Issue 7, 2005
From the journal:

Physical Chemistry Chemical Physics

Temperature and timescale dependence of protein dynamics in methanol : water mixtures

Alexander L. Tournier,†a   Valerie Réat,b   Rachel Dunn,c   Roy Daniel,c   Jeremy C. Smitha  and  John Finney*d  

* Corresponding authors

a Computational Molecular Biophysics, Interdisciplinary Centre for Scientific Computing (IWR), University of Heidelberg, Heidelberg, Germany

b Institut de Pharmacologie et de Biologie Structurale, CNRS and UPS, Toulouse, France

c Department of Biological Sciences, University of Waikato, Hamilton, New Zealand

d Department of Physics and Astronomy, University College London, London, UK
E-mail: j.finney@ucl.ac.uk

Abstract

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 behaviour 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 ∼100 ps timescale motions and the other to ∼ns timescale motions. The results reveal distinctly different behaviour 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 behaviour 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.

Graphical abstract: Temperature and timescale dependence of protein dynamics in methanol : water mixtures

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Article information

DOI
https://doi.org/10.1039/B416103C
Article type
Paper
Submitted
11 Nov 2004
Accepted
21 Feb 2005
First published
02 Mar 2005

Phys. Chem. Chem. Phys., 2005,7, 1388-1393

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Temperature and timescale dependence of protein dynamics in methanol : water mixtures

A. L. Tournier, V. Réat, R. Dunn, R. Daniel, J. C. Smith and J. Finney, Phys. Chem. Chem. Phys., 2005, 7, 1388 DOI: 10.1039/B416103C

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