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Temperature, stability, and the hydrophobic interaction.

Authors
  • Schellman, J A
Type
Published Article
Journal
Biophysical journal
Publication Date
Dec 01, 1997
Volume
73
Issue
6
Pages
2960–2964
Identifiers
PMID: 9414210
Source
Medline
License
Unknown

Abstract

Changes in free energy are normally used to track the effect of temperature on the stability of proteins and hydrophobic interactions. Use of this procedure on the aqueous solubility of hydrocarbons, a standard representation of the hydrophobic effect, leads to the conclusion that the hydrophobic effect increases in strength as the temperature is raised to approximately 140 degrees C. Acceptance of this interpretation leads to a number of far-reaching conclusions that are at variance with the original conception of the hydrophobic effect and add considerably to the complexity of interpretation. There are two legitimate thermodynamic functions that can be used to look at stability as a function of temperature: the standard Gibbs free energy change, deltaG degrees, and deltaG degrees/T. The latter is proportional to the log of the equilibrium constant and is sometimes called the Massieu-Planck function. Arguments are presented for using deltaG degrees/T rather than deltaG degrees for variations in stability with temperature. This makes a considerable difference in the interpretation of the hydrophobic interaction, but makes little change in the stability profile of proteins. Protein unfolding and the aqueous solubility of benzene are given as examples. The contrast between protein unfolding and the hydration of nonpolar molecules provides a rough estimate of the contribution of other factors that stabilize and destabilize protein structure.

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