Dynamics of protein and its hydration water: neutron scattering studies on fully deuterated GFP.
We present a detailed analysis of the picosecond-to-nanosecond motions of green fluorescent protein (GFP) and its hydration water using neutron scattering spectroscopy and hydrogen/deuterium contrast. The analysis reveals that hydration water suppresses protein motions at lower temperatures (<~ 200 K), and facilitates protein dynamics at high temperatures. Experimental data demonstrate that the hydration water is harmonic at temperatures <~ 180-190 K and is not affected by the proteins' methyl group rotations. The dynamics of the hydration water exhibits changes at ~ 180-190 K that we ascribe to the glass transition in the hydrated protein. Our results confirm significant differences in the dynamics of protein and its hydration water at high temperatures: on the picosecond-to-nanosecond timescale, the hydration water exhibits diffusive dynamics, while the protein motions are localized to <~3 Å. The diffusion of the GFP hydration water is similar to the behavior of hydration water previously observed for other proteins. Comparison with other globular proteins (e.g., lysozyme) reveals that on the timescale of 1 ns and at equivalent hydration level, GFP dynamics (mean-square displacements and quasielastic intensity) are of much smaller amplitude. Moreover, the suppression of the protein dynamics by the hydration water at low temperatures appears to be stronger in GFP than in other globular proteins. We ascribe this observation to the barrellike structure of GFP.
Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
Jonathan D
JD
Nickels
Hugh
H
O'Neill
Liang
L
Hong
Madhusudan
M
Tyagi
Georg
G
Ehlers
Kevin L
KL
Weiss
Qiu
Q
Zhang
Zheng
Z
Yi
Eugene
E
Mamontov
Jeremy C
JC
Smith
Alexei P
AP
Sokolov
D003903:Deuterium / Q000737:chemistry*; D049452:Green Fluorescent Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D033363:Neutron Diffraction; D017433:Protein Structure, Secondary; D013696:Temperature; D014867:Water / Q000737:chemistry*
D014867:Water; D049452:Green Fluorescent Proteins; D003903:Deuterium