Temperature and timescale dependence of protein dynamics imethanol:water mixtures
- Cancer Research UK
- ORNL
- University of Waikato, New Zealand
- University College, London
Experimental and computer simulation studies have suggested the presence of a transition in the dynamics of hydrated proteins at around 180-220 K. This transition is manifested by nonlinear behavior in the temperature dependence of the average atomic mean-square displacement which increases at high temperature. Here, we present results of a dynamic neutron scattering analysis of the transition for a simple enzyme: xylanase in water : methanol solutions of varying methanol concentrations. In order to investigate motions on different timescales, two different instruments were used: one sensitive to {approx}100 ps timescale motions and the other to {approx}ns timescale motions. The results reveal distinctly different behavior on the two timescales examined. On the shorter timescale the dynamics are dictated by the properties of the surrounding solvent: the temperature of the dynamical transition lowers with increasing methanol concentration closely following the melting behavior of the corresponding water : methanol solution. This contrasts with the longer (ns) timescale results in which the dynamical transition appears at temperatures lower than the corresponding melting point of the cryosolvent. These results are suggested to arise from a collaborative effect between the protein surface and the solvent which lowers the effective melting temperature of the protein hydration layer. Taken together, the results suggest that the protein solvation shell may play a major role in the temperature dependence of protein solution dynamics.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Laboratory Directed Research and Development (LDRD) Program
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 932187
- Journal Information:
- Physical Chemistry Chemical Physics, Vol. 7; ISSN 1463-9076
- Country of Publication:
- United States
- Language:
- English
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