1 research outputs found
High-Precision Megahertz-to-Terahertz Dielectric Spectroscopy of Protein Collective Motions and Hydration Dynamics
The
low-frequency collective vibrational modes in proteins as well
as the protein–water interface have been suggested as dominant
factors controlling the efficiency of biochemical reactions and biological
energy transport. It is thus crucial to uncover the mystery of the
hydration structure and dynamics as well as their coupling to collective
motions of proteins in aqueous solutions. Here, we report dielectric
properties of aqueous bovine serum albumin protein solutions as a
model system using an extremely sensitive dielectric spectrometer
with frequencies spanning from megahertz to terahertz. The dielectric
relaxation spectra reveal several polarization mechanisms at the molecular
level with different time constants and dielectric strengths, reflecting
the complexity of protein–water interactions. Combining the
effective-medium approximation and molecular dynamics simulations,
we have determined collective vibrational modes at terahertz frequencies
and the number of water molecules in the tightly bound and loosely
bound hydration layers. High-precision measurements of the number
of hydration water molecules indicate that the dynamical influence
of proteins extends beyond the first solvation layer, to around 7
Ă… distance from the protein surface, with the largest slowdown
arising from water molecules directly hydrogen-bonded to the protein.
Our results reveal critical information of protein dynamics and protein–water
interfaces, which determine biochemical functions and reactivity of
proteins