Abstract:
Protein dynamics is strongly influenced by the surrounding
environment and physiological conditions. Here we employ broadband
megahertz-to-terahertz spectroscopy to explore the dynamics of water and
myoglobin protein on an extended time scale from femto- to nanosecond. The
dielectric spectra reveal several relaxations corresponding to the orientational
polarization mechanism, including the dynamics of loosely bound, tightly bound,
and bulk water, as well as collective vibrational modes of protein in an aqueous
environment. The dynamics of loosely bound and bulk water follow non-Arrhenius
behavior; however, the dynamics of water molecules in the tightly bound layer
obeys the Arrhenius-type relation. Combining molecular simulations and effectivemedium
approximation, we have determined the number of water molecules in the tightly bound hydration layer and studied the
dynamics of protein as a function of temperature. The results provide the important impact of water on the biochemical functions of
proteins.
