Towards a Quantitative Understanding of Protein Hydration and Volumetric Properties |
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Authors: | Lally Mitra Jean‐Baptiste Rouget Bertrand Garcia‐Moreno Prof Dr Catherine A Royer Prof Dr Roland Winter Prof Dr |
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Institution: | 1. Dortmund University of Technology, Department of Chemistry, Physical Chemistry I—Biophysical Chemistry, Otto‐Hahn Str. 6, 44227 Dortmund (Germany), Fax: (+49)?231?755 3901;2. 3 CNRS, UMR5048, Centre de Biochimie Structurale, 34090 Montpellier (France), Fax: (+33)?467?417913;3. Department of Biophysics, Johns Hopkins University, Baltimore MD 21218 (USA), Fax: (+1)?(410)?516‐4118 |
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Abstract: | Herein, we probe by pressure perturbation calorimetry (PPC) the coefficient of thermal expansion, the volumetric and the hydration properties of variants of a hyperstable variant of staphylococcal nuclease (SNase), Δ+PHS. The temperature‐dependent volumetric properties of the folded and unfolded states of the wild‐type protein are calculated with previously published data. The present PPC results are used to interpret the volume diagram and expansivity at a molecular level. We conclude that the expansivity of the unfolded state is, to a first approximation, temperature independent, while that of the folded state decreases with increasing temperature. Our data suggest that at low temperature the defining contribution to ΔV comes mainly from excluded volume differences and ΔV for unfolding is negative. In contrast, at high temperatures, differential solvation due to the increased exposed surface area of the unfolded state and, in particular, its larger thermal volume linked to the increased conformational dynamics of the unfolded state ensemble takes over and ΔV for unfolding eventually becomes positive. |
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Keywords: | pressure perturbation calorimetry (PPC) protein hydration protein folding temperature dependence volumetric properties |
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