Abstract
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.
| Original language | English |
|---|---|
| Pages (from-to) | 1566-1575 |
| Number of pages | 10 |
| Journal | Biophysical Journal |
| Volume | 103 |
| Issue number | 7 |
| DOIs | |
| State | Published - Oct 3 2012 |
Funding
J.D.N. and A.P.S. acknowledge Department of Energy support through the Experimental Program to Stimulate Competitive Research program (grant No. DE-FG02-08ER46528) and support from Spallation Neutron Source through UT-Battelle. The research at Oak Ridge National Laboratory's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. J.C.S. acknowledges support from the National Science Foundation (Molecular Biosystems Cluster). H.O’N., Q.Z., and K.W. acknowledge the support of the Center for Structural Molecular Biology at the Oak Ridge National Laboratory supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research Project No. ERKP291. This work utilized facilities supported in part by the National Science Foundation under Agreement No. DMR-0944772.