Hydration dynamics near a model protein surface
The evolution of water dynamics from dilute to very high concentration solutions of a prototypical hydrophobic amino acid with its polar backbone, N-acetyl-leucine-methylamide (NALMA), is studied by quasi-elastic neutron scattering and molecular dynamics simulation for both the completely deuterated and completely hydrogenated leucine monomer. We observe several unexpected features in the dynamics of these biological solutions under ambient conditions. The NALMA dynamics shows evidence of de Gennes narrowing, an indication of coherent long timescale structural relaxation dynamics. The translational water dynamics are analyzed in a first approximation with a jump diffusion model. At the highest solute concentrations, the hydration water dynamics is significantly suppressed and characterized by a long residential time and a slow diffusion coefficient. The analysis of the more dilute concentration solutions takes into account the results of the 2.0M solution as a model of the first hydration shell. Subtracting the first hydration layer based on the 2.0M spectra, the translational diffusion dynamics is still suppressed, although the rotational relaxation time and residential time are converged to bulk-water values. Molecular dynamics analysis shows spatially heterogeneous dynamics at high concentration that becomes homogeneous at more dilute concentrations. We discuss the hydration dynamics results of this model protein system in the context of glassy systems, protein function, and protein-protein interfaces.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science. Office of Computational and Technology Research; National Institutes of Health Grant GM65239-01, National Science Foundation Agreement DMR-0086210 (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 834632
- Report Number(s):
- LBNL-53863; R&D Project: 449801; TRN: US0407290
- Journal Information:
- Biophysical Journal, Vol. 86, Issue 3; Other Information: Submitted to Biophysical Journal, Volume 86, No.3; Journal Publication Date: 03/2004; PBD: 1 Sep 2003
- Country of Publication:
- United States
- Language:
- English
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