Hydrophobic solvation in aqueous trifluoroethanol solution.

The titration of an aqueous solution of a de novo designed peptide with trifluoroethanol (TFE) shows complete helix formation with the addition of only 30% TFE. A molecular simulation of the peptide, in which a single shell of TFE molecules initially surrounds the peptide, reveals preferred sites of solvent interaction. The TFE molecules show greater preference for the hydrophobic compared with hydrophilic side chains. The helix-enhancing ability of TFE in aqueous solution may be rationalized in terms of stabilizing the hydrophobic collapse of apolar side chains of the formed helix.