Charles Tanford

The Solubility of Hydrocarbons in Water. Solubility of Amphiphiles in Water and Organic Solvents. The Effect of Temperature: Anomalous Entropy and Heat Capacity. The Structure of Water. Micelles: Introduction. Thermodynamics of Micelle Formation. Micelle Size and Shape. Mixed Micelles. Monolayers. Biological Lipids. Motility and Order. Proteins: Hydrophobic Side Chains and Conformational Change. The Association of Hydrocarbons and Amphiphiles with Common Soluble Proteins. Serum Lipoproteins. Biological Membranes. Membrane Proteins. Author and Subject Indices.

This chapter reviews theoretical models that may be constructed and equations that may be derived from them to understand the process of protein denaturation. Given that the native state is stable under physiological conditions, the question arises whether the effects of environmental changes on the equilibrium between native and denatured states can be predicted, so as to account for the loss of stability of the native state and the appearance of different denatured states under specified conditions. This question involves not the absolute values for the free energies and other thermodynamic parameters for denaturation processes, but the changes in these parameters, along with changes in environmental variables. These changes can be predicted semiquantitatively. Furthermore, one can account both for the products formed under different conditions and for the character of the transitions from native to denatured state, at least for the simple proteins that have been studied in detail.

The solubilities of amino acids, diglycine, and triglycine have been measured in water and aqueous ethanol as well as dioxane solutions. Free energies of transfer of amino acid side chains and backbone peptide units from water to ethanol and dioxane solutions have been calculated from these data. The results show the similarity between the effects of ethanol and dioxane on the stability of those side chains and peptide units. In particular, the free energies of transfer of hydrophobic side chains to 100% ethanol and dioxane are essentially identical, and have been used to establish a hydrophobicity scale for hydrophobic side chains.