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Amino acid substitutions affecting protein dynamics in eglin C do not affect heat capacity change upon unfolding
Author(s) -
Gribenko Alexey V.,
Keiffer Timothy R.,
Makhatadze George I.
Publication year - 2006
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.20974
Subject(s) - heat capacity , chemistry , rigidity (electromagnetism) , thermodynamics , differential scanning calorimetry , calorimetry , crystallography , biophysics , materials science , physics , biology , composite material
The heat capacity change upon unfolding (Δ C p ) is a thermodynamic parameter that defines the temperature dependence of the thermodynamic stability of proteins; however, physical basis of the heat capacity change is not completely understood. Although empirical surface area‐based calculations can predict heat capacity changes reasonably well, accumulating evidence suggests that changes in hydration of those surfaces is not the only parameter contributing to the observed heat capacity changes upon unfolding. Because packing density in the protein interior is similar to that observed in organic crystals, we hypothesized that changes in protein dynamics resulting in increased rigidity of the protein structure might contribute to the observed heat capacity change upon unfolding. Using differential scanning calorimetry we characterized the thermodynamic behavior of a serine protease inhibitor eglin C and two eglin C variants with altered native state dynamics, as determined by NMR. We found no evidence of changes in Δ C p in either of the variants, suggesting that changes in rigidity do not contribute to the heat capacity change upon unfolding in this model system. Proteins 2006. © 2006 Wiley‐Liss, Inc.