propose quasi-elastic neutron scattering of dry Poly(ethylene glycol) (PEG) and PEG solvated with a single layer of water bellow and up the liquid-liquid transition of confined water at about 200 K.