  The molecular mechanism of the solvent motion that is required to instigate
the protein structural relaxation above a critical hydration level or
transition temperature has yet to be determined. In this work we use
quasi-elastic neutron scattering (QENS) and molecular dynamics simulation to
investigate hydration water dynamics near a greatly simplified protein surface.
We consider the hydration water dynamics near the completely deuterated
N-acetyl-leucine-methylamide (NALMA) solute, a hydrophobic amino acid side
chain attached to a polar blocked polypeptide backbone, as a function of
concentration between 0.5M-2.0M, under ambient conditions. In this
Communication, we focus our results of hydration dynamics near a model protein
surface on the issue of how enzymatic activity is restored once a critical
hydration level is reached, and provide a hypothesis for the molecular
mechanism of the solvent motion that is required to trigger protein structural
relaxation when above the hydration transition.
