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Dynamics of a globular protein and its hydration water studied by neutron scattering and MD simulations

Author(s)
Chen, Sow-Hsin; Lagi, Marco; Chu, Xiang-qiang; Zhang, Yang; Faraone, Antonio; Fratini, Emiliano; Baglioni, Piero; Kim, Chansoo, S.M. Massachusetts Institute of Technology; ... Show more Show less
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Abstract
This review article describes our neutron scattering experiments made in the past four years for the understanding of the single-particle (hydrogen atom) dynamics of a protein and its hydration water and the strong coupling between them. We found that the key to this strong coupling is the existence of a fragile-to-strong dynamic crossover (FSC) phenomenon occurring at around T[subscript L] = 225±5 K in the hydration water. On lowering of the temperature toward FSC, the structure of hydration water makes a transition from predominantly the high density form (HDL), a more fluid state, to predominantly the low density form (LDL), a less fluid state, derived from the existence of a liquid–liquid critical point at an elevated pressure. We show experimentally that this sudden switch in the mobility of hydration water on Lysozyme, B-DNA and RNA triggers the dynamic transition, at a temperature T[subscript D] = 220 K, for these biopolymers. In the glassy state, below T[subscript D], the biopolymers lose their vital conformational flexibility resulting in a substantial diminishing of their biological functions. We also performed molecular dynamics (MD) simulations on a realistic model of hydrated lysozyme powder, which confirms the existence of the FSC and the hydration level dependence of the FSC temperature. Furthermore, we show a striking feature in the short time relaxation (β-relaxation) of protein dynamics, which is the logarithmic decay spanning 3 decades (from ps to ns). The long time α-relaxation shows instead a diffusive behavior, which supports the liquid-like motions of protein constituents. We then discuss our recent high-resolution X-ray inelastic scattering studies of globular proteins, Lysozyme and Bovine Serum Albumin. We were able to measure the dispersion relations of collective, intra-protein phonon-like excitations in these proteins for the first time. We found that the phonon energies show a marked softening and at the same time their population increases substantially in a certain wave vector range when temperature crosses over the T[subscript D]. Thus the increase of biological activities above T[subscript D] has positive correlation with activation of slower and large amplitude collective motions of a protein.
Date issued
2010
URI
http://hdl.handle.net/1721.1/96233
Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Journal
Journal of Spectroscopy
Publisher
Hindawi Publishing Corporation
Citation
Chen, Sow-Hsin, Marco Lagi, Xiang-qiang Chu, Yang Zhang, Chansoo Kim, Antonio Faraone, Emiliano Fratini, and Piero Baglioni. “Dynamics of a Globular Protein and Its Hydration Water Studied by Neutron Scattering and MD Simulations.” Spectroscopy 24, no. 1–2 (2010): 1–24. © 2010 Hindawi Publishing Corporation
Version: Final published version
ISSN
2314-4920
2314-4939

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